WTNT41 KNHC 081459
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST WED SEP 08 2010
 
THE LOW OVER THE FAR EASTERN TROPICAL ATLANTIC OCEAN HAS BECOME
BETTER DEFINED AND DEEP CONVECTION NEAR THE CENTER HAS PERSISTED
LONG ENOUGH FOR THIS SYSTEM TO BE CONSIDERED A TROPICAL CYCLONE. A
1042 UTC ASCAT PASS SHOWED WINDS OF 35 KT...AND THE INITIAL
INTENSITY WILL BE SET TO THAT VALUE.  EASTERLY SHEAR IS PRESENT
OVER IGOR...BUT IS FORECAST TO LIGHTEN IN A DAY OR SO.  ALL
RELIABLE MODELS SHOW INTENSIFICATION INTO A HURRICANE IN THE NEXT
SEVERAL DAYS.  BECAUSE OF THE SHEAR...THE NHC INTENSITY FORECAST
WILL ONLY SHOW RELATIVELY SLOW STRENGTHENING...BELOW THE GUIDANCE
INITIALLY...BUT THE FORECAST ENDS UP CLOSE TO THE CONSENSUS AT DAY
5.  IF THE UPPER ANTICYCLONE PATTERN SEEN IN MOST OF THE GLOBAL
MODELS VERIFY...THE OFFICIAL FORECAST COULD BE CONSERVATIVE IN THE
LATTER PART OF THE FORECAST PERIOD.
 
THE INITIAL MOTION IS 265/7.  A MID-LEVEL RIDGE OVER THE EASTERN
ATLANTIC OCEAN IS FORECAST TO STRENGTHEN OVER THE NEXT FEW
DAYS...WHICH SHOULD CAUSE A WESTWARD MOTION AT AN INCREASING
FORWARD SPEED.  AT THE END OF THE PERIOD...A TROUGH OVER THE
CENTRAL ATLANTIC COULD WEAKEN THE RIDGE...FORCING THE STORM TO MOVE
MORE TO THE WEST-NORTHWEST.  THE MODEL GUIDANCE IS IN RELATIVELY
GOOD AGREEMENT ON THIS SCENARIO...ALTHOUGH THERE IS SOME SHORT-TERM
UNCERTAINTY ON HOW IGOR WILL INTERACT WITH THE LARGE CONVECTIVE
SYSTEM TO THE NORTHEAST OF THE STORM. THE NHC FORECAST IS NEAR OR
SLIGHTLY SOUTH OF THE MODEL CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 13.7N  23.5W    35 KT
 12HR VT     09/0000Z 13.7N  24.6W    40 KT
 24HR VT     09/1200Z 13.8N  26.6W    45 KT
 36HR VT     10/0000Z 14.0N  29.0W    50 KT
 48HR VT     10/1200Z 14.5N  31.5W    55 KT
 72HR VT     11/1200Z 15.5N  36.5W    65 KT
 96HR VT     12/1200Z 16.8N  41.2W    75 KT
120HR VT     13/1200Z 18.0N  46.0W    85 KT
 
$$
FORECASTER BLAKE/PASCH
 

WTNT41 KNHC 081459
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST WED SEP 08 2010

THE LOW OVER THE FAR EASTERN TROPICAL ATLANTIC OCEAN HAS BECOME
BETTER DEFINED AND DEEP CONVECTION NEAR THE CENTER HAS PERSISTED
LONG ENOUGH FOR THIS SYSTEM TO BE CONSIDERED A TROPICAL CYCLONE. A
1042 UTC ASCAT PASS SHOWED WINDS OF 35 KT...AND THE INITIAL
INTENSITY WILL BE SET TO THAT VALUE.  EASTERLY SHEAR IS PRESENT
OVER IGOR...BUT IS FORECAST TO LIGHTEN IN A DAY OR SO.  ALL
RELIABLE MODELS SHOW INTENSIFICATION INTO A HURRICANE IN THE NEXT
SEVERAL DAYS.  BECAUSE OF THE SHEAR...THE NHC INTENSITY FORECAST
WILL ONLY SHOW RELATIVELY SLOW STRENGTHENING...BELOW THE GUIDANCE
INITIALLY...BUT THE FORECAST ENDS UP CLOSE TO THE CONSENSUS AT DAY
5.  IF THE UPPER ANTICYCLONE PATTERN SEEN IN MOST OF THE GLOBAL
MODELS VERIFY...THE OFFICIAL FORECAST COULD BE CONSERVATIVE IN THE
LATTER PART OF THE FORECAST PERIOD.

THE INITIAL MOTION IS 265/7.  A MID-LEVEL RIDGE OVER THE EASTERN
ATLANTIC OCEAN IS FORECAST TO STRENGTHEN OVER THE NEXT FEW
DAYS...WHICH SHOULD CAUSE A WESTWARD MOTION AT AN INCREASING
FORWARD SPEED.  AT THE END OF THE PERIOD...A TROUGH OVER THE
CENTRAL ATLANTIC COULD WEAKEN THE RIDGE...FORCING THE STORM TO MOVE
MORE TO THE WEST-NORTHWEST.  THE MODEL GUIDANCE IS IN RELATIVELY
GOOD AGREEMENT ON THIS SCENARIO...ALTHOUGH THERE IS SOME SHORT-TERM
UNCERTAINTY ON HOW IGOR WILL INTERACT WITH THE LARGE CONVECTIVE
SYSTEM TO THE NORTHEAST OF THE STORM. THE NHC FORECAST IS NEAR OR
SLIGHTLY SOUTH OF THE MODEL CONSENSUS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      08/1500Z 13.7N  23.5W    35 KT
12HR VT     09/0000Z 13.7N  24.6W    40 KT
24HR VT     09/1200Z 13.8N  26.6W    45 KT
36HR VT     10/0000Z 14.0N  29.0W    50 KT
48HR VT     10/1200Z 14.5N  31.5W    55 KT
72HR VT     11/1200Z 15.5N  36.5W    65 KT
96HR VT     12/1200Z 16.8N  41.2W    75 KT
120HR VT     13/1200Z 18.0N  46.0W    85 KT

$$
FORECASTER BLAKE/PASCH




WTNT41 KNHC 082038
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST WED SEP 08 2010
 
MODERATE TO STRONG CONVECTION CONTINUES TO BE LOCATED TO THE WEST OF
THE CENTER...A SYMPTOM OF EASTERLY SHEAR.  HIGH-RESOLUTION ASCAT
DATA EARLIER INDICATED PEAK WINDS OF 35-40 KT...AND WITH SATELLITE
CLASSIFICATIONS INCREASING...THE WIND SPEED IS RAISED TO 40 KT.  
 
AN UNCERTAIN ESTIMATE OF THE INITIAL MOTION IS 275/5.  THE
MOTION HAS SLOWED SIGNIFICANTLY...POSSIBLY DUE TO THE LOW PRESSURE
AREA APPROACHING THE NORTHERN CAPE VERDE ISLANDS.  THE GLOBAL
MODELS ARE SHOWING A DIFFERENT SCENARIO IN THE SHORT-TERM AND HAVE
TRENDED TOWARD THE 00/12Z ECMWF SOLUTIONS.  AS THE SMALL LOW TO
THE NORTHEAST OF IGOR MOVES WESTWARD...THE RIDGE IS FORECAST TO
WEAKEN SLIGHTLY...WHICH ALLOWS IGOR TO MOVE TO THE WEST-NORTHWEST
OR EVEN NORTHWEST BRIEFLY.  AFTERWARDS...THE RIDGE RESTRENGTHENS...
WHICH SHOULD TURN IGOR WESTWARD AGAIN.   THE NHC FORECAST IS
SHIFTED TO THE NORTH TO ACCOUNT FOR THE INTERACTION OF THE TWO
SYSTEMS AND THE NORTHWARD SHIFT IN THE MODELS...BUT STILL LIES
ALONG THE SOUTHERN EDGE OF THE ENVELOPE. 
 
THE INTENSITY FORECAST...AT LEAST IN THE SHORT-TERM...SEEMS TRICKY
WITH IGOR ONLY ABOUT 210 NM SOUTHWEST OF THE AFOREMENTIONED LOW. 
THERE CERTAINLY IS THE POTENTIAL FOR SOME SORT OF INTERACTION THAT
COULD SLOW THE STRENGTHENING PROCESS. THUS THE INTENSITY FORECAST
WILL ONLY SHOW SLOW INTENSIFICATION IN THE SHORT-TERM...GENERALLY A
LITTLE LOWER THAN THE MODELS.  IN THE LONGER-RANGE...THERE IS
PLENTY OF WARM WATER AND LIGHT SHEAR FORECAST IN THE PATH OF
IGOR...WHICH WOULD PROMOTE THE DEVELOPMENT OF A LARGE AND POWERFUL
HURRICANE.  THE NHC FORECAST IS INCREASED FROM THE PREVIOUS
ONE...CLOSE TO THE CONSENSUS...AND STILL MIGHT BE CONSERVATIVE AT
THE END.  HOWEVER...WITH THE TRACK FORECAST SHIFTING NORTHWARD... I
AM HESITANT TO FORECAST A MUCH STRONGER HURRICANE AT THIS TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 13.9N  23.9W    40 KT
 12HR VT     09/0600Z 14.0N  24.8W    45 KT
 24HR VT     09/1800Z 14.7N  26.5W    50 KT
 36HR VT     10/0600Z 15.5N  29.1W    55 KT
 48HR VT     10/1800Z 16.3N  32.2W    60 KT
 72HR VT     11/1800Z 17.0N  37.5W    70 KT
 96HR VT     12/1800Z 17.5N  42.5W    80 KT
120HR VT     13/1800Z 18.5N  47.5W    90 KT
 
$$
FORECASTER BLAKE/PASCH
 

WTNT41 KNHC 090257
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST WED SEP 08 2010
 

IGOR REMAINS A SHEARED TROPICAL CYCLONE. THE MAIN CONVECTIVE CLOUD
MASS IS DISPLACED WEST OF THE PARTIALLY EXPOSED LOW-LEVEL CENTER...
AND THERE IS A SHARP EASTERN EDGE TO THE CENTRAL CONVECTION. IN
ADDITION...THE CLOUD PATTERN HAS BECOME SOMEWHAT LESS ORGANIZED
DURING THE PAST SEVERAL HOURS...WITH CLOUD TOP TEMPERATURES
RECENTLY WARMING. DVORAK INTENSITY ESTIMATES ARE AT 2.5 FROM
TAFB...AND THE 3-HOURLY AVERAGED ADT VALUE IS CLOSE TO 3.0. THE
INITIAL INTENSITY ESTIMATE REPRESENTS A BLEND OF CURRENT INTENSITY
ESTIMATES AND IS UNCHANGED AT 40 KT. THE COMBINATION OF MODERATE TO
STRONG EASTERLY VERTICAL WIND SHEAR AND THE ONGOING INTERACTION OF
IGOR WITH ANOTHER LOW LOCATED 150 N MI TO ITS NORTH IS EXPECTED TO
IMPEDE THE INTENSIFICATION OF THE CYCLONE DURING THE NEXT DAY OR
SO. BEYOND THAT TIME...THE CONSOLIDATION OF IGOR WITH THIS
FEATURE...AS WELL AS A REDUCTION IN THE EASTERLY SHEAR...SHOULD
RESULT IN A STEADY STRENGTHENING.  THE NHC INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE LGEM/SHIPS
STATISTICAL-DYNAMICAL INTENSITY GUIDANCE.

THE INITIAL MOTION ESTIMATE IS 270/06. THE FORECAST PHILOSOPHY
REMAINS UNCHANGED. IN THE SHORT-TERM...GLOBAL MODELS SHOW IGOR
INTERACTING WITH AND ABSORBING THE AFOREMENTIONED LOW DURING THE
NEXT 24 HOURS. THIS SHOULD RESULT IN A SLIGHTLY WEAKER SUBTROPICAL
RIDGE TO ITS NORTH AND TEMPORARILY IMPART A WEST-NORTHWESTWARD
MOTION. FROM 24-96 HOURS...A RE-STRENGTHENING OF THE RIDGE IS
FORECAST TO CAUSE IGOR TO TURN MORE WESTWARD. AFTER 96 HOURS...IGOR
IS EXPECTED TO ENCOUNTER A DEVELOPING WEAKNESS IN THE SUBTROPICAL
RIDGE AND TURN WEST-NORTHWESTWARD...SIMILAR TO BUT NOT AS FAR NORTH
AS THE GFDL/HWRF SOLUTIONS. THE NHC OFFICIAL FORECAST TRACK IS
SIMILAR TO THE PREVIOUS ONE IN THE SHORT-TERM...BUT HAS BEEN
ADJUSTED SLIGHTLY NORTHWARD IN LINE WITH THE MULTI-MODEL CONSENSUS
AT LATER FORECAST PERIODS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 13.8N  24.6W    40 KT
 12HR VT     09/1200Z 14.3N  25.7W    45 KT
 24HR VT     10/0000Z 15.1N  27.9W    50 KT
 36HR VT     10/1200Z 15.8N  30.7W    55 KT
 48HR VT     11/0000Z 16.4N  33.6W    60 KT
 72HR VT     12/0000Z 17.0N  39.0W    75 KT
 96HR VT     13/0000Z 18.0N  43.5W    85 KT
120HR VT     14/0000Z 19.5N  47.5W    90 KT
 
$$
FORECASTER KIMBERLAIN/STEWART
 

WTNT41 KNHC 090837
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST THU SEP 09 2010
 
THE CLOUD PATTERN HAS DETERIORATED DURING THE PAST 6 HOURS AND
CONTINUES TO BE HIGHLY SHEARED.  NEITHER SATELLITE INTENSITY
ESTIMATES NOR ASCAT MEASUREMENTS SUPPORT TROPICAL STORM INTENSITY.
THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWN TO 35 KNOTS AND THIS
ESTIMATE IS GENEROUS. IGOR COULD WEAKEN A LITTLE MORE TODAY BUT
GIVEN THAT THE CYCLONE STILL HAS A LARGE CIRCULATION AND IS MOVING
TOWARD A MORE FAVORABLE ENVIRONMENT OF LOWER SHEAR AND WARMER
OCEAN...A GRADUAL STRENGTHENING COULD BEGIN IN 24 HOUR OR SO.  IGOR
IS STILL FORECAST TO BECOME A HURRICANE IN ABOUT 3 DAYS.
 
FIRST VISIBLE SATELLITE IMAGES INDICATE THAT THE CENTER IS STILL
LOCATED SOUTH OF THE CAPE VERDE ISLANDS SUGGESTING THAT IGOR HAS
BEEN MEANDERING DURING THE PAST FEW HOURS. HOWEVER...THE LARGE
CIRCULATION SHOULD BEGIN TO MOVE SLOWLY TOWARD THE WEST-NORTHWEST
LATER TODAY. THE STEERING PATTERN OVER THE ATLANTIC HAS BEEN QUITE
PERSISTENT AND CONSISTS OF A SUBTROPICAL RIDGE OVER THE EASTERN
PART OF THE BASIN AND A BROAD TROUGH OSCILLATING BETWEEN THE
EASTERN UNITED STATES AND THE WESTERN PORTION OF THE BASIN. THIS
STEERING PATTERN WHICH IS FORECAST BY THE GLOBAL MODELS TO
CONTINUE...WOULD FAVOR A GENERAL WESTWARD MOTION WITH AN INCREASE
IN FORWARD SPEED DURING THE NEXT DAY OR TWO AND THEN A TURN MORE TO
THE WEST-NORTHWEST BY THE END OF THE FORECAST PERIOD. TRACK
GUIDANCE DEPICTS THIS SCENARIO WHICH IS REFLECTED IN THE OFFICIAL
FORECAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0900Z 13.8N  24.3W    35 KT
 12HR VT     09/1800Z 14.0N  25.3W    30 KT
 24HR VT     10/0600Z 15.0N  28.0W    40 KT
 36HR VT     10/1800Z 16.0N  31.0W    45 KT
 48HR VT     11/0600Z 16.5N  34.0W    55 KT
 72HR VT     12/0600Z 17.0N  40.0W    65 KT
 96HR VT     13/0600Z 18.0N  44.5W    75 KT
120HR VT     14/0600Z 19.5N  49.0W    85 KT
 
$$
FORECASTER AVILA
 

WTNT41 KNHC 091431
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 09 2010
 
DEEP CONVECTION FORMED NEAR THE LOW-LEVEL CENTER OF IGOR AROUND 1030
UTC...AND HAS EXPANDED SINCE THAT TIME. HOWEVER...THIS CONVECTION
REMAINS WEST OF THE CENTER DUE TO ABOUT 20 KT OF EASTERLY SHEAR
...AS SHOWN BY UW-CIMSS ANALYSES. ALTHOUGH AN ASCAT PASS AROUND
0000 UTC ONLY SHOWED MAXIMUM WINDS OF 25-30 KT...THE WINDS ARE
ASSUMED TO BE A LITTLE STRONGER NOW DUE TO THE INCREASE IN
CONVECTION. THEREFORE...IGOR WILL REMAIN A TROPICAL STORM WITH AN
INITIAL WIND SPEED ESTIMATE OF 35 KT. THE SHIPS MODEL SHOWS THE
EASTERLY SHEAR DECREASING OVER THE NEXT FEW DAYS. THIS...COMBINED
WITH WARM WATERS AND A RELATIVELY MOIST ATMOSPHERE SHOULD ALLOW FOR
STEADY INTENSIFICATION. THE STATISTICAL AND DYNAMICAL INTENSITY
MODELS BRING IGOR TO HURRICANE STRENGTH IN ABOUT 3 DAYS AND SHOW
ADDITIONAL STRENGTHENING THEREAFTER. THE NHC OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS ONE AND IS IN CLOSEST AGREEMENT WITH THE
STATISTICAL GUIDANCE.
 
IGOR HAS BEEN GENERALLY MOVING NORTH-NORTHWESTWARD DURING THE LAST
SEVERAL HOURS...AND THE 6-HOUR INITIAL MOTION ESTIMATE IS 330/5.
HOWEVER...THE LAST FEW FEW VISIBLE IMAGES SUGGEST A SLIGHTLY FASTER
NORTHWESTWARD MOTION. NOW THAT IGOR APPEARS TO HAVE ABSORBED THE
WEAK LOW THAT HAD BEEN IN ITS VICINITY...A LOW- TO MID-LEVEL RIDGE
NORTH AND NORTHEAST OF IGOR SHOULD STEER THE CYCLONE WESTWARD OR
WEST-NORTHWESTWARD WITH A GRADUAL INCREASE IN FORWARD SPEED.  BY
THE END OF THE PERIOD...THE GLOBAL MODELS SHOW IGOR NEARING A
CENTRAL ATLANTIC TROUGH WHICH SHOULD CAUSE A NORTHWESTWARD TURN.
THE OFFICIAL FORECAST IS ADJUSTED TO THE NORTH IN THE SHORT-TERM
DUE TO THE INITIAL POSITION AND MOTION...AND IS A LITTLE SLOWER AT
THE END OF THE FORECAST PERIOD AS SUGGESTED BY THE GUIDANCE SUITE.
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/1500Z 14.7N  24.8W    35 KT
 12HR VT     10/0000Z 15.0N  26.3W    35 KT
 24HR VT     10/1200Z 15.8N  29.0W    40 KT
 36HR VT     11/0000Z 16.4N  32.0W    50 KT
 48HR VT     11/1200Z 16.7N  35.0W    60 KT
 72HR VT     12/1200Z 17.3N  40.4W    70 KT
 96HR VT     13/1200Z 18.5N  44.5W    80 KT
120HR VT     14/1200Z 20.0N  48.5W    85 KT
 
$$
FORECASTER CANGIALOSI/BRENNAN
 

WTNT41 KNHC 092038
TCDAT1
TROPICAL DEPRESSION IGOR DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST THU SEP 09 2010
 
THE DEEP CONVECTION THAT WAS LOCATED NEAR THE CENTER EARLIER TODAY
HAS ERODED AND NOW TAKES THE SHAPE OF A CURVED BAND OVER
THE WESTERN SEMICIRCLE...SITUATED ABOUT 90 N MI WEST OF THE CENTER.
THIS ASYMMETRIC CONVECTIVE PATTERN IS DUE TO ABOUT 20-25 KT OF
EASTERLY SHEAR. SINCE THE CONVECTION IS WELL REMOVED FROM THE
CENTER AND BECAUSE EARLIER ASCAT DATA DID NOT SHOW WINDS OF
TROPICAL STORM FORCE...IGOR IS BEING DOWNGRADED TO A TROPICAL
DEPRESSION AT THIS TIME. ALTHOUGH IGOR HAS WEAKENED TODAY...
INTENSIFICATION IS STILL EXPECTED DURING THE FORECAST PERIOD. THE
SHIPS MODEL SHOWS THE SHEAR DECREASING SIGNIFICANTLY DURING THE
NEXT COUPLE OF DAYS.  THIS...IN COMBINATION WITH A RELATIVELY WARM
OCEAN AND MOIST ATMOSPHERE SHOULD ALLOW IGOR TO STRENGTHEN.
HOWEVER...THE CYCLONE WILL BE PASSING THROUGH AN AREA OF SLIGHTLY
COOLER SSTS IN A COUPLE DAYS...SO THE NEW OFFICIAL FORECAST SHOWS A
MORE GRADUAL STRENGTHENING THAN THE PREVIOUS ONE...BUT STILL MAKES
IGOR A HURRICANE IN 3 DAYS.
 
THE LOW-LEVEL CENTER HAS BEEN RACING NORTHWESTWARD DURING
THE LAST FEW HOURS...AND IS NOW LOCATED NORTH OF THE
PREVIOUS FORECAST TRACK. HOWEVER...A WEST-NORTHWESTWARD MOTION IS
EXPECTED TO BEGIN SOON AND PERSIST FOR THE NEXT FEW DAYS AS A LOW-
TO MID-LEVEL RIDGE LOCATED NORTH AND NORTHEAST OF IGOR BECOMES
THE PRIMARY STEERING MECHANISM. THE GLOBAL MODELS SHOW IGOR
APPROACHING A LARGE BUT RATHER FLAT TROUGH IN 4 TO 5 DAYS...WHICH
SHOULD CAUSE THE CYCLONE TO TURN NORTHWESTWARD WITH A DECREASE IN
FORWARD SPEED. THE NEW NHC TRACK FORECAST IS ADJUSTED TO THE NORTH
IN THE SHORT-TERM BUT IS OTHERWISE SIMILAR TO THE PREVIOUS ONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 16.0N  26.4W    30 KT
 12HR VT     10/0600Z 16.7N  27.9W    30 KT
 24HR VT     10/1800Z 17.3N  30.8W    35 KT
 36HR VT     11/0600Z 17.5N  33.9W    45 KT
 48HR VT     11/1800Z 17.8N  36.8W    55 KT
 72HR VT     12/1800Z 18.4N  41.9W    65 KT
 96HR VT     13/1800Z 19.5N  46.0W    75 KT
120HR VT     14/1800Z 21.0N  49.0W    85 KT
 
$$
FORECASTER CANGIALOSI/BRENNAN
 

WTNT41 KNHC 100237
TCDAT1
TROPICAL DEPRESSION IGOR DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST THU SEP 09 2010
 
INFRARED SATELLITE IMAGES INDICATE A BURST OF DEEP CONVECTION OVER
THE WESTERN SEMICIRCLE OF IGOR DURING THE LAST SEVERAL HOURS...WITH
CLOUD TOP TEMPERATURES AS COLD AS -90 C. THIS BURSTING PATTERN
SUGGESTS THAT EASTERLY VERTICAL WIND SHEAR CONTINUES OVER
THE CYCLONE...AND THIS IS CONFIRMED BY UW-CIMSS SHEAR ANALYSES
SHOWING ABOUT 20 KT OF EASTERLY SHEAR.  DVORAK INTENSITY ESTIMATES
ARE AT 2.5/35 KT FROM TAFB...AND 3-HOURLY AVERAGED ADT VALUES ARE
CLOSE TO THIS VALUE. A STRICT INTERPRETATION OF THE SATELLITE
ESTIMATES SUGGEST THAT IGOR MAY BE NEARING TROPICAL STORM STRENGTH
AGAIN.  HOWEVER...GIVEN THE LACK OF PERSISTENCE OF THE CURRENT
BURST OF CONVECTION...THE INITIAL INTENSITY IS HELD AT 30 KT FOR
THIS ADVISORY.
 
A REFORMATION OF THE LOW-LEVEL CENTER DURING THE LAST 12 HOURS HAS
MADE DISCERNING AN INITIAL MOTION ESTIMATE MORE DIFFICULT THAN
NORMAL.  GIVEN THE DISCONTINUITY IN CENTER FIXES...A LONGER-TERM
MOTION WAS COMPUTED AND YIELDS AN UNCERTAIN 295/11. GLOBAL
DYNAMICAL MODELS ARE GENERALLY IN GOOD AGREEMENT THAT IGOR WILL BE
STEERED ON A MORE WESTWARD TRACK AT A FASTER FORWARD SPEED BY THE
FLOW ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE THROUGH ABOUT 72
HOURS.  THEREAFTER...IGOR IS EXPECTED TO TURN MORE WEST-
NORTHWESTWARD AND SLOW LATE IN THE FORECAST PERIOD AS IT APPROACHES
A WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC.
THE SPREAD IN THE MODEL GUIDANCE HAS INCREASED THIS CYCLE IN
RESPONSE TO THE DIFFERENCES IN THE WAY MODELS HANDLE THE EVOLUTION
OF THIS WEAKNESS.  THE REFORMATION OF THE CENTER AND A NOTABLE
SOUTHWARD AND WESTWARD SHIFT TO THE GUIDANCE HAS PROMPTED A FAIRLY
SIGNIFICANT THE OFFICIAL NHC TRACK FORECAST IN THAT DIRECTION...
THOUGH THE TRACK FORECAST REMAINS ON THE NORTHERN SIDE OF THE
GUIDANCE ENVELOPE.
 
A CONTINUATION OF MODERATE EASTERLY SHEAR SHOULD SLOW OR POSSIBLY
EVEN HALT FURTHER INTENSIFICATION FOR AT LEAST THE NEXT 24 HOURS.
SHIPS MODEL OUTPUT INDICATES A REDUCTION IN THE SHEAR...A FAIRLY
MOIST ATMOSPHERE...AND RELATIVELY WARM SEA SURFACE TEMPERATURES
AHEAD OF IGOR FROM 24-72 HOURS.  THESE INGREDIENTS SHOULD FAVOR A
STEADIER RATE OF INTENSIFICATION DURING THAT TIME.  THEREAFTER...THE
INTENSITY FORECAST BECOMES A BIT TRICKIER. THE STATISTICAL GUIDANCE
INDICATES POSSIBLE NEGATIVE EFFECTS OF SOUTHWESTERLY SHEAR IN
ASSOCIATION WITH THE AFOREMENTIONED WEAKNESS OVER THE CENTRAL
ATLANTIC WHILE SEVERAL OF THE GLOBAL MODELS SHOW LESS SHEAR. THE
OFFICIAL NHC INTENSITY FORECAST IS A BIT LOWER EARLY IN THE PERIOD
GIVEN CURRENT TRENDS BUT REMAINS CLOSE TO BOTH THE PREVIOUS FORECAST
AND THE STATISTICAL-DYNAMICAL INTENSITY GUIDANCE. REGARDLESS OF THE
EXACT INTENSITY...GLOBAL MODELS ARE IN GOOD AGREEMENT THAT IGOR
WILL GROW IN SIZE...POTENTIALLY BECOMING A LARGE-SIZED HURRICANE.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 15.4N  28.0W    30 KT
 12HR VT     10/1200Z 15.9N  30.0W    30 KT
 24HR VT     11/0000Z 16.3N  33.1W    35 KT
 36HR VT     11/1200Z 16.5N  36.1W    40 KT
 48HR VT     12/0000Z 16.7N  39.0W    50 KT
 72HR VT     13/0000Z 17.5N  44.0W    65 KT
 96HR VT     14/0000Z 18.5N  48.0W    80 KT
120HR VT     15/0000Z 19.5N  50.5W    85 KT
 
$$
FORECASTER KIMBERLAIN/MUSHER
 

WTNT41 KNHC 100833
TCDAT1
TROPICAL DEPRESSION IGOR DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST FRI SEP 10 2010
 
IGOR IS STILL STRONGLY SHEARED WITH THE CENTER LOCATED TO THE EAST
OF A STRONG AND CIRCULAR CONVECTIVE MASS AS OBSERVED IN BOTH
MICROWAVE DATA AND CONVENTIONAL IR IMAGERY. AS WE SPEAK...FIRST
METEOSAT VISIBLE IMAGE CONFIRMED THAT THE CENTER IS EXPOSED BUT
BETTER DEFINED. INITIAL INTENSITY IS KEPT AT 30 KNOTS BUT IT WILL
NOT TAKE MUCH FOR IGOR TO REGAIN TROPICAL STORM STATUS AND IN
FACT...THIS IS EXPECTED TO OCCUR LATER TODAY. THE CYCLONE IS
ESCAPING FROM THE MONSOON-TYPE LOW-LEVEL SOUTHWESTERLY FLOW AND IS
BECOMING EMBEDDED IN THE TRADE WINDS. THIS WOULD RESULT IN LESS
SHEAR AND WILL LEAD TO INTENSIFICATION...AS INDICATED IN THE
OFFICIAL FORECAST. GLOBAL MODELS FORECAST IGOR TO BE A LARGE
HURRICANE OVER THE CENTRAL TROPICAL ATLANTIC BY THE END OF THE
FORECAST PERIOD AND BEYOND.
 
THE INITIAL MOTION IS UNCERTAIN SINCE IT WAS DIFFICULT TO FOLLOW
VARIOUS LOW-LEVEL CENTERS THAT WERE ROTATING AROUND A LARGER GYRE
DURING THE PAST 12 HOURS OR SO. THE BEST ESTIMATE IS 280 DEGREES AT
11 TO 12 KNOTS. THE SUBTROPICAL RIDGE IS FORECAST TO BUILD WESTWARD
AND THIS PATTERN SHOULD STEER IGOR WESTWARD WITH AN INCREASE IN
FORWARD SPEED DURING THE NEXT 3 TO 4 DAYS. BY THE END OF THE
FORECAST PERIOD...IGOR SHOULD BE ON THE SOUTHWESTERN EDGE OF THE
RIDGE AND SHOULD BEGIN TO GAIN MORE LATITUDE. TRACK GUIDANCE
OVERALL IS FAIRLY CONSISTENT IN TAKING IGOR WESTWARD. HOWEVER...A
COUPLE OF MODELS FORECAST A STRONGER SUBTROPICAL RIDGE TO THE NORTH
OF THE CYCLONE...RESULTING IN A MORE PRONOUNCED WESTWARD TRACK. THE
OFFICIAL FORECAST IS HEAVILY BIASED TOWARD THE GFS AND THE ECMWF
MODELS WHICH FORECAST A MODERATE BUT A MORE REALISTIC SUBTROPICAL
RIDGE TO THE NORTH.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 16.0N  29.3W    30 KT
 12HR VT     10/1800Z 16.0N  31.1W    35 KT
 24HR VT     11/0600Z 16.3N  34.2W    40 KT
 36HR VT     11/1800Z 16.5N  37.5W    45 KT
 48HR VT     12/0600Z 16.8N  40.2W    55 KT
 72HR VT     13/0600Z 17.0N  45.0W    65 KT
 96HR VT     14/0600Z 18.0N  49.5W    80 KT
120HR VT     15/0600Z 19.5N  53.5W    90 KT
 
$$
FORECASTER AVILA
 

WTNT41 KNHC 101455
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST FRI SEP 10 2010
 
IGOR REMAINS A SHEARED TROPICAL CYCLONE. DURING THE PAST FEW
HOURS...HOWEVER...THE SHEAR HAS BEGUN TO SHOW SIGNS OF ABATING AND
THE LOW-LEVEL CENTER IS NOW FARTHER INTO THE EASTERN PORTION OF THE
CENTRAL DEEP CONVECTION. THE UPGRADE TO STORM STATUS IS BASED ON A
SATELLITE INTENSITY ESTIMATE OF 35 KT FROM TAFB AND A 47-KT
UW-CIMSS 3-HR AVERAGE ADT.
 
THE INITIAL MOTION IS 280/14. THE INITIAL POSITION AND MOTION ARE
STILL SOMEWHAT UNCERTAIN DUE TO MULTIPLE CIRCULATIONS ROTATING
AROUND THE CENTER OF A LARGER CYCLONIC GYRE. HOWEVER...THE MOTION
IS EXPECTED TO BE BASICALLY WESTWARD FOR THE NEXT 96 HOURS OR SO
ALONG THE SOUTHERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE LOCATED
TO THE NORTH OF THE CYCLONE. BY DAY 5...A SERIES OF WEAK SHORTWAVE
TROUGHS MOVING THROUGH THE BASE OF A BROAD LONGWAVE TROUGH FORECAST
TO BE OFF THE U.S. EAST COAST IS FORECAST BY ALL OF THE GLOBAL
MODELS TO CREATE A WEAKNESS IN THE RIDGE BETWEEN 50W-60W LONGITUDE.
THIS IS EXPECTED TO WEAKEN THE STEERING FLOW AND CAUSE IGOR TO SLOW
DOWN AND ALSO TURN WEST-NORTHWESTWARD. THE OFFICIAL FORECAST TRACK
IS SIMILAR TO THE PREVIOUS ADVISORY AND THE TVCN MODEL CONSENSUS.  
 
CURRENT SHEAR ANALYSES FROM SHIPS AND UW-CIMSS...ALONG WITH WATER
VAPOR WINDS...INDICATE THE VERTICAL SHEAR ACROSS IGOR HAS DECREASED
FROM 20 KT DOWN TO 10 KT DURING THE PAST 24 HOURS. THIS DECEASING
SHEAR TENDENCY IS EXPECTED TO CONTINUE THROUGHOUT THE FORECAST
PERIOD AS IGOR MOVES OVER GRADUALLY INCREASING SSTS...ESPECIALLY
AFTER 48 HOURS. THE RESULT SHOULD BE STEADY INTENSIFICATION WITH
IGOR POSSIBLY REACHING HURRICANE STATUS ON SUNDAY AND MAJOR
HURRICANE STATUS BY DAY 5...AS INDICATED BY THE SHIPS...GFDL...AND
HWRF MODELS. THE OFFICIAL INTENSITY FORECAST IS A LITTLE BELOW THE
GUIDANCE THROUGH 48 HOURS DUE TO UNCERTAINTY ABOUT WHEN IGOR WILL
DEVELOP A CONSOLIDATED CENTER OF CIRCULATION...BUT IS CLOSE TO THE
GUIDANCE THEREAFTER.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 16.4N  31.0W    35 KT
 12HR VT     11/0000Z 16.6N  33.2W    40 KT
 24HR VT     11/1200Z 16.8N  36.2W    45 KT
 36HR VT     12/0000Z 17.0N  39.2W    50 KT
 48HR VT     12/1200Z 17.1N  41.7W    60 KT
 72HR VT     13/1200Z 17.3N  46.2W    70 KT
 96HR VT     14/1200Z 18.2N  50.3W    85 KT
120HR VT     15/1200Z 19.5N  53.5W    95 KT
 
$$
FORECASTER STEWART
 

WTNT41 KNHC 102044
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST FRI SEP 10 2010
 
THE UPPER-LEVEL SHEAR THAT HAS BEEN PLAGUING IGOR FOR THE PAST
SEVERAL DAYS HAS FINALLY STARTED TO ABATE AND CIRRUS OUTFLOW HAS
NOW BECOME PRONOUNCED IN ALL QUADRANTS. HOWEVER...SOME MID-LEVEL
SHEAR AND DRY AIR ENTRAINMENT IS STILL AFFECTING THE CYCLONE...
WHICH HAS RESULTED IN A VERY ASYMMETRIC CONVECTIVE CLOUD PATTERN
WITH THE LOW-LEVEL CENTER DISPLACED AT LEAST 30 NMI TO THE EAST OF
THE COLDEST CLOUD TOPS. INTENSITY ESTIMATES ARE 30 KT FROM SAB...55
KT FROM TAFB...AND UW-CIMSS 3-HR AVERAGE ADT VALUES OF 49 KT AND
AMSU ESTIMATES OF 53 KT. THE INITIAL INTENSITY HAS BEEN
CONSERVATIVELY INCREASED TO 40 KT...WHICH WILL BE TOO LOW IF THE
LOW-LEVEL CENTER IS ACTUALLY CLOSER TO THE DEEP CONVECTION.

THE INITIAL MOTION IS 280/18. THERE IS NO CHANGE TO THE PREVIOUS
TRACK FORECAST OR REASONING. IGOR IS EXPECTED TO MOVE WESTWARD...
ACCOMPANIED BY A GRADUAL DECREASE IN FORWARD SPEED...FOR THE NEXT 96
HOURS AS THE CYCLONE MOVES ALONG THE SOUTHERN PERIPHERY OF A LARGE
AND STRONG SUBTROPICAL RIDGE SITUATED TO THE NORTH. BY DAY 5...A
BROAD LONGWAVE TROUGH IS FORECAST TO MOVE OFF THE U.S. EAST COAST
AND CREATE A WEAKNESS IN THE RIDGE TO THE NORTHEAST OF THE LESSER
ANTILLES. THIS SHOULD CAUSE THE STEERING FLOW TO WEAKEN AND ALLOW
WHAT IS EXPECTED TO BE A LARGE HURRICANE IGOR AT THAT TIME TO
GRADUALLY TURN WEST-NORTHWESTWARD. THE LATEST MODEL GUIDANCE IS
MORE TIGHTLY PACKED AROUND THE PREVIOUS NHC TRACK...ESPECIALLY AT
DAYS 4 AND 5.  IN PARTICULAR...THE GFDL AND ECMWF SHOW LESS OF A
NORTHWARD TURN THAT MIGHT BE RELATED TO A FLATTER LONGWAVE TROUGH
IN THE LATEST GLOBAL RUNS.  THE OFFICIAL FORECAST TRACK REQUIRES
LITTLE CHANGE AND IS AN EXTENSION OF THE PREVIOUS ADVISORY.
 
THE VERTICAL SHEAR IS EXPECTED TO CONTINUE TO DECREASE TO 5 TO 10 KT
FOR THE NEXT 5 DAYS. THIS FAVORABLE UPPER-LEVEL ENVIRONMENT...IN
CONJUNCTION WITH SSTS INCREASING TO 29C BY THE END OF THE FORECAST
PERIOD...SHOULD RESULT IN STEADY INTENSIFICATION. IGOR IS EXPECTED
TO REACH HURRICANE STATUS BY SUNDAY AND MAJOR HURRICANE STATUS BY
DAYS 4 OR 5. THIS SCENARIO IS SUPPORTED BY THE SHIPS...LGEM...
HWRF...AND GFDL MODELS. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/2100Z 16.7N  33.3W    40 KT
 12HR VT     11/0600Z 16.8N  35.4W    45 KT
 24HR VT     11/1800Z 17.1N  38.4W    50 KT
 36HR VT     12/0600Z 17.2N  41.0W    60 KT
 48HR VT     12/1800Z 17.3N  43.4W    70 KT
 72HR VT     13/1800Z 17.7N  47.8W    80 KT
 96HR VT     14/1800Z 18.7N  51.6W    90 KT
120HR VT     15/1800Z 20.0N  55.0W   105 KT
 
$$
FORECASTER STEWART
 

WTNT41 KNHC 110234
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST FRI SEP 10 2010
 
CONVENTIONAL SATELLITE IMAGES INDICATE THAT IGOR IS MAINTAINING A
BURSTING PATTERN...CHARACTERISTIC OF A SHEARED TROPICAL CYCLONE. 
THE PARTIALLY EXPOSED LOW-LEVEL CENTER LIES NEAR THE NORTHEAST SIDE
OF A LARGE AND CIRCULAR CONVECTIVE MASS IN THIS IMAGERY...BUT
SEVERAL EARLIER MICROWAVE OVERPASSES INDICATED THE POSSIBILITY OF
THE LOW-LEVEL CENTER LYING UNDERNEATH THE CONVECTION.  AN EXPANDING
UPPER-LEVEL OUTFLOW IS WELL ESTABLISHED IN ALL QUADRANTS EXCEPT TO
THE EAST.  DVORAK INTENSITY ESTIMATES ARE AT 3.0/45 KT AND 3.5/55
KT FROM SAB AND TAFB...AND THE LATEST 3-HOURLY AVERAGED ADT VALUE
IS 3.3.  GIVEN THE UNCERTAINTY WITH REGARD TO THE LOCATION OF THE
CENTER...THE ADVISORY INTENSITY IS INCREASED CONSERVATIVELY TO 45
KT.
 
THE INITIAL MOTION ESTIMATE OF 285/18 IS SOMEWHAT UNCERTAIN AND
REPRESENTS A LONGER-TERM AVERAGE...GIVEN DIFFERENCES BETWEEN
CONVENTIONAL AND MICROWAVE SATELLITE FIXES. THE FORECAST REASONING
REMAINS UNCHANGED. DYNAMICAL MODELS SHOW IGOR MOVING ON A WESTWARD
COURSE ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE EAST
CENTRAL ATLANTIC DURING THE NEXT 72 HOURS.  DURING THIS
PERIOD...THE MODEL GUIDANCE IS IN GOOD AGREEMENT THAT IGOR SHOULD
SLOW ITS FORWARD SPEED AND THEN TURN WEST-NORTHWESTWARD BEYOND 72
HOURS IN RESPONSE TO A LARGE BREAK IN THE SUBTROPICAL RIDGE OVER
THE WESTERN AND CENTRAL ATLANTIC.  THE OFFICIAL NHC TRACK LIES NEAR
THE MIDDLE OF THE GUIDANCE ENVELOPE...BUT IS A BIT NORTH OF THE
MULTI-MODEL CONSENSUS WHICH HAS TRENDED SLIGHTLY SOUTHWARD THIS
CYCLE.
 
UW-CIMSS ANALYSES STILL INDICATE AROUND 15 KT OF NORTHEASTERLY
VERTICAL WIND SHEAR OVER IGOR...A LESS THAN IDEAL ENVIRONMENT FOR
INTENSIFICATION.  THE STATISTICAL-DYNAMICAL GUIDANCE INDICATES A
QUICK REDUCTION TO THE SHEAR DURING THE NEXT 24 HOURS...AND A LOW
SHEAR ENVIRONMENT OVER GRADUALLY WARMER WATERS ARE LIKELY TO LEAD
TO A STEADIER STRENGTHENING OVER THE NEXT COUPLE OF DAYS.  THE
INTENSITY GUIDANCE PRESENTS A DILEMMA LATER IN THE FORECAST
PERIOD...HOWEVER.  THE STATISTICAL MODEL OUTPUT INDICATES POSSIBLE
SOUTHWESTERLY SHEAR RELATED TO THE LONGWAVE TROUGH FORECAST OVER
THE WEST CENTRAL ATLANTIC...AS DO A FEW OF THE GLOBAL DYNAMICAL
MODELS.  ON THE OTHER HAND...THE HWRF AND ECMWF SOLUTIONS A
CONTINUATION OF THE LOW SHEAR ENVIRONMENT AND A STRONGER IGOR.  THE
OFFICIAL NHC INTENSITY FORECAST IS ABOUT THE SAME AS THE PREVIOUS
ONE...EXCEPT SLIGHTLY REDUCED LATE IN THE PERIOD IN DEFERENCE TO
THE STATISTICAL MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 17.1N  34.9W    45 KT
 12HR VT     11/1200Z 17.2N  37.2W    50 KT
 24HR VT     12/0000Z 17.4N  40.1W    55 KT
 36HR VT     12/1200Z 17.5N  42.8W    65 KT
 48HR VT     13/0000Z 17.6N  45.3W    75 KT
 72HR VT     14/0000Z 18.0N  49.5W    85 KT
 96HR VT     15/0000Z 19.0N  53.0W    90 KT
120HR VT     16/0000Z 20.5N  56.0W   100 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 110835
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST SAT SEP 11 2010
 
 
IGOR IS STRENGTHENING AND IN FACT...THERE WAS A PERIOD FOR ABOUT TWO
HOURS...BETWEEN 04 AND 06 UTC THAT A SMALL EYE-LIKE FEATURE BECAME
APPARENT ON SATELLITE. HOWEVER...SINCE THEN...SUCH FEATURE HAS
BECOME INTERMITTENT...OTHERWISE I COULD HAVE DECLARED IGOR A
HURRICANE. ALTHOUGH THE CLOUD PATTERN IS BETTER ORGANIZED...THE
OVERALL CONVECTION HAS DECREASED A LITTLE AND NOW CONSISTS OF TWO
WELL-DEFINED CYCLONICALLY CURVED BANDS LOCATED PRIMARILY TO THE
SOUTH OF THE CENTER. THE OUTFLOW HAS BECOME ESTABLISHED IN ALL
QUADRANTS. BASED ON A BLEND OF T-NUMBERS FROM TAFB AND SAB WHICH
ARE 4.0 AND 3.5 ON THE DVORAK SCALE...THE INITIAL INTENSITY HAS
BEEN INCREASED TO 60 KNOTS. GIVEN THE CURRENT INTENSITY TREND...THE
CYCLONE WILL LIKELY BECOME A HURRICANE LATER TODAY. ALL OF THE
ENVIRONMENTAL PARAMETERS APPEAR TO BE FAVORABLE FOR IGOR TO
INTENSIFY...AND THE FORECAST CALLS FOR IGOR TO BE AN INTENSE
HURRICANE IN ABOUT 3 DAYS. GLOBAL MODELS SUGGEST THAT IGOR COULD
ALSO BECOME LARGE.   
 
IGOR IS MOVING TOWARD TOWARD THE WEST OR 270 DEGREES AT 18 KNOTS.
THIS IS BASED ON THE MOTION OF THE EYE-LIKE FEATURE AND CONTINUITY.
THE CYCLONE IS BEING STEERED BY A BUILDING SUBTROPICAL RIDGE OVER
THE EASTERN ATLANTIC...AND THIS PATTERN IS FORECAST BY GLOBAL
MODELS TO PERSIST. ON THIS BASIS...THE OFFICIAL FORECAST CALLS FOR
A GENERAL WESTWARD MOTION FOR THE NEXT 3 DAYS OR SO. BY THEN...IGOR
WILL BE REACHING THE SOUTHWESTERN EDGE OF THE SUBTROPICAL HIGH
WHERE THE STEERING CURRENTS ARE WEAKER...AND BEGIN TO APPROACH A
BROAD TROUGH OVER THE WESTERN ATLANTIC. THIS PATTERN SHOULD FORCE
IGOR TO SLOW DOWN AND BEGIN TO TURN MORE TO THE WEST-NORTHWEST AND
NORTHWEST. THE TRACK FORECAST IS VERY CLOSE TO THE CONSENSUS AND
BIASED TO THE ECMWF AND THE GFS. 
  
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 17.1N  37.8W    60 KT
 12HR VT     11/1800Z 17.1N  40.2W    70 KT
 24HR VT     12/0600Z 17.2N  43.1W    75 KT
 36HR VT     12/1800Z 17.4N  46.0W    80 KT
 48HR VT     13/0600Z 17.5N  48.5W    90 KT
 72HR VT     14/0600Z 17.5N  52.5W   100 KT
 96HR VT     15/0600Z 18.5N  55.5W   100 KT
120HR VT     16/0600Z 20.5N  59.0W   100 KT
 
$$
FORECASTER AVILA
 

WTNT41 KNHC 111449
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST SAT SEP 11 2010
 
ALTHOUGH THE CONVECTIVE CLOUD TOPS HAVE WARMED...VISIBLE SATELLITE
IMAGES SHOW A BANDING EYE PRESENTATION WITH IGOR.  WHILE THE
WEAKENING OF THE CONVECTION HAS LED TO A DECREASE IN DVORAK
T-NUMBERS...IT IS PREMATURE TO LOWER THE INTENSITY AND 60 KT WILL BE
KEPT FOR THIS ADVISORY.  

ALTHOUGH EASTERLY SHEAR REMAINS PRESENT...IT HAS DECREASED SINCE
YESTERDAY AND IS FORECAST TO FURTHER DIMINISH DURING THE NEXT DAY
OR SO.  AROUND THAT TIME...THE CYCLONE IS FORECAST TO MOVE OVER 
WATERS WARMER THAN 28C.  THESE CONDITIONS SHOULD PROMOTE GRADUAL
STRENGTHENING IN THE SHORT-TERM...WITH THE POTENTIAL FOR A MORE
SIGNIFICANT INTENSIFICATION IN A COUPLE OF DAYS.  INTERESTINGLY...
WHILE THE STATISTICAL MODELS MAKE IGOR A CATEGORY 4 HURRICANE...THE
GFDL AND HWRF MODELS SHOW SOME WEAKENING WITH IGOR BEFORE
RESTRENGTHENING THE CYCLONE IN A FEW DAYS.  AT THIS POINT...I AM
INCLINED TO LEAN ON THE STATISTICAL MODELS AT THE END OF THE
PERIOD GIVEN THE FORECAST UPPER-LEVEL WIND PATTERN...AND HAVE RAISED
THE WINDS FOR THAT TIME.  

MICROWAVE AND VISIBLE IMAGES SUGGEST THE SYSTEM HAS SLOWED A BIT AND
IS MOVING 275/17.  THE GLOBAL MODELS ARE IN GOOD AGREEMENT ON A
WESTWARD TRACK OF IGOR FOR THE NEXT FEW DAYS AS RIDGING REMAINS
ENTRENCHED TO THE NORTH.  IN ABOUT 3 DAYS...THE WESTERN PART OF THE
RIDGE WEAKENS DUE TO A LARGE MID-LATITUDE TROUGH.  THIS PATTERN
SHOULD ALLOW IGOR TO GAIN A BIT MORE LATITUDE AND SLOW DOWN.  WHILE
THE MODELS ARE IN GENERAL AGREEMENT WITH THIS SCENARIO...THERE ARE
SOME LARGE SPEED DIFFERENCES...AS THE ECMWF IS SIGNIFICANTLY SLOWER
THAN MOST OF THE OTHER GUIDANCE.  THE NHC FORECAST IS CLOSE TO THE
PREVIOUS ONE...ON THE SOUTHERN AND WESTERN SIDES OF THE GUIDANCE
ENVELOPE...ATTEMPTING TO ACCOUNT FOR THE MODEL TENDENCIES OF BEING
TOO SLOW AND POLEWARD WITH LOW-LATITUDE SYSTEMS.  

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/1500Z 17.4N  39.5W    60 KT
 12HR VT     12/0000Z 17.5N  42.0W    65 KT
 24HR VT     12/1200Z 17.6N  44.9W    70 KT
 36HR VT     13/0000Z 17.7N  47.5W    80 KT
 48HR VT     13/1200Z 17.7N  49.7W    90 KT
 72HR VT     14/1200Z 18.0N  53.5W   105 KT
 96HR VT     15/1200Z 19.5N  56.5W   110 KT
120HR VT     16/1200Z 21.0N  59.5W   110 KT
 
$$
FORECASTER BLAKE
 

WTNT41 KNHC 112038
TCDAT1
TROPICAL STORM IGOR DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST SAT SEP 11 2010
 
IGOR IS VERY CLOSE TO BECOMING A HURRICANE.  SATELLITE IMAGES SHOW
THAT CONVECTION HAS INCREASED AROUND THE CENTER AND HAVE RECENTLY
SUGGESTED THAT AN EYEWALL COULD BE FORMING.  ALTHOUGH MOST OF THE
INTENSITY ESTIMATION TECHNIQUES SUGGEST IGOR IS A HURRICANE...IT IS
PREFERABLE TO WAIT AND SEE IF THE CONVECTION STICKS AROUND AND TO
GET MICROWAVE CONFIRMATION OF THE INNER CORE STRUCTURE.    

MOST OF THE ENVIRONMENTAL FACTORS NEAR THE CYCLONE SEEM RATHER
CONDUCIVE FOR STRENGTHENING.  GLOBAL MODELS ALL BUILD AN UPPER
ANTICYCLONE JUST TO THE NORTH OF IGOR...A RATHER FAVORABLE PATTERN
FOR THE DEVELOPMENT OF A MAJOR HURRICANE.  SSTS AND OCEAN HEAT
CONTENT ALSO INCREASE STEADILY ALONG THE FORECAST TRACK.  THE MOST
OBVIOUS INHIBITING FACTOR IS PERHAPS A WEDGE OF DRIER AIR THAT HAS
WORKED ITS WAY INTO THE NORTHERN PART OF THE CIRCULATION. 
HOWEVER...THAT DRY AIR PROBABLY WILL NOT BE ABLE TO MAKE IT INTO
THE INNER CORE WITHOUT SOME SHEAR...AND THAT DOES NOT SEEM LIKELY AT
THIS TIME.  THUS...THE INTENSITY FORECAST IS RAISED FROM THE
PREVIOUS ONE...BUT PEAKS BELOW THE LGEM AND SHIPS MODELS.  IT IS OF
NOTE THAT ALL OF THE GLOBAL MODELS SHOW THE DEVELOPMENT OF A LARGE
AND POWERFUL HURRICANE...AND THE FORECAST WIND RADII HAVE BEEN
INCREASED.

IGOR REMAINS ON TRACK AND IS MOVING 275/16.  THE SYNOPTIC STEERING
FOR THE NEXT SEVERAL DAYS APPEARS WELL DEFINED WITH A RIDGE TO THE
NORTH OF THE TROPICAL CYCLONE GUIDING THE CYCLONE GENERALLY
WESTWARD.  HOWEVER...THE STRENGTH OF THIS RIDGE IS CRITICAL TO WHEN
IGOR BEGINS A MORE WEST-NORTHWEST MOTION.  THE MODELS THAT MOVE THE
STORM FASTER TO THE WEST INITIALLY...SUCH AS THE NOGAPS OR
UKMET...ALLOW IGOR TO GET A LITTLE CLOSER TO THE NORTHERN LEEWARD
ISLANDS BEFORE MAKING A WEST-NORTHWEST TURN IN TWO OR THREE DAYS.
HOWEVER...ANOTHER GROUP OF MODELS...INCLUDING THE GFS/GFDL
SOLUTIONS...SHOW THAT TURN OCCURRING IN THE NEXT DAY OR TWO.   THE
MODEL SPREAD HAS INCREASED SINCE THE LAST ADVISORY...AND I HAVE
ELECTED NOT TO CHANGE THE FORECAST MUCH...WHICH REMAINS TO THE
SOUTH AND WEST OF THE DYNAMICAL MODEL CONSENSUS FOR NOW.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 17.4N  41.2W    60 KT
 12HR VT     12/0600Z 17.5N  43.6W    70 KT
 24HR VT     12/1800Z 17.6N  46.4W    80 KT
 36HR VT     13/0600Z 17.7N  48.8W    90 KT
 48HR VT     13/1800Z 17.9N  51.0W   100 KT
 72HR VT     14/1800Z 18.8N  54.8W   115 KT
 96HR VT     15/1800Z 20.3N  57.7W   115 KT
120HR VT     16/1800Z 22.0N  60.5W   115 KT
 
$$
FORECASTER BLAKE
 

WTNT41 KNHC 120233
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SAT SEP 11 2010
 
THE CLOUD PATTERN ASSOCIATED WITH IGOR HAS INCREASED IN ORGANIZATION
DURING THE PAST SEVERAL HOURS.  A TIGHTLY-COILED BAND...WITH CLOUD
TOP TEMPERATURES TO -85C...WRAPS AROUND THE EASTERN SEMICIRCLE INTO
A DEVELOPING CENTRAL DENSE OVERCAST.  AN EYE FEATURE HAS ALSO BEEN
BRIEFLY INTERMITTENT IN CONVENTIONAL SATELLITE IMAGERY...AND A
NUMBER OF MICROWAVE PASSES SEVERAL HOURS AGO REVEALED A DISTINCT
CONVECTIVE RING SURROUNDING THE CENTER.  SUBJECTIVE DVORAK T-NUMBERS
AT 0000 UTC WERE A CONSENSUS 4.0 FROM BOTH SATELLITE AGENCIES...AND
3-HOURLY AVERAGED ADT VALUES FROM UW-CIMSS ARE 4.3.  THE INITIAL
INTENSITY IS RAISED TO 65 KT THIS ADVISORY...MAKING IGOR THE FOURTH
HURRICANE OF THE 2010 ATLANTIC HURRICANE SEASON. THE UNDERLYING
OCEAN ONLY GETS WARMER ALONG THE FORECAST TRACK OF IGOR...PEAKING
AROUND 29C IN ABOUT 3 DAYS.  THAT...COMBINED WITH A LIGHT SHEAR
ENVIRONMENT...WOULD FAVOR A STRENGTHENING TREND FOR THE NEXT FEW
DAYS...AND NEARLY ALL THE INTENSITY GUIDANCE MAKES IGOR A MAJOR
HURRICANE BY 72 HOURS. THEREAFTER...WHILE FLUCTUATIONS IN INTENSITY
MAY OCCUR...IGOR IS EXPECTED TO MAINTAIN MAJOR HURRICANE STATUS AND
BE A LARGE HURRICANE OVER THE CENTRAL NORTH ATLANTIC.
 
IGOR HAS MAINTAINED ROUGHLY THE SAME MOTION...275/15...THOUGH
PERHAPS A TAD SLOWER THAN EARLIER.  SUBTROPICAL RIDGING NORTH OF
THE CYCLONE SHOULD BE THE DOMINANT STEERING FEATURE FOR THE NEXT 2
TO 3 DAYS...CARRYING IGOR ON A GENERAL WESTWARD TRACK.  BEYOND THIS
TIME...DYNAMICAL MODELS SHOW IGOR SLOWING AND TURNING WEST-
NORTHWESTWARD AS IT APPROACHES AND THEN MOVES INTO A SUBSTANTIAL
BREAK IN THE SUBTROPICAL RIDGE.  AS WAS THE CASE IN THE PREVIOUS
MODEL CYCLE...THERE CONTINUES TO BE CONSIDERABLE SPREAD IN THE
TRACK GUIDANCE...WITH THE GFDL/HWRF THE RIGHTMOST OF MODEL
SOLUTIONS AND THE UKMET/NOGAPS THE LEFTMOST.  THESE DIFFERENCES
SEEM TO HINGE ON THE STRENGTH AND POSITION OF THE SUBTROPICAL
RIDGE...WITH THE FORMER MODELS FORECASTING A WEAKER RIDGE DISPLACED
TO THE EAST WHILE LATTER INDICATE A MORE ROBUST RIDGE EXTENDING
FARTHER WEST.  THE OFFICIAL NHC FORECAST TRACK HAS BEEN ADJUSTED TO
THE RIGHT...FOLLOWING THE TREND IN THE GUIDANCE... BUT IS NOT AS
FAR RIGHT AS THE MULTI-MODEL CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0300Z 17.7N  42.5W    65 KT
 12HR VT     12/1200Z 17.8N  44.8W    75 KT
 24HR VT     13/0000Z 17.9N  47.4W    80 KT
 36HR VT     13/1200Z 18.1N  49.7W    90 KT
 48HR VT     14/0000Z 18.4N  51.9W   100 KT
 72HR VT     15/0000Z 19.5N  55.0W   110 KT
 96HR VT     16/0000Z 21.5N  58.0W   115 KT
120HR VT     17/0000Z 23.5N  61.0W   115 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 120840
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST SUN SEP 12 2010
 
SATELLITE IMAGES SUGGEST THAT IGOR HAS STRENGTHENED A LITTLE MORE
THIS MORNING. ALTHOUGH DVORAK CLASSIFICATIONS WERE 65 KT FROM BOTH
TAFB AND SAB AT 0600 UTC...THE CURVED BAND OVER THE EASTERN
SEMICIRCLE HAS BECOME BETTER DEFINED AND THE OVERALL CLOUD PATTERN
IS NOW MORE SYMMETRIC. THEREFORE...THE INITIAL INTENSITY IS RAISED
TO 70 KT FOR THIS ADVISORY...WHICH IS IN AGREEMENT WITH THE ADT
ESTIMATES.
 
CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL STRENGTHENING DURING THE
NEXT FEW DAYS AS IGOR MOVES OVER STEADILY INCREASING SEA SURFACE
TEMPERATURES AND REMAINS IN A LOW WIND SHEAR ENVIRONMENT. MOST OF
THE INTENSITY MODELS BRING IGOR TO MAJOR HURRICANE STATUS WITHIN A
COUPLE OF DAYS...AND THE OFFICIAL FORECAST FOLLOWS THIS GUIDANCE.
BEYOND A FEW DAYS...THE MODELS ARE MIXED WITH SOME SHOWING LITTLE
CHANGE IN STRENGTH AND OTHERS GRADUAL WEAKENING. THE OFFICIAL
FORECAST IS SIMILAR TO THE PREVIOUS ONE...AND CLOSER TO THE LGEM
AND SHIPS MODELS...PREDICTING IGOR TO MAINTAIN MAJOR HURRICANE
STATUS.
 
IGOR CONTINUES TO MOVE WESTWARD ABOUT THE SAME SPEED AS ESTIMATED
EARLIER...275/16. A SUBTROPICAL RIDGE LOCATED TO THE NORTH OF THE
HURRICANE IS EXPECTED TO KEEP IGOR ON A WESTWARD TRACK FOR THE NEXT
2 TO 3 DAYS. THEREAFTER...THE GLOBAL MODELS ARE IN AGREEMENT IN
SHOWING THE RIDGE ERODE DUE TO PERSISTENT BROAD TROUGHING OVER THE
WESTERN ATLANTIC. THIS FLOW PATTERN SHOULD ALLOW IGOR TO TURN
WEST-NORTHWESTWARD TO NORTHWESTWARD DURING THAT TIME PERIOD. THE
MODEL GUIDANCE HAS NOT CHANGED MUCH FROM THE LAST CYCLE...AND
THE OFFICIAL FORECAST IS GENERALLY AN UPDATE OF THE PREVIOUS ONE.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0900Z 17.7N  44.4W    70 KT
 12HR VT     12/1800Z 17.9N  46.5W    75 KT
 24HR VT     13/0600Z 18.1N  49.1W    80 KT
 36HR VT     13/1800Z 18.3N  51.3W    90 KT
 48HR VT     14/0600Z 18.7N  53.2W   100 KT
 72HR VT     15/0600Z 20.2N  56.3W   115 KT
 96HR VT     16/0600Z 22.5N  59.0W   115 KT
120HR VT     17/0600Z 24.5N  62.0W   115 KT
 
$$
FORECASTER CANGIALOSI
 

WTNT41 KNHC 121503
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST SUN SEP 12 2010
 
CONVENTIONAL AND MICROWAVE IMAGERY SHOWS THAT IGOR IS GOING THROUGH
A PERIOD OF RAPID INTENSIFICATION.  VISIBLE IMAGERY DEPICTS A
CLEARING EYE AND INFRARED IMAGERY AND AN SSMIS OVERPASS REVEAL AN
INTENSE FULLY-DEVELOPED INNER RING OF DEEP CONVECTION. THE OUTFLOW
HAS BECOME QUITE IMPRESSIVE...PARTICULARLY OVER THE EASTERN PORTION
OF THE CYCLONE WHERE THE COLDEST CLOUD TOPS RESIDE. THE INITIAL
INTENSITY OF 90 KT IS BASED ON A COMPROMISE OF SATELLITE INTENSITY
ESTIMATES OF 77 AND 90 KT FROM SAB AND TAFB...RESPECTIVELY...A
UW-CIMSS ADT OF 107 KT...AND A SATELLITE CONSENSUS OF 86 KT...THAT
INCLUDES A BLEND OF AMSU MICROWAVE ESTIMATES.  THE INTENSITY
FORECAST HAS BEEN ADJUSTED UPWARD FROM THE PREVIOUS FORECAST TO
ACCOUNT FOR THE RI TREND...AND INDICATES STRENGTHENING TO A MAJOR
HURRICANE IN 12 HOURS...WITH FURTHER INTENSIFICATION TO A CATEGORY
FOUR HURRICANE BY DAY 2.  THE FORECAST IS BASED ON THE ICON
CONSENSUS BUT IS HEDGED A BIT MORE TOWARD THE SHIPS AND LGEM BEYOND
48 HOURS.
 
THE INITIAL MOTION IS ESTIMATED TO BE 270/11...WITHIN THE DEEP-LAYER
EASTERLY FLOW OF THE SUBTROPICAL RIDGE NORTH OF IGOR. THE LARGE-
SCALE MODELS SUGGEST THAT A DEVELOPING WEAKNESS IN THE RIDGE
OVER THE WESTERN ATLANTIC WILL RESULT IN A WEST-NORTHWESTWARD TURN
IN ABOUT 36 HOURS.  AFTERWARD...A TURN TOWARD THE NORTHWEST IS
INDICATED AS IGOR ROUNDS THE SOUTHWESTERN PERIPHERY OF THE RIDGE
AND MOVES INTO THE WEAKNESS.  THERE IS CONSIDERABLE SPREAD IN THE
DYNAMICAL MODEL GUIDANCE BEYOND DAY 2.  A CLUSTER THAT INCLUDES THE
GFDL...THE GFS AND THE GEFS ENSEMBLE MEAN SUGGESTS A WEAKER RIDGE
AND AN EARLIER TURN TOWARD THE NORTHWEST.  THE OFFICIAL FORECAST IS
BASED ON PRIMARILY ON THE TVCN MULTI-MODEL CONSENSUS BUT IS
ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS ADVISORY BEYOND DAY 3
AND CLOSER TO THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/1500Z 17.7N  45.7W    90 KT
 12HR VT     13/0000Z 17.8N  47.5W   105 KT
 24HR VT     13/1200Z 18.0N  49.8W   110 KT
 36HR VT     14/0000Z 18.4N  51.8W   115 KT
 48HR VT     14/1200Z 19.0N  53.6W   115 KT
 72HR VT     15/1200Z 20.7N  56.7W   125 KT
 96HR VT     16/1200Z 22.6N  59.6W   125 KT
120HR VT     17/1200Z 24.5N  62.5W   125 KT
 
$$
FORECASTER ROBERTS/BRENNAN
 

WTNT41 KNHC 121823
TCDAT1
HURRICANE IGOR SPECIAL DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
130 PM AST SUN SEP 12 2010
 
SATELLITE IMAGERY AND THE UW-CIMSS ADVANCED DVORAK TECHNIQUE
INDICATE THAT IGOR HAS CONTINUED TO RAPIDLY INTENSIFY AND IS NOW A
CATEGORY FOUR HURRICANE. THE VISIBLE AND BD-CURVE INFRARED 
ENHANCEMENT PICTURES REVEAL A CLEAR 20 NMI DIAMETER EYE WITH A
SURROUNDING INTENSE INNER CORE RING OF -80 DEGREE CELSIUS CLOUD TOP
TEMPERATURES.  THE OFFICIAL INTENSITY FORECAST HAS BEEN MODIFIED TO
INDICATE SOME ADDITIONAL INTENSIFICATION DURING THE NEXT 3 DAYS AND
THEN SHOWS A SLIGHT DECREASE AT DAYS 4 AND 5.  ALSO...FLUCTUATIONS
IN STRENGTH DUE TO EYEWALL REPLACEMENT CYCLES ARE POSSIBLE...BUT
THERE IS LITTLE SKILL IN FORECASTING THE TIMING OF THESE CYCLES.  

THE WIND RADII FORECAST HAS ALSO BEEN ADJUSTED TO ACCOUNT FOR THE
INCREASE IN THE INTENSITY.  THE OFFICIAL NHC TRACK FORECAST REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY. 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/1830Z 17.7N  46.1W   115 KT
 12HR VT     13/0000Z 17.8N  47.5W   125 KT
 24HR VT     13/1200Z 18.0N  49.8W   125 KT
 36HR VT     14/0000Z 18.4N  51.8W   125 KT
 48HR VT     14/1200Z 19.0N  53.6W   130 KT
 72HR VT     15/1200Z 20.7N  56.7W   130 KT
 96HR VT     16/1200Z 22.6N  59.6W   125 KT
120HR VT     17/1200Z 24.5N  62.5W   125 KT
 
$$
FORECASTER ROBERTS/BRENNAN
 

WTNT41 KNHC 122038
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST SUN SEP 12 2010
 
IGOR CONTINUES TO INTENSIFY AT A RAPID PACE.  DVORAK INTENSITY
ESTIMATES AND THE UW-CIMSS ADT HAVE INCREASED FURTHER...AND THE
INITIAL INTENSITY IS ADJUSTED SLIGHTLY UPWARD TO 120 KT BASED ON A
COMPROMISE OF THESE DATA AND THE LATEST SATCON INTENSITY ESTIMATE. 
THE OFFICIAL INTENSITY FORECAST HAS ALSO BEEN ADJUSTED TO SHOW SOME
FURTHER STRENGTHENING AND A PEAK INTENSITY AT DAY 3 OF 135
KT...SIMILAR TO SHIPS MODEL. FOR THE REMAINDER OF THE PERIOD...THE
OFFICIAL FORECAST CALLS FOR SOME GRADUAL WEAKENING AND IS BASED
PRIMARILY ON THE ICON CONSENSUS MODEL. IT IS WORTH NOTING THAT
FLUCTUATIONS IN STRENGTH DUE TO EYEWALL REPLACEMENT CYCLES ARE
POSSIBLE...HOWEVER...THERE IS LITTLE SKILL IN FORECASTING THE
TIMING OF THESE CYCLES.

THE INITIAL MOTION ESTIMATE REMAINS 270/12. THE TRACK FORECAST
PHILOSOPHY REMAINS UNCHANGED FOR THIS ADVISORY...HOWEVER THERE IS
STILL CONSIDERABLE DYNAMICAL MODEL SPREAD AFTER 36 HOURS.  THE
HWRF...UKMET AND ECMWF REMAIN TO THE LEFT OF THE CONSENSUS AND ARE
SLIGHTLY SLOWER...WHILE THE OTHER REGIONAL AND GLOBAL MODELS
SUGGEST A MORE PRONOUNCED WEAKNESS WITH TIME IN THE MID- TO
UPPER-LEVEL RIDGE. THE NHC TRACK FORECAST IS NUDGED TO THE RIGHT OF
THE PREVIOUS FORECAST AFTER DAY 3...CLOSER TO THE TVCN CONSENSUS
MODEL...BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF
MODEL.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/2100Z 17.7N  46.9W   120 KT
 12HR VT     13/0600Z 17.8N  48.7W   125 KT
 24HR VT     13/1800Z 18.1N  50.8W   125 KT
 36HR VT     14/0600Z 18.7N  52.6W   130 KT
 48HR VT     14/1800Z 19.4N  54.3W   130 KT
 72HR VT     15/1800Z 21.3N  57.1W   135 KT
 96HR VT     16/1800Z 23.5N  60.0W   125 KT
120HR VT     17/1800Z 25.8N  62.9W   120 KT
 
$$
FORECASTER ROBERTS/BRENNAN
 

WTNT41 KNHC 130248
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SUN SEP 12 2010
 
IGOR HAS CONTINUED TO INTENSIFY WITH VERY COLD CLOUD TOPS...LOWER
THAN -70C...WRAPPING AROUND THE SLOWLY-SHRINKING EYE DURING THE
PAST SEVERAL HOURS.  ALTHOUGH THE TOPS HAVE RECENTLY WARMED A
LITTLE OVER THE SOUTHWEST QUADRANT...SUBJECTIVE DVORAK ESTIMATES
FROM TAFB AND SAB ARE T6.5/127 KT AND OBJECTIVE ESTIMATES FROM THE
ADT AND HIE ALGORITHMS ARE T6.6/130 KT AND T6.9/137 KT...
RESPECTIVELY.  AS A COMPROMISE...THE INITIAL INTENSITY IS SET AT
130 KT.  AN EXPERIMENTAL PRODUCT FROM UW-CIMSS RUN AT NHC INDICATES
THAT THERE IS A 42 PERCENT CHANCE OF SECONDARY EYEWALL FORMATION
WITHIN THE NEXT 12 HOURS...AND A 90 PERCENT CHANCE WITHIN 24 HOURS.
THE PERIOD OF RAPID INTENSIFICATION IS LIKELY TO END SOON...BUT THE
OFFICIAL FORECAST FOLLOWS THE SHIPS/LGEM MODELS BY SHOWING IGOR
REACHING THE THRESHOLD OF CATEGORY 5 STRENGTH BEFORE THAT HAPPENS.
SOME WEAKENING IS THEN INDICATED AFTER EYEWALL REPLACEMENT
OCCURS...BUT IGOR IS EXPECTED TO REMAIN A POWERFUL HURRICANE FOR
SEVERAL DAYS.  AS IS ALWAYS THE CASE WITH STRONG HURRICANES LIKE
IGOR...FLUCTUATIONS IN INTENSITY ARE LIKELY BUT ARE ALSO DIFFICULT
TO FORECAST.
 
THE MEAN MOTION IS 270/11...BUT IGOR HAS BEEN WOBBLING A LITTLE TO
THE SOUTH OF THAT VECTOR.  IGOR IS MOVING INTO AN ENVIRONMENT WHERE
THE STEERING FLOW IS BECOMING INCREASINGLY DICTATED BY A LARGE
LONGWAVE TROUGH OVER THE WESTERN ATLANTIC...AND THE HURRICANE IS
EXPECTED TO RESPOND BY TURNING TOWARD THE WEST-NORTHWEST WITHIN THE
NEXT 24-48 HOURS.  SOME OF THE GLOBAL MODELS INDICATE THAT THE
TROUGH COULD FLATTEN A LITTLE BY DAY 3 AND ALLOW THE SUBTROPICAL
RIDGE TO BUILD WESTWARD...BUT AT THIS TIME THERE IS TOO MUCH
DISAGREEMENT TO INDICATE A WESTWARD TURN IN THE FORECAST.  THE
TRACK GUIDANCE HAS SHIFTED A LITTLE TO THE NORTH...BUT THE NEW
OFFICIAL FORECAST STILL LIES ON THE SOUTHERN SIDE OF THE GUIDANCE
ENVELOPE UNTIL IT BECOMES CLEAR THAT IGOR IS READY TO TURN.  THIS
SOLUTION ALSO GIVES CREDENCE TO THE MORE SOUTHERN ECMWF AND UKMET
MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 17.6N  47.8W   130 KT
 12HR VT     13/1200Z 17.8N  49.5W   140 KT
 24HR VT     14/0000Z 18.2N  51.3W   135 KT
 36HR VT     14/1200Z 18.9N  53.0W   130 KT
 48HR VT     15/0000Z 19.8N  54.6W   125 KT
 72HR VT     16/0000Z 22.0N  57.5W   125 KT
 96HR VT     17/0000Z 24.0N  60.0W   120 KT
120HR VT     18/0000Z 27.0N  63.0W   110 KT
 
$$
FORECASTER BERG
 

WTNT41 KNHC 130835
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST MON SEP 13 2010
 
IGOR REMAINS A POWERFUL AND WELL ORGANIZED HURRICANE WITH A
SYMMETRIC EYEWALL...CLOUD TOPS COLDER THAN -70 C...A 15 N MI
CIRCULAR EYE...AND SPIRAL RAINBANDS.  SATELLITE CLASSIFICATIONS
FROM ALL AGENCIES HAVE NOT CHANGED MUCH FROM 0000 UTC...AND
THEREFORE THE INITIAL INTENSITY IS HELD AT 130 KT FOR THIS
ADVISORY.  AS IS COMMON FOR MAJOR HURRICANES IN FAVORABLE OCEANIC
AND ATMOSPHERIC ENVIRONMENTS...INTERNAL DYNAMICS WILL LIKELY GOVERN
THE INTENSITY CHANGE OF IGOR DURING THE NEXT DAY OR TWO.  SINCE IT
APPEARS THAT AN EYEWALL REPLACEMENT CYCLE HAS NOT YET BEGUN...THE
OFFICIAL FORECAST WILL ALLOW FOR A LITTLE MORE STRENGTHENING TODAY. 
THEREAFTER...A GRADUAL WEAKENING IS SHOWN FOLLOWING THE TREND IN
THE INTENSITY GUIDANCE.  IGOR IS FORECAST TO MOVE INTO AN AREA OF
STRONGER SHEAR BY THE END OF THE PERIOD...WHICH SHOULD CAUSE A
LITTLE MORE WEAKENING. 
 
THE HURRICANE CONTINUES TO MOVE WESTWARD AT 11 KT...AND IS ON THE
PREVIOUS FORECAST TRACK.  IGOR IS EXPECTED TO TURN WEST-
NORTHWESTWARD IN ABOUT 24 HOURS AND THEN NORTHWESTWARD IN A
COUPLE OF DAYS AS IT APPROACHES A BROAD TROUGH OVER THE CENTRAL AND
WESTERN ATLANTIC.  ALTHOUGH MOST OF THE GLOBAL MODELS SHOW THE
TROUGH FLATTENING IN 3 TO 4 DAYS...THERE ARE DISAGREEMENTS IN HOW
MUCH...IF ANY...SUBTROPICAL RIDGING BUILDS IN THE WAKE OF THE
TROUGH.  THE ECMWF AND UKMET MODELS CONTINUE TO BUILD MORE RIDGING
NORTH OF IGOR...RESULTING IN A TRACK FARTHER WEST THAN THE OTHER
MODELS.  OVERALL...THE MODEL GUIDANCE HAS SHIFTED SLIGHTLY TO THE
RIGHT FROM THE LAST CYCLE AND THE OFFICIAL FORECAST IS NUDGED IN
THAT DIRECTION...BUT REMAINS ON THE SOUTH SIDE OF THE GUIDANCE
ENVELOPE.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0900Z 17.7N  48.8W   130 KT
 12HR VT     13/1800Z 17.9N  50.2W   140 KT
 24HR VT     14/0600Z 18.5N  51.8W   135 KT
 36HR VT     14/1800Z 19.3N  53.4W   130 KT
 48HR VT     15/0600Z 20.4N  54.9W   125 KT
 72HR VT     16/0600Z 22.5N  57.7W   120 KT
 96HR VT     17/0600Z 25.0N  60.0W   115 KT
120HR VT     18/0600Z 28.0N  63.0W   105 KT
 
$$
FORECASTER CANGIALOSI
 

WTNT41 KNHC 131448
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST MON SEP 13 2010
 
IGOR CONTINUES TO HAVE A DISTINCT EYE SURROUNDED BY TOPS OF -60C TO
-70C.  DVORAK CLASSIFICATIONS FROM TAFB AND SAB WERE 6.5...AND THE
INITIAL INTENSITY REMAINS 130 KT.  THE UW-CIMSS SECONDARY EYEWALL
FORMATION INDEX STRONGLY SUGGESTS THAT A SECONDARY EYEWALL WILL
FORM IN THE NEXT DAY OR TWO...AND THIS WILL LIKELY RESULT IN SOME
SHORT TERM INTENSITY FLUCTUATIONS THAT ARE NOT REPRESENTED IN THE
OFFICIAL FORECAST.  ON LONGER TIME SCALES...ALL OF THE INTENSITY
GUIDANCE SUGGESTS THAT IGOR IS NEAR PEAK INTENSITY...AND SHOW
GRADUAL WEAKENING THROUGH THE PERIOD.  HOWEVER...SINCE THE CYCLONE
REMAINS IN WHAT APPEARS TO BE AN IDEAL ENVIRONMENT FOR THE NEXT 72
HOURS...THE OFFICIAL FORECAST IS ADJUSTED ONLY SLIGHTLY DOWNWARD
THROUGH THAT TIME.  AT DAYS 4 AND 5...VERTICAL SHEAR MAY BEGIN TO
INCREASE OVER THE HURRICANE...HOWEVER...THIS INCREASE WILL BE
SENSITIVE TO THE VERY UNCERTAIN TRACK FORECAST AT THOSE TIME
RANGES.  THEREFORE...AT THOSE TIMES THE OFFICIAL FORECAST IS CLOSE
TO OR A LITTLE ABOVE THE STRONGEST MODEL...THE SHIPS.
 
THE INITIAL MOTION ESTIMATE IS 265/9 KNOTS...A LITTLE SLOWER THAN
BEFORE...AND A BIT SOUTH OF THE PREVIOUS FORECAST.  MOST OF THE
GUIDANCE...WITH THE EXCEPTION OF THE UKMET...SHOWS IGOR TURNING
TOWARD THE WEST-NORTHWEST BY TONIGHT AND THEN TURNING NORTHWESTWARD
BY 48 HOURS AS IT MOVES INTO A LARGE BREAK IN THE SUBTROPICAL
RIDGE. THE OFFICIAL FORECAST IS A LITTLE SOUTH OF THE PREVIOUS ONE
THROUGH 12 HOURS GIVEN THE INITIAL POSITION AND MOTION. FROM 12
THROUGH 48 HOURS THE OFFICIAL FORECAST IS SIMILAR TO BUT A LITTLE
SLOWER THAN THE PREVIOUS PACKAGE AND TRENDS TOWARD THE TVCN
CONSENSUS MODEL FORWARD SPEED. AT 72 HOURS AND BEYOND THERE IS
CONSIDERABLE UNCERTAINTY WITH THE EVOLUTION OF THE LARGE-SCALE FLOW
AND THE TRACK OF IGOR.  THE ECMWF AND UKMET SHOW MORE MID-LEVEL
RIDGING NORTH AND NORTHEAST OF IGOR OVER THE CENTRAL ATLANTIC AND
MOVE IGOR SLOWER AND FARTHER SOUTH THAN THE REST OF THE GUIDANCE AT
DAYS 3 THROUGH 5. THE GFS...GFDL...AND GFDN KEEP THIS RIDGE FARTHER
EAST AND ALLOW IGOR TO GAIN MORE LATITUDE AND RECURVE AHEAD OF A
LONGWAVE TROUGH SITUATED OFFSHORE OF THE NORTHEASTERN UNITED
STATES.  THE NOGAPS AND HWRF ARE BETWEEN THESE TWO CAMPS AND SHOW A
NORTHWESTWARD MOTION AT DAY 5. GIVEN THE INCREASING SPREAD OF THE
GUIDANCE LATE IN THE PERIOD...THE OFFICIAL FORECAST IS SIMPLY AN
UPDATE OF THE PREVIOUS ADVISORY AT THESE TIMES AND IS OF LOWER
CONFIDENCE THAN NORMAL. THE NHC TRACK IS CLOSE TO THE NOGAPS AND
WELL TO THE NORTH OF THE UKMET AND ECMWF AT THE END OF THE PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 17.5N  49.7W   130 KT
 12HR VT     14/0000Z 17.9N  50.8W   135 KT
 24HR VT     14/1200Z 18.7N  52.3W   130 KT
 36HR VT     15/0000Z 19.5N  53.7W   130 KT
 48HR VT     15/1200Z 20.6N  55.2W   125 KT
 72HR VT     16/1200Z 23.0N  58.0W   115 KT
 96HR VT     17/1200Z 25.5N  60.5W   110 KT
120HR VT     18/1200Z 29.0N  63.5W   100 KT
 
$$
FORECASTER BRENNAN
 

WTNT41 KNHC 132038
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST MON SEP 13 2010
 
THE STRUCTURE OF IGOR HAS CHANGED LITTLE OVER THE PAST FEW HOURS.
THE EYE REMAINS VERY DISTINCT IN IR AND VISIBLE IMAGERY...AND
ALTHOUGH THE TOPS SURROUNDING THE EYE HAVE WARMED A BIT...DVORAK
CLASSIFICATIONS STILL SUPPORT AN INTENSITY OF 130 KT.  IGOR WILL
REMAIN IN A FAVORABLE ENVIRONMENT FOR MAINTAINING ITS CURRENT
INTENSITY FOR THE NEXT COUPLE OF DAYS...AND THE OFFICIAL FORECAST
DOES NOT SHOW ANY WEAKENING UNTIL AFTER 48 HOURS.  WHILE A 1640 UTC
AMSR-E PASS DOES NOT SHOW ANY EVIDENCE OF A SECONDARY EYEWALL
YET...IT IS POSSIBLE THAT AN EYEWALL REPLACEMENT CYCLE WILL OCCUR
IN THE FIRST COUPLE OF DAYS...WHICH COULD RESULT IN SOME INTENSITY
FLUCTUATIONS NOT REPRESENTED IN THE OFFICIAL FORECAST.  BEYOND 36
HOURS...ALL OF THE INTENSITY GUIDANCE SUGGEST THAT SLOW WEAKENING
SHOULD BEGIN...ALTHOUGH THERE ARE NO OVERLY NEGATIVE FACTORS UNTIL
THE VERY END OF THE PERIOD WHEN THE VERTICAL SHEAR MAY INCREASE.
THE OFFICIAL FORECAST SHOWS A GRADUAL WEAKENING AT DAYS 3 THROUGH 5
BUT IS HIGHER THAN MOST OF THE GUIDANCE THROUGH THE PERIOD.
 
THE INITIAL MOTION IS STILL DUE WEST...270 DEGREES...AT 9 KNOTS.
ALL OF THE GUIDANCE...EXCEPT THE UKMET...INSISTS ON A TURN TOWARD
THE WEST-NORTHWEST IN THE NEXT 12 HOURS AS IGOR BEGINS TO MOVE INTO
A LARGE WEAKNESS IN THE SUBTROPICAL RIDGE.  HOWEVER...DUE TO THE
INITIAL POSITION AND MOTION...THE OFFICIAL FORECAST HAS AGAIN BEEN
ADJUSTED A LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY THROUGH 48
HOURS.  BEYOND THAT TIME...THERE IS STILL SOME SPREAD IN THE TRACK
GUIDANCE.  THE ECMWF AND UKMET STILL SHOW A STRONGER RIDGE NORTH OF
IGOR THROUGH MUCH OF THE PERIOD...TAKING THE CYCLONE FARTHER WEST
THAN THE REST OF THE GUIDANCE.  THE GFS AND GFDL CONTINUE TO SHOW
THE LEAST RIDGING AND TURN IGOR NORTH-NORTHWESTWARD AT THE END OF
THE PERIOD AHEAD OF A MID-LATITUDE TROUGH.  WHILE CONFIDENCE IN THE
TRACK FORECAST LATE IN THE PERIOD REMAINS LOW...THE GUIDANCE SHOWS
A LITTLE LESS SPREAD NOW THAN EARLIER TODAY.  THE NEW OFFICIAL
FORECAST SHOWS A NORTHWESTWARD MOTION AT DAYS 3 THROUGH 5...AND IS
SIMILAR TO THE PREVIOUS FORECAST.  THIS ENDS UP BEING VERY CLOSE TO
THE TVCN MULTI-MODEL CONSENSUS AND A BLEND OF THE GFS AND ECMWF
MODELS.

LARGE SWELLS FROM IGOR WILL BEGIN AFFECTING THE LEEWARD ISLANDS
TOMORROW AND REACH PUERTO RICO AND THE VIRGIN ISLANDS BY WEDNESDAY.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/2100Z 17.7N  50.5W   130 KT
 12HR VT     14/0600Z 18.1N  51.7W   130 KT
 24HR VT     14/1800Z 18.9N  53.2W   130 KT
 36HR VT     15/0600Z 20.0N  54.7W   130 KT
 48HR VT     15/1800Z 21.1N  56.1W   130 KT
 72HR VT     16/1800Z 23.5N  58.5W   120 KT
 96HR VT     17/1800Z 26.5N  61.5W   110 KT
120HR VT     18/1800Z 30.0N  64.0W   105 KT
 
$$
FORECASTER BRENNAN
 

WTNT41 KNHC 140246
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST MON SEP 13 2010
 
MICROWAVE AND GEOSTATIONARY SATELLITE IMAGERY SUGGESTS THAT AN
EYEWALL REPLACEMENT CYCLE MAY HAVE BEGUN.  TRMM...WINDSAT...AND
SSMIS PASSES FROM ABOUT 5-6 HOURS AGO ALL INDICATED THAT A
SECONDARY EYEWALL WAS BEGINNING TO FORM...AND MORE RECENTLY
CONVECTIVE TOPS AROUND THE EYE HAVE BEEN WARMING.  SUBJECTIVE
DVORAK FINAL-T ESTIMATES HAD FALLEN TO T6.0 TAFB AND SAB AT 0000
UTC...AND THE LATEST OBJECTIVE ADT ESTIMATE IS T6.0/6.4.  BASED ON
THESE DATA...THE INITIAL INTENSITY IS LOWERED TO 120 KT.  FOLLOWING
A CONSENSUS OF THE INTENSITY GUIDANCE...THE OFFICIAL FORECAST KEEPS
IGOR AT THIS INTENSITY FOR THE NEXT 24 HOURS OR SO...BUT IT IS
POSSIBLE THAT ADDITIONAL WEAKENING COULD OCCUR WHILE THE EYEWALL
REPLACEMENT IS IN PROGRESS.  SINCE IGOR IS STILL EXPECTED TO BE
OVER WARM OCEAN WATERS AND REMAIN IN A LOW SHEAR ENVIRONMENT...THE
FORECAST ALLOWS FOR THE POSSIBILITY OF SOME RE-STRENGTHENING
BETWEEN 36-48 HOURS...WHICH IS HINTED AT IN THE SHIPS OUTPUT. 
WEAKENING IS THEN INDICATED DURING DAYS 3 THROUGH 5...BUT IT IS
CONSERVATIVE AND STILL LIES JUST ABOVE THE UPPER BOUND OF THE
GUIDANCE.
 
IGOR JUST WILL NOT BUDGE VERY MUCH TO THE NORTH AND IS MOVING 275
DEGREES AT 8 KT.  THE UKMET MODEL HAS CAPTURED THIS MOTION WELL
OVER THE PAST COUPLE OF DAYS AND HAS CONSISTENTLY BEEN LOCATED ON
THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE.  SINCE THERE IS STILL
NO CLEAR EVIDENCE OF THE BEGINNING OF A TURN...THE NHC FORECAST
TRACK LIES ALONG THE SOUTHERN PERIPHERY OF THE TRACK GUIDANCE FOR
THE FIRST 24 HOURS...ALTHOUGH STILL NOT AS FAR SOUTH AS THE UKMET.
A TURN TOWARD THE NORTHWEST IS EXPECTED BY 36 HOURS WHEN IGOR
SHOULD HAVE REACHED THE BREAK IN THE SUBTROPICAL RIDGE.  THE SPREAD
IN THE MODELS FROM DAYS 3 THROUGH 5 HAS AGAIN TIGHTENED...AND THE
OFFICIAL FORECAST IS CHANGED LITTLE FROM THE PREVIOUS ONE.  THIS
FORECAST ALSO LIES CLOSE TO A MULTI-MODEL CONSENSUS THAT EXCLUDES
THE GFDN...WHICH HAS BEEN FASTER THAN THE OTHER GUIDANCE FOR
SEVERAL CYCLES.
 
LARGE SWELLS FROM IGOR WILL BEGIN AFFECTING THE LEEWARD ISLANDS
TOMORROW AND REACH PUERTO RICO AND THE VIRGIN ISLANDS BY WEDNESDAY.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 17.7N  51.2W   120 KT
 12HR VT     14/1200Z 18.0N  52.3W   120 KT
 24HR VT     15/0000Z 18.8N  53.7W   120 KT
 36HR VT     15/1200Z 19.9N  55.2W   125 KT
 48HR VT     16/0000Z 21.1N  56.6W   125 KT
 72HR VT     17/0000Z 24.0N  59.5W   115 KT
 96HR VT     18/0000Z 27.0N  62.5W   105 KT
120HR VT     19/0000Z 30.5N  64.5W    95 KT
 
$$
FORECASTER BERG
 

WTNT41 KNHC 140834
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST TUE SEP 14 2010

ENHANCED INFRARED SATELLITE IMAGES SHOW THAT THE CLOUD TOPS
SURROUNDING THE EYE OF THE HURRICANE HAVE WARMED A LITTLE...AND
DVORAK DATA T-NUMBERS FROM BOTH TAFB AND SAB HAVE DECREASED.  THE
ADVISORY INTENSITY IS SET AT 115 KT WHICH IS A BLEND OF THE DVORAK
CURRENT INTENSITY AND T-NUMBERS.  THIS IS ALSO CLOSE TO THE LATEST
OBJECTIVE DVORAK INTENSITY ESTIMATES FROM UW-CIMSS.  AS STATED
EARLIER...FLUCTUATIONS IN STRENGTH DUE TO INNER CORE EVOLUTION ARE
PROBABLE OVER THE NEXT COUPLE OF DAYS.  HOWEVER...THE LARGE-SCALE
ATMOSPHERIC AND OCEANIC ENVIRONMENT IS LIKELY TO REMAIN QUITE
CONDUCIVE FOR THE MAINTENANCE OF A MAJOR HURRICANE FOR THE NEXT 48
TO 72 HOURS.  THEREFORE AT LEAST SLIGHT RESTRENGTHENING IS A
DISTINCT POSSIBILITY.  THE OFFICIAL FORECAST IS CONSISTENT WITH
THIS REASONING AND IS CLOSE TO THE LATEST INTENSITY MODEL CONSENSUS
THROUGH DAY 3 AND IS QUITE SIMILAR TO THE STATISTICAL-DYNAMICAL
LGEM MODEL AT DAYS 4 AND 5.

SATELLITE FIXES OF THE WELL-DEFINED EYE OF IGOR INDICATE THAT THE
MUCH-AWAITED TURN TOWARD THE WEST-NORTHWEST HAS OCCURRED...AND THE
INITIAL MOTION IS ESTIMATED TO BE 285/7.  VERY LITTLE CHANGE HAS
BEEN MADE TO THE NHC FORECAST TRACK ON THIS PACKAGE.  WATER VAPOR
IMAGES AND GLOBAL MODEL INITIALIZATIONS SHOW A BROAD TROUGH JUST
EAST OF THE EASTERN U.S. SEABOARD.  THE DYNAMICAL MODELS SHOW A
SERIES OF SHORT WAVE TROUGHS PASSING THROUGH THIS FEATURE DURING
THE NEXT SEVERAL DAYS.  THE RESULTING WEAKNESS IN THE SUBTROPICAL
RIDGE SHOULD CAUSE THE HURRICANE TO GRADUALLY TURN TOWARD THE
NORTHWEST AND NORTH-NORTHWEST DURING THE FORECAST PERIOD.  THE
OFFICIAL FORECAST TRACK IS VERY CLOSE TO A CONSENSUS OF THE
DYNAMICAL MODELS EXCLUDING THE U.K. MET. OFFICE TRACK...WHICH IS
LOOKING MORE AND MORE LIKE A WESTERN OUTLIER.

INTERESTS IN BERMUDA SHOULD NOT FOCUS ON THE 5-DAY POINT...SINCE
TRACK ERRORS COULD EASILY BE A FEW HUNDRED MILES AT THAT FORECAST
INTERVAL.  IT IS STILL TOO EARLY TO SAY WITH CERTAINTY WHETHER IGOR
WILL HAVE A SIGNIFICANT IMPACT ON THAT ISLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 17.9N  51.7W   115 KT
 12HR VT     14/1800Z 18.4N  52.8W   115 KT
 24HR VT     15/0600Z 19.4N  54.2W   115 KT
 36HR VT     15/1800Z 20.5N  55.7W   120 KT
 48HR VT     16/0600Z 21.7N  57.1W   120 KT
 72HR VT     17/0600Z 24.4N  60.2W   115 KT
 96HR VT     18/0600Z 27.5N  63.0W   100 KT
120HR VT     19/0600Z 31.5N  64.5W    90 KT
 
$$
FORECASTER PASCH
 

WTNT41 KNHC 141443
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST TUE SEP 14 2010

THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE OF IGOR DURING THE
PAST SEVERAL HOURS...WITH THE 20 NM WIDE EYE REMAINING WELL DEFINED
AND EYEWALL CONVECTIVE TOPS REMAINING COLDER THAN -70C.  SATELLITE
INTENSITY ESTIMATES ARE UNCHANGED FROM SIX HRS AGO...SO THE INITIAL
INTENSITY REMAINS 115 KT.  RECENT MICROWAVE OVERPASSES DO NOT YET
SHOW AN OUTER EYEWALL...BUT DO SHOW THAT A LARGE RAIN-FREE MOAT HAS
FORMED BETWEEN THE EYEWALL AND THE OUTER CONVECTIVE BANDS.  THE
CIRRUS OUTFLOW IS GOOD IN ALL DIRECTIONS.

THE INITIAL MOTION IS NOW 290/6.  IGOR IS MOVING TOWARD A WEAKNESS
IN THE SUBTROPICAL RIDGED CAUSED BY A BROAD DEEP-LAYER TROUGH OVER
THE NORTHEASTERN UNITED STATES AND THE NORTHWESTERN ATLANTIC.  THE
DYNAMICAL MODELS FORECAST THIS WEAKNESS TO PERSIST FOR THE NEXT
SEVERAL DAYS AS A SERIES OF SHORTWAVE TROUGHS MOVE THROUGH THE
BROADER TROUGH.  IN ADDITION...THE DYNAMICAL MODELS FORECAST AN
UPPER-LEVEL TROUGH TO DEVELOP NEAR THE SOUTHEASTERN COAST OF THE
UNITED STATES BY 96-120 HR...WITH A LARGE UPPER-LEVEL HIGH FORMING
OVER THE CENTRAL ATLANTIC.  THIS EVOLUTION SHOULD STEER IGOR
WEST-NORTHWESTWARD TO NORTHWESTWARD FOR THE NEXT 48-72 HR...
FOLLOWED BY A MORE NORTHWARD MOTION.  THE TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH THIS SCENARIO...ALTHOUGH THERE REMAINS SOME SPREAD
BETWEEN THE MORE WESTWARD UKMET/NOGAPS AND THE MORE EASTWARD GFDL. 
THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE WEST OF THE
PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE GUIDANCE ENVELOPE.

IGOR REMAINS IN AN ENVIRONMENT OF LIGHT VERTICAL WIND SHEAR AND WARM
SEA SURFACE TEMPERATURES...AND THESE CONDITIONS ARE FORECAST TO
PERSIST FOR THE NEXT 48-72 HR.  THUS...THE INTENSITY IS LIKELY TO
BE CONTROLLED BY HARD-TO-TIME EYEWALL REPLACEMENT CYCLES DURING
THIS TIME.  THE INTENSITY FORECAST CALLS FOR SOME INTENSIFICATION
BY 24 HR ON THE PREMISE THAT THE CURRENT INTERNAL CYCLE WILL BE
COMPLETE.  AFTER 72 HR...THE SEA SURFACE TEMPERATURES GRADUALLY
COOL ALONG THE FORECAST TRACK...AND SOUTHERLY UPPER-LEVEL WINDS
BETWEEN THE PREVIOUSLY MENTIONED TROUGH AND HIGH ARE EXPECTED TO
CAUSE INCREASED SHEAR.  THESE FACTORS SHOULD CAUSE IGOR TO
GRADUALLY WEAKEN...AND THE NEW INTENSITY FORECAST IS THE SAME AS
THE PREVIOUS FORECAST AT 96-120 HR.

INTERESTS IN BERMUDA SHOULD NOT FOCUS ON THE 5-DAY POINT...SINCE
TRACK ERRORS COULD EASILY BE A FEW HUNDRED MILES AT THAT FORECAST
INTERVAL.  IT IS STILL TOO EARLY TO SAY WITH CERTAINTY WHETHER IGOR
WILL HAVE A SIGNIFICANT IMPACT ON THAT ISLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/1500Z 18.3N  52.3W   115 KT
 12HR VT     15/0000Z 18.8N  53.3W   115 KT
 24HR VT     15/1200Z 19.8N  54.8W   120 KT
 36HR VT     16/0000Z 20.8N  56.3W   120 KT
 48HR VT     16/1200Z 21.9N  57.8W   120 KT
 72HR VT     17/1200Z 24.5N  61.0W   115 KT
 96HR VT     18/1200Z 28.0N  64.0W   100 KT
120HR VT     19/1200Z 32.0N  65.5W    90 KT
 
$$
FORECASTER BEVEN
 

WTNT41 KNHC 142059
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST TUE SEP 14 2010
 
CLOUD TOPS SURROUNDING THE EYE HAVE COOLED CONSIDERABLY DURING THE
AFTERNOON AND THE EYE HAS ALSO WARMED AND BECOME MORE DISTINCT IN
BOTH VISIBLE AND INFRARED SATELLITE IMAGERY. SEVERAL DISTINCT
VORTICES INSIDE THE EYE WERE ALSO NOTED...SIMILAR TO WHAT HAS BEEN
SEEN WITH PAST HURRICANES THAT WERE NEAR CATEGORY 5 STRENGTH. THE
INITIAL INTENSITY IS INCREASED TO 125 KT AND IS SUPPORTED BY
SATELLITE INTENSITY ESTIMATES OF T6.5/127 KT FROM SAB...3-HR
AVERAGE ODT VALUES OF T6.7/133 KT FROM TAFB...AND UW-CIMSS ADT
VALUES OF T6.5/127 KT.

THE INITIAL MOTION ESTIMATE IS 295/07...BASED ON A 12-HR AVERAGE OF
SMOOTHING OUT THE MANY TROCHOIDAL WOBBLES IN THE TRACK. IGOR MAY
BRIEFLY WOBBLE BACK TO THE WEST DURING THE NEXT SEVERAL HOURS...BUT
THE GENERAL MOTION OVER THE NEXT 24 HOURS SHOULD BE TOWARD THE
WEST-NORTHWEST...FOLLOWED BY A TURN TO THE NORTHWEST AFTER THAT
THROUGH 72 HOURS. A SERIES OF SHORTWAVE TROUGHS MOVING QUICKLY IN
THE MID-LATITUDE WESTERLIES ACROSS THE NORTHERN U.S. AND THE NORTH
ATLANTIC IS FORECAST TO GRADUALLY WEAKEN THE SUBTROPICAL RIDGE
BETWEEN 60W-70W LONGITUDE ABOUT EVERY 24-36 HOURS. AS A RESULT...
IGOR IS EXPECTED TO TURN NORTHWARD IN 96-120 HOURS AS DEEP-LAYER
SOUTHERLY FLOW TO THE EAST OF IGOR STRENGTHENS BETWEEN IT AND A
STRONG SUBTROPICAL HIGH FORECAST OT BE NEAR 30N/40W BY THAT TIME.
THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND
IS CLOSE TO THE MIDDLE OF THE TIGHTLY CLUSTERED MODEL GUIDANCE. BY
120 HOURS...IGOR IS EXPECTED TO BE A VERY LARGE HURRICANE AND BE
CLOSE ENOUGH TO BERMUDA TO BRING ADVERSE WEATHER CONDITIONS TO THAT
ISLAND.

IGOR IS FORECAST TO REMAIN IN AN ENVIRONMENT OF LIGHT VERTICAL WIND
SHEAR...WARM SEA-SURFACE TEMPERATURES OF NEAR 29C...AND MAINTAIN A
VERY FAVORABLE OUTFLOW PATTERN THROUGH THE FORECAST PERIOD. AS A
RESULT...THERE MAY BE SOME ADDITIONAL STRENGTHENING DURING THE NEXT
12-24 HOURS...ESPECIALLY LATER TONIGHT DURING THE CONVECTIVE
MAXIMUM PERIOD. HOWEVER...OWING TO THE LARGE SIZE OF IGOR...ITS
STRONG CATEGORY 4 INTENSITY...AND ITS RELATIVELY SLOW FORWARD
MOTION OF LESS THAN 10 KT...SOME COLD UPWELLING MAY OCCUR BENEATH
THE CORE OF THE HURRICANE AND CAUSE SOME WEAKENING OF THE CYCLONE
DESPITE THE AFOREMENTIONED FAVORABLE CONDITIONS. EYEWALL
REPLACEMENT CYCLES ARE ALSO A DISTINCT POSSIBILITY. REGARDLESS...
IGOR IS STILL EXPECTED TO REMAIN A MAJOR HURRICANE THROUGH THE
FORECAST PERIOD. THE OFFICIAL INTENSITY FORECAST IS A LITTLE HIGHER
THAN THE PREVIOUS ADVISORY AND IS SIMILAR TO A BLEND OF THE
SHIPS-LGEM INTENSITY MODELS THROUGH 72 HOURS.  IT APPEARS AS THOUGH
THE SHIPS GUIDANCE AT FOUR AND FIVE DAYS MAY BE ADVERSELY AFFECTED
BY THE REPRESENTATION OF THE WARM CORE OF THE HURRICANE IN THE GFS
MODEL.  IN ADDITION...ALL THE GLOBAL MODELS FORECAST A VERY
FAVORABLE OUTFLOW PATTERN THROUGH DAY FIVE...AND SO THE OFFICIAL
FORECAST IS HELD A LITTLE ABOVE THE GUIDANCE NEAR THE END OF THE
FORECAST PERIOD.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 18.8N  53.1W   125 KT
 12HR VT     15/0600Z 19.5N  54.3W   130 KT
 24HR VT     15/1800Z 20.5N  55.6W   125 KT
 36HR VT     16/0600Z 21.5N  57.2W   125 KT
 48HR VT     16/1800Z 22.6N  58.8W   120 KT
 72HR VT     17/1800Z 25.4N  62.1W   115 KT
 96HR VT     18/1800Z 28.6N  64.5W   110 KT
120HR VT     19/1800Z 33.0N  65.5W   100 KT
 
$$
FORECASTER STEWART
 

WTNT41 KNHC 150257
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST TUE SEP 14 2010
 
CONVECTIVE CLOUD TOPS HAVE CONTINUED TO COOL...AND A SOLID WHITE
RING ON THE DVORAK ENHANCEMENT HAS INTERMITTENTLY WRAPPED ENTIRELY
AROUND THE EYE DURING THE PAST FEW HOURS.  DVORAK T-NUMBERS WERE UP
TO T7.0 FROM TAFB AND SAB AT 0000 UTC...AND T6.5 AND T7.0 FROM TWO
FORMS OF THE UW-CIMSS ADT.  SINCE THE WHITE RING DOES NOT ENTIRELY
WRAP AROUND THE EYE AT THIS TIME...THE INITIAL INTENSITY IS BEING
RAISED TO 135 KT.  IGOR REMAINS OVER WARM WATERS AND IS IN AN
ENVIRONMENT OF LOW VERTICAL SHEAR...SO THE OFFICIAL FORECAST
MAINTAINS THIS INTENSITY FOR THE NEXT 12-24 HOURS.  GRADUAL
WEAKENING IS EXPECTED THEREAFTER WHEN IT IS LIKELY THAT INTERNAL
DYNAMICS...WHICH ARE NOT WELL UNDERSTOOD...WILL INFLUENCE THE
INTENSITY.  THE OFFICIAL FORECAST IS VERY CLOSE TO A CONSENSUS OF
THE STATISTICAL AND DYNAMICAL GUIDANCE THROUGH DAY 4 BUT IS A
LITTLE HIGHER THAN THAT GUIDANCE AT DAY 5 TO MAINTAIN CONTINUITY
WITH THE PREVIOUS PACKAGE.

IGOR IS MOVING AT 295/8.  THE HURRICANE HAS REACHED THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE...AND IT SHOULD MAKE A TURN
TOWARD THE NORTHWEST SOON.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT
FOR THE FIRST 3-4 DAYS BUT THEN SHOWS MORE DIVERGENCE ON DAY 5 WITH
THE GFDL WELL TO THE NORTHEAST OF BERMUDA AND THE ECMWF WELL TO THE
SOUTHWEST OF BERMUDA.  THE OFFICIAL FORECAST LIES VERY CLOSE TO THE
CONSENSUS THROUGH THE FORECAST PERIOD AND ENDED UP BEING SIMILAR TO
THE PREVIOUS FORECAST.

REGARDLESS OF WHERE IGOR ENDS UP IN 5 DAYS...THE LARGE WIND FIELD OF
THE HURRICANE IS EXPECTED TO BE VERY CLOSE TO OR NEAR BERMUDA
WITHIN THE NEXT 3 TO 4 DAYS.  INTERESTS ON BERMUDA SHOULD CONTINUE
TO MONITOR THE PROGRESS OF IGOR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0300Z 19.0N  53.9W   135 KT
 12HR VT     15/1200Z 19.8N  55.0W   135 KT
 24HR VT     16/0000Z 20.7N  56.4W   130 KT
 36HR VT     16/1200Z 21.7N  58.0W   125 KT
 48HR VT     17/0000Z 22.8N  59.6W   125 KT
 72HR VT     18/0000Z 25.5N  63.0W   115 KT
 96HR VT     19/0000Z 29.0N  65.0W   105 KT
120HR VT     20/0000Z 33.5N  65.5W    95 KT
 
$$
FORECASTER BERG
 

WTNT41 KNHC 150843
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST WED SEP 15 2010
 
IGOR HAS WEAKENED A LITTLE DURING THE PAST FEW HOURS.  ENHANCED
INFRARED SATELLITE IMAGES INDICATE THAT CLOUD TOPS HAVE WARMED OVER
THE WESTERN SEMICIRCLE AND THE EYE HAS COOLED.  IN ADDITION...AN
0352 UTC TRMM OVERPASS SHOWED THAT THE SOUTHWESTERN PORTION OF THE
EYEWALL HAS ERODED.  BASED ON THIS DEGRADED APPEARANCE AND A BLEND
OF SATELLITE INTENSITY ESTIMATES...THE INITIAL WIND SPEED IS
LOWERED TO 125 KT.  IGOR REMAINS IN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING...SO INTERNAL DYNAMICS WILL LIKELY BE THE DOMINANT
FACTOR FOR THE FUTURE INTENSITY OF IGOR FOR THE NEXT COUPLE OF
DAYS.  THESE SMALL SCALE DYNAMICS...WHICH ARE NOT WELL
UNDERSTOOD...USUALLY CAUSE FLUCTUATIONS IN INTENSITY...AND THAT IS
REFLECTED IN THE OFFICIAL FORECAST.  SOUTHERLY WIND SHEAR IS
EXPECTED TO INCREASE IN 3 TO 4 DAYS...WHICH SHOULD CAUSE SOME
WEAKENING BY THAT TIME.
 
THE INITIAL MOTION IS 300/8...AND THE EYE OF IGOR IS ON THE PREVIOUS
FORECAST TRACK.  A CONTINUED WEST-NORTHWEST TO NORTHWEST MOTION IS
EXPECTED OVER THE NEXT COUPLE OF DAYS AS THE HURRICANE MOVES ALONG
THE SOUTHWESTERN SIDE OF A SUBTROPICAL RIDGE.  BEYOND THAT TIME...A
NORTH-NORTHWESTWARD AND THEN NORTHWARD MOTION WITH AN INCREASE IN
FORWARD SPEED IS FORECAST AS IGOR ROUNDS THE RIDGE AND MOVES INTO
A PRONOUNCED WEAKNESS.  IN GENERAL...THE NEW TRACK GUIDANCE HAS
SHIFTED A LITTLE TO THE EAST AT DAYS 4 AND 5...AND THE OFFICIAL
FORECAST IS NUDGED ONLY SLIGHTLY IN THAT DIRECTION.
 
REGARDLESS OF THE EXACT TRACK OF IGOR...THE LARGE WIND FIELD OF
THE HURRICANE IS EXPECTED TO BE VERY CLOSE TO OR NEAR BERMUDA
WITHIN THE NEXT 3 TO 4 DAYS.  INTERESTS ON BERMUDA SHOULD CONTINUE
TO MONITOR THE PROGRESS OF IGOR. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0900Z 19.5N  54.5W   125 KT
 12HR VT     15/1800Z 20.2N  55.6W   130 KT
 24HR VT     16/0600Z 21.1N  57.0W   130 KT
 36HR VT     16/1800Z 21.9N  58.4W   125 KT
 48HR VT     17/0600Z 22.9N  60.2W   120 KT
 72HR VT     18/0600Z 25.8N  63.3W   110 KT
 96HR VT     19/0600Z 29.5N  65.0W   100 KT
120HR VT     20/0600Z 34.0N  64.5W    90 KT
 
$$
FORECASTER CANGIALOSI
 

WTNT41 KNHC 151439
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST WED SEP 15 2010
 
THE CLOUD PATTERN ASSOCIATED WITH IGOR WAS DETERIORATING DURING THE
PAST SEVERAL HOURS...WITH CLOUD TOP TEMPERATURES WARMING AND A DRY
SLOT EVIDENT NORTHWEST OF THE CENTER. SEVERAL MICROWAVE OVERPASSES
ALSO INDICATED A FURTHER EROSION OF THE INNER EYEWALL AND THE
FORMATION OF AN OUTER EYEWALL AT ABOUT 60-70 NMI RADIUS. SINCE
ABOUT 1300 UTC...THERE APPEARS TO BE SOME EVIDENCE OF A RE-
ORGANIZATION OF THE INNER CORE. DVORAK T-NUMBERS AT 1200 UTC ARE
5.5 AND 6.0 FROM SAB AND TAFB...RESPECTIVELY. BASED UPON THESE
ESTIMATES...THE INITIAL WIND SPEED IS DECREASED TO 115 KT FOR THIS
ADVISORY. THERE DO NOT APPEAR TO BE ANY NEGATIVE LARGE-SCALE
FACTORS THAT COULD PRODUCE A SIGNIFICANT WEAKENING DURING THE NEXT
TWO TO THREE DAYS. INSTEAD...FLUCTUATIONS IN INTENSITY ARE LIKELY
TO BE GOVERNED BY INTERNAL DYNAMICS FOR WHICH PREDICTABILITY IS
POOR. IN ABOUT 3 TO 4 DAYS...GLOBAL MODELS SHOW THAT IGOR SHOULD
ENCOUNTER AN INCREASE IN SOUTHERLY SHEAR. THE OFFICIAL NHC
INTENSITY FORECAST HAS BEEN LOWERED IN THE SHORT TERM BECAUSE OF
THE CURRENT WEAKENING TREND. SHOULD THE CURRENT EYEWALL REPLACEMENT
CYCLE END DURING THE NEXT DAY OR TWO...THERE MAY BE AN OPPORTUNITY
FOR RE-INTENSIFICATION BEFORE GRADUAL WEAKENING COMMENCES LATER IN
THE FORECAST PERIOD.
 
THE INITIAL MOTION IS ABOUT THE SAME AS BEFORE...300/07...AND THE
TRACK PHILOSOPHY IS ESSENTIALLY UNCHANGED.  IGOR IS MOVING AROUND
THE SOUTHWEST SIDE OF THE SUBTROPICAL RIDGE OVER THE EASTERN
ATLANTIC AND SHOULD GRADUALLY ENTER A LARGE WEAKNESS OVER THE
WESTERN ATLANTIC DURING THE NEXT COUPLE OF DAYS.  THIS PATTERN
SHOULD STEER IGOR NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD...
POSSIBLY WITH A SLIGHT INCREASE IN FORWARD SPEED.  DURING THIS
TIME...A SERIES OF SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN
THE WESTERN ATLANTIC SHOULD HAVE LITTLE IMPACT ON IGOR.  HOWEVER...
IN ABOUT 4-5 DAYS...DYNAMICAL MODELS ARE IN GOOD AGREEMENT ON THE
PRESENCE OF A SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN
UNITED STATES THAT SHOULD BEGIN TO INDUCE RECURVATURE.  THERE ARE
STILL SOME TIMING AND AMPLITUDE DIFFERENCES IN THE MODELS REGARDING
THIS FEATURE...WHICH COULD AFFECT HOW CLOSE IGOR PASSES TO BERMUDA.
THE OFFICIAL NHC TRACK FORECAST IS LARGELY UNCHANGED FROM THE
PREVIOUS ADVISORY...CLOSE TO BUT JUST RIGHT OF THE MULTI-MODEL
CONSENSUS.
 
REGARDLESS OF THE EXACT TRACK...IGOR HAS A VERY LARGE WIND FIELD AND
IS EXPECTED TO BRING ADVERSE CONDITIONS TO BERMUDA.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 19.8N  55.0W   115 KT
 12HR VT     16/0000Z 20.5N  56.1W   110 KT
 24HR VT     16/1200Z 21.3N  57.5W   110 KT
 36HR VT     17/0000Z 22.1N  59.1W   115 KT
 48HR VT     17/1200Z 23.3N  60.8W   120 KT
 72HR VT     18/1200Z 26.0N  63.5W   110 KT
 96HR VT     19/1200Z 30.0N  65.0W    95 KT
120HR VT     20/1200Z 34.5N  63.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 152035
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST WED SEP 15 2010
 
INFRARED SATELLITE PICTURES INDICATE THAT IGOR IS MAINTAINING ITS
CONVECTIVE ORGANIZATION...WITH INNER CORE CONVECTION MORE VIGOROUS
THAN EARLIER. HOWEVER...VISIBLE SATELLITE IMAGES SUGGEST THAT THE
EYEWALL REPLACEMENT CYCLE IGOR IS EXPERIENCING IS STILL OCCURRING.
A DISTINCT BUT PARTIAL INNER EYEWALL IS EVIDENT AND AN OUTER
EYEWALL NOW AT 30-40 NM RADIUS SEEMS TO BE GRADUALLY CONTRACTING.
SUBJECTIVE DVORAK CLASSIFICATIONS ARE AT 5.5 AND 6.0 FROM SAB AND
TAFB...RESPECTIVELY...WHILE THE LATEST 3-HOURLY AVERAGED ADT VALUE
IS CLOSE TO 6.0. THESE ESTIMATES ARE THE BASIS FOR KEEPING THE
INITIAL INTENSITY AT 115 KT FOR THIS ADVISORY. THERE ARE NO OBVIOUS
LARGE-SCALE FACTORS THAT COULD CAUSE A SIGNIFICANT WEAKENING OF
IGOR DURING THE NEXT 2-3 DAYS. ANY CHANGES IN INTENSITY DURING THIS
TIME ARE MOST LIKELY TO BE RELATED TO INNER CORE DYNAMICS FOR WHICH
PREDICTABILITY IS LOW. IN 3-4 DAYS...GLOBAL DYNAMICAL MODELS
CONTINUE TO SHOW AN INCREASE IN SOUTHERLY SHEAR...AND IGOR SHOULD
REACH MARGINAL SEA SURFACE TEMPERATURES TOWARD THE END OF THE
PERIOD. THE STATISTICAL-DYNAMICAL GUIDANCE RESPONDS TO THESE
FACTORS BY SHOWING A GRADUAL WEAKENING BEYOND 72 HOURS. THE
OFFICIAL NHC INTENSITY IS BASICALLY UNCHANGED...WITH THE FORECAST
STILL INDICATING SOME POTENTIAL FOR RE-INTENSIFICATION IN THE SHORT
TERM AFTER THE CURRENT EYEWALL REPLACEMENT CYCLE ENDS.
 
THERE HAS BEEN LITTLE CHANGE TO THE MOTION...AND THE LATEST ESTIMATE
IS 295/07. IGOR IS MOVING AROUND THE SOUTHWEST PERIPHERY OF THE
SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC AND IS GRADUALLY
ENTERING A PRONOUNCED WEAKNESS IN THE WESTERN ATLANTIC. THIS
SYNOPTIC PATTERN SHOULD STEER IGOR ON A NORTHWESTWARD AND THEN
NORTH-NORTHWESTWARD COURSE DURING THE NEXT 2-3 DAYS. DURING THIS
TIME...SEVERAL SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN THE
WESTERN ATLANTIC SHOULD HAVE LITTLE EFFECT ON IGOR. HOWEVER...
DYNAMICAL MODELS ARE IN GENERALLY GOOD AGREEMENT THAT A VIGOROUS
SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN STATES/CANADIAN
MARITIMES IN ABOUT 4-5 DAYS SHOULD BEGIN TO INDUCE RECURVATURE. THE
GFS/HWRF/GFDL HAVE BEEN INDICATING A MORE ROBUST SHORTWAVE FEATURE
AND A SHARPER RECURVATURE DURING THE PAST SEVERAL RUNS. ON THE
OTHER HAND...THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN HAVE
HAD A WEAKER AND MORE PROGRESSIVE SHORTWAVE THAT COULD DELAY
RECURVATURE AND ALLOW FOR A MORE WESTWARD TRACK. THE OFFICIAL NHC
TRACK FORECAST REMAINS ABOUT THE SAME AS BEFORE AND IS VERY NEAR THE
MULTI-MODEL CONSENSUS...CONTINUING TO SHOW IGOR PASSING CLOSE TO
BERMUDA IN ABOUT 4 DAYS.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 20.1N  55.6W   115 KT
 12HR VT     16/0600Z 20.6N  56.7W   110 KT
 24HR VT     16/1800Z 21.4N  58.2W   115 KT
 36HR VT     17/0600Z 22.4N  59.8W   120 KT
 48HR VT     17/1800Z 23.5N  61.5W   120 KT
 72HR VT     18/1800Z 26.5N  64.0W   105 KT
 96HR VT     19/1800Z 31.0N  65.0W    95 KT
120HR VT     20/1800Z 36.0N  61.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 160242
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST WED SEP 15 2010
 
BASED ON RECENT MICROWAVE DATA...IGOR APPEARS TO BE COMPLETING AN
EYEWALL REPLACEMENT.  IN ADDITION...INFRARED GEOSTATIONARY
SATELLITE IMAGERY SHOWS THE INNER CORE CONVECTION DIMINISHING WITH
AN OUTER RING OF CONVECTION BECOMING MORE PROMINENT.  DVORAK
ESTIMATES FROM TAFB REMAIN AT T6.0/6.5 AND HAVE FALLEN TO T5.0/5.5
FROM SAB...AND THE LATEST ADT ESTIMATE IS T6.3.  THE INITIAL
INTENSITY IS HELD AT 115 KT FOR THIS ADVISORY.  IGOR IS EXPECTED TO
REMAIN IN AN ENVIRONMENT OF LOW SHEAR FOR THE NEXT 60 HOURS OR
SO...AND LITTLE CHANGE IN INTENSITY IS EXPECTED DURING THAT TIME. 
FLUCTUATIONS IN INTENSITY ARE STILL POSSIBLE HOWEVER...ESPECIALLY
IF THE NEW OUTER EYEWALL CONTRACTS OVER THE NEXT COUPLE OF DAYS. 
BY DAYS 3 THROUGH 5...SOUTHERLY SHEAR IS EXPECTED TO INCREASE AND
SHOULD INDUCE SOME WEAKENING.  THE INTENSITY GUIDANCE IS IN FAIRLY
GOOD AGREEMENT DURING THAT TIME...AND THE OFFICIAL FORECAST WILL
SHOW WEAKENING TO CATEGORY 1 OR 2 STRENGTH BY DAYS 4 AND 5.

IGOR IS MOVING 295 DEGREES AT 8 KT.  THE HURRICANE IS LOCATED NEAR
THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE OVER THE CENTRAL
ATLANTIC AND IS BEING INCREASINGLY INFLUENCED BY A LARGE BUT FLAT
MID- TO UPPER-LEVEL TROUGH NEAR THE U.S. EAST COAST.  SINCE THE
TROUGH IS NOT THAT SHARP...IGOR IS EXPECTED TO MAINTAIN ITS CURRENT
MOTION FOR THE NEXT 36 HOURS OR SO.  IT SHOULD THEN BEGIN TO TURN
MORE SHARPLY ON DAYS 3 THROUGH 5...WITH ITS CENTER PASSING NEAR
BERMUDA IN ABOUT 96 HOURS.  THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
BUT DOES SHOW SOME SPEED DIFFERENCES BY DAY 5.  THE OFFICIAL
FORECAST IS JUST A LITTLE TO THE WEST OF THE MODEL CONSENSUS TVCN
SINCE THE USUALLY-RELIABLE ECMWF LIES ON THE WESTERN SIDE OF THE
GUIDANCE ENVELOPE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 20.2N  56.5W   115 KT
 12HR VT     16/1200Z 20.8N  57.6W   115 KT
 24HR VT     17/0000Z 21.7N  59.2W   115 KT
 36HR VT     17/1200Z 22.6N  60.8W   115 KT
 48HR VT     18/0000Z 24.0N  62.6W   115 KT
 72HR VT     19/0000Z 27.5N  65.0W   105 KT
 96HR VT     20/0000Z 31.5N  65.0W    95 KT
120HR VT     21/0000Z 36.5N  60.5W    80 KT
 
$$
FORECASTER BERG
 

WTNT41 KNHC 160855
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST THU SEP 16 2010
 
MICROWAVE AND INFRARED SATELLITE IMAGERY SUGGEST THAT THE EYEWALL
REPLACEMENT WITH IGOR IS COMPLETE.   THE NEW EYEWALL APPEARS TO BE
CONSOLIDATING AT A RADIUS OF ABOUT 30-35 N MI AND IS PRODUCING
RATHER DEEP CONVECTION...SUGGESTING THE INTENSITY IS INCREASING
AGAIN. A BLEND OF THE SATELLITE ESTIMATES GIVES AN INITIAL
INTENSITY OF 125 KT.
 
A LARGE-SCALE ENVIRONMENT OF LIGHT SHEAR AND WARM WATER IS FAVORABLE
FOR THE MAINTENANCE OF AN EXTREMELY DANGEROUS HURRICANE FOR THE
NEXT FEW DAYS. THE EXACT INTENSITY OF IGOR WILL BE PRIMARILY
DICTATED BY EYEWALL CYCLES...WHICH ARE WELL BEYOND OUR FORECAST
ABILITIES. THE MAJORITY OF THE MODEL GUIDANCE INDICATES THAT SLOW
WEAKENING IS THE MOST LIKELY SOLUTION...AND THE NHC FORECAST REFLECT
THIS. HOWEVER...IT IS MORE IMPORTANT TO RECOGNIZE THAT ALL OF THE
GUIDANCE...AND THE NHC FORECAST...KEEPS IGOR AS A LARGE AND
DANGEROUS HURRICANE FOR THE NEXT SEVERAL DAYS.
 
THE INITIAL MOTION IS AN UNSTEADY 300/6.  IGOR IS EXPECTED TO MOVE
SLOWLY AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE OVER THE
CENTRAL ATLANTIC.  WEAK TROUGHING ALONG ABOUT 70W SHOULD RECURVE
THE CYCLONE IN 3 OR 4 DAYS.  THE MAIN DIFFERENCE IN THE MODELS IS
HOW QUICKLY IGOR ACCELERATES TO THE NORTHEAST IN THE MID-LATITUDES. 
SINCE THE TROUGHING OVER THE WESTERN ATLANTIC IS RATHER FLAT...
THERE HAS BEEN A TREND IN THE MODELS TO SHOW WEAKER FLOW NEAR
IGOR...AND CONSEQUENTLY DELAY THE INCREASE IN FORWARD SPEED.  THE
OFFICIAL FORECAST IS A BIT SLOWER THAN THE PREVIOUS ONE...
ESPECIALLY AT THE END OF THE PERIOD.  WITH REGARDS TO HOW CLOSE
IGOR COMES TO BERMUDA...THE ECMWF IS NOW THE MOST EASTERN MODEL
AFTER BEING THE WESTERNMOST YESTERDAY.  THIS APPEARS TO BE DUE TO
THAT MODEL SHOWING A SLIGHTLY WEAKER RIDGE TODAY...WHICH ALLOWS
IGOR TO GAIN A LITTLE MORE LATITUDE EARLY ON AND EVENTUALLY PASS A
LITTLE FARTHER EAST OF BERMUDA.  HOWEVER...ALL OF THE GUIDANCE IS
WELL CLUSTERED ON A TRACK CLOSE TO THAT ISLAND...AND LITTLE CHANGE
HAS BEEN MADE TO THE OFFICIAL TRACK NEAR BERMUDA.  SINCE THIS IS
SUCH A LARGE HURRICANE...SIGNIFICANT IMPACTS ARE EXPECTED ON
BERMUDA...BUT IT IS TOO EARLY TO TELL HOW CLOSE THE CORE OF THE
HURRICANE...AND THE STRONGEST WINDS...WILL COME TO THAT ISLAND. 
 
SO FAR...NOAA BUOY 41044 HAS REPORTED A PEAK 1-MINUTE WIND OF 45
KT...GUSTING TO 56 KT...ALONG WITH A MINIMUM PRESSURE OF 995
MB...AND A SIGNIFICANT WAVE HEIGHT OF 29 FT.  HOWEVER...THE WORST
IS YET TO COME FOR THAT STATION...AS IGOR WILL MOVE VERY CLOSE TO
THE BUOY TONIGHT. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0900Z 20.5N  56.8W   125 KT
 12HR VT     16/1800Z 21.1N  57.8W   125 KT
 24HR VT     17/0600Z 22.0N  59.4W   125 KT
 36HR VT     17/1800Z 23.2N  61.1W   120 KT
 48HR VT     18/0600Z 24.7N  62.7W   120 KT
 72HR VT     19/0600Z 28.0N  65.0W   110 KT
 96HR VT     20/0600Z 32.5N  64.5W    95 KT
120HR VT     21/0600Z 37.5N  59.0W    80 KT
 
$$
FORECASTER BLAKE
 

WTNT41 KNHC 161444
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 16 2010
 
IGOR IS MAINTAINING VERY DEEP CONVECTION AND A 30-35 NMI WIDE EYE
WITHIN A CENTRAL DENSE OVERCAST...BUT THE OVERALL CONVECTIVE
PATTERN HAS BECOME MORE ASYMMETRIC. THE RESTRICTED NATURE OF THE
OUTFLOW TO THE WEST OF THE CYCLONE SUGGESTS SOME UPPER-LEVEL
WESTERLY FLOW IMPINGING ON THE CIRCULATION...WHICH MAY ALSO BE
CONTRIBUTING TO THE RAGGED APPEARANCE OF THE CDO. SUBJECTIVE DVORAK
T-NUMBERS ARE A CONSENSUS 6.0 AT 1200 UTC AND SERVE AS THE BASIS
FOR LOWERING THE INTENSITY TO 115 KT FOR THIS ADVISORY. AN AIR
FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IGOR IN A FEW HOURS AND WILL PROVIDE A MORE ACCURATE
ASSESSMENT OF ITS INTENSITY.
 
WATER VAPOR IMAGERY SUGGESTS THAT THE COMBINATION OF A SHEAR AXIS
NORTHWEST OF IGOR AND THE SOUTHWESTWARD DISPLACEMENT OF THE
UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH IGOR MAY BE IMPARTING WEAK
TO MODERATE WESTERLY SHEAR TO THE HURRICANE. SHIPS MODEL OUTPUT
INDICATES THAT THIS SHEAR MAY PERSIST FOR NEXT 12-24 HOURS AND THEN
DECREASE...ALLOWING FOR SOME INTENSIFICATION BEFORE ABOUT 48 HOURS.
ALTHOUGH INNER CORE DYNAMICS WILL LIKELY INDUCE SOME DIFFICULT TO
PREDICT FLUCTUATIONS IN INTENSITY...IGOR IS EXPECTED TO REMAIN A
LARGE AND FORMIDABLE HURRICANE FOR THE NEXT 3 TO 4 DAYS. AFTER
THAT...INCREASING SOUTHWESTERLY SHEAR AND GRADUALLY COOLER WATERS
SHOULD LEAD TO WEAKENING OF THE CYCLONE...WITH THE WEAKENING
POSSIBLY GREATER THAN INDICATED IF THE 30 TO 45 KT OF SHEAR
PREDICTED BY THE GFS VERIFIES. THE GUIDANCE ALSO INDICATES THAT
EXTRATROPICAL TRANSITION WILL BE UNDERWAY BY DAY 5. THE OFFICIAL
FORECAST IS SLIGHTLY HIGHER THAN SOME OF THE STATISTICAL-DYNAMICAL
GUIDANCE BUT SIMILAR TO THE PREVIOUS INTENSITY FORECAST.
 
IGOR HAS BEEN WOBBLING ABOUT AN INITIAL MOTION OF 305/06. LITTLE HAS
CHANGED REGARDING THE OVERALL TRACK PHILOSOPHY. THE HURRICANE IS
EXPECTED TO MOVE NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE DURING THE NEXT 72 HOURS. BEYOND 72 HOURS...IGOR
SHOULD BECOME EMBEDDED WITHIN THE MID-LATITUDE WEST-SOUTHWESTERLY
FLOW AHEAD OF A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE
NORTHEASTERN U.S. AND THE CANADIAN MARITIMES...AND TURN NORTH AND
THEN NORTHEAST WITH INCREASING FORWARD SPEED. THE SPREAD IN THE
MODEL GUIDANCE HAS DECREASED SINCE YESTERDAY...WITH THE LATEST
SOLUTIONS TRENDING SLIGHTLY LEFTWARD AND TIGHTLY CLUSTERED AROUND
THE OFFICIAL FORECAST.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 21.0N  57.2W   120 KT
 12HR VT     17/0000Z 21.5N  58.3W   115 KT
 24HR VT     17/1200Z 22.4N  60.0W   120 KT
 36HR VT     18/0000Z 23.8N  61.7W   120 KT
 48HR VT     18/1200Z 25.3N  63.2W   120 KT
 72HR VT     19/1200Z 29.0N  65.0W   105 KT
 96HR VT     20/1200Z 33.5N  63.5W    95 KT
120HR VT     21/1200Z 39.0N  56.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 161508
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  34...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 16 2010

CORRECT INITIAL INTENSITY FROM 115 KT TO 120 KT
 
IGOR IS MAINTAINING VERY DEEP CONVECTION AND A 30-35 NMI WIDE EYE
WITHIN A CENTRAL DENSE OVERCAST...BUT THE OVERALL CONVECTIVE
PATTERN HAS BECOME MORE ASYMMETRIC. THE RESTRICTED NATURE OF THE
OUTFLOW TO THE WEST OF THE CYCLONE SUGGESTS SOME UPPER-LEVEL
WESTERLY FLOW IMPINGING ON THE CIRCULATION...WHICH MAY ALSO BE
CONTRIBUTING TO THE RAGGED APPEARANCE OF THE CDO. SUBJECTIVE DVORAK
T-NUMBERS ARE A CONSENSUS 6.0 AT 1200 UTC AND SERVE AS THE BASIS
FOR LOWERING THE INTENSITY TO 120 KT FOR THIS ADVISORY. AN AIR
FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IGOR IN A FEW HOURS AND WILL PROVIDE A MORE ACCURATE
ASSESSMENT OF ITS INTENSITY.
 
WATER VAPOR IMAGERY SUGGESTS THAT THE COMBINATION OF A SHEAR AXIS
NORTHWEST OF IGOR AND THE SOUTHWESTWARD DISPLACEMENT OF THE
UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH IGOR MAY BE IMPARTING WEAK
TO MODERATE WESTERLY SHEAR TO THE HURRICANE. SHIPS MODEL OUTPUT
INDICATES THAT THIS SHEAR MAY PERSIST FOR NEXT 12-24 HOURS AND THEN
DECREASE...ALLOWING FOR SOME INTENSIFICATION BEFORE ABOUT 48 HOURS.
ALTHOUGH INNER CORE DYNAMICS WILL LIKELY INDUCE SOME DIFFICULT TO
PREDICT FLUCTUATIONS IN INTENSITY...IGOR IS EXPECTED TO REMAIN A
LARGE AND FORMIDABLE HURRICANE FOR THE NEXT 3 TO 4 DAYS. AFTER
THAT...INCREASING SOUTHWESTERLY SHEAR AND GRADUALLY COOLER WATERS
SHOULD LEAD TO WEAKENING OF THE CYCLONE...WITH THE WEAKENING
POSSIBLY GREATER THAN INDICATED IF THE 30 TO 45 KT OF SHEAR
PREDICTED BY THE GFS VERIFIES. THE GUIDANCE ALSO INDICATES THAT
EXTRATROPICAL TRANSITION WILL BE UNDERWAY BY DAY 5. THE OFFICIAL
FORECAST IS SLIGHTLY HIGHER THAN SOME OF THE STATISTICAL-DYNAMICAL
GUIDANCE BUT SIMILAR TO THE PREVIOUS INTENSITY FORECAST.
 
IGOR HAS BEEN WOBBLING ABOUT AN INITIAL MOTION OF 305/06. LITTLE HAS
CHANGED REGARDING THE OVERALL TRACK PHILOSOPHY. THE HURRICANE IS
EXPECTED TO MOVE NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE DURING THE NEXT 72 HOURS. BEYOND 72 HOURS...IGOR
SHOULD BECOME EMBEDDED WITHIN THE MID-LATITUDE WEST-SOUTHWESTERLY
FLOW AHEAD OF A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE
NORTHEASTERN U.S. AND THE CANADIAN MARITIMES...AND TURN NORTH AND
THEN NORTHEAST WITH INCREASING FORWARD SPEED. THE SPREAD IN THE
MODEL GUIDANCE HAS DECREASED SINCE YESTERDAY...WITH THE LATEST
SOLUTIONS TRENDING SLIGHTLY LEFTWARD AND TIGHTLY CLUSTERED AROUND
THE OFFICIAL FORECAST.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 21.0N  57.2W   120 KT
 12HR VT     17/0000Z 21.5N  58.3W   115 KT
 24HR VT     17/1200Z 22.4N  60.0W   120 KT
 36HR VT     18/0000Z 23.8N  61.7W   120 KT
 48HR VT     18/1200Z 25.3N  63.2W   120 KT
 72HR VT     19/1200Z 29.0N  65.0W   105 KT
 96HR VT     20/1200Z 33.5N  63.5W    95 KT
120HR VT     21/1200Z 39.0N  56.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 162041
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST THU SEP 16 2010
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REACHED THE CENTER OF
IGOR AROUND 1600 UTC. THE HURRICANE HUNTERS MEASURED A MINIMUM
PRESSURE OF 940 MB AND MAXIMUM FLIGHT-LEVEL AND SFMR WINDS OF 130
AND 98 KT...RESPECTIVELY. SINCE THAT TIME..THE CLOUD PATTERN
ASSOCIATED WITH IGOR HAS CHANGED LITTLE IN ORGANIZATION...AND
DVORAK T-NUMBERS REMAIN AT 5.5 FROM SAB AND TAFB. BASED UPON THE
AIRCRAFT DATA AND THE LOWER SATELLITE INTENSITY ESTIMATES...THE
INITIAL INTENSITY IS REDUCED TO 110 KT. THE EXTENSION OF AN
UPPER-LEVEL TROUGH PASSING NORTH OF IGOR IS STILL PRODUCING ABOUT
15 KT OF WESTERLY SHEAR OVER THE CYCLONE...ACCORDING TO THE LATEST
UW-CIMSS ANALYSES. THE SHIPS MODEL OUTPUT SHOWS A REDUCTION IN THE
SHEAR WITHIN THE NEXT 12 HOURS AS THIS FEATURE MOVES AWAY...WHICH
COULD ALLOW AN OPPORTUNITY FOR SOME RE-INTENSIFICATION IN THE
SHORT-TERM. THE GUIDANCE INDICATES THAT IGOR WILL BE MOVING INTO AN
ENVIRONMENT OF GRADUALLY INCREASING SOUTHERLY TO SOUTH-
SOUTHWESTERLY SHEAR IN ABOUT TWO DAYS...AND OVER COOLER WATERS BY
THE END OF THE FORECAST PERIOD. THE COMBINATION OF THESE TWO
FACTORS SHOULD RESULT IN A SLOW WEAKENING BEYOND 48 HOURS...AND THE
NHC OFFICIAL FORECAST REFLECTS THIS. BY DAY 5...GLOBAL MODELS
INDICATE THAT IGOR WILL BE AT LEAST BEGINNING TO UNDERGO
EXTRATROPICAL TRANSITION.
 
IGOR CONTINUES TO MAINTAIN ABOUT THE SAME MOTION...310/7. THE
REASONING FOR THE TRACK FORECAST IS UNCHANGED. THE HURRICANE IS
FORECAST TO MOVE NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD WITH
SOME INCREASE IN FORWARD SPEED AROUND THE WESTERN EXTENT OF A
SUBTROPICAL RIDGE DURING THE NEXT 48-72 HOURS. BEYOND 72 HOURS...
IGOR SHOULD BEGIN ACCELERATING WHILE TURNING NORTH AND THEN
NORTHEAST AHEAD OF AN APPROACHING MID-LATITUDE SHORTWAVE TROUGH
MOVING THROUGH THE NORTHEAST U.S. AND CANADIAN MARITIMES. THE
LATEST MODEL GUIDANCE HAS SHIFTED TO THE LEFT THIS CYCLE APPARENTLY
DUE TO TIMING DIFFERENCES ASSOCIATED WITH THE AFORMENTIONED
SHORTWAVE TROUGH.  THE OFFICIAL NHC TRACK FORECAST HAS BEEN NUDGED
WESTWARD...FOLLOWING THE MULTI-MODEL CONSENSUS...AND LIES IN THE
MIDDLE OF THE GUIDANCE ENVELOPE.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/2100Z 21.7N  58.1W   110 KT
 12HR VT     17/0600Z 22.4N  59.2W   110 KT
 24HR VT     17/1800Z 23.5N  61.0W   115 KT
 36HR VT     18/0600Z 24.9N  62.7W   115 KT
 48HR VT     18/1800Z 26.5N  64.0W   110 KT
 72HR VT     19/1800Z 30.5N  65.5W   100 KT
 96HR VT     20/1800Z 35.5N  62.5W    90 KT
120HR VT     21/1800Z 42.0N  53.0W    70 KT
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 170259
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  36
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST THU SEP 16 2010
 
THE CLOUD PATTERN OF IGOR HAS CHANGED LITTLE THIS EVENING.  DVORAK
CURRENT INTENSITY NUMBERS FROM SAB AND TAFB ARE 5.5 AND 6.0...
RESPECTIVELY.  THIS SUPPORTS MAINTAINING AN INITIAL INTENSITY OF
110 KT.  THE EYE OF IGOR IS PASSING VERY NEAR NOAA BUOY 41044.
THROUGH 0200 UTC...THE 5-METER HIGH ANEMOMETER ON THE BUOY HAS
REPORTED PEAK 1-MINUTE SUSTAINED WINDS OF 69 KT WITH A GUST TO 91
KT.  A MINIMUM PRESSURE OF 940.3 MB WAS RECORDED AT 0050 UTC WITH
WINDS AROUND 60 KT.  THIS SUGGESTS THAT THE MINIMUM PRESSURE IS
AROUND 935 MB.  DUE TO THE LARGE SIZE AND RELATIVELY SLOW MOTION OF
THE HURRICANE...THE BUOY HAS NOW REPORTED TROPICAL STORM FORCE
WINDS FOR 21 CONSECUTIVE HOURS.
 
IGOR IS EXPECTED TO REMAIN OVER WARM WATER AND IN A FAVORABLE
UPPER-LEVEL ENVIRONMENT WITH SHEAR LESS THAN 15 KT DURING THE NEXT
DAY OR TWO.  SOME RE-STRENGTHENING IS POSSIBLE DURING THIS
TIME...AND THE SHORT-TERM INTENSITY WILL LIKELY BE DICTATED BY
EYEWALL CYCLES THAT ARE DIFFICULT TO PREDICT.  AFTER 48 HOURS...
SOUTHWESTERLY SHEAR IS FORECAST TO GRADUALLY INCREASE AND IGOR
WILL BE MOVING OVER COOLER SSTS IN 4-5 DAYS.  THIS WILL RESULT IN
GRADUAL WEAKENING...HOWEVER IGOR IS EXPECTED TO REMAIN A LARGE AND
POWERFUL HURRICANE FOR SEVERAL MORE DAYS. BY THE END OF THE
FORECAST PERIOD IGOR WILL BE UNDERGOING EXTRATROPICAL TRANSITION.
 
IGOR HAS BEEN MOVING NORTHWESTWARD OR 310 DEGREES AT 7 KT.  THE
HURRICANE IS FORECAST TO MOVE AROUND THE WESTERN PORTION OF THE
SUBTROPICAL RIDGE DURING THE NEXT 2-3 DAYS. THEREAFTER...IGOR
WILL ACCELERATE AND TURN NORTHEASTWARD AHEAD OF A MID-LATITUDE
TROUGH THAT IS FORECAST TO MOVE THROUGH THE NORTHEAST UNITED
STATES IN A FEW DAYS.  THE TRACK GUIDANCE HAS CHANGED LITTLE AND
NEITHER HAS THE OFFICIAL FORECAST...WHICH LIES NEAR THE MULTI-MODEL
CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0300Z 22.0N  58.7W   110 KT
 12HR VT     17/1200Z 23.0N  60.0W   115 KT
 24HR VT     18/0000Z 24.2N  61.7W   115 KT
 36HR VT     18/1200Z 25.7N  63.3W   115 KT
 48HR VT     19/0000Z 27.3N  64.4W   110 KT
 72HR VT     20/0000Z 31.7N  65.1W   100 KT
 96HR VT     21/0000Z 37.5N  60.0W    85 KT
120HR VT     22/0000Z 45.5N  47.0W    70 KT
 
$$
FORECASTER BROWN
 

WTNT41 KNHC 170833
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  37
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST FRI SEP 17 2010
 
THE CLOUD PATTERN OF IGOR HAS BECOME A LITTLE LESS ORGANIZED
OVERNIGHT WITH WEAKER EYEWALL CONVECTION NOTED.   SATELLITE
CLASSIFICATIONS RANGE FROM 102 KT FROM TAFB AND SAB...TO UW-CIMSS
ADT NUMBERS NEAR 125 KT.  A BLEND OF THESE DATA SUGGEST THAT
KEEPING THE INITIAL INTENSITY AT 110 KT IS REASONABLE.  DATA FROM
NOAA BUOY 41044 SUGGESTED THAT THE PRESSURE WAS SEVERAL MB LOWER
THAN THE LAST AIRCRAFT FIX FROM THIS AFTERNOON...WHEN THE INTENSITY
WAS ALSO NEAR 110 KT.  
 
IGOR IS LIKELY TO REMAIN A MAJOR HURRICANE FOR THE NEXT TWO TO THREE
DAYS WHILE IT STAYS IN A WARM WATER AND MOSTLY LIGHT SHEAR
ENVIRONMENT.  THEREAFTER...WATERS GRADUALLY COOL...WHILE
SOUTHWESTERLY SHEAR IS FORECAST TO INCREASE.  MODEL GUIDANCE IS IN
RELATIVELY GOOD AGREEMENT ON THIS SCENARIO...AND THE NHC FORECAST
IS CLOSE TO THE PREVIOUS ONE.  REGARDLESS OF THE EXACT INTENSITY...
IGOR IS EXPECTED TO BE A VERY LARGE AND DANGEROUS HURRICANE WHEN IT
PASSES CLOSE TO BERMUDA.  IN THE LONG RANGE... EXTRATROPICAL
TRANSITION SHOULD BE COMPLETED AROUND 120 HOURS...AND GLOBAL MODELS
ARE SHOWING A RATHER INTENSE CYCLONE AT THAT TIME.
 
THE INITIAL MOTION HAS SHIFTED A LITTLE TO THE LEFT OR 305 DEGREES
AT 8 KT.  THE SYNOPTIC STEERING HAS BEEN RELATIVELY WELL DEFINED
FOR THE LAST SEVERAL DAYS AS IGOR TRAVELS AROUND THE SOUTHWESTERN
PERIPHERY OF A SUBTROPICAL RIDGE.  A TURN TO THE NORTH SHOULD OCCUR
IN ABOUT TWO DAYS...WITH ALMOST ALL OF THE MODEL GUIDANCE VERY
CLOSE TO BERMUDA IN ABOUT 3 DAYS TIME. THE NEW NHC FORECAST IS
BASICALLY AN UPDATE OF THE PREVIOUS ONE FOR THE FIRST FEW DAYS. 
AFTER PASSING BERMUDA...IGOR SHOULD ACCELERATE AS IT BEGINS TO GET
CAUGHT UP INTO THE MID-LATITUDE SOUTHWESTERLIES.  MOST OF THE
GUIDANCE IS A LITTLE FASTER IN THE LONG RANGE...AND THE OFFICIAL
FORECAST GOES ALONG WITH THAT IDEA.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 22.4N  59.4W   110 KT
 12HR VT     17/1800Z 23.2N  60.8W   110 KT
 24HR VT     18/0600Z 24.5N  62.5W   110 KT
 36HR VT     18/1800Z 26.1N  64.0W   105 KT
 48HR VT     19/0600Z 27.8N  64.9W   105 KT
 72HR VT     20/0600Z 32.5N  64.5W    95 KT
 96HR VT     21/0600Z 40.0N  56.0W    80 KT
120HR VT     22/0600Z 50.0N  45.0W    70 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BLAKE/BRENNAN
 

WTNT41 KNHC 171440
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  38
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST FRI SEP 17 2010
 
THE OVERALL CLOUD PATTERN OF IGOR HAS CHANGED LITTLE IN ORGANIZATION
OVER THE PAST SEVERAL HOURS...ALTHOUGH DVORAK CI NUMBERS HAVE
DECREASED TO 5.0 AND 5.5 FROM SAB AND TAFB...RESPECTIVELY.  BASED
UPON THESE DATA...THE INITIAL WIND SPEED IS LOWERED TO 105 KT. AN
0915 UTC SSMIS OVERPASS SHOWED THE EXISTENCE OF A NEW OUTER WIND
MAXIMUM AT ABOUT 90 NMI RADIUS...WITH AN INNER EYEWALL PARTIALLY
BROKEN TO THE WEST.  INNER CORE DYNAMICS ASIDE...THERE IS STILL AN 
OPPORTUNITY FOR RE-INTENSIFICATION DURING THE NEXT DAY OR TWO WHILE
IGOR IS LOCATED IN A LIGHT SHEAR ENVIRONMENT AND MOVING OVER WARM
WATERS.  GLOBAL MODELS FORECAST A GRADUAL INCREASE IN SOUTHERLY TO
SOUTHWESTERLY SHEAR OVER THE CYCLONE AFTER ABOUT 48 HOURS AND
WATERS GRADUALLY BECOME COOLER AFTER THAT.  BOTH OF THESE FACTORS
SUGGEST A SLOW WEAKENING OF IGOR BEGINNING AFTER ABOUT TWO
DAYS...AND THE OFFICIAL NHC FORECAST IS ABOUT THE SAME AS BEFORE.
THE GUIDANCE SUGGESTS THAT EXTRATROPICAL TRANSITION SHOULD BE
COMPLETED BETWEEN 96 AND 120 HOURS.
 
IGOR IS MAINTAINING A FAIRLY STEADY MOTION OF 305/08.  THE STEERING
FLOW AROUND THE SOUTHWEST SIDE OF A SUBTROPICAL RIDGE SHOULD GUIDE
IGOR ON A NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD COURSE DURING
THE NEXT COUPLE OF DAYS.  AFTER THAT...THE APPROACH OF A VIGOROUS
SHORTWAVE TROUGH OVER THE NORTHEASTERN U.S. SHOULD GRADUALLY TURN
THE HURRICANE NORTHWARD AND THEN NORTHEASTWARD WITH A SUBSTANTIAL
INCREASE IN FORWARD SPEED.  THE OFFICIAL NHC TRACK FORECAST IS CLOSE
TO THE PREVIOUS ONE...EXCEPT FOR BEING SOMEWHAT SLOWER AT
96 AND 120 HOURS IN LINE WITH THE LATEST GUIDANCE.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 23.1N  60.1W   105 KT
 12HR VT     18/0000Z 24.0N  61.5W   105 KT
 24HR VT     18/1200Z 25.4N  63.2W   105 KT
 36HR VT     19/0000Z 27.0N  64.5W   100 KT
 48HR VT     19/1200Z 28.8N  65.1W   100 KT
 72HR VT     20/1200Z 34.0N  63.5W    90 KT
 96HR VT     21/1200Z 41.0N  55.0W    75 KT...POST-TROP/EXTRATROP
120HR VT     22/1200Z 51.0N  44.5W    60 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 171512
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  38...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST FRI SEP 17 2010

CORRECT SAB SATELLITE CLASSIFICATION
 
THE OVERALL CLOUD PATTERN OF IGOR HAS CHANGED LITTLE IN ORGANIZATION
OVER THE PAST SEVERAL HOURS...ALTHOUGH DVORAK CI NUMBERS HAVE
DECREASED TO 5.5 FROM SAB AND TAFB...RESPECTIVELY.  BASED UPON THESE
DATA...THE INITIAL WIND SPEED IS LOWERED TO 105 KT. AN 0915 UTC
SSMIS OVERPASS SHOWED THE EXISTENCE OF A NEW OUTER WIND MAXIMUM AT
ABOUT 90 NMI RADIUS...WITH AN INNER EYEWALL PARTIALLY BROKEN TO THE
WEST.  INNER CORE DYNAMICS ASIDE...THERE IS STILL AN  OPPORTUNITY
FOR RE-INTENSIFICATION DURING THE NEXT DAY OR TWO WHILE IGOR IS
LOCATED IN A LIGHT SHEAR ENVIRONMENT AND MOVING OVER WARM WATERS. 
GLOBAL MODELS FORECAST A GRADUAL INCREASE IN SOUTHERLY TO
SOUTHWESTERLY SHEAR OVER THE CYCLONE AFTER ABOUT 48 HOURS AND
WATERS GRADUALLY BECOME COOLER AFTER THAT.  BOTH OF THESE FACTORS
SUGGEST A SLOW WEAKENING OF IGOR BEGINNING AFTER ABOUT TWO
DAYS...AND THE OFFICIAL NHC FORECAST IS ABOUT THE SAME AS BEFORE.
THE GUIDANCE SUGGESTS THAT EXTRATROPICAL TRANSITION SHOULD BE
COMPLETED BETWEEN 96 AND 120 HOURS.
 
IGOR IS MAINTAINING A FAIRLY STEADY MOTION OF 305/08.  THE STEERING
FLOW AROUND THE SOUTHWEST SIDE OF A SUBTROPICAL RIDGE SHOULD GUIDE
IGOR ON A NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD COURSE DURING
THE NEXT COUPLE OF DAYS.  AFTER THAT...THE APPROACH OF A VIGOROUS
SHORTWAVE TROUGH OVER THE NORTHEASTERN U.S. SHOULD GRADUALLY TURN
THE HURRICANE NORTHWARD AND THEN NORTHEASTWARD WITH A SUBSTANTIAL
INCREASE IN FORWARD SPEED.  THE OFFICIAL NHC TRACK FORECAST IS CLOSE
TO THE PREVIOUS ONE...EXCEPT FOR BEING SOMEWHAT SLOWER AT
96 AND 120 HOURS IN LINE WITH THE LATEST GUIDANCE.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 23.1N  60.1W   105 KT
 12HR VT     18/0000Z 24.0N  61.5W   105 KT
 24HR VT     18/1200Z 25.4N  63.2W   105 KT
 36HR VT     19/0000Z 27.0N  64.5W   100 KT
 48HR VT     19/1200Z 28.8N  65.1W   100 KT
 72HR VT     20/1200Z 34.0N  63.5W    90 KT
 96HR VT     21/1200Z 41.0N  55.0W    75 KT...POST-TROP/EXTRATROP
120HR VT     22/1200Z 51.0N  44.5W    60 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 172040
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST FRI SEP 17 2010
  
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING IGOR
EARLY THIS AFTERNOON MEASURED A MINIMUM PRESSURE OF 946 MB. THE
HURRICANE HUNTER ALSO MEASURED MAXIMUM FLIGHT-LEVEL AND SFMR WINDS
OF 102 AND 79 KT...RESPECTIVELY. THE INITIAL INTENSITY IS LOWERED
TO 90 KT BASED UPON THE AIRCRAFT OBSERVATIONS. DATA FROM THE PLANE
ALSO INDICATED A RATHER BROAD WIND FIELD...WITH THE PRESENCE OF A
DOUBLE WIND MAXIMA. SINCE THE PLANE DEPARTED...THE CLOUD PATTERN OF
IGOR HAS INCREASED IN ORGANIZATION...WITH COLDER CLOUD TOPS
DEVELOPING WITHIN THE INNER CORE AND THE EYE BECOMING VISIBLE
AGAIN. INNER CORE DYNAMICS NOTWITHSTANDING...THERE APPEARS TO BE A
FINAL WINDOW OF OPPORTUNITY FOR RE-INTENSIFICATION DURING THE NEXT
DAY OR SO AS IGOR REMAINS IN A LIGHT SHEAR ENVIRONMENT AND MOVES
OVER WARM WATERS. AFTER ABOUT 36 HOURS...A GRADUAL INCREASE IN
SOUTHERLY AND SOUTHWESTERLY SHEAR AND COOLER WATERS ALONG THE
FORECAST TRACK SHOULD PROMOTE A WEAKENING OF IGOR. THE OFFICIAL
INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD A BIT IN THE SHORT
TERM BASED UPON CURRENT TRENDS BUT IS NEARLY THE SAME LATER IN THE
PERIOD. IN AGREEMENT WITH THE GUIDANCE...IGOR IS FORECAST TO BECOME
A LARGE AND STRONG EXTRATROPICAL CYCLONE OVER THE FAR NORTH
ATLANTIC BEYOND 96 HOURS.
 
IGOR APPEARS TO BE ON TRACK...AND THE INITIAL MOTION ESTIMATE IS
305/09.  THE TRACK FORECAST PHILOSOPHY HAS NOT CHANGED.  IGOR
SHOULD BE STEERED NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD AROUND
THE WESTERN SIDE OF A SUBTROPICAL RIDGE DURING THE NEXT 36 HOURS.
AFTER THAT...A VIGOROUS SHORTWAVE TROUGH MOVING ACROSS THE
NORTHEASTERN U.S. SHOULD GRADUALLY TURN THE HURRICANE NORTHWARD IN
THE VICINITY OF BERMUDA...AND THEN NORTHEASTWARD WITH A SUBSTANTIAL
INCREASE IN FORWARD SPEED.  THE OFFICIAL NHC TRACK FORECAST IS VERY
CLOSE TO THE PREVIOUS ONE AND REMAINS CLOSE TO THE MULTI-MODEL
CONSENSUS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.

THE WIND RADII HAVE BEEN EXPANDED BASED UPON DATA FROM THE
RECONNAISSANCE AIRCRAFT AND AN EARLIER ASCAT OVERPASS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 23.7N  61.1W    90 KT
 12HR VT     18/0600Z 24.8N  62.4W    95 KT
 24HR VT     18/1800Z 26.2N  64.0W   100 KT
 36HR VT     19/0600Z 27.9N  64.9W    95 KT
 48HR VT     19/1800Z 30.0N  65.1W    90 KT
 72HR VT     20/1800Z 35.5N  62.0W    85 KT
 96HR VT     21/1800Z 43.5N  52.5W    75 KT...POST-TROP/EXTRATROP
120HR VT     22/1800Z 52.0N  44.0W    65 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT41 KNHC 180301
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  40
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST FRI SEP 17 2010
 
INFRARED SATELLITE IMAGERY INDICATES IGOR HAS BECOME BETTER
ORGANIZED WITH A RING OF CONVECTIVE CLOUD TOPS OF -70C AND COLDER
ENCIRCLING A 20-25 NMI DIAMETER EYE THAT HAS BECOME MORE DISTINCT
DURING THE PAST COUPLE OF HOURS. A 17/2026Z AMSU OVERPASS ALSO
INDICATED THE UPPER-LEVEL WARM CORE HAS STRENGTHENED AND MOVED
UPWARD FROM 300 MB TO THE 200 MB...SUGGESTING THAT IGOR IS LIKELY
STRENGTHENING. AN AIR FORCE RESERVE RECON AIRCRAFT WILL BE
INVESTIGATING IGOR AROUND 06Z AND PROVIDE A BETTER INTENSITY
ESTIMATE.
 
THE INITIAL MOTION ESTIMATE IS 315/11. IGOR HAS MADE A TROCHOIDAL
WOBBLE TO THE RIGHT OF THE PREVIOUS FORECAST TRACK...BUT THIS IS
LIKELY JUST A TEMPORARY MOTION. IGOR IS EXPECTED TO MOVE BACK ON OR
CLOSE TO THE PREVIOUS ADVISORY TRACK BASED ON 00Z UPPER-AIR DATA
FROM BERMUDA SHOWING 24-HOUR MID-LEVEL HEIGHTS HAVE INCREASED BY 20
METERS AND WINDS HAVE SHIFTED AROUND TO AN EASTERLY DIRECTION...
WHICH INDICATES THE SUBTROPICAL RIDGE HAS BUILT WESTWARD TO THE
NORTH OF BERMUDA. UNFORTUNATELY...THIS RIDGING PATTERN WILL BE
SHORT-LIVED DUE TO A STRONG SHORTWAVE TROUGH CURRENTLY LOCATED JUST
OFF THE U.S. EAST COAST FORECAST BY ALL THE GLOBAL AND REGIONAL
MODELS TO CONTINUE TO MOVE EASTWARD AND CREATE A WEAKNESS IN THE
RIDGE BETWEEN 60W-70W LONGITUDE BY 24 HOURS. THIS WILL ALLOW IGOR
TO GRADUALLY MOVE NORTHWARD THROUGH THIS BREAK IN THE SUBTROPICAL
RIDGE PATTERN AND PASS VERY CLOSE TO BERMUDA IN ABOUT 48 HOURS. BY
72 HOURS...IGOR IS FORECAST TO BE CAPTURED BY A SECOND SHORTWAVE
TROUGH AND BE ACCELERATED OVER THE FAR NORTH ATLANTIC AS A POWERFUL
EXTRATROPICAL LOW PRESSURE SYSTEM. THE OFFICIAL FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE MODEL CONSENSUS.
 
IGOR IS EXHIBITING AN IMPRESSIVE OUTFLOW PATTERN THAT CONTINUES TO
EXPAND IN ALL QUADRANTS. THE HURRICANE IS EXPECTED TO MAINTAIN THIS
FAVORABLE OUTFLOW REGIME FOR THE NEXT 36-48 HOURS.  AFTERWARDS...
INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW AHEAD OF A MID- TO
UPPER-LEVEL TROUGH WILL INCREASE THE SHEAR ACROSS THE CYCLONE...
WHICH COUPLED WITH DECREASING SSTS...SHOULD INDUCE WEAKENING. BY 96
HOURS...IGOR IS FORECAST TO TRANSITION INTO A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE OVER THE FAR NORTH ATLANTIC WHEN IGOR MERGES
WITH A FRONTAL SYSTEM. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
TO THE SHIPS INTENSITY MODEL.

THE EXTRATROPICAL FORECAST TRACK AND INTENSITIES AT 96 AND 120 HOURS
IS BASED ON GUIDANCE FROM THE NOAA OCEAN PREDICTION CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 24.6N  62.0W    95 KT
 12HR VT     18/1200Z 25.6N  63.2W   100 KT
 24HR VT     19/0000Z 27.1N  64.4W   105 KT
 36HR VT     19/1200Z 29.1N  65.0W   105 KT
 48HR VT     20/0000Z 31.7N  64.5W   100 KT
 72HR VT     21/0000Z 36.2N  61.2W    85 KT
 96HR VT     22/0000Z 45.0N  50.0W    65 KT...POST-TROP/EXTRATROP
120HR VT     23/0000Z 52.5N  42.0W    65 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT41 KNHC 140834
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST TUE SEP 14 2010

ENHANCED INFRARED SATELLITE IMAGES SHOW THAT THE CLOUD TOPS
SURROUNDING THE EYE OF THE HURRICANE HAVE WARMED A LITTLE...AND
DVORAK DATA T-NUMBERS FROM BOTH TAFB AND SAB HAVE DECREASED.  THE
ADVISORY INTENSITY IS SET AT 115 KT WHICH IS A BLEND OF THE DVORAK
CURRENT INTENSITY AND T-NUMBERS.  THIS IS ALSO CLOSE TO THE LATEST
OBJECTIVE DVORAK INTENSITY ESTIMATES FROM UW-CIMSS.  AS STATED
EARLIER...FLUCTUATIONS IN STRENGTH DUE TO INNER CORE EVOLUTION ARE
PROBABLE OVER THE NEXT COUPLE OF DAYS.  HOWEVER...THE LARGE-SCALE
ATMOSPHERIC AND OCEANIC ENVIRONMENT IS LIKELY TO REMAIN QUITE
CONDUCIVE FOR THE MAINTENANCE OF A MAJOR HURRICANE FOR THE NEXT 48
TO 72 HOURS.  THEREFORE AT LEAST SLIGHT RESTRENGTHENING IS A
DISTINCT POSSIBILITY.  THE OFFICIAL FORECAST IS CONSISTENT WITH
THIS REASONING AND IS CLOSE TO THE LATEST INTENSITY MODEL CONSENSUS
THROUGH DAY 3 AND IS QUITE SIMILAR TO THE STATISTICAL-DYNAMICAL
LGEM MODEL AT DAYS 4 AND 5.

SATELLITE FIXES OF THE WELL-DEFINED EYE OF IGOR INDICATE THAT THE
MUCH-AWAITED TURN TOWARD THE WEST-NORTHWEST HAS OCCURRED...AND THE
INITIAL MOTION IS ESTIMATED TO BE 285/7.  VERY LITTLE CHANGE HAS
BEEN MADE TO THE NHC FORECAST TRACK ON THIS PACKAGE.  WATER VAPOR
IMAGES AND GLOBAL MODEL INITIALIZATIONS SHOW A BROAD TROUGH JUST
EAST OF THE EASTERN U.S. SEABOARD.  THE DYNAMICAL MODELS SHOW A
SERIES OF SHORT WAVE TROUGHS PASSING THROUGH THIS FEATURE DURING
THE NEXT SEVERAL DAYS.  THE RESULTING WEAKNESS IN THE SUBTROPICAL
RIDGE SHOULD CAUSE THE HURRICANE TO GRADUALLY TURN TOWARD THE
NORTHWEST AND NORTH-NORTHWEST DURING THE FORECAST PERIOD.  THE
OFFICIAL FORECAST TRACK IS VERY CLOSE TO A CONSENSUS OF THE
DYNAMICAL MODELS EXCLUDING THE U.K. MET. OFFICE TRACK...WHICH IS
LOOKING MORE AND MORE LIKE A WESTERN OUTLIER.

INTERESTS IN BERMUDA SHOULD NOT FOCUS ON THE 5-DAY POINT...SINCE
TRACK ERRORS COULD EASILY BE A FEW HUNDRED MILES AT THAT FORECAST
INTERVAL.  IT IS STILL TOO EARLY TO SAY WITH CERTAINTY WHETHER IGOR
WILL HAVE A SIGNIFICANT IMPACT ON THAT ISLAND.

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/0900Z 17.9N  51.7W   115 KT
12HR VT     14/1800Z 18.4N  52.8W   115 KT
24HR VT     15/0600Z 19.4N  54.2W   115 KT
36HR VT     15/1800Z 20.5N  55.7W   120 KT
48HR VT     16/0600Z 21.7N  57.1W   120 KT
72HR VT     17/0600Z 24.4N  60.2W   115 KT
96HR VT     18/0600Z 27.5N  63.0W   100 KT
120HR VT     19/0600Z 31.5N  64.5W    90 KT

$$
FORECASTER PASCH



000

WTNT41 KNHC 141443
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST TUE SEP 14 2010

THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE OF IGOR DURING THE
PAST SEVERAL HOURS...WITH THE 20 NM WIDE EYE REMAINING WELL DEFINED
AND EYEWALL CONVECTIVE TOPS REMAINING COLDER THAN -70C.  SATELLITE
INTENSITY ESTIMATES ARE UNCHANGED FROM SIX HRS AGO...SO THE INITIAL
INTENSITY REMAINS 115 KT.  RECENT MICROWAVE OVERPASSES DO NOT YET
SHOW AN OUTER EYEWALL...BUT DO SHOW THAT A LARGE RAIN-FREE MOAT HAS
FORMED BETWEEN THE EYEWALL AND THE OUTER CONVECTIVE BANDS.  THE
CIRRUS OUTFLOW IS GOOD IN ALL DIRECTIONS.

THE INITIAL MOTION IS NOW 290/6.  IGOR IS MOVING TOWARD A WEAKNESS
IN THE SUBTROPICAL RIDGED CAUSED BY A BROAD DEEP-LAYER TROUGH OVER
THE NORTHEASTERN UNITED STATES AND THE NORTHWESTERN ATLANTIC.  THE
DYNAMICAL MODELS FORECAST THIS WEAKNESS TO PERSIST FOR THE NEXT
SEVERAL DAYS AS A SERIES OF SHORTWAVE TROUGHS MOVE THROUGH THE
BROADER TROUGH.  IN ADDITION...THE DYNAMICAL MODELS FORECAST AN
UPPER-LEVEL TROUGH TO DEVELOP NEAR THE SOUTHEASTERN COAST OF THE
UNITED STATES BY 96-120 HR...WITH A LARGE UPPER-LEVEL HIGH FORMING
OVER THE CENTRAL ATLANTIC.  THIS EVOLUTION SHOULD STEER IGOR
WEST-NORTHWESTWARD TO NORTHWESTWARD FOR THE NEXT 48-72 HR...
FOLLOWED BY A MORE NORTHWARD MOTION.  THE TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH THIS SCENARIO...ALTHOUGH THERE REMAINS SOME SPREAD
BETWEEN THE MORE WESTWARD UKMET/NOGAPS AND THE MORE EASTWARD GFDL.
THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE WEST OF THE
PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE GUIDANCE ENVELOPE.

IGOR REMAINS IN AN ENVIRONMENT OF LIGHT VERTICAL WIND SHEAR AND WARM
SEA SURFACE TEMPERATURES...AND THESE CONDITIONS ARE FORECAST TO
PERSIST FOR THE NEXT 48-72 HR.  THUS...THE INTENSITY IS LIKELY TO
BE CONTROLLED BY HARD-TO-TIME EYEWALL REPLACEMENT CYCLES DURING
THIS TIME.  THE INTENSITY FORECAST CALLS FOR SOME INTENSIFICATION
BY 24 HR ON THE PREMISE THAT THE CURRENT INTERNAL CYCLE WILL BE
COMPLETE.  AFTER 72 HR...THE SEA SURFACE TEMPERATURES GRADUALLY
COOL ALONG THE FORECAST TRACK...AND SOUTHERLY UPPER-LEVEL WINDS
BETWEEN THE PREVIOUSLY MENTIONED TROUGH AND HIGH ARE EXPECTED TO
CAUSE INCREASED SHEAR.  THESE FACTORS SHOULD CAUSE IGOR TO
GRADUALLY WEAKEN...AND THE NEW INTENSITY FORECAST IS THE SAME AS
THE PREVIOUS FORECAST AT 96-120 HR.

INTERESTS IN BERMUDA SHOULD NOT FOCUS ON THE 5-DAY POINT...SINCE
TRACK ERRORS COULD EASILY BE A FEW HUNDRED MILES AT THAT FORECAST
INTERVAL.  IT IS STILL TOO EARLY TO SAY WITH CERTAINTY WHETHER IGOR
WILL HAVE A SIGNIFICANT IMPACT ON THAT ISLAND.

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/1500Z 18.3N  52.3W   115 KT
12HR VT     15/0000Z 18.8N  53.3W   115 KT
24HR VT     15/1200Z 19.8N  54.8W   120 KT
36HR VT     16/0000Z 20.8N  56.3W   120 KT
48HR VT     16/1200Z 21.9N  57.8W   120 KT
72HR VT     17/1200Z 24.5N  61.0W   115 KT
96HR VT     18/1200Z 28.0N  64.0W   100 KT
120HR VT     19/1200Z 32.0N  65.5W    90 KT

$$
FORECASTER BEVEN



000

WTNT41 KNHC 142059
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST TUE SEP 14 2010

CLOUD TOPS SURROUNDING THE EYE HAVE COOLED CONSIDERABLY DURING THE
AFTERNOON AND THE EYE HAS ALSO WARMED AND BECOME MORE DISTINCT IN
BOTH VISIBLE AND INFRARED SATELLITE IMAGERY. SEVERAL DISTINCT
VORTICES INSIDE THE EYE WERE ALSO NOTED...SIMILAR TO WHAT HAS BEEN
SEEN WITH PAST HURRICANES THAT WERE NEAR CATEGORY 5 STRENGTH. THE
INITIAL INTENSITY IS INCREASED TO 125 KT AND IS SUPPORTED BY
SATELLITE INTENSITY ESTIMATES OF T6.5/127 KT FROM SAB...3-HR
AVERAGE ODT VALUES OF T6.7/133 KT FROM TAFB...AND UW-CIMSS ADT
VALUES OF T6.5/127 KT.

THE INITIAL MOTION ESTIMATE IS 295/07...BASED ON A 12-HR AVERAGE OF
SMOOTHING OUT THE MANY TROCHOIDAL WOBBLES IN THE TRACK. IGOR MAY
BRIEFLY WOBBLE BACK TO THE WEST DURING THE NEXT SEVERAL HOURS...BUT
THE GENERAL MOTION OVER THE NEXT 24 HOURS SHOULD BE TOWARD THE
WEST-NORTHWEST...FOLLOWED BY A TURN TO THE NORTHWEST AFTER THAT
THROUGH 72 HOURS. A SERIES OF SHORTWAVE TROUGHS MOVING QUICKLY IN
THE MID-LATITUDE WESTERLIES ACROSS THE NORTHERN U.S. AND THE NORTH
ATLANTIC IS FORECAST TO GRADUALLY WEAKEN THE SUBTROPICAL RIDGE
BETWEEN 60W-70W LONGITUDE ABOUT EVERY 24-36 HOURS. AS A RESULT...
IGOR IS EXPECTED TO TURN NORTHWARD IN 96-120 HOURS AS DEEP-LAYER
SOUTHERLY FLOW TO THE EAST OF IGOR STRENGTHENS BETWEEN IT AND A
STRONG SUBTROPICAL HIGH FORECAST OT BE NEAR 30N/40W BY THAT TIME.
THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND
IS CLOSE TO THE MIDDLE OF THE TIGHTLY CLUSTERED MODEL GUIDANCE. BY
120 HOURS...IGOR IS EXPECTED TO BE A VERY LARGE HURRICANE AND BE
CLOSE ENOUGH TO BERMUDA TO BRING ADVERSE WEATHER CONDITIONS TO THAT
ISLAND.

IGOR IS FORECAST TO REMAIN IN AN ENVIRONMENT OF LIGHT VERTICAL WIND
SHEAR...WARM SEA-SURFACE TEMPERATURES OF NEAR 29C...AND MAINTAIN A
VERY FAVORABLE OUTFLOW PATTERN THROUGH THE FORECAST PERIOD. AS A
RESULT...THERE MAY BE SOME ADDITIONAL STRENGTHENING DURING THE NEXT
12-24 HOURS...ESPECIALLY LATER TONIGHT DURING THE CONVECTIVE
MAXIMUM PERIOD. HOWEVER...OWING TO THE LARGE SIZE OF IGOR...ITS
STRONG CATEGORY 4 INTENSITY...AND ITS RELATIVELY SLOW FORWARD
MOTION OF LESS THAN 10 KT...SOME COLD UPWELLING MAY OCCUR BENEATH
THE CORE OF THE HURRICANE AND CAUSE SOME WEAKENING OF THE CYCLONE
DESPITE THE AFOREMENTIONED FAVORABLE CONDITIONS. EYEWALL
REPLACEMENT CYCLES ARE ALSO A DISTINCT POSSIBILITY. REGARDLESS...
IGOR IS STILL EXPECTED TO REMAIN A MAJOR HURRICANE THROUGH THE
FORECAST PERIOD. THE OFFICIAL INTENSITY FORECAST IS A LITTLE HIGHER
THAN THE PREVIOUS ADVISORY AND IS SIMILAR TO A BLEND OF THE
SHIPS-LGEM INTENSITY MODELS THROUGH 72 HOURS.  IT APPEARS AS THOUGH
THE SHIPS GUIDANCE AT FOUR AND FIVE DAYS MAY BE ADVERSELY AFFECTED
BY THE REPRESENTATION OF THE WARM CORE OF THE HURRICANE IN THE GFS
MODEL.  IN ADDITION...ALL THE GLOBAL MODELS FORECAST A VERY
FAVORABLE OUTFLOW PATTERN THROUGH DAY FIVE...AND SO THE OFFICIAL
FORECAST IS HELD A LITTLE ABOVE THE GUIDANCE NEAR THE END OF THE
FORECAST PERIOD.

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/2100Z 18.8N  53.1W   125 KT
12HR VT     15/0600Z 19.5N  54.3W   130 KT
24HR VT     15/1800Z 20.5N  55.6W   125 KT
36HR VT     16/0600Z 21.5N  57.2W   125 KT
48HR VT     16/1800Z 22.6N  58.8W   120 KT
72HR VT     17/1800Z 25.4N  62.1W   115 KT
96HR VT     18/1800Z 28.6N  64.5W   110 KT
120HR VT     19/1800Z 33.0N  65.5W   100 KT

$$
FORECASTER STEWART




WTNT41 KNHC 150257
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST TUE SEP 14 2010

CONVECTIVE CLOUD TOPS HAVE CONTINUED TO COOL...AND A SOLID WHITE
RING ON THE DVORAK ENHANCEMENT HAS INTERMITTENTLY WRAPPED ENTIRELY
AROUND THE EYE DURING THE PAST FEW HOURS.  DVORAK T-NUMBERS WERE UP
TO T7.0 FROM TAFB AND SAB AT 0000 UTC...AND T6.5 AND T7.0 FROM TWO
FORMS OF THE UW-CIMSS ADT.  SINCE THE WHITE RING DOES NOT ENTIRELY
WRAP AROUND THE EYE AT THIS TIME...THE INITIAL INTENSITY IS BEING
RAISED TO 135 KT.  IGOR REMAINS OVER WARM WATERS AND IS IN AN
ENVIRONMENT OF LOW VERTICAL SHEAR...SO THE OFFICIAL FORECAST
MAINTAINS THIS INTENSITY FOR THE NEXT 12-24 HOURS.  GRADUAL
WEAKENING IS EXPECTED THEREAFTER WHEN IT IS LIKELY THAT INTERNAL
DYNAMICS...WHICH ARE NOT WELL UNDERSTOOD...WILL INFLUENCE THE
INTENSITY.  THE OFFICIAL FORECAST IS VERY CLOSE TO A CONSENSUS OF
THE STATISTICAL AND DYNAMICAL GUIDANCE THROUGH DAY 4 BUT IS A
LITTLE HIGHER THAN THAT GUIDANCE AT DAY 5 TO MAINTAIN CONTINUITY
WITH THE PREVIOUS PACKAGE.

IGOR IS MOVING AT 295/8.  THE HURRICANE HAS REACHED THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE...AND IT SHOULD MAKE A TURN
TOWARD THE NORTHWEST SOON.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT
FOR THE FIRST 3-4 DAYS BUT THEN SHOWS MORE DIVERGENCE ON DAY 5 WITH
THE GFDL WELL TO THE NORTHEAST OF BERMUDA AND THE ECMWF WELL TO THE
SOUTHWEST OF BERMUDA.  THE OFFICIAL FORECAST LIES VERY CLOSE TO THE
CONSENSUS THROUGH THE FORECAST PERIOD AND ENDED UP BEING SIMILAR TO
THE PREVIOUS FORECAST.

REGARDLESS OF WHERE IGOR ENDS UP IN 5 DAYS...THE LARGE WIND FIELD OF
THE HURRICANE IS EXPECTED TO BE VERY CLOSE TO OR NEAR BERMUDA
WITHIN THE NEXT 3 TO 4 DAYS.  INTERESTS ON BERMUDA SHOULD CONTINUE
TO MONITOR THE PROGRESS OF IGOR.

FORECAST POSITIONS AND MAX WINDS

INITIAL      15/0300Z 19.0N  53.9W   135 KT
12HR VT     15/1200Z 19.8N  55.0W   135 KT
24HR VT     16/0000Z 20.7N  56.4W   130 KT
36HR VT     16/1200Z 21.7N  58.0W   125 KT
48HR VT     17/0000Z 22.8N  59.6W   125 KT
72HR VT     18/0000Z 25.5N  63.0W   115 KT
96HR VT     19/0000Z 29.0N  65.0W   105 KT
120HR VT     20/0000Z 33.5N  65.5W    95 KT

$$
FORECASTER BERG




WTNT41 KNHC 150843
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST WED SEP 15 2010

IGOR HAS WEAKENED A LITTLE DURING THE PAST FEW HOURS.  ENHANCED
INFRARED SATELLITE IMAGES INDICATE THAT CLOUD TOPS HAVE WARMED OVER
THE WESTERN SEMICIRCLE AND THE EYE HAS COOLED.  IN ADDITION...AN
0352 UTC TRMM OVERPASS SHOWED THAT THE SOUTHWESTERN PORTION OF THE
EYEWALL HAS ERODED.  BASED ON THIS DEGRADED APPEARANCE AND A BLEND
OF SATELLITE INTENSITY ESTIMATES...THE INITIAL WIND SPEED IS
LOWERED TO 125 KT.  IGOR REMAINS IN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING...SO INTERNAL DYNAMICS WILL LIKELY BE THE DOMINANT
FACTOR FOR THE FUTURE INTENSITY OF IGOR FOR THE NEXT COUPLE OF
DAYS.  THESE SMALL SCALE DYNAMICS...WHICH ARE NOT WELL
UNDERSTOOD...USUALLY CAUSE FLUCTUATIONS IN INTENSITY...AND THAT IS
REFLECTED IN THE OFFICIAL FORECAST.  SOUTHERLY WIND SHEAR IS
EXPECTED TO INCREASE IN 3 TO 4 DAYS...WHICH SHOULD CAUSE SOME
WEAKENING BY THAT TIME.

THE INITIAL MOTION IS 300/8...AND THE EYE OF IGOR IS ON THE PREVIOUS
FORECAST TRACK.  A CONTINUED WEST-NORTHWEST TO NORTHWEST MOTION IS
EXPECTED OVER THE NEXT COUPLE OF DAYS AS THE HURRICANE MOVES ALONG
THE SOUTHWESTERN SIDE OF A SUBTROPICAL RIDGE.  BEYOND THAT TIME...A
NORTH-NORTHWESTWARD AND THEN NORTHWARD MOTION WITH AN INCREASE IN
FORWARD SPEED IS FORECAST AS IGOR ROUNDS THE RIDGE AND MOVES INTO
A PRONOUNCED WEAKNESS.  IN GENERAL...THE NEW TRACK GUIDANCE HAS
SHIFTED A LITTLE TO THE EAST AT DAYS 4 AND 5...AND THE OFFICIAL
FORECAST IS NUDGED ONLY SLIGHTLY IN THAT DIRECTION.

REGARDLESS OF THE EXACT TRACK OF IGOR...THE LARGE WIND FIELD OF
THE HURRICANE IS EXPECTED TO BE VERY CLOSE TO OR NEAR BERMUDA
WITHIN THE NEXT 3 TO 4 DAYS.  INTERESTS ON BERMUDA SHOULD CONTINUE
TO MONITOR THE PROGRESS OF IGOR.

FORECAST POSITIONS AND MAX WINDS

INITIAL      15/0900Z 19.5N  54.5W   125 KT
12HR VT     15/1800Z 20.2N  55.6W   130 KT
24HR VT     16/0600Z 21.1N  57.0W   130 KT
36HR VT     16/1800Z 21.9N  58.4W   125 KT
48HR VT     17/0600Z 22.9N  60.2W   120 KT
72HR VT     18/0600Z 25.8N  63.3W   110 KT
96HR VT     19/0600Z 29.5N  65.0W   100 KT
120HR VT     20/0600Z 34.0N  64.5W    90 KT

$$
FORECASTER CANGIALOSI



000

WTNT41 KNHC 151439
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST WED SEP 15 2010

THE CLOUD PATTERN ASSOCIATED WITH IGOR WAS DETERIORATING DURING THE
PAST SEVERAL HOURS...WITH CLOUD TOP TEMPERATURES WARMING AND A DRY
SLOT EVIDENT NORTHWEST OF THE CENTER. SEVERAL MICROWAVE OVERPASSES
ALSO INDICATED A FURTHER EROSION OF THE INNER EYEWALL AND THE
FORMATION OF AN OUTER EYEWALL AT ABOUT 60-70 NMI RADIUS. SINCE
ABOUT 1300 UTC...THERE APPEARS TO BE SOME EVIDENCE OF A RE-
ORGANIZATION OF THE INNER CORE. DVORAK T-NUMBERS AT 1200 UTC ARE
5.5 AND 6.0 FROM SAB AND TAFB...RESPECTIVELY. BASED UPON THESE
ESTIMATES...THE INITIAL WIND SPEED IS DECREASED TO 115 KT FOR THIS
ADVISORY. THERE DO NOT APPEAR TO BE ANY NEGATIVE LARGE-SCALE
FACTORS THAT COULD PRODUCE A SIGNIFICANT WEAKENING DURING THE NEXT
TWO TO THREE DAYS. INSTEAD...FLUCTUATIONS IN INTENSITY ARE LIKELY
TO BE GOVERNED BY INTERNAL DYNAMICS FOR WHICH PREDICTABILITY IS
POOR. IN ABOUT 3 TO 4 DAYS...GLOBAL MODELS SHOW THAT IGOR SHOULD
ENCOUNTER AN INCREASE IN SOUTHERLY SHEAR. THE OFFICIAL NHC
INTENSITY FORECAST HAS BEEN LOWERED IN THE SHORT TERM BECAUSE OF
THE CURRENT WEAKENING TREND. SHOULD THE CURRENT EYEWALL REPLACEMENT
CYCLE END DURING THE NEXT DAY OR TWO...THERE MAY BE AN OPPORTUNITY
FOR RE-INTENSIFICATION BEFORE GRADUAL WEAKENING COMMENCES LATER IN
THE FORECAST PERIOD.

THE INITIAL MOTION IS ABOUT THE SAME AS BEFORE...300/07...AND THE
TRACK PHILOSOPHY IS ESSENTIALLY UNCHANGED.  IGOR IS MOVING AROUND
THE SOUTHWEST SIDE OF THE SUBTROPICAL RIDGE OVER THE EASTERN
ATLANTIC AND SHOULD GRADUALLY ENTER A LARGE WEAKNESS OVER THE
WESTERN ATLANTIC DURING THE NEXT COUPLE OF DAYS.  THIS PATTERN
SHOULD STEER IGOR NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD...
POSSIBLY WITH A SLIGHT INCREASE IN FORWARD SPEED.  DURING THIS
TIME...A SERIES OF SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN
THE WESTERN ATLANTIC SHOULD HAVE LITTLE IMPACT ON IGOR.  HOWEVER...
IN ABOUT 4-5 DAYS...DYNAMICAL MODELS ARE IN GOOD AGREEMENT ON THE
PRESENCE OF A SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN
UNITED STATES THAT SHOULD BEGIN TO INDUCE RECURVATURE.  THERE ARE
STILL SOME TIMING AND AMPLITUDE DIFFERENCES IN THE MODELS REGARDING
THIS FEATURE...WHICH COULD AFFECT HOW CLOSE IGOR PASSES TO BERMUDA.
THE OFFICIAL NHC TRACK FORECAST IS LARGELY UNCHANGED FROM THE
PREVIOUS ADVISORY...CLOSE TO BUT JUST RIGHT OF THE MULTI-MODEL
CONSENSUS.

REGARDLESS OF THE EXACT TRACK...IGOR HAS A VERY LARGE WIND FIELD AND
IS EXPECTED TO BRING ADVERSE CONDITIONS TO BERMUDA.


FORECAST POSITIONS AND MAX WINDS

INITIAL      15/1500Z 19.8N  55.0W   115 KT
12HR VT     16/0000Z 20.5N  56.1W   110 KT
24HR VT     16/1200Z 21.3N  57.5W   110 KT
36HR VT     17/0000Z 22.1N  59.1W   115 KT
48HR VT     17/1200Z 23.3N  60.8W   120 KT
72HR VT     18/1200Z 26.0N  63.5W   110 KT
96HR VT     19/1200Z 30.0N  65.0W    95 KT
120HR VT     20/1200Z 34.5N  63.5W    80 KT

$$
FORECASTER KIMBERLAIN



000

WTNT41 KNHC 152035
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST WED SEP 15 2010

INFRARED SATELLITE PICTURES INDICATE THAT IGOR IS MAINTAINING ITS
CONVECTIVE ORGANIZATION...WITH INNER CORE CONVECTION MORE VIGOROUS
THAN EARLIER. HOWEVER...VISIBLE SATELLITE IMAGES SUGGEST THAT THE
EYEWALL REPLACEMENT CYCLE IGOR IS EXPERIENCING IS STILL OCCURRING.
A DISTINCT BUT PARTIAL INNER EYEWALL IS EVIDENT AND AN OUTER
EYEWALL NOW AT 30-40 NM RADIUS SEEMS TO BE GRADUALLY CONTRACTING.
SUBJECTIVE DVORAK CLASSIFICATIONS ARE AT 5.5 AND 6.0 FROM SAB AND
TAFB...RESPECTIVELY...WHILE THE LATEST 3-HOURLY AVERAGED ADT VALUE
IS CLOSE TO 6.0. THESE ESTIMATES ARE THE BASIS FOR KEEPING THE
INITIAL INTENSITY AT 115 KT FOR THIS ADVISORY. THERE ARE NO OBVIOUS
LARGE-SCALE FACTORS THAT COULD CAUSE A SIGNIFICANT WEAKENING OF
IGOR DURING THE NEXT 2-3 DAYS. ANY CHANGES IN INTENSITY DURING THIS
TIME ARE MOST LIKELY TO BE RELATED TO INNER CORE DYNAMICS FOR WHICH
PREDICTABILITY IS LOW. IN 3-4 DAYS...GLOBAL DYNAMICAL MODELS
CONTINUE TO SHOW AN INCREASE IN SOUTHERLY SHEAR...AND IGOR SHOULD
REACH MARGINAL SEA SURFACE TEMPERATURES TOWARD THE END OF THE
PERIOD. THE STATISTICAL-DYNAMICAL GUIDANCE RESPONDS TO THESE
FACTORS BY SHOWING A GRADUAL WEAKENING BEYOND 72 HOURS. THE
OFFICIAL NHC INTENSITY IS BASICALLY UNCHANGED...WITH THE FORECAST
STILL INDICATING SOME POTENTIAL FOR RE-INTENSIFICATION IN THE SHORT
TERM AFTER THE CURRENT EYEWALL REPLACEMENT CYCLE ENDS.

THERE HAS BEEN LITTLE CHANGE TO THE MOTION...AND THE LATEST ESTIMATE
IS 295/07. IGOR IS MOVING AROUND THE SOUTHWEST PERIPHERY OF THE
SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC AND IS GRADUALLY
ENTERING A PRONOUNCED WEAKNESS IN THE WESTERN ATLANTIC. THIS
SYNOPTIC PATTERN SHOULD STEER IGOR ON A NORTHWESTWARD AND THEN
NORTH-NORTHWESTWARD COURSE DURING THE NEXT 2-3 DAYS. DURING THIS
TIME...SEVERAL SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN THE
WESTERN ATLANTIC SHOULD HAVE LITTLE EFFECT ON IGOR. HOWEVER...
DYNAMICAL MODELS ARE IN GENERALLY GOOD AGREEMENT THAT A VIGOROUS
SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN STATES/CANADIAN
MARITIMES IN ABOUT 4-5 DAYS SHOULD BEGIN TO INDUCE RECURVATURE. THE
GFS/HWRF/GFDL HAVE BEEN INDICATING A MORE ROBUST SHORTWAVE FEATURE
AND A SHARPER RECURVATURE DURING THE PAST SEVERAL RUNS. ON THE
OTHER HAND...THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN HAVE
HAD A WEAKER AND MORE PROGRESSIVE SHORTWAVE THAT COULD DELAY
RECURVATURE AND ALLOW FOR A MORE WESTWARD TRACK. THE OFFICIAL NHC
TRACK FORECAST REMAINS ABOUT THE SAME AS BEFORE AND IS VERY NEAR THE
MULTI-MODEL CONSENSUS...CONTINUING TO SHOW IGOR PASSING CLOSE TO
BERMUDA IN ABOUT 4 DAYS.




FORECAST POSITIONS AND MAX WINDS

INITIAL      15/2100Z 20.1N  55.6W   115 KT
12HR VT     16/0600Z 20.6N  56.7W   110 KT
24HR VT     16/1800Z 21.4N  58.2W   115 KT
36HR VT     17/0600Z 22.4N  59.8W   120 KT
48HR VT     17/1800Z 23.5N  61.5W   120 KT
72HR VT     18/1800Z 26.5N  64.0W   105 KT
96HR VT     19/1800Z 31.0N  65.0W    95 KT
120HR VT     20/1800Z 36.0N  61.5W    80 KT

$$
FORECASTER KIMBERLAIN



000

WTNT41 KNHC 160242
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST WED SEP 15 2010

BASED ON RECENT MICROWAVE DATA...IGOR APPEARS TO BE COMPLETING AN
EYEWALL REPLACEMENT.  IN ADDITION...INFRARED GEOSTATIONARY
SATELLITE IMAGERY SHOWS THE INNER CORE CONVECTION DIMINISHING WITH
AN OUTER RING OF CONVECTION BECOMING MORE PROMINENT.  DVORAK
ESTIMATES FROM TAFB REMAIN AT T6.0/6.5 AND HAVE FALLEN TO T5.0/5.5
FROM SAB...AND THE LATEST ADT ESTIMATE IS T6.3.  THE INITIAL
INTENSITY IS HELD AT 115 KT FOR THIS ADVISORY.  IGOR IS EXPECTED TO
REMAIN IN AN ENVIRONMENT OF LOW SHEAR FOR THE NEXT 60 HOURS OR
SO...AND LITTLE CHANGE IN INTENSITY IS EXPECTED DURING THAT TIME.
FLUCTUATIONS IN INTENSITY ARE STILL POSSIBLE HOWEVER...ESPECIALLY
IF THE NEW OUTER EYEWALL CONTRACTS OVER THE NEXT COUPLE OF DAYS.
BY DAYS 3 THROUGH 5...SOUTHERLY SHEAR IS EXPECTED TO INCREASE AND
SHOULD INDUCE SOME WEAKENING.  THE INTENSITY GUIDANCE IS IN FAIRLY
GOOD AGREEMENT DURING THAT TIME...AND THE OFFICIAL FORECAST WILL
SHOW WEAKENING TO CATEGORY 1 OR 2 STRENGTH BY DAYS 4 AND 5.

IGOR IS MOVING 295 DEGREES AT 8 KT.  THE HURRICANE IS LOCATED NEAR
THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE OVER THE CENTRAL
ATLANTIC AND IS BEING INCREASINGLY INFLUENCED BY A LARGE BUT FLAT
MID- TO UPPER-LEVEL TROUGH NEAR THE U.S. EAST COAST.  SINCE THE
TROUGH IS NOT THAT SHARP...IGOR IS EXPECTED TO MAINTAIN ITS CURRENT
MOTION FOR THE NEXT 36 HOURS OR SO.  IT SHOULD THEN BEGIN TO TURN
MORE SHARPLY ON DAYS 3 THROUGH 5...WITH ITS CENTER PASSING NEAR
BERMUDA IN ABOUT 96 HOURS.  THE TRACK GUIDANCE IS TIGHTLY CLUSTERED
BUT DOES SHOW SOME SPEED DIFFERENCES BY DAY 5.  THE OFFICIAL
FORECAST IS JUST A LITTLE TO THE WEST OF THE MODEL CONSENSUS TVCN
SINCE THE USUALLY-RELIABLE ECMWF LIES ON THE WESTERN SIDE OF THE
GUIDANCE ENVELOPE.

FORECAST POSITIONS AND MAX WINDS

INITIAL      16/0300Z 20.2N  56.5W   115 KT
12HR VT     16/1200Z 20.8N  57.6W   115 KT
24HR VT     17/0000Z 21.7N  59.2W   115 KT
36HR VT     17/1200Z 22.6N  60.8W   115 KT
48HR VT     18/0000Z 24.0N  62.6W   115 KT
72HR VT     19/0000Z 27.5N  65.0W   105 KT
96HR VT     20/0000Z 31.5N  65.0W    95 KT
120HR VT     21/0000Z 36.5N  60.5W    80 KT

$$
FORECASTER BERG



000

WTNT41 KNHC 160855
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST THU SEP 16 2010

MICROWAVE AND INFRARED SATELLITE IMAGERY SUGGEST THAT THE EYEWALL
REPLACEMENT WITH IGOR IS COMPLETE.   THE NEW EYEWALL APPEARS TO BE
CONSOLIDATING AT A RADIUS OF ABOUT 30-35 N MI AND IS PRODUCING
RATHER DEEP CONVECTION...SUGGESTING THE INTENSITY IS INCREASING
AGAIN. A BLEND OF THE SATELLITE ESTIMATES GIVES AN INITIAL
INTENSITY OF 125 KT.

A LARGE-SCALE ENVIRONMENT OF LIGHT SHEAR AND WARM WATER IS FAVORABLE
FOR THE MAINTENANCE OF AN EXTREMELY DANGEROUS HURRICANE FOR THE
NEXT FEW DAYS. THE EXACT INTENSITY OF IGOR WILL BE PRIMARILY
DICTATED BY EYEWALL CYCLES...WHICH ARE WELL BEYOND OUR FORECAST
ABILITIES. THE MAJORITY OF THE MODEL GUIDANCE INDICATES THAT SLOW
WEAKENING IS THE MOST LIKELY SOLUTION...AND THE NHC FORECAST REFLECT
THIS. HOWEVER...IT IS MORE IMPORTANT TO RECOGNIZE THAT ALL OF THE
GUIDANCE...AND THE NHC FORECAST...KEEPS IGOR AS A LARGE AND
DANGEROUS HURRICANE FOR THE NEXT SEVERAL DAYS.

THE INITIAL MOTION IS AN UNSTEADY 300/6.  IGOR IS EXPECTED TO MOVE
SLOWLY AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE OVER THE
CENTRAL ATLANTIC.  WEAK TROUGHING ALONG ABOUT 70W SHOULD RECURVE
THE CYCLONE IN 3 OR 4 DAYS.  THE MAIN DIFFERENCE IN THE MODELS IS
HOW QUICKLY IGOR ACCELERATES TO THE NORTHEAST IN THE MID-LATITUDES.
SINCE THE TROUGHING OVER THE WESTERN ATLANTIC IS RATHER FLAT...
THERE HAS BEEN A TREND IN THE MODELS TO SHOW WEAKER FLOW NEAR
IGOR...AND CONSEQUENTLY DELAY THE INCREASE IN FORWARD SPEED.  THE
OFFICIAL FORECAST IS A BIT SLOWER THAN THE PREVIOUS ONE...
ESPECIALLY AT THE END OF THE PERIOD.  WITH REGARDS TO HOW CLOSE
IGOR COMES TO BERMUDA...THE ECMWF IS NOW THE MOST EASTERN MODEL
AFTER BEING THE WESTERNMOST YESTERDAY.  THIS APPEARS TO BE DUE TO
THAT MODEL SHOWING A SLIGHTLY WEAKER RIDGE TODAY...WHICH ALLOWS
IGOR TO GAIN A LITTLE MORE LATITUDE EARLY ON AND EVENTUALLY PASS A
LITTLE FARTHER EAST OF BERMUDA.  HOWEVER...ALL OF THE GUIDANCE IS
WELL CLUSTERED ON A TRACK CLOSE TO THAT ISLAND...AND LITTLE CHANGE
HAS BEEN MADE TO THE OFFICIAL TRACK NEAR BERMUDA.  SINCE THIS IS
SUCH A LARGE HURRICANE...SIGNIFICANT IMPACTS ARE EXPECTED ON
BERMUDA...BUT IT IS TOO EARLY TO TELL HOW CLOSE THE CORE OF THE
HURRICANE...AND THE STRONGEST WINDS...WILL COME TO THAT ISLAND.

SO FAR...NOAA BUOY 41044 HAS REPORTED A PEAK 1-MINUTE WIND OF 45
KT...GUSTING TO 56 KT...ALONG WITH A MINIMUM PRESSURE OF 995
MB...AND A SIGNIFICANT WAVE HEIGHT OF 29 FT.  HOWEVER...THE WORST
IS YET TO COME FOR THAT STATION...AS IGOR WILL MOVE VERY CLOSE TO
THE BUOY TONIGHT.

FORECAST POSITIONS AND MAX WINDS

INITIAL      16/0900Z 20.5N  56.8W   125 KT
12HR VT     16/1800Z 21.1N  57.8W   125 KT
24HR VT     17/0600Z 22.0N  59.4W   125 KT
36HR VT     17/1800Z 23.2N  61.1W   120 KT
48HR VT     18/0600Z 24.7N  62.7W   120 KT
72HR VT     19/0600Z 28.0N  65.0W   110 KT
96HR VT     20/0600Z 32.5N  64.5W    95 KT
120HR VT     21/0600Z 37.5N  59.0W    80 KT

$$
FORECASTER BLAKE



000

WTNT41 KNHC 161444
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 16 2010

IGOR IS MAINTAINING VERY DEEP CONVECTION AND A 30-35 NMI WIDE EYE
WITHIN A CENTRAL DENSE OVERCAST...BUT THE OVERALL CONVECTIVE
PATTERN HAS BECOME MORE ASYMMETRIC. THE RESTRICTED NATURE OF THE
OUTFLOW TO THE WEST OF THE CYCLONE SUGGESTS SOME UPPER-LEVEL
WESTERLY FLOW IMPINGING ON THE CIRCULATION...WHICH MAY ALSO BE
CONTRIBUTING TO THE RAGGED APPEARANCE OF THE CDO. SUBJECTIVE DVORAK
T-NUMBERS ARE A CONSENSUS 6.0 AT 1200 UTC AND SERVE AS THE BASIS
FOR LOWERING THE INTENSITY TO 115 KT FOR THIS ADVISORY. AN AIR
FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IGOR IN A FEW HOURS AND WILL PROVIDE A MORE ACCURATE
ASSESSMENT OF ITS INTENSITY.

WATER VAPOR IMAGERY SUGGESTS THAT THE COMBINATION OF A SHEAR AXIS
NORTHWEST OF IGOR AND THE SOUTHWESTWARD DISPLACEMENT OF THE
UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH IGOR MAY BE IMPARTING WEAK
TO MODERATE WESTERLY SHEAR TO THE HURRICANE. SHIPS MODEL OUTPUT
INDICATES THAT THIS SHEAR MAY PERSIST FOR NEXT 12-24 HOURS AND THEN
DECREASE...ALLOWING FOR SOME INTENSIFICATION BEFORE ABOUT 48 HOURS.
ALTHOUGH INNER CORE DYNAMICS WILL LIKELY INDUCE SOME DIFFICULT TO
PREDICT FLUCTUATIONS IN INTENSITY...IGOR IS EXPECTED TO REMAIN A
LARGE AND FORMIDABLE HURRICANE FOR THE NEXT 3 TO 4 DAYS. AFTER
THAT...INCREASING SOUTHWESTERLY SHEAR AND GRADUALLY COOLER WATERS
SHOULD LEAD TO WEAKENING OF THE CYCLONE...WITH THE WEAKENING
POSSIBLY GREATER THAN INDICATED IF THE 30 TO 45 KT OF SHEAR
PREDICTED BY THE GFS VERIFIES. THE GUIDANCE ALSO INDICATES THAT
EXTRATROPICAL TRANSITION WILL BE UNDERWAY BY DAY 5. THE OFFICIAL
FORECAST IS SLIGHTLY HIGHER THAN SOME OF THE STATISTICAL-DYNAMICAL
GUIDANCE BUT SIMILAR TO THE PREVIOUS INTENSITY FORECAST.

IGOR HAS BEEN WOBBLING ABOUT AN INITIAL MOTION OF 305/06. LITTLE HAS
CHANGED REGARDING THE OVERALL TRACK PHILOSOPHY. THE HURRICANE IS
EXPECTED TO MOVE NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE DURING THE NEXT 72 HOURS. BEYOND 72 HOURS...IGOR
SHOULD BECOME EMBEDDED WITHIN THE MID-LATITUDE WEST-SOUTHWESTERLY
FLOW AHEAD OF A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE
NORTHEASTERN U.S. AND THE CANADIAN MARITIMES...AND TURN NORTH AND
THEN NORTHEAST WITH INCREASING FORWARD SPEED. THE SPREAD IN THE
MODEL GUIDANCE HAS DECREASED SINCE YESTERDAY...WITH THE LATEST
SOLUTIONS TRENDING SLIGHTLY LEFTWARD AND TIGHTLY CLUSTERED AROUND
THE OFFICIAL FORECAST.


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/1500Z 21.0N  57.2W   120 KT
12HR VT     17/0000Z 21.5N  58.3W   115 KT
24HR VT     17/1200Z 22.4N  60.0W   120 KT
36HR VT     18/0000Z 23.8N  61.7W   120 KT
48HR VT     18/1200Z 25.3N  63.2W   120 KT
72HR VT     19/1200Z 29.0N  65.0W   105 KT
96HR VT     20/1200Z 33.5N  63.5W    95 KT
120HR VT     21/1200Z 39.0N  56.5W    80 KT

$$
FORECASTER KIMBERLAIN



000

WTNT41 KNHC 161508
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  34...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST THU SEP 16 2010

CORRECT INITIAL INTENSITY FROM 115 KT TO 120 KT

IGOR IS MAINTAINING VERY DEEP CONVECTION AND A 30-35 NMI WIDE EYE
WITHIN A CENTRAL DENSE OVERCAST...BUT THE OVERALL CONVECTIVE
PATTERN HAS BECOME MORE ASYMMETRIC. THE RESTRICTED NATURE OF THE
OUTFLOW TO THE WEST OF THE CYCLONE SUGGESTS SOME UPPER-LEVEL
WESTERLY FLOW IMPINGING ON THE CIRCULATION...WHICH MAY ALSO BE
CONTRIBUTING TO THE RAGGED APPEARANCE OF THE CDO. SUBJECTIVE DVORAK
T-NUMBERS ARE A CONSENSUS 6.0 AT 1200 UTC AND SERVE AS THE BASIS
FOR LOWERING THE INTENSITY TO 120 KT FOR THIS ADVISORY. AN AIR
FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IGOR IN A FEW HOURS AND WILL PROVIDE A MORE ACCURATE
ASSESSMENT OF ITS INTENSITY.

WATER VAPOR IMAGERY SUGGESTS THAT THE COMBINATION OF A SHEAR AXIS
NORTHWEST OF IGOR AND THE SOUTHWESTWARD DISPLACEMENT OF THE
UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH IGOR MAY BE IMPARTING WEAK
TO MODERATE WESTERLY SHEAR TO THE HURRICANE. SHIPS MODEL OUTPUT
INDICATES THAT THIS SHEAR MAY PERSIST FOR NEXT 12-24 HOURS AND THEN
DECREASE...ALLOWING FOR SOME INTENSIFICATION BEFORE ABOUT 48 HOURS.
ALTHOUGH INNER CORE DYNAMICS WILL LIKELY INDUCE SOME DIFFICULT TO
PREDICT FLUCTUATIONS IN INTENSITY...IGOR IS EXPECTED TO REMAIN A
LARGE AND FORMIDABLE HURRICANE FOR THE NEXT 3 TO 4 DAYS. AFTER
THAT...INCREASING SOUTHWESTERLY SHEAR AND GRADUALLY COOLER WATERS
SHOULD LEAD TO WEAKENING OF THE CYCLONE...WITH THE WEAKENING
POSSIBLY GREATER THAN INDICATED IF THE 30 TO 45 KT OF SHEAR
PREDICTED BY THE GFS VERIFIES. THE GUIDANCE ALSO INDICATES THAT
EXTRATROPICAL TRANSITION WILL BE UNDERWAY BY DAY 5. THE OFFICIAL
FORECAST IS SLIGHTLY HIGHER THAN SOME OF THE STATISTICAL-DYNAMICAL
GUIDANCE BUT SIMILAR TO THE PREVIOUS INTENSITY FORECAST.

IGOR HAS BEEN WOBBLING ABOUT AN INITIAL MOTION OF 305/06. LITTLE HAS
CHANGED REGARDING THE OVERALL TRACK PHILOSOPHY. THE HURRICANE IS
EXPECTED TO MOVE NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE DURING THE NEXT 72 HOURS. BEYOND 72 HOURS...IGOR
SHOULD BECOME EMBEDDED WITHIN THE MID-LATITUDE WEST-SOUTHWESTERLY
FLOW AHEAD OF A VIGOROUS SHORTWAVE TROUGH MOVING THROUGH THE
NORTHEASTERN U.S. AND THE CANADIAN MARITIMES...AND TURN NORTH AND
THEN NORTHEAST WITH INCREASING FORWARD SPEED. THE SPREAD IN THE
MODEL GUIDANCE HAS DECREASED SINCE YESTERDAY...WITH THE LATEST
SOLUTIONS TRENDING SLIGHTLY LEFTWARD AND TIGHTLY CLUSTERED AROUND
THE OFFICIAL FORECAST.


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/1500Z 21.0N  57.2W   120 KT
12HR VT     17/0000Z 21.5N  58.3W   115 KT
24HR VT     17/1200Z 22.4N  60.0W   120 KT
36HR VT     18/0000Z 23.8N  61.7W   120 KT
48HR VT     18/1200Z 25.3N  63.2W   120 KT
72HR VT     19/1200Z 29.0N  65.0W   105 KT
96HR VT     20/1200Z 33.5N  63.5W    95 KT
120HR VT     21/1200Z 39.0N  56.5W    80 KT

$$
FORECASTER KIMBERLAIN




WTNT41 KNHC 162041
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST THU SEP 16 2010

AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REACHED THE CENTER OF
IGOR AROUND 1600 UTC. THE HURRICANE HUNTERS MEASURED A MINIMUM
PRESSURE OF 940 MB AND MAXIMUM FLIGHT-LEVEL AND SFMR WINDS OF 130
AND 98 KT...RESPECTIVELY. SINCE THAT TIME..THE CLOUD PATTERN
ASSOCIATED WITH IGOR HAS CHANGED LITTLE IN ORGANIZATION...AND
DVORAK T-NUMBERS REMAIN AT 5.5 FROM SAB AND TAFB. BASED UPON THE
AIRCRAFT DATA AND THE LOWER SATELLITE INTENSITY ESTIMATES...THE
INITIAL INTENSITY IS REDUCED TO 110 KT. THE EXTENSION OF AN
UPPER-LEVEL TROUGH PASSING NORTH OF IGOR IS STILL PRODUCING ABOUT
15 KT OF WESTERLY SHEAR OVER THE CYCLONE...ACCORDING TO THE LATEST
UW-CIMSS ANALYSES. THE SHIPS MODEL OUTPUT SHOWS A REDUCTION IN THE
SHEAR WITHIN THE NEXT 12 HOURS AS THIS FEATURE MOVES AWAY...WHICH
COULD ALLOW AN OPPORTUNITY FOR SOME RE-INTENSIFICATION IN THE
SHORT-TERM. THE GUIDANCE INDICATES THAT IGOR WILL BE MOVING INTO AN
ENVIRONMENT OF GRADUALLY INCREASING SOUTHERLY TO SOUTH-
SOUTHWESTERLY SHEAR IN ABOUT TWO DAYS...AND OVER COOLER WATERS BY
THE END OF THE FORECAST PERIOD. THE COMBINATION OF THESE TWO
FACTORS SHOULD RESULT IN A SLOW WEAKENING BEYOND 48 HOURS...AND THE
NHC OFFICIAL FORECAST REFLECTS THIS. BY DAY 5...GLOBAL MODELS
INDICATE THAT IGOR WILL BE AT LEAST BEGINNING TO UNDERGO
EXTRATROPICAL TRANSITION.

IGOR CONTINUES TO MAINTAIN ABOUT THE SAME MOTION...310/7. THE
REASONING FOR THE TRACK FORECAST IS UNCHANGED. THE HURRICANE IS
FORECAST TO MOVE NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD WITH
SOME INCREASE IN FORWARD SPEED AROUND THE WESTERN EXTENT OF A
SUBTROPICAL RIDGE DURING THE NEXT 48-72 HOURS. BEYOND 72 HOURS...
IGOR SHOULD BEGIN ACCELERATING WHILE TURNING NORTH AND THEN
NORTHEAST AHEAD OF AN APPROACHING MID-LATITUDE SHORTWAVE TROUGH
MOVING THROUGH THE NORTHEAST U.S. AND CANADIAN MARITIMES. THE
LATEST MODEL GUIDANCE HAS SHIFTED TO THE LEFT THIS CYCLE APPARENTLY
DUE TO TIMING DIFFERENCES ASSOCIATED WITH THE AFORMENTIONED
SHORTWAVE TROUGH.  THE OFFICIAL NHC TRACK FORECAST HAS BEEN NUDGED
WESTWARD...FOLLOWING THE MULTI-MODEL CONSENSUS...AND LIES IN THE
MIDDLE OF THE GUIDANCE ENVELOPE.


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/2100Z 21.7N  58.1W   110 KT
12HR VT     17/0600Z 22.4N  59.2W   110 KT
24HR VT     17/1800Z 23.5N  61.0W   115 KT
36HR VT     18/0600Z 24.9N  62.7W   115 KT
48HR VT     18/1800Z 26.5N  64.0W   110 KT
72HR VT     19/1800Z 30.5N  65.5W   100 KT
96HR VT     20/1800Z 35.5N  62.5W    90 KT
120HR VT     21/1800Z 42.0N  53.0W    70 KT

$$
FORECASTER KIMBERLAIN



000

WTNT41 KNHC 172040
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST FRI SEP 17 2010

AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING IGOR
EARLY THIS AFTERNOON MEASURED A MINIMUM PRESSURE OF 946 MB. THE
HURRICANE HUNTER ALSO MEASURED MAXIMUM FLIGHT-LEVEL AND SFMR WINDS
OF 102 AND 79 KT...RESPECTIVELY. THE INITIAL INTENSITY IS LOWERED
TO 90 KT BASED UPON THE AIRCRAFT OBSERVATIONS. DATA FROM THE PLANE
ALSO INDICATED A RATHER BROAD WIND FIELD...WITH THE PRESENCE OF A
DOUBLE WIND MAXIMA. SINCE THE PLANE DEPARTED...THE CLOUD PATTERN OF
IGOR HAS INCREASED IN ORGANIZATION...WITH COLDER CLOUD TOPS
DEVELOPING WITHIN THE INNER CORE AND THE EYE BECOMING VISIBLE
AGAIN. INNER CORE DYNAMICS NOTWITHSTANDING...THERE APPEARS TO BE A
FINAL WINDOW OF OPPORTUNITY FOR RE-INTENSIFICATION DURING THE NEXT
DAY OR SO AS IGOR REMAINS IN A LIGHT SHEAR ENVIRONMENT AND MOVES
OVER WARM WATERS. AFTER ABOUT 36 HOURS...A GRADUAL INCREASE IN
SOUTHERLY AND SOUTHWESTERLY SHEAR AND COOLER WATERS ALONG THE
FORECAST TRACK SHOULD PROMOTE A WEAKENING OF IGOR. THE OFFICIAL
INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD A BIT IN THE SHORT
TERM BASED UPON CURRENT TRENDS BUT IS NEARLY THE SAME LATER IN THE
PERIOD. IN AGREEMENT WITH THE GUIDANCE...IGOR IS FORECAST TO BECOME
A LARGE AND STRONG EXTRATROPICAL CYCLONE OVER THE FAR NORTH
ATLANTIC BEYOND 96 HOURS.

IGOR APPEARS TO BE ON TRACK...AND THE INITIAL MOTION ESTIMATE IS
305/09.  THE TRACK FORECAST PHILOSOPHY HAS NOT CHANGED.  IGOR
SHOULD BE STEERED NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD AROUND
THE WESTERN SIDE OF A SUBTROPICAL RIDGE DURING THE NEXT 36 HOURS.
AFTER THAT...A VIGOROUS SHORTWAVE TROUGH MOVING ACROSS THE
NORTHEASTERN U.S. SHOULD GRADUALLY TURN THE HURRICANE NORTHWARD IN
THE VICINITY OF BERMUDA...AND THEN NORTHEASTWARD WITH A SUBSTANTIAL
INCREASE IN FORWARD SPEED.  THE OFFICIAL NHC TRACK FORECAST IS VERY
CLOSE TO THE PREVIOUS ONE AND REMAINS CLOSE TO THE MULTI-MODEL
CONSENSUS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.

THE WIND RADII HAVE BEEN EXPANDED BASED UPON DATA FROM THE
RECONNAISSANCE AIRCRAFT AND AN EARLIER ASCAT OVERPASS.


FORECAST POSITIONS AND MAX WINDS

INITIAL      17/2100Z 23.7N  61.1W    90 KT
12HR VT     18/0600Z 24.8N  62.4W    95 KT
24HR VT     18/1800Z 26.2N  64.0W   100 KT
36HR VT     19/0600Z 27.9N  64.9W    95 KT
48HR VT     19/1800Z 30.0N  65.1W    90 KT
72HR VT     20/1800Z 35.5N  62.0W    85 KT
96HR VT     21/1800Z 43.5N  52.5W    75 KT...POST-TROP/EXTRATROP
120HR VT     22/1800Z 52.0N  44.0W    65 KT...POST-TROP/EXTRATROP

$$
FORECASTER KIMBERLAIN



000

WTNT41 KNHC 180301
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  40
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST FRI SEP 17 2010

INFRARED SATELLITE IMAGERY INDICATES IGOR HAS BECOME BETTER
ORGANIZED WITH A RING OF CONVECTIVE CLOUD TOPS OF -70C AND COLDER
ENCIRCLING A 20-25 NMI DIAMETER EYE THAT HAS BECOME MORE DISTINCT
DURING THE PAST COUPLE OF HOURS. A 17/2026Z AMSU OVERPASS ALSO
INDICATED THE UPPER-LEVEL WARM CORE HAS STRENGTHENED AND MOVED
UPWARD FROM 300 MB TO THE 200 MB...SUGGESTING THAT IGOR IS LIKELY
STRENGTHENING. AN AIR FORCE RESERVE RECON AIRCRAFT WILL BE
INVESTIGATING IGOR AROUND 06Z AND PROVIDE A BETTER INTENSITY
ESTIMATE.

THE INITIAL MOTION ESTIMATE IS 315/11. IGOR HAS MADE A TROCHOIDAL
WOBBLE TO THE RIGHT OF THE PREVIOUS FORECAST TRACK...BUT THIS IS
LIKELY JUST A TEMPORARY MOTION. IGOR IS EXPECTED TO MOVE BACK ON OR
CLOSE TO THE PREVIOUS ADVISORY TRACK BASED ON 00Z UPPER-AIR DATA
FROM BERMUDA SHOWING 24-HOUR MID-LEVEL HEIGHTS HAVE INCREASED BY 20
METERS AND WINDS HAVE SHIFTED AROUND TO AN EASTERLY DIRECTION...
WHICH INDICATES THE SUBTROPICAL RIDGE HAS BUILT WESTWARD TO THE
NORTH OF BERMUDA. UNFORTUNATELY...THIS RIDGING PATTERN WILL BE
SHORT-LIVED DUE TO A STRONG SHORTWAVE TROUGH CURRENTLY LOCATED JUST
OFF THE U.S. EAST COAST FORECAST BY ALL THE GLOBAL AND REGIONAL
MODELS TO CONTINUE TO MOVE EASTWARD AND CREATE A WEAKNESS IN THE
RIDGE BETWEEN 60W-70W LONGITUDE BY 24 HOURS. THIS WILL ALLOW IGOR
TO GRADUALLY MOVE NORTHWARD THROUGH THIS BREAK IN THE SUBTROPICAL
RIDGE PATTERN AND PASS VERY CLOSE TO BERMUDA IN ABOUT 48 HOURS. BY
72 HOURS...IGOR IS FORECAST TO BE CAPTURED BY A SECOND SHORTWAVE
TROUGH AND BE ACCELERATED OVER THE FAR NORTH ATLANTIC AS A POWERFUL
EXTRATROPICAL LOW PRESSURE SYSTEM. THE OFFICIAL FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE MODEL CONSENSUS.

IGOR IS EXHIBITING AN IMPRESSIVE OUTFLOW PATTERN THAT CONTINUES TO
EXPAND IN ALL QUADRANTS. THE HURRICANE IS EXPECTED TO MAINTAIN THIS
FAVORABLE OUTFLOW REGIME FOR THE NEXT 36-48 HOURS.  AFTERWARDS...
INCREASING SOUTHWESTERLY UPPER-LEVEL FLOW AHEAD OF A MID- TO
UPPER-LEVEL TROUGH WILL INCREASE THE SHEAR ACROSS THE CYCLONE...
WHICH COUPLED WITH DECREASING SSTS...SHOULD INDUCE WEAKENING. BY 96
HOURS...IGOR IS FORECAST TO TRANSITION INTO A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE OVER THE FAR NORTH ATLANTIC WHEN IGOR MERGES
WITH A FRONTAL SYSTEM. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
TO THE SHIPS INTENSITY MODEL.

THE EXTRATROPICAL FORECAST TRACK AND INTENSITIES AT 96 AND 120 HOURS
IS BASED ON GUIDANCE FROM THE NOAA OCEAN PREDICTION CENTER.


FORECAST POSITIONS AND MAX WINDS

INITIAL      18/0300Z 24.6N  62.0W    95 KT
12HR VT     18/1200Z 25.6N  63.2W   100 KT
24HR VT     19/0000Z 27.1N  64.4W   105 KT
36HR VT     19/1200Z 29.1N  65.0W   105 KT
48HR VT     20/0000Z 31.7N  64.5W   100 KT
72HR VT     21/0000Z 36.2N  61.2W    85 KT
96HR VT     22/0000Z 45.0N  50.0W    65 KT...POST-TROP/EXTRATROP
120HR VT     23/0000Z 52.5N  42.0W    65 KT...POST-TROP/EXTRATROP

$$
FORECASTER STEWART



000

WTNT41 KNHC 180837
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  41
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST SAT SEP 18 2010
 
DATA FROM THE HURRICANE HUNTER AIRCRAFT INDICATE THAT WHILE THE
CENTRAL PRESSURE OF IGOR HAD FALLEN TO 939 MB...THE WINDS AT FLIGHT
LEVEL WERE NOT EFFICIENTLY MIXING DOWN TO THE SURFACE.  THE INITIAL
INTENSITY IS HELD AT 95 KT BASED ON A BLEND OF THE 115 KT FLIGHT-
LEVEL WIND MAXIMUM AND A MAXIMUM WIND OF 77 KT FROM THE SFMR. THE
OUTFLOW IS WELL ESTABLISHED...PARTICULARLY TO THE NORTH OF THE
CENTER...AND THE ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR A
LITTLE MORE STRENGTHENING OVER THE NEXT DAY OR SO BEFORE THE SHEAR
INCREASES.  THE OFFICIAL FORECAST SHOWS A PEAK AT 105 KT IN 24
HOURS AND THEN A SLOW WEAKENING THROUGH 48 HOURS. REGARDLESS OF THE
DETAILS OF THE INTENSITY FORECAST...IGOR WILL BE A LARGE AND
DANGEROUS HURRICANE AS IT APPROACHES BERMUDA ON SUNDAY. WEAKENING
IS EXPECTED TO CONTINUE BEYOND 48 HOURS...AS IGOR MOVES OVER COOLER
WATERS AND THE SHEAR INCREASES FURTHER.  ONCE IGOR COMPLETES
EXTRATROPICAL TRANSITION...IT WILL BE A LARGE AND POWERFUL CYCLONE
OVER THE NORTH ATLANTIC.
 
AFTER A SHORT TERM WOBBLE TOWARD THE WEST-NORTHWEST...THE LONG-TERM
INITIAL MOTION ESTIMATE IS 310/11.  IGOR IS SITUATED SOUTH OF A
MID-LEVEL RIDGE EXTENDING ALONG 35N...AND THIS RIDGE IS FORECAST BY
ALL OF THE MODELS TO WEAKEN AS A SHORTWAVE TROUGH PROGRESSES EAST
OFF THE U.S. EAST COAST IN THE NEXT DAY OR SO.  IGOR WILL TURN
NORTHWARD INTO THE WEAKNESS ALONG 65W ON SUNDAY AND PASS VERY NEAR
BERMUDA BEFORE TURNING NORTHEASTWARD ON MONDAY AHEAD OF ANOTHER
SHORTWAVE TROUGH MOVING OFF THE COAST OF NORTH AMERICA.  THE GLOBAL
MODELS SHOW THE RIDGE NORTH OF IGOR REMAINING A LITTLE STRONGER
THAN PREVIOUSLY FORECAST...AND AS A RESULT MOST OF THE GUIDANCE HAS
SHIFTED A LITTLE TO THE LEFT AND SLOWER THROUGH 48 HOURS.  THE
OFFICIAL FORECAST HAS BEEN ADJUSTED IN THIS DIRECTION...BUT REMAINS
TO THE RIGHT OF MOST OF THE GUIDANCE AND A LITTLE FASTER THAN
THE CONSENSUS.  BEYOND 48 HOURS...THE NEW NHC FORECAST IS LARGELY
AN UPDATE OF THE PREVIOUS PACKAGE...AND SHOWS IGOR ACCELERATING
TOWARD THE NORTHEAST AS IT BECOMES EXTRATROPICAL.
 
IGOR HAS A VERY LARGE WIND FIELD...WITH A RADIUS OF MAXIMUM WINDS OF
AROUND 45 NAUTICAL MILES AND HURRICANE FORCE WINDS EXTENDING OUT UP
TO 90 NM FROM THE CENTER.  CONDITIONS WILL BEGIN TO DETERIORATE ON
BERMUDA BY TONIGHT...WELL IN ADVANCE OF THE CENTER.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0900Z 25.1N  62.8W    95 KT
 12HR VT     18/1800Z 26.2N  64.1W   100 KT
 24HR VT     19/0600Z 27.8N  65.1W   105 KT
 36HR VT     19/1800Z 29.9N  65.3W   100 KT
 48HR VT     20/0600Z 32.2N  64.7W    95 KT
 72HR VT     21/0600Z 38.5N  58.5W    80 KT
 96HR VT     22/0600Z 47.5N  46.5W    65 KT...POST-TROP/EXTRATROP
120HR VT     23/0600Z 51.5N  39.5W    55 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT41 KNHC 181448
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  42
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST SAT SEP 18 2010

THERE HAS BEEN LITTLE CHANGE IN THE STRUCTURE OF IGOR DURING THE
PAST SEVERAL HOURS.  RECENT MICROWAVE OVERPASSES SUGGEST THE
HURRICANE IS UNDERGOING AN EYEWALL REPLACEMENT CYCLE...WITH THE
20 NM WIDE INNER EYE SEEN IN THE PREVIOUS AIRCRAFT MISSION GRADUALLY
WEAKENING.  SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN
102 KT...AND THE INITIAL INTENSITY REMAINS 95 KT.  AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN ROUTE TO
INVESTIGATE IGOR.

THE INITIAL MOTION IS 310/10.  DURING THE NEXT 36-72 HR...IGOR WILL
ROUND THE WESTERN END OF A DEEP-LAYER RIDGE OVER THE CENTRAL AND
EASTERN ATLANTIC AND ENTER THE WESTERLIES TO THE EAST OF A
SHORTWAVE TROUGH MOVING OFF THE COAST OF EASTERN NORTH AMERICA. 
THE TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THIS SCENARIO AND
HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY.  THIS PART OF THE
THE NEW FORECAST TRACK IS THUS AN UPDATE OF THE PREVIOUS ONE...WITH
THE CENTER OF IGOR PASSING NEAR OR OVER BERMUDA IN 36-48 HR.  AFTER
72 HR...THERE IS SOME SPREAD IN THE GUIDANCE AS IGOR UNDERGOES
EXTRATROPICAL TRANSITION.  THE ECMWF TURNS THE CYCLONE SHARPLY TO
THE NORTH...WHILE THE OTHER DYNAMICAL MODELS SHOW A MORE
NORTHEASTWARD TO EASTWARD MOTION.  THIS PART OF THE TRACK IS SHIFTED
TO THE EAST OF THE PREVIOUS FORECAST BASED ON A BLEND OF THE
DYNAMICAL MODELS...BUT LIES TO THE NORTH OF THE CENTER OF THE
GUIDANCE ENVELOPE.

IGOR IS IN AN ENVIRONMENT OF LIGHT SOUTHERLY VERTICAL SHEAR...AND
THIS IS FORECAST TO CONTINUE FOR THE NEXT 24 HR OR SO.  AFTER
THAT...THE HURRICANE IS FORECAST TO ENCOUNTER INCREASING SHEAR.  IT
IS UNCERTAIN IF THE CURRENT EYEWALL REPLACEMENT CYCLE WILL BE
COMPLETE ENOUGH TO ALLOW STRENGTHENING BEFORE THE SHEAR
INCREASES...BUT CURRENT TRENDS SUGGEST IT WILL NOT.  MOST OF THE
INTENSITY GUIDANCE NOW SHOWS LITTLE CHANGE IN STRENGTH OR SLOW
WEAKENING DURING THE FIRST 36 HR...WITH ONLY THE SHIPS MODEL
SHOWING MODEST STRENGTHENING.  THE NEW INTENSITY FORECAST CALLS FOR
IGOR TO MAINTAIN A 95 KT INTENSITY FOR 36 HR OR SO...FOLLOWED BY
WEAKENING DUE TO SHEAR.  IT CANNOT BE RULED OUT THAT IGOR COULD
REGAIN MAJOR HURRICANE STATUS BEFORE REACHING BERMUDA...BUT IT
APPEARS LESS LIKELY THAN PREVIOUSLY THOUGHT.  EXTRATROPICAL
TRANSITION SHOULD BE UNDERWAY BY 72 HR AND BE COMPLETE BY 96 HR. 
IGOR IS EXPECTED TO REMAIN A LARGE AND POWERFUL CYCLONE AFTER
EXTRATROPICAL TRANSITION.

IGOR CONTINUES TO HAVE A VERY LARGE WIND FIELD...AND CONDITIONS WILL
BEGIN TO DETERIORATE ON BERMUDA BY TONIGHT WELL IN ADVANCE OF THE
CENTER.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/1500Z 26.0N  63.6W    95 KT
 12HR VT     19/0000Z 27.1N  64.6W    95 KT
 24HR VT     19/1200Z 28.9N  65.3W    95 KT
 36HR VT     20/0000Z 31.1N  65.2W    95 KT
 48HR VT     20/1200Z 33.9N  64.2W    90 KT
 72HR VT     21/1200Z 40.5N  56.0W    75 KT
 96HR VT     22/1200Z 47.5N  44.0W    65 KT...POST-TROP/EXTRATROP
120HR VT     23/1200Z 50.0N  36.5W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT41 KNHC 182039
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST SAT SEP 18 2010

IGOR CONTINUES WORKING ITS WAY THROUGH AN EYEWALL REPLACEMENT CYCLE. 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING IGOR
FOUND A FRAGMENT OF THE INNER EYEWALL REMAINING INSIDE AN 85 N MI
WIDE OUTER EYEWALL.  THE CENTRAL PRESSURE WAS 945 MB.  THE MAXIMUM
700-MB FLIGHT-LEVEL WINDS WERE 113 KT...WHILE THE MAXIMUM ESTIMATED
SURFACE WINDS FROM THE SFMR WERE 73 KT.  SURFACE WIND ESTIMATES
FROM TWO EYEWALL DROPSONDES WERE NEAR 70 KT AND CONSISTENT WITH THE
COINCIDENT SFMR READINGS.  BASED ON THESE DATA...THE INITIAL
INTENSITY IS REDUCED TO 85 KT...AND IT IS POSSIBLE THAT THIS IS A
LITTLE GENEROUS.
 
THE INITIAL MOTION IS 320/12.  THERE IS NO CHANGE TO THE FORECAST
PHILOSOPHY...AND ONLY MINOR TWEAKS TO THE FORECAST TRACK FROM THE
PREVIOUS ADVISORY.  DURING THE NEXT 36-72 HR...IGOR WILL ROUND THE
WESTERN END OF A DEEP-LAYER RIDGE OVER THE CENTRAL AND EASTERN
ATLANTIC AND ENTER THE WESTERLIES TO THE EAST OF A SHORTWAVE TROUGH
MOVING OFF THE COAST OF EASTERN NORTH AMERICA.  THE TRACK GUIDANCE
REMAINS IN GOOD AGREEMENT WITH THIS SCENARIO...WITH THE CENTER OF
IGOR PASSING NEAR OR OVER BERMUDA IN ABOUT 36 HR.  AFTER 72 HR...
THERE REMAINS SPREAD IN THE GUIDANCE AS IGOR UNDERGOES
EXTRATROPICAL TRANSITION.  THIS PART OF THE TRACK IS SHIFTED A
LITTLE TO THE EAST OF THE PREVIOUS FORECAST BASED ON A BLEND OF THE
DYNAMICAL MODELS...AND IT NOW LIES NEAR THE MIDDLE OF THE GUIDANCE
ENVELOPE.

IT APPEARS UNLIKELY THAT IGOR WILL COMPLETE THE EYEWALL REPLACEMENT
CYCLE IN TIME TO SIGNIFICANTLY STRENGTHEN GIVEN THE CURRENT
INTERNAL TRENDS AND THE EXPECTATION OF INCREASED VERTICAL WIND
SHEAR AFTER 24 HR.  NONE OF THE GUIDANCE SHOWS SIGNIFICANT
STRENGTHENING...AND THE NEW INTENSITY FORECAST NOW CALLS FOR LITTLE
CHANGE IN STRENGTH DURING THE NEXT 36 HR.  AFTER THAT...IGOR SHOULD
WEAKEN DUE TO INCREASING SHEAR.  EXTRATROPICAL TRANSITION SHOULD BE
UNDERWAY BY 72 HR AND BE COMPLETE BY 96 HR.  IGOR IS EXPECTED TO
REMAIN A LARGE AND POWERFUL CYCLONE AFTER EXTRATROPICAL
TRANSITION...AND THIS IS REFLECTED IN THE 96-120 HR INTENSITY
FORECAST.
 
IGOR CONTINUES TO HAVE A VERY LARGE WIND FIELD...AND CONDITIONS WILL
BEGIN TO DETERIORATE ON BERMUDA TONIGHT WELL IN ADVANCE OF THE
CENTER.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 27.1N  64.3W    85 KT
 12HR VT     19/0600Z 28.4N  65.0W    85 KT
 24HR VT     19/1800Z 30.5N  65.4W    85 KT
 36HR VT     20/0600Z 33.1N  64.9W    85 KT
 48HR VT     20/1800Z 36.1N  62.6W    80 KT
 72HR VT     21/1800Z 42.5N  52.5W    75 KT
 96HR VT     22/1800Z 48.0N  42.0W    75 KT...POST-TROP/EXTRATROP
120HR VT     23/1800Z 50.0N  35.0W    60 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT41 KNHC 190233
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  44
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SAT SEP 18 2010
 
THE CLOUD PATTERN IS NOT AS IMPRESSIVE AS IT WAS 12 HOURS AGO AND IT
APPEARS THAT IGOR COULD BE A LITTLE BIT WEAKER TONIGHT. THE AREA OF
DEEP CONVECTION HAS DECREASED AND THERE IS NO EYE OBSERVED ON
CONVENTIONAL SATELLITE IMAGERY. A MICROWAVE PASS A FEW HOURS AGO
SHOWS A PARTIAL RING OF CONVECTION ASSOCIATED WITH WHAT IS LEFT OF
THE EYEWALL. DVORAK T-NUMBERS HAVE DECREASED...BUT STILL SUPPORT AN
INITIAL INTENSITY OF 85 KNOTS. I WAS TEMPTED TO LOWER THE INTENSITY
JUST A LITTLE BIT GIVEN THE CURRENT SATELLITE PRESENTATION...BUT I
WOULD RATHER WAIT FOR DATA FROM THE RECONNAISSANCE AIRCRAFT...WHICH
WILL BE IN THE AREA SOON. FOR THE NEXT 24 HOURS...IGOR WILL BE
WITHIN AN ENVIRONMENT FAVORABLE TO MAINTAIN ITS CURRENT INTENSITY
AND IN FACT...THE INTENSITY CONSENSUS MODEL KEEPS IGOR WITH NO
CHANGE FOR THE NEXT 12 TO 24 HOURS. ALTHOUGH THE OFFICIAL FORECAST
SHOWS IGOR WITH 85 KNOTS AS IT PASSES NEAR OR OVER BERMUDA...THE
HURRICANE COULD EASILY EXPERIENCE SOME MINOR FLUCTUATIONS IN
INTENSITY. THEREAFTER...ONCE IGOR BECOMES EMBEDDED WITHIN THE
MID-LATITUDE WESTERLY FLOW WELL NORTHEAST OF BERMUDA...IT SHOULD
BEGIN TO BECOME POST-TROPICAL/EXTRATROPICAL.
 
THE STEERING FLOW HAS BEEN WELL ESTABLISHED AND WELL DEPICTED BY
GLOBAL MODELS SINCE IGOR FORMED MANY DAYS AGO...AND IT HAS BEEN
DESCRIBED IN DETAIL IN PREVIOUS DISCUSSIONS. IGOR IS NOW MOVING
TOWARD THE NORTH-NORTHWEST OR 330 DEGREES AT 11 KNOTS...AND A TURN
TO THE NORTH AROUND THE WESTERN EDGE OF THE SUBTROPICAL RIDGE
SHOULD BEGIN SOON. IN 36 HOUR...THE CYCLONE SHOULD BE MOVING
NORTHEASTWARD FULLY EMBEDDED WITHIN THE MID-LATITUDE FLOW AHEAD OF
A LARGE TROUGH. GIVEN THE WELL ESTABLISHED STEERING CURRENTS
FORECAST BY THE GLOBAL MODELS...TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT FOR THE NEXT 12 TO 36 HOURS...INCREASING THE CONFIDENCE
IN THE FORECAST DURING THIS PERIOD. HOWEVER...THERE IS A LARGE
SPREAD IN MODELS BEYOND 48 HOURS AS IGOR BECOMES POST-TROPICAL/
EXTRATROPICAL AND MOVES RAPIDLY NORTHEASTWARD OVER THE NORTH
ATLANTIC.
 
IGOR CONTINUES TO HAVE A VERY LARGE WIND FIELD...AND CONDITIONS
SHOULD DETERIORATE ON BERMUDA SOON WELL IN ADVANCE OF THE
CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 28.2N  64.7W    85 KT
 12HR VT     19/1200Z 29.7N  65.4W    85 KT
 24HR VT     20/0000Z 32.0N  65.1W    85 KT
 36HR VT     20/1200Z 35.0N  64.0W    80 KT
 48HR VT     21/0000Z 38.5N  60.5W    80 KT
 72HR VT     22/0000Z 46.0N  50.0W    70 KT...POST-TROP/EXTRATROP
 96HR VT     23/0000Z 49.5N  40.0W    60 KT...POST-TROP/EXTRATROP
120HR VT     24/0000Z 53.0N  35.5W    45 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

WTNT41 KNHC 190853
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  45
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST SUN SEP 19 2010

DATA FROM THE HURRICANE HUNTER AIRCRAFT AND SATELLITE IMAGERY
INDICATE THAT IGOR HAS CONTINUED TO SLOWLY WEAKEN.  THE AIRCRAFT
DID NOT REPORT AN EYEWALL...AND SOME DRY AIR ALSO APPEARS TO BE
WORKING ITS WAY INTO THE CIRCULATION...PARTICULARLY OVER THE
WESTERN SEMICIRCLE.  THE INITIAL INTENSITY IS LOWERED TO 75 KT
BASED ON A BLEND OF THE FLIGHT LEVEL MAXIMUM WIND OF 91 KT AND A
MAXIMUM SFMR READING OF 68 KT.  WHILE THE STRONGEST WINDS HAVE
DECREASED...THE SFMR DATA SHOWS THAT THE WIND FIELD OF IGOR
CONTINUES TO BROADEN...AND THE 50-KT AND 64-KT WIND RADII HAVE BEEN
INCREASED.  LITTLE CHANGE IN INTENSITY IS EXPECTED FOR THE NEXT
COUPLE OF DAYS...AND IGOR WILL BE A LARGE HURRICANE AS IT PASSES BY
BERMUDA IN THE NEXT 24 HOURS AND SUBJECTS THAT ISLAND TO A LONG
PERIOD OF STRONG WINDS...WITH TROPICAL STORM CONDITIONS LIKELY
LASTING AT LEAST 24 HOURS.  BY 72 HOURS...IGOR WILL TRANSITION TO A
POWERFUL AND LARGE EXTRATROPICAL CYCLONE AND THEN SLOWLY WEAKEN
THROUGH THE END OF THE PERIOD. 
 
THE INITIAL MOTION ESTIMATE IS 340/10.  THE LATEST AIRCRAFT FIXES
WERE LOCATED A LITTLE TO THE WEST OF THE APPARENT CENTER IN
GEOSTATIONARY IMAGERY...AND ALSO A LITTLE TO THE LEFT OF THE
PREVIOUS FORECAST TRACK.  THE OVERALL TRACK FORECAST REASONING
REMAINS UNCHANGED...AS IGOR WILL TURN NORTHWARD SOON AS IT MOVES
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE...AND THEN
ACCELERATE TOWARD THE NORTHEAST ON MONDAY AS IT RECURVES AHEAD
OF A MID-LATITUDE TROUGH MOVING OFF THE COAST OF NORTH AMERICA. 
THROUGH 36 HOURS THE OFFICIAL FORECAST HAS BEEN ADJUSTED A LITTLE
TO THE LEFT OF THE PREVIOUS ONE TO ACCOUNT FOR THE INITIAL POSITION
AND LIES ALONG THE EASTERN EDGE OF THE TIGHTLY CLUSTERED GUIDANCE
ENVELOPE.  THE SPREAD IN THE GUIDANCE INCREASES BEYOND 48 HOURS DUE
TO VARIATIONS IN THE DETAILS OF HOW IGOR INTERACTS WITH THE 
MID-LATITUDE FLOW DURING AND AFTER EXTRATROPICAL TRANSITION.  THE
OFFICIAL FORECAST HAS BEEN ADJUSTED NORTHWARD AT DAYS 3 AND 4 AND
IS IN BEST AGREEMENT WITH THE GFS MODEL.  AT DAY 5 THE OFFICIAL
FORECAST SHOWS POST-TROPICAL IGOR SLOWING AND TURNING MORE NORTHWARD
...HOWEVER CONFIDENCE IS LOW IN THIS SCENARIO AS THE SPREAD IN THE
GUIDANCE IS VERY LARGE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0900Z 28.9N  65.3W    75 KT
 12HR VT     19/1800Z 30.5N  65.5W    75 KT
 24HR VT     20/0600Z 33.4N  64.9W    75 KT
 36HR VT     20/1800Z 37.0N  62.5W    75 KT
 48HR VT     21/0600Z 41.0N  57.5W    75 KT
 72HR VT     22/0600Z 49.0N  47.0W    70 KT...POST-TROP/EXTRATROP
 96HR VT     23/0600Z 53.0N  38.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     24/0600Z 56.5N  36.5W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT41 KNHC 191453
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  46
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST SUN SEP 19 2010
 
SATELLITE AND MICROWAVE IMAGERY SHOWS THAT THE ORGANIZATION OF IGOR
HAS CHANGED LITTLE SINCE THE RECONNAISSANCE AIRCRAFT DEPARTED
THE HURRICANE THIS MORNING.  THEREFORE...THE INITIAL INTENSITY WILL
REMAIN 75 KT...BASED ON A BLEND OF SUBJECTIVE AND OBJECTIVE DVORAK
INTENSITY ESTIMATES.  DRIFTING BUOY 44903...RECENTLY REPORTED A
PRESSURE OF 951 MB...WHICH SUGGESTS THAT THERE HAS BEEN LITTLE
CHANGE TO THE MINIMUM PRESSURE THAT WAS REPORTED EARLIER BY THE
AIRCRAFT. THE NEXT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO REACH
THE HURRICANE AROUND 1800 UTC THIS AFTERNOON.

IGOR HAS TURNED NORTHWARD AND IS MOVING A LITTLE FASTER THAN
BEFORE...WITH AN INITIAL MOTION OF 360/12.  THE HURRICANE IS
FORECAST TO CONTINUE NORTHWARD FOR THE NEXT 12 HOURS OR SO...THEN
TURN NORTHEASTWARD AND ACCELERATE AHEAD OF A MID-LATITUDE TROUGH
MOVING OFF THE COAST OF NORTH AMERICA.  THE OFFICIAL FORECAST TRACK
IS VERY CLOSE TO THE PREVIOUS ADVISORY DURING THE FIRST 36 HOURS
AND LIES JUST EAST OF THE MULTI-MODEL CONSENSUS. THE MODELS ARE IN
RELATIVELY GOOD AGREEMENT SHOWING THE SYSTEM PASSING NEAR OR JUST
SOUTHEAST OF NEWFOUNDLAND IN 2-3 DAYS.  THEREAFTER...THE SPREAD IN
THE TRACK GUIDANCE INCREASES SIGNIFICANTLY.  AT THE LONGER
RANGE...THE NEW NHC TRACK FORECAST IS CLOSE THE CONSENSUS AND 
IS IN BEST AGREEMENT WITH THE GFS AND UKMET SOLUTIONS.

IGOR WILL REMAIN A LARGE HURRICANE AS IT PASSES BERMUDA...AND 
LITTLE CHANGE IN INTENSITY IS FORECAST WHILE IGOR REMAINS A
TROPICAL CYCLONE.  EXTRATROPICAL TRANSITION SHOULD BEGIN IN 
ABOUT A DAY AND SHOULD BE COMPLETE IN ABOUT 48 HOURS.  AFTER 72
HOURS...GRADUAL WEAKENING IS INDICATED BY THE GLOBAL MODELS AND
THIS IS FOLLOWED IN THE OFFICIAL FORECAST.

SUSTAINED TROPICAL STORM FORCE WINDS HAVE BEEN OBSERVED AT THE
OFFICIAL OBSERVING SITE IN BERMUDA...WITH WIND GUSTS TO NEAR
HURRICANE FORCE ALREADY REPORTED.  THE 34-KT WIND RADII WAS
EXPENDED OVER THE NORTHWEST QUADRANT BASED ON DATA FROM NOAA 
BUOY 41048.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1500Z 30.4N  65.4W    75 KT
 12HR VT     20/0000Z 32.3N  65.2W    75 KT
 24HR VT     20/1200Z 35.4N  63.9W    75 KT
 36HR VT     21/0000Z 39.3N  60.5W    75 KT
 48HR VT     21/1200Z 43.5N  55.0W    70 KT...POST-TROP/EXTRATROP
 72HR VT     22/1200Z 50.5N  45.5W    65 KT...POST-TROP/EXTRATROP
 96HR VT     23/1200Z 54.5N  40.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     24/1200Z 59.0N  39.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 

WTNT41 KNHC 191453
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  46
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST SUN SEP 19 2010
 
SATELLITE AND MICROWAVE IMAGERY SHOWS THAT THE ORGANIZATION OF IGOR
HAS CHANGED LITTLE SINCE THE RECONNAISSANCE AIRCRAFT DEPARTED
THE HURRICANE THIS MORNING.  THEREFORE...THE INITIAL INTENSITY WILL
REMAIN 75 KT...BASED ON A BLEND OF SUBJECTIVE AND OBJECTIVE DVORAK
INTENSITY ESTIMATES.  DRIFTING BUOY 44903...RECENTLY REPORTED A
PRESSURE OF 951 MB...WHICH SUGGESTS THAT THERE HAS BEEN LITTLE
CHANGE TO THE MINIMUM PRESSURE THAT WAS REPORTED EARLIER BY THE
AIRCRAFT. THE NEXT RECONNAISSANCE AIRCRAFT IS SCHEDULED TO REACH
THE HURRICANE AROUND 1800 UTC THIS AFTERNOON.

IGOR HAS TURNED NORTHWARD AND IS MOVING A LITTLE FASTER THAN
BEFORE...WITH AN INITIAL MOTION OF 360/12.  THE HURRICANE IS
FORECAST TO CONTINUE NORTHWARD FOR THE NEXT 12 HOURS OR SO...THEN
TURN NORTHEASTWARD AND ACCELERATE AHEAD OF A MID-LATITUDE TROUGH
MOVING OFF THE COAST OF NORTH AMERICA.  THE OFFICIAL FORECAST TRACK
IS VERY CLOSE TO THE PREVIOUS ADVISORY DURING THE FIRST 36 HOURS
AND LIES JUST EAST OF THE MULTI-MODEL CONSENSUS. THE MODELS ARE IN
RELATIVELY GOOD AGREEMENT SHOWING THE SYSTEM PASSING NEAR OR JUST
SOUTHEAST OF NEWFOUNDLAND IN 2-3 DAYS.  THEREAFTER...THE SPREAD IN
THE TRACK GUIDANCE INCREASES SIGNIFICANTLY.  AT THE LONGER
RANGE...THE NEW NHC TRACK FORECAST IS CLOSE THE CONSENSUS AND 
IS IN BEST AGREEMENT WITH THE GFS AND UKMET SOLUTIONS.

IGOR WILL REMAIN A LARGE HURRICANE AS IT PASSES BERMUDA...AND 
LITTLE CHANGE IN INTENSITY IS FORECAST WHILE IGOR REMAINS A
TROPICAL CYCLONE.  EXTRATROPICAL TRANSITION SHOULD BEGIN IN 
ABOUT A DAY AND SHOULD BE COMPLETE IN ABOUT 48 HOURS.  AFTER 72
HOURS...GRADUAL WEAKENING IS INDICATED BY THE GLOBAL MODELS AND
THIS IS FOLLOWED IN THE OFFICIAL FORECAST.

SUSTAINED TROPICAL STORM FORCE WINDS HAVE BEEN OBSERVED AT THE
OFFICIAL OBSERVING SITE IN BERMUDA...WITH WIND GUSTS TO NEAR
HURRICANE FORCE ALREADY REPORTED.  THE 34-KT WIND RADII WAS
EXPENDED OVER THE NORTHWEST QUADRANT BASED ON DATA FROM NOAA 
BUOY 41048.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/1500Z 30.4N  65.4W    75 KT
 12HR VT     20/0000Z 32.3N  65.2W    75 KT
 24HR VT     20/1200Z 35.4N  63.9W    75 KT
 36HR VT     21/0000Z 39.3N  60.5W    75 KT
 48HR VT     21/1200Z 43.5N  55.0W    70 KT...POST-TROP/EXTRATROP
 72HR VT     22/1200Z 50.5N  45.5W    65 KT...POST-TROP/EXTRATROP
 96HR VT     23/1200Z 54.5N  40.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     24/1200Z 59.0N  39.0W    35 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 


WTNT41 KNHC 192046
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  47
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST SUN SEP 19 2010
 
THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS MEASURED PEAK
FLIGHT-LEVEL AND SFMR WINDS OF 82 KT AND 68 KT...RESPECTIVELY. 
BASED ON THESE DATA...THE INITIAL INTENSITY IS LOWERED SLIGHTLY 
TO 70 KT.  THE WIND FIELD REMAINS QUITE LARGE AND SOME OF THE WIND
RADII HAVE BEEN EXPENDED OUTWARD BASED ON THE AIRCRAFT AND EARLIER
ASCAT DATA.  LITTLE CHANGE IN INTENSITY IS EXPECTED WHILE IGOR
REMAINS A TROPICAL CYCLONE.  THE GLOBAL MODELS INDICATE THAT
EXTRATROPICAL TRANSITION SHOULD BEGIN ON MONDAY...AND BE 
COMPLETED IN ABOUT 48 HOURS.  GRADUAL WEAKENING IS SHOWN BY THE
DYNAMICAL MODELS AFTER IGOR BECOMES EXTRATROPICAL...AND THIS IS
REFLECTED IN THE OFFICIAL FORECAST. 

THE AIRCRAFT FIXES WERE A FEW TENTHS OF A DEGREE WEST OF THE EARLIER
SATELLITE ESTIMATES.  THIS HAS REQUIRED A LITTLE ADJUSTMENT TO THE
INITIAL POSITION AND MOTION.  THE UPDATED POSITION HAS ALSO REQUIRED
A SMALL WESTWARD SHIFT IN THE EARLY PORTION OF THE FORECAST TRACK. 
THERE HAVE BEEN NO CHANGES TO THE TRACK FORECAST PHILOSOPHY...
HOWEVER...AND IGOR IS EXPECTED TO TURN NORTHEAST TONIGHT AHEAD OF A
MID-LATITUDE TROUGH MOVING OFF THE COAST OF NORTH AMERICA.  THE
GLOBAL MODELS HAVE BEEN VERY INCONSISTENT IN THE EXTRATROPICAL
PORTION OF THE TRACK AND THERE REMAINS A VERY LARGE SPREAD IN THE
GUIDANCE AT 3 TO 5 DAYS.  THE OFFICIAL FORECAST HAS BEEN ADJUSTED A
LITTLE EASTWARD AT 72 HOURS AND BEYOND...TO BE IN BETTER AGREEMENT 
WITH THE MULTI-MODEL CONSENSUS.
  
ALTHOUGH THE CENTER OF IGOR IS LIKELY TO PASS WEST OF
BERMUDA...HURRICANE FORCE WINDS EXTEND A LARGE DISTANCE FROM THE
CENTER AND SIGNIFICANT IMPACTS ARE BEING FELT ON THE ISLAND. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/2100Z 31.5N  65.9W    70 KT
 12HR VT     20/0600Z 33.6N  65.3W    70 KT
 24HR VT     20/1800Z 36.9N  62.8W    70 KT
 36HR VT     21/0600Z 40.6N  58.1W    70 KT
 48HR VT     21/1800Z 45.0N  52.0W    65 KT...POST-TROP/EXTRATROP
 72HR VT     22/1800Z 51.0N  41.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     23/1800Z 55.0N  37.5W    50 KT...POST-TROP/EXTRATROP
120HR VT     24/1800Z 60.0N  37.5W    45 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 

WTNT41 KNHC 200235
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  48
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SUN SEP 19 2010
 
THE LAST OBSERVATIONS FROM THE AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT SHOWED THAT THE CENTRAL PRESSURE WAS SLOWLY RISING AND
MAXIMUM FLIGHT LEVEL WINDS HAD DECREASED TO 68 KT.  THERE WERE A
FEW SFMR-OBSERVED SURFACE WINDS OF 65 TO 69 KT ABOUT 90 N MI TO THE
SOUTHWEST OF THE CENTER BUT MOST OF THESE WERE FLAGGED AS
QUESTIONABLE.  THE CURRENT INTENSITY IS SET AT 65 KT...WHICH IS
REMARKABLY LOW FOR THE ESTIMATED CENTRAL PRESSURE OF 955 MB.  NOT
MUCH ADDITIONAL WEAKENING IS ANTICIPATED OVER THE NEXT DAY OR SO. 
BY 36 HOURS...THE GFS SHOWS WELL-DEFINED THERMAL ADVECTION WITHIN
THE CIRCULATION AND THEREFORE IGOR IS LIKELY TO HAVE BEEN
TRANSFORMED INTO A VIGOROUS EXTRATROPICAL CYCLONE AROUND THAT TIME.

THE LATEST CENTER FIXES INDICATE THAT THE TRACK IS BEGINNING TO
BEND TO THE RIGHT AND THE INITIAL MOTION IS ESTIMATED TO BE 015/12. 
NOT MUCH CHANGE IS MADE TO THE OFFICIAL FORECAST TRACK FOR THE NEXT
24 TO 36 HOURS.  IGOR IS EXPECTED TO TURN NORTHEASTWARD ON MONDAY
AND ACCELERATE AHEAD OF A DEEP-LAYER TROUGH MOVING EASTWARD FROM
THE NORTHEASTERN U.S. AND THE CANADIAN MARITIMES. IN THE LATTER HALF
OF THE FORECAST PERIOD...POST-TROPICAL IGOR IS LIKELY TO TURN BACK
TO THE NORTH AND NORTH-NORTHWEST AS IT INTERACTS WITH ANOTHER
EXTRATROPICAL CYCLONE AT HIGH LATITUDES.

SUSTAINED WINDS OF 64 KT WITH GUSTS TO 81 KT WERE REPORTED AT
BERMUDA DURING THE PAST HOUR.  SINCE IGOR HAS A VERY LARGE
CIRCULATION...SIGNIFICANT IMPACTS ON THE ISLAND WILL PROBABLY
CONTINUE THROUGH THE NIGHT. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 32.4N  65.5W    65 KT
 12HR VT     20/1200Z 34.6N  64.4W    65 KT
 24HR VT     21/0000Z 38.1N  60.9W    65 KT
 36HR VT     21/1200Z 42.5N  55.5W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/0000Z 46.5N  49.0W    70 KT...POST-TROP/EXTRATROP
 72HR VT     23/0000Z 49.5N  38.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     24/0000Z 58.0N  37.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     25/0000Z 62.0N  42.0W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER PASCH
 

WTNT41 KNHC 200235
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  48
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST SUN SEP 19 2010
 
THE LAST OBSERVATIONS FROM THE AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT SHOWED THAT THE CENTRAL PRESSURE WAS SLOWLY RISING AND
MAXIMUM FLIGHT LEVEL WINDS HAD DECREASED TO 68 KT.  THERE WERE A
FEW SFMR-OBSERVED SURFACE WINDS OF 65 TO 69 KT ABOUT 90 N MI TO THE
SOUTHWEST OF THE CENTER BUT MOST OF THESE WERE FLAGGED AS
QUESTIONABLE.  THE CURRENT INTENSITY IS SET AT 65 KT...WHICH IS
REMARKABLY LOW FOR THE ESTIMATED CENTRAL PRESSURE OF 955 MB.  NOT
MUCH ADDITIONAL WEAKENING IS ANTICIPATED OVER THE NEXT DAY OR SO. 
BY 36 HOURS...THE GFS SHOWS WELL-DEFINED THERMAL ADVECTION WITHIN
THE CIRCULATION AND THEREFORE IGOR IS LIKELY TO HAVE BEEN
TRANSFORMED INTO A VIGOROUS EXTRATROPICAL CYCLONE AROUND THAT TIME.

THE LATEST CENTER FIXES INDICATE THAT THE TRACK IS BEGINNING TO
BEND TO THE RIGHT AND THE INITIAL MOTION IS ESTIMATED TO BE 015/12. 
NOT MUCH CHANGE IS MADE TO THE OFFICIAL FORECAST TRACK FOR THE NEXT
24 TO 36 HOURS.  IGOR IS EXPECTED TO TURN NORTHEASTWARD ON MONDAY
AND ACCELERATE AHEAD OF A DEEP-LAYER TROUGH MOVING EASTWARD FROM
THE NORTHEASTERN U.S. AND THE CANADIAN MARITIMES. IN THE LATTER HALF
OF THE FORECAST PERIOD...POST-TROPICAL IGOR IS LIKELY TO TURN BACK
TO THE NORTH AND NORTH-NORTHWEST AS IT INTERACTS WITH ANOTHER
EXTRATROPICAL CYCLONE AT HIGH LATITUDES.

SUSTAINED WINDS OF 64 KT WITH GUSTS TO 81 KT WERE REPORTED AT
BERMUDA DURING THE PAST HOUR.  SINCE IGOR HAS A VERY LARGE
CIRCULATION...SIGNIFICANT IMPACTS ON THE ISLAND WILL PROBABLY
CONTINUE THROUGH THE NIGHT. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0300Z 32.4N  65.5W    65 KT
 12HR VT     20/1200Z 34.6N  64.4W    65 KT
 24HR VT     21/0000Z 38.1N  60.9W    65 KT
 36HR VT     21/1200Z 42.5N  55.5W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/0000Z 46.5N  49.0W    70 KT...POST-TROP/EXTRATROP
 72HR VT     23/0000Z 49.5N  38.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     24/0000Z 58.0N  37.0W    40 KT...POST-TROP/EXTRATROP
120HR VT     25/0000Z 62.0N  42.0W    30 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER PASCH
 


WTNT41 KNHC 200853
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST MON SEP 20 2010
 
DEEP CONVECTION HAS BEEN SPUTTERING NEAR THE CENTER OF IGOR OVER THE
PAST FEW HOURS...HOWEVER SATELLITE CLASSIFICATIONS AND EARLIER
SURFACE OBSERVATIONS FROM BERMUDA SUPPORT KEEPING IGOR AT HURRICANE
INTENSITY.  LITTLE CHANGE IN STRENGTH IS EXPECTED BEFORE IGOR
UNDERGOES EXTRATROPICAL TRANSITION...WHICH SHOULD BE COMPLETE BY 36
HOURS WHEN GLOBAL MODEL FIELDS SHOW THE CYCLONE BECOMING FULLY
EMBEDDED WITHIN A BAROCLINIC ZONE.  POST-TROPICAL IGOR IS EXPECTED
TO REMAIN A STRONG EXTRATROPICAL CYCLONE FOR A DAY OR TWO BEFORE
WEAKENING LATE IN THE PERIOD.
 
THE LATEST SATELLITE FIXES SUGGEST THAT THE FORWARD MOTION OF IGOR
HAS INCREASED...AND THE INITIAL MOTION ESTIMATE IS 025/17. IGOR
WILL CONTINUE TO ACCELERATE TOWARD THE NORTHEAST AS IT RECURVES
AHEAD OF A MID-LATITUDE TROUGH OVER THE CANADIAN MARITIMES DURING
THE NEXT COUPLE OF DAYS.  BY DAYS 3 AND 4 IGOR WILL TURN NORTHWARD
AND THEN NORTHWESTWARD AS IT INTERACTS WITH AN UPPER-LEVEL LOW
MOVING EASTWARD FROM NORTHERN QUEBEC INTO THE DAVIS STRAIT. THE
GLOBAL MODEL GUIDANCE SHOWS A FASTER FORWARD SPEED IN THE FIRST
COUPLE OF DAYS...AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED IN
THAT DIRECTION AND LIES ON THE LEFT SIDE OF THE GUIDANCE
SUITE...BUT TO THE RIGHT OF THE GFS. FROM 48 HOURS ONWARD...THE NEW
FORECAST IS A BLEND OF THE PREVIOUS NHC FORECAST AND THE GFS
ENSEMBLE MEAN. HOWEVER...MODEL SPREAD IS QUITE LARGE AT THE END OF
THE PERIOD DUE TO DIFFERENCES IN HOW IGOR INTERACTS WITH THE UPPER
LOW...AND CONFIDENCE IN TRACK FORECAST NEAR THE END OF THE PERIOD
IS LOW.
 
TROPICAL STORM CONDITIONS ARE STILL BEING FELT ON BERMUDA...BUT
SHOULD GRADUALLY DIMINISH TODAY.  STRONG WINDS ARE POSSIBLE
ALONG THE COAST OF NEWFOUNDLAND AS IGOR PASSES BY...AND THE
CANADIAN HURRICANE CENTRE HAS ISSUED A TROPICAL STORM WATCH FOR A
PORTION OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 34.2N  64.4W    65 KT
 12HR VT     20/1800Z 36.7N  62.4W    65 KT
 24HR VT     21/0600Z 40.6N  57.6W    65 KT
 36HR VT     21/1800Z 45.6N  50.8W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/0600Z 47.7N  44.5W    65 KT...POST-TROP/EXTRATROP
 72HR VT     23/0600Z 55.0N  37.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/0600Z 61.0N  41.0W    35 KT...POST-TROP/EXTRATROP
120HR VT     25/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT41 KNHC 201439
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST MON SEP 20 2010
 
STRONG SOUTHERLY SHEAR HAS DISPLACED ALL OF THE DEEP CONVECTION TO
THE NORTH OF THE EXPOSED LOW-LEVEL CENTER.  THERE HAVE BEEN NO
RECENT OBSERVATIONS NEAR THE CENTER OF IGOR...BUT SATELLITE
INTENSITY ESTIMATES SUPPORT AN INTENSITY AT OR JUST BELOW 65 KT.
THE INTENSITY WILL BE HELD AT 65 KT...AND IT IS POSSIBLE THAT IGOR
COULD REGAIN A LITTLE BIT OF STRENGTH AS IT BEGINS TO GO THROUGH
EXTRATROPICAL TRANSITION.  THAT PROCESS IS EXPECTED TO BE COMPLETE
BY 36 HOURS WHEN IGOR SHOULD BE COMPLETELY EMBEDDED WITHIN A
FRONTAL ZONE.  THE OFFICIAL FORECAST SHOWS SOME RE-STRENGTHENING
DURING THE FIRST 24 HOURS AND GRADUAL WEAKENING FROM 36-96 HOURS. 
THE CYCLONE IS EXPECTED TO DISSIPATE BY 120 HOURS.  THIS FORECAST
IS MORE OR LESS A BLEND OF DYNAMICAL GUIDANCE AND GUIDANCE PROVIDED
BY THE OCEAN PREDICTION CENTER.

IGOR CONTINUES TO ACCELERATE TO THE NORTH-NORTHEAST WITH A MOTION OF
025/21.  THERE IS LITTLE SPREAD IN THE TRACK GUIDANCE DURING THE
NEXT 36 HOURS...AND THE OFFICIAL TRACK FORECAST ONLY HAD TO BE
SHIFTED A SMALL DISTANCE TO THE WEST OF THE PREVIOUS FORECAST. 
AFTER 36 HOURS...THERE IS MORE SPREAD IN THE GUIDANCE...BUT THE
BULK OF THE MODELS SHOW POST-TROPICAL IGOR TURNING NORTHWESTWARD
TOWARD GREENLAND.  THE NHC FORECAST BY 96 HOURS IS TO THE WEST OF
THE MODEL CONSENSUS TO PUT MORE WEIGHT ON THE GLOBAL MODELS AND
LESS ON THE GFDL.

THE OCEAN PREDICTION CENTER ALSO PROVIDED THE CURRENT 12-FOOT SEAS
RADII AND THE WIND RADII DURING THE EXTRATROPICAL PHASE...ALL OF
WHICH HAVE BEEN EXPANDED IN THIS ADVISORY PACKAGE.  IGOR WILL
CONTINUE TO BE A LARGE CYCLONE AS IT MOVES PAST NEWFOUNDLAND TOWARD
GREENLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 36.1N  63.3W    65 KT
 12HR VT     21/0000Z 38.9N  60.6W    70 KT
 24HR VT     21/1200Z 42.9N  55.0W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/0000Z 46.8N  48.9W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/1200Z 50.4N  44.0W    60 KT...POST-TROP/EXTRATROP
 72HR VT     23/1200Z 56.5N  40.5W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/1200Z 62.5N  47.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     25/1200Z...DISSIPATED
 
$$
FORECASTER BERG
 

WTNT41 KNHC 202040
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  51
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST MON SEP 20 2010
 
IGOR APPEARS TO BE STARTING EXTRATROPICAL TRANSITION.  SURFACE
OBSERVATIONS INDICATE THAT A FRONTAL BOUNDARY EXTENDS FROM
NEWFOUNDLAND SOUTHWARD TOWARDS THE HURRICANE...AND COLD ADVECTION
IS INCREASING OVER THE WESTERN SIDE OF ITS CIRCULATION.  GLOBAL
MODEL FIELDS SUGGEST THAT IGOR SHOULD BE FULLY INCORPORATED INTO
THE FRONTAL ZONE BY 24 HOURS...IF NOT SOONER.  ASCAT DATA FROM
EARLIER THIS MORNING SHOWED A LARGE AREA OF STRONG WINDS...
BETWEEN 55-64 KT...OVER THE SOUTHWESTERN QUADRANT OF THE STORM AND
SUPPORTS AN INITIAL INTENSITY OF 65 KT.  THE ORIENTATION OF THE
STRONG WINDS OVER THE SOUTHWESTERN QUADRANT ALSO SUGGESTS THAT
EXTRATROPICAL TRANSITION IS OCCURRING.  IGOR COULD BE REINVIGORATED
DURING THE NEXT 24 HOURS AS IT BECOMES EXTRATROPICAL...AND THE NHC
FORECAST CONTINUES TO SHOW SOME STRENGTHENING IN THE SHORT TERM...
FOLLOWED BY GRADUAL WEAKENING AND DISSIPATION BY 120 HOURS.
 
THE INITIAL MOTION IS NOW 040/24.  THE TRACK GUIDANCE IS STILL
TIGHTLY CLUSTERED FOR THE NEXT 24 HOURS AND THEN SHOWS INCREASING
SPREAD AFTER THAT TIME.  THERE IS GREATER AGREEMENT THAT IGOR WILL
TURN NORTHWARD AND THEN NORTHWESTWARD TOWARD GREENLAND AFTER 24
HOURS...BUT THERE IS NOT AS MUCH AGREEMENT IN THE FORWARD SPEED. 
THE NEW TRACK FORECAST IS A BLEND OF THE PREVIOUS FORECAST...THE
MODEL CONSENSUS TVCN...AND GUIDANCE PROVIDED BY THE OCEAN
PREDICTION CENTER.
 
EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL STORM FORCE WINDS COULD REACH THE COAST OF
NEWFOUNDLAND BEFORE THE TRANSITION IS COMPLETE.  THEREFORE...
ENVIRONMENT CANADA HAS ISSUED A TROPICAL STORM WARNING FOR THE
EASTERN PART OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/2100Z 38.2N  61.5W    65 KT
 12HR VT     21/0600Z 41.0N  57.9W    70 KT
 24HR VT     21/1800Z 45.3N  52.3W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/0600Z 50.1N  47.5W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/1800Z 54.6N  45.8W    60 KT...POST-TROP/EXTRATROP
 72HR VT     23/1800Z 60.0N  46.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     24/1800Z 66.0N  56.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     25/1800Z...DISSIPATED
 
$$
FORECASTER BERG
 

WTNT41 KNHC 210233
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  52
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST MON SEP 20 2010

IGOR CONTINUES TO GRADUALLY LOSE TROPICAL CHARACTERISTICS...HOWEVER
THERE IS STILL SOME ORGANIZED DEEP CONVECTION OVER THE NORTHERN
SEMICIRCLE OF THE SYSTEM.  MOREOVER...SHORT-TERM GLOBAL MODEL
FORECASTS INDICATE THAT THE BAROCLINIC ZONE THAT IS WITHIN THE
CIRCULATION HAS NOT YET REACHED THE CENTER.  IGOR IS THEREFORE NOT
COMPLETELY EMBEDDED IN THE FRONT AND WILL BE MAINTAINED AS A
TROPICAL CYCLONE FOR THIS ADVISORY.  IT IS...HOWEVER...EXPECTED TO
BECOME FULLY EXTRATROPICAL ON TUESDAY.  SOME BAROCLINICALLY INDUCED
STRENGTHENING IS PREDICTED UNTIL THE CYCLONE MOVES PAST THE
CANADIAN MARITIMES.  LATE IN THE FORECAST PERIOD THE SYSTEM WILL BE
MERGING WITH ANOTHER EXTRATROPICAL LOW OVER HIGH LATITUDES.

INITIAL MOTION IS A SOMEWHAT FASTER 045/25.  IGOR...OR ITS
POST-TROPICAL COUNTERPART...IS LIKELY TO BE STEERED AROUND A LARGE
MID-LEVEL CYCLONIC GYRE OVER NORTHEASTERN NORTH AMERICA OVER THE
NEXT FEW DAYS.  THE OFFICIAL FORECAST TRACK BEYOND 12 HOURS HAS
BEEN ADJUSTED SOMEWHAT TO THE LEFT OF THE PREVIOUS ONE.

EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL STORM FORCE WINDS COULD REACH THE COAST OF
NEWFOUNDLAND BEFORE THE TRANSITION IS COMPLETE.  ENVIRONMENT CANADA
IS THEREFORE MAINTAINING THE TROPICAL STORM WARNING FOR THE EASTERN
PART OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0300Z 39.9N  59.3W    65 KT
 12HR VT     21/1200Z 43.2N  55.0W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/0000Z 48.9N  49.4W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/1200Z 54.8N  47.9W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/0000Z 59.0N  52.7W    60 KT...POST-TROP/EXTRATROP
 72HR VT     24/0000Z 63.5N  59.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     25/0000Z 68.5N  62.0W    25 KT...POST-TROP/EXTRATROP
120HR VT     26/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 

WTNT41 KNHC 210855
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  53
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST TUE SEP 21 2010

IGOR CONTINUES TO LOSE TROPICAL CYCLONE CHARACTERISTICS AS IT
BECOMES MORE INVOLVED WITH A BAROCLINIC ZONE.  HOWEVER...A SMALL
AREA OF CONVECTION HAS DEVELOPED NORTH OF THE CENTER...AND THE
CYCLONE HAS NOT YET DEVELOPED A WELL-DEFINED FRONTAL BOUNDARY SOUTH
OF THE CENTER.  THUS...IGOR IS AGAIN MAINTAINED AS A TROPICAL
CYCLONE.  EXTRATROPICAL TRANSITION IS LIKELY TO BE COMPLETE LATER
TODAY...WITH SOME BAROCLINICALLY-INDUCED STRENGTHENING EXPECTED. 
LATE IN THE FORECAST PERIOD...THE SYSTEM WILL BE MERGING WITH
ANOTHER EXTRATROPICAL LOW OVER HIGH LATITUDES.
 
THE INITIAL MOTION IS 045/36.  IGOR...OR THE EXTRATROPICAL LOW IT IS
FORECAST TO BECOME...IS LIKELY TO BE STEERED AROUND A LARGE
MID-LEVEL CYCLONIC GYRE OVER NORTHEASTERN NORTH AMERICA OVER THE
NEXT FEW DAYS.  THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS
FORECAST THROUGH 48 HR...THEN ADJUSTED SOMEWHAT TO THE SOUTH
THEREAFTER DURING THE FORECAST NORTHWESTWARD MOTION AT 72-96 HR.
 
EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL-STORM AND POSSIBLY HURRICANE-FORCE WINDS
COULD REACH THE COAST OF NEWFOUNDLAND BEFORE THE TRANSITION IS
COMPLETE.  ENVIRONMENT CANADA HAS ISSUED A HURRICANE WATCH AND
EXTENDED THE TROPICAL STORM WARNING FOR THE EASTERN PART OF THAT
PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0900Z 42.8N  55.1W    65 KT
 12HR VT     21/1800Z 46.7N  51.3W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/0600Z 52.3N  48.4W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/1800Z 56.7N  48.3W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/0600Z 60.5N  52.5W    65 KT...POST-TROP/EXTRATROP
 72HR VT     24/0600Z 62.5N  59.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     25/0600Z 64.0N  61.0W    35 KT...POST-TROP/EXTRATROP
120HR VT     26/0600Z...DISSIPATED
 
$$
FORECASTER BEVEN
 

WTNT41 KNHC 211445
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  54
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST TUE SEP 21 2010
 
IGOR IS VERY CLOSE TO LOSING ALL ITS TROPICAL CHARACTERISTICS AND
WILL LIKELY BECOME FULLY EXTRATROPICAL BY THIS AFTERNOON.  THE
INITIAL INTENSITY IS BEING HELD AT 65 KT...ALTHOUGH IT IS POSSIBLE
THAT THE CYCLONE HAS STRENGTHENED OVER THE PAST FEW HOURS.  ASCAT
DATA SHOULD BE RECEIVED FROM NEAR THE HURRICANE SOON...AND A
RE-ASSESSMENT OF THE INTENSITY WILL BE MADE AT THAT TIME.  IGOR
COULD STILL GAIN SOME STRENGTH DURING THE NEXT 12-24 HOURS AS IT
MOVES NORTHWARD PAST NEWFOUNDLAND BUT THEN ALL THE MODELS SHOW
GRADUAL WEAKENING AS IT MOVES NEAR GREENLAND.  THE OFFICIAL
INTENSITY FORECAST IS A BLEND OF THE MODEL GUIDANCE...AND GUIDANCE
PROVIDED BY THE NOAA OCEAN PREDICTION CENTER.

IGOR IS MOVING RAPIDLY NORTHEASTWARD AT 40 KT.  MODEL GUIDANCE IS IN
GOOD AGREEMENT THAT IGOR WILL BE TURNING NORTHWARD DURING THE NEXT
24 HOURS AS IT SWINGS AROUND NEWFOUNDLAND AND MOVES THROUGH THE
DAVIS STRAITS.  THE EXTRATROPICAL CYCLONE IS EXPECTED TO SLOW DOWN
MARKEDLY FROM 36-96 HOURS AS IT INTERACTS AND POSSIBLY MERGES WITH
ANOTHER AREA OF LOW PRESSURE OFF THE NORTHEASTERN COAST OF QUEBEC. 
THE OFFICIAL FORECAST IS JUST A LITTLE FASTER THAN THE PREVIOUS ONE
AND REMAINS RELATIVELY NEAR THE MODEL CONSENSUS TVCN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/1500Z 46.2N  52.8W    65 KT
 12HR VT     22/0000Z 50.2N  49.4W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/1200Z 55.3N  48.5W    70 KT...POST-TROP/EXTRATROP
 36HR VT     23/0000Z 59.8N  51.6W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/1200Z 62.7N  57.8W    50 KT...POST-TROP/EXTRATROP
 72HR VT     24/1200Z 63.5N  61.0W    40 KT...POST-TROP/EXTRATROP
 96HR VT     25/1200Z 62.0N  60.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     26/1200Z...DISSIPATED
 
$$
FORECASTER BERG/STEWART
 

WTNT41 KNHC 212032
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  55
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST TUE SEP 21 2010
 
LAND AND BUOY OBSERVATIONS IN NEWFOUNDLAND AND THE ADJACENT WATERS
INDICATE THAT IGOR HAS BECOME FULLY EMBEDDED WITHIN A FRONTAL ZONE.
JUST AFTER THE CENTER OF IGOR PASSED OVER CANADIAN BUOY 44251 NEAR
CAPE RACE EARLIER IN THE DAY...THE TEMPERATURE DROPPED BY ABOUT 10
DEGREES F.  HOWEVER...THE CYCLONE IS STILL PRODUCING HURRICANE-
FORCE WINDS...AND THE INITIAL INTENSITY OF 70 KT IS BASED ON
REPORTED SUSTAINED WINDS OF 63 KT AT BONAVISTA NEWFOUNDLAND.  IGOR
IS EXPECTED TO CONTINUE TO PRODUCE HURRICANE-FORCE WINDS FOR
ANOTHER DAY OR SO...AND THEN SHOULD GRADUALLY WEAKEN AS IT MOVES
NORTHWARD INTO THE DAVIS STRAITS.
 
THE INITIAL MOTION IS ESTIMATED TO BE 25 DEGREES AT 34 KT.  THE
TRACK GUIDANCE CONTINUES TO BE IN RELATIVELY GOOD AGREEMENT IN
SHOWING IGOR TURNING NORTHWESTWARD TO THE WEST OF GREENLAND IN A
COUPLE OF DAYS AND INTERACTING WITH ANOTHER AREA OF LOW PRESSURE
NEAR NORTHERN QUEBEC.  THE MODELS DO SHOW VARYING SOLUTIONS...
HOWEVER...ON WHICH OF THESE TWO SYSTEMS WILL BECOME THE DOMINANT
ONE.  THE OFFICIAL FORECAST...IN ACCORDANCE WITH GUIDANCE
PROVIDED BY THE OCEAN PREDICTION CENTER...WILL KEEP IGOR AS A
DISTINCT CYCLONE THROUGH 96 HOURS.  THE OFFICIAL FORECAST INDICATES
VERY LITTLE MOTION FROM 72 TO 96 HOURS SINCE THE CYCLONE WILL BE
NORTH OF THE BELT OF STRONG WESTERLIES BY THEN.

THE 12-FT SEAS RADII PROVIDED BY THE OCEAN PREDICTION CENTER ARE 480
NE...900 SE...1320 SW...AND 380 NW.  RADII IN THE FORECAST/ADVISORY
ARE LIMITED TO 995 N MI...BUT 12-FT SEAS ARE ACTUALLY OCCURRING AT
A GREATER DISTANCE THAN THAT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 49.3N  51.7W    70 KT...POST-TROP/EXTRATROP
 12HR VT     22/0600Z 53.0N  49.8W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/1800Z 57.2N  51.0W    70 KT...POST-TROP/EXTRATROP
 36HR VT     23/0600Z 61.6N  57.5W    55 KT...POST-TROP/EXTRATROP
 48HR VT     23/1800Z 62.5N  60.5W    45 KT...POST-TROP/EXTRATROP
 72HR VT     24/1800Z 62.0N  60.5W    40 KT...POST-TROP/EXTRATROP
 96HR VT     25/1800Z 61.5N  59.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     26/1800Z...DISSIPATED
 
$$
FORECASTER BERG
 

WTNT41 KNHC 200853
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST MON SEP 20 2010
 
DEEP CONVECTION HAS BEEN SPUTTERING NEAR THE CENTER OF IGOR OVER THE
PAST FEW HOURS...HOWEVER SATELLITE CLASSIFICATIONS AND EARLIER
SURFACE OBSERVATIONS FROM BERMUDA SUPPORT KEEPING IGOR AT HURRICANE
INTENSITY.  LITTLE CHANGE IN STRENGTH IS EXPECTED BEFORE IGOR
UNDERGOES EXTRATROPICAL TRANSITION...WHICH SHOULD BE COMPLETE BY 36
HOURS WHEN GLOBAL MODEL FIELDS SHOW THE CYCLONE BECOMING FULLY
EMBEDDED WITHIN A BAROCLINIC ZONE.  POST-TROPICAL IGOR IS EXPECTED
TO REMAIN A STRONG EXTRATROPICAL CYCLONE FOR A DAY OR TWO BEFORE
WEAKENING LATE IN THE PERIOD.
 
THE LATEST SATELLITE FIXES SUGGEST THAT THE FORWARD MOTION OF IGOR
HAS INCREASED...AND THE INITIAL MOTION ESTIMATE IS 025/17. IGOR
WILL CONTINUE TO ACCELERATE TOWARD THE NORTHEAST AS IT RECURVES
AHEAD OF A MID-LATITUDE TROUGH OVER THE CANADIAN MARITIMES DURING
THE NEXT COUPLE OF DAYS.  BY DAYS 3 AND 4 IGOR WILL TURN NORTHWARD
AND THEN NORTHWESTWARD AS IT INTERACTS WITH AN UPPER-LEVEL LOW
MOVING EASTWARD FROM NORTHERN QUEBEC INTO THE DAVIS STRAIT. THE
GLOBAL MODEL GUIDANCE SHOWS A FASTER FORWARD SPEED IN THE FIRST
COUPLE OF DAYS...AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED IN
THAT DIRECTION AND LIES ON THE LEFT SIDE OF THE GUIDANCE
SUITE...BUT TO THE RIGHT OF THE GFS. FROM 48 HOURS ONWARD...THE NEW
FORECAST IS A BLEND OF THE PREVIOUS NHC FORECAST AND THE GFS
ENSEMBLE MEAN. HOWEVER...MODEL SPREAD IS QUITE LARGE AT THE END OF
THE PERIOD DUE TO DIFFERENCES IN HOW IGOR INTERACTS WITH THE UPPER
LOW...AND CONFIDENCE IN TRACK FORECAST NEAR THE END OF THE PERIOD
IS LOW.
 
TROPICAL STORM CONDITIONS ARE STILL BEING FELT ON BERMUDA...BUT
SHOULD GRADUALLY DIMINISH TODAY.  STRONG WINDS ARE POSSIBLE
ALONG THE COAST OF NEWFOUNDLAND AS IGOR PASSES BY...AND THE
CANADIAN HURRICANE CENTRE HAS ISSUED A TROPICAL STORM WATCH FOR A
PORTION OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 34.2N  64.4W    65 KT
 12HR VT     20/1800Z 36.7N  62.4W    65 KT
 24HR VT     21/0600Z 40.6N  57.6W    65 KT
 36HR VT     21/1800Z 45.6N  50.8W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/0600Z 47.7N  44.5W    65 KT...POST-TROP/EXTRATROP
 72HR VT     23/0600Z 55.0N  37.0W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/0600Z 61.0N  41.0W    35 KT...POST-TROP/EXTRATROP
120HR VT     25/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 


WTNT41 KNHC 201439
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST MON SEP 20 2010
 
STRONG SOUTHERLY SHEAR HAS DISPLACED ALL OF THE DEEP CONVECTION TO
THE NORTH OF THE EXPOSED LOW-LEVEL CENTER.  THERE HAVE BEEN NO
RECENT OBSERVATIONS NEAR THE CENTER OF IGOR...BUT SATELLITE
INTENSITY ESTIMATES SUPPORT AN INTENSITY AT OR JUST BELOW 65 KT.
THE INTENSITY WILL BE HELD AT 65 KT...AND IT IS POSSIBLE THAT IGOR
COULD REGAIN A LITTLE BIT OF STRENGTH AS IT BEGINS TO GO THROUGH
EXTRATROPICAL TRANSITION.  THAT PROCESS IS EXPECTED TO BE COMPLETE
BY 36 HOURS WHEN IGOR SHOULD BE COMPLETELY EMBEDDED WITHIN A
FRONTAL ZONE.  THE OFFICIAL FORECAST SHOWS SOME RE-STRENGTHENING
DURING THE FIRST 24 HOURS AND GRADUAL WEAKENING FROM 36-96 HOURS. 
THE CYCLONE IS EXPECTED TO DISSIPATE BY 120 HOURS.  THIS FORECAST
IS MORE OR LESS A BLEND OF DYNAMICAL GUIDANCE AND GUIDANCE PROVIDED
BY THE OCEAN PREDICTION CENTER.

IGOR CONTINUES TO ACCELERATE TO THE NORTH-NORTHEAST WITH A MOTION OF
025/21.  THERE IS LITTLE SPREAD IN THE TRACK GUIDANCE DURING THE
NEXT 36 HOURS...AND THE OFFICIAL TRACK FORECAST ONLY HAD TO BE
SHIFTED A SMALL DISTANCE TO THE WEST OF THE PREVIOUS FORECAST. 
AFTER 36 HOURS...THERE IS MORE SPREAD IN THE GUIDANCE...BUT THE
BULK OF THE MODELS SHOW POST-TROPICAL IGOR TURNING NORTHWESTWARD
TOWARD GREENLAND.  THE NHC FORECAST BY 96 HOURS IS TO THE WEST OF
THE MODEL CONSENSUS TO PUT MORE WEIGHT ON THE GLOBAL MODELS AND
LESS ON THE GFDL.

THE OCEAN PREDICTION CENTER ALSO PROVIDED THE CURRENT 12-FOOT SEAS
RADII AND THE WIND RADII DURING THE EXTRATROPICAL PHASE...ALL OF
WHICH HAVE BEEN EXPANDED IN THIS ADVISORY PACKAGE.  IGOR WILL
CONTINUE TO BE A LARGE CYCLONE AS IT MOVES PAST NEWFOUNDLAND TOWARD
GREENLAND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/1500Z 36.1N  63.3W    65 KT
 12HR VT     21/0000Z 38.9N  60.6W    70 KT
 24HR VT     21/1200Z 42.9N  55.0W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/0000Z 46.8N  48.9W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/1200Z 50.4N  44.0W    60 KT...POST-TROP/EXTRATROP
 72HR VT     23/1200Z 56.5N  40.5W    55 KT...POST-TROP/EXTRATROP
 96HR VT     24/1200Z 62.5N  47.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     25/1200Z...DISSIPATED
 
$$
FORECASTER BERG
 


WTNT41 KNHC 202040
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  51
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST MON SEP 20 2010
 
IGOR APPEARS TO BE STARTING EXTRATROPICAL TRANSITION.  SURFACE
OBSERVATIONS INDICATE THAT A FRONTAL BOUNDARY EXTENDS FROM
NEWFOUNDLAND SOUTHWARD TOWARDS THE HURRICANE...AND COLD ADVECTION
IS INCREASING OVER THE WESTERN SIDE OF ITS CIRCULATION.  GLOBAL
MODEL FIELDS SUGGEST THAT IGOR SHOULD BE FULLY INCORPORATED INTO
THE FRONTAL ZONE BY 24 HOURS...IF NOT SOONER.  ASCAT DATA FROM
EARLIER THIS MORNING SHOWED A LARGE AREA OF STRONG WINDS...
BETWEEN 55-64 KT...OVER THE SOUTHWESTERN QUADRANT OF THE STORM AND
SUPPORTS AN INITIAL INTENSITY OF 65 KT.  THE ORIENTATION OF THE
STRONG WINDS OVER THE SOUTHWESTERN QUADRANT ALSO SUGGESTS THAT
EXTRATROPICAL TRANSITION IS OCCURRING.  IGOR COULD BE REINVIGORATED
DURING THE NEXT 24 HOURS AS IT BECOMES EXTRATROPICAL...AND THE NHC
FORECAST CONTINUES TO SHOW SOME STRENGTHENING IN THE SHORT TERM...
FOLLOWED BY GRADUAL WEAKENING AND DISSIPATION BY 120 HOURS.
 
THE INITIAL MOTION IS NOW 040/24.  THE TRACK GUIDANCE IS STILL
TIGHTLY CLUSTERED FOR THE NEXT 24 HOURS AND THEN SHOWS INCREASING
SPREAD AFTER THAT TIME.  THERE IS GREATER AGREEMENT THAT IGOR WILL
TURN NORTHWARD AND THEN NORTHWESTWARD TOWARD GREENLAND AFTER 24
HOURS...BUT THERE IS NOT AS MUCH AGREEMENT IN THE FORWARD SPEED. 
THE NEW TRACK FORECAST IS A BLEND OF THE PREVIOUS FORECAST...THE
MODEL CONSENSUS TVCN...AND GUIDANCE PROVIDED BY THE OCEAN
PREDICTION CENTER.
 
EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL STORM FORCE WINDS COULD REACH THE COAST OF
NEWFOUNDLAND BEFORE THE TRANSITION IS COMPLETE.  THEREFORE...
ENVIRONMENT CANADA HAS ISSUED A TROPICAL STORM WARNING FOR THE
EASTERN PART OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/2100Z 38.2N  61.5W    65 KT
 12HR VT     21/0600Z 41.0N  57.9W    70 KT
 24HR VT     21/1800Z 45.3N  52.3W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/0600Z 50.1N  47.5W    70 KT...POST-TROP/EXTRATROP
 48HR VT     22/1800Z 54.6N  45.8W    60 KT...POST-TROP/EXTRATROP
 72HR VT     23/1800Z 60.0N  46.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     24/1800Z 66.0N  56.0W    30 KT...POST-TROP/EXTRATROP
120HR VT     25/1800Z...DISSIPATED
 
$$
FORECASTER BERG
 


WTNT41 KNHC 210233
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  52
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 PM AST MON SEP 20 2010

IGOR CONTINUES TO GRADUALLY LOSE TROPICAL CHARACTERISTICS...HOWEVER
THERE IS STILL SOME ORGANIZED DEEP CONVECTION OVER THE NORTHERN
SEMICIRCLE OF THE SYSTEM.  MOREOVER...SHORT-TERM GLOBAL MODEL
FORECASTS INDICATE THAT THE BAROCLINIC ZONE THAT IS WITHIN THE
CIRCULATION HAS NOT YET REACHED THE CENTER.  IGOR IS THEREFORE NOT
COMPLETELY EMBEDDED IN THE FRONT AND WILL BE MAINTAINED AS A
TROPICAL CYCLONE FOR THIS ADVISORY.  IT IS...HOWEVER...EXPECTED TO
BECOME FULLY EXTRATROPICAL ON TUESDAY.  SOME BAROCLINICALLY INDUCED
STRENGTHENING IS PREDICTED UNTIL THE CYCLONE MOVES PAST THE
CANADIAN MARITIMES.  LATE IN THE FORECAST PERIOD THE SYSTEM WILL BE
MERGING WITH ANOTHER EXTRATROPICAL LOW OVER HIGH LATITUDES.

INITIAL MOTION IS A SOMEWHAT FASTER 045/25.  IGOR...OR ITS
POST-TROPICAL COUNTERPART...IS LIKELY TO BE STEERED AROUND A LARGE
MID-LEVEL CYCLONIC GYRE OVER NORTHEASTERN NORTH AMERICA OVER THE
NEXT FEW DAYS.  THE OFFICIAL FORECAST TRACK BEYOND 12 HOURS HAS
BEEN ADJUSTED SOMEWHAT TO THE LEFT OF THE PREVIOUS ONE.

EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL STORM FORCE WINDS COULD REACH THE COAST OF
NEWFOUNDLAND BEFORE THE TRANSITION IS COMPLETE.  ENVIRONMENT CANADA
IS THEREFORE MAINTAINING THE TROPICAL STORM WARNING FOR THE EASTERN
PART OF THAT PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0300Z 39.9N  59.3W    65 KT
 12HR VT     21/1200Z 43.2N  55.0W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/0000Z 48.9N  49.4W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/1200Z 54.8N  47.9W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/0000Z 59.0N  52.7W    60 KT...POST-TROP/EXTRATROP
 72HR VT     24/0000Z 63.5N  59.5W    50 KT...POST-TROP/EXTRATROP
 96HR VT     25/0000Z 68.5N  62.0W    25 KT...POST-TROP/EXTRATROP
120HR VT     26/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 


WTNT41 KNHC 210855
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  53
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 AM AST TUE SEP 21 2010

IGOR CONTINUES TO LOSE TROPICAL CYCLONE CHARACTERISTICS AS IT
BECOMES MORE INVOLVED WITH A BAROCLINIC ZONE.  HOWEVER...A SMALL
AREA OF CONVECTION HAS DEVELOPED NORTH OF THE CENTER...AND THE
CYCLONE HAS NOT YET DEVELOPED A WELL-DEFINED FRONTAL BOUNDARY SOUTH
OF THE CENTER.  THUS...IGOR IS AGAIN MAINTAINED AS A TROPICAL
CYCLONE.  EXTRATROPICAL TRANSITION IS LIKELY TO BE COMPLETE LATER
TODAY...WITH SOME BAROCLINICALLY-INDUCED STRENGTHENING EXPECTED. 
LATE IN THE FORECAST PERIOD...THE SYSTEM WILL BE MERGING WITH
ANOTHER EXTRATROPICAL LOW OVER HIGH LATITUDES.
 
THE INITIAL MOTION IS 045/36.  IGOR...OR THE EXTRATROPICAL LOW IT IS
FORECAST TO BECOME...IS LIKELY TO BE STEERED AROUND A LARGE
MID-LEVEL CYCLONIC GYRE OVER NORTHEASTERN NORTH AMERICA OVER THE
NEXT FEW DAYS.  THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS
FORECAST THROUGH 48 HR...THEN ADJUSTED SOMEWHAT TO THE SOUTH
THEREAFTER DURING THE FORECAST NORTHWESTWARD MOTION AT 72-96 HR.
 
EVEN THOUGH IGOR IS FORECAST TO BE EXTRATROPICAL AS IT PASSES
NEWFOUNDLAND...TROPICAL-STORM AND POSSIBLY HURRICANE-FORCE WINDS
COULD REACH THE COAST OF NEWFOUNDLAND BEFORE THE TRANSITION IS
COMPLETE.  ENVIRONMENT CANADA HAS ISSUED A HURRICANE WATCH AND
EXTENDED THE TROPICAL STORM WARNING FOR THE EASTERN PART OF THAT
PROVINCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0900Z 42.8N  55.1W    65 KT
 12HR VT     21/1800Z 46.7N  51.3W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/0600Z 52.3N  48.4W    75 KT...POST-TROP/EXTRATROP
 36HR VT     22/1800Z 56.7N  48.3W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/0600Z 60.5N  52.5W    65 KT...POST-TROP/EXTRATROP
 72HR VT     24/0600Z 62.5N  59.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     25/0600Z 64.0N  61.0W    35 KT...POST-TROP/EXTRATROP
120HR VT     26/0600Z...DISSIPATED
 
$$
FORECASTER BEVEN
 


WTNT41 KNHC 211445
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  54
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
1100 AM AST TUE SEP 21 2010
 
IGOR IS VERY CLOSE TO LOSING ALL ITS TROPICAL CHARACTERISTICS AND
WILL LIKELY BECOME FULLY EXTRATROPICAL BY THIS AFTERNOON.  THE
INITIAL INTENSITY IS BEING HELD AT 65 KT...ALTHOUGH IT IS POSSIBLE
THAT THE CYCLONE HAS STRENGTHENED OVER THE PAST FEW HOURS.  ASCAT
DATA SHOULD BE RECEIVED FROM NEAR THE HURRICANE SOON...AND A
RE-ASSESSMENT OF THE INTENSITY WILL BE MADE AT THAT TIME.  IGOR
COULD STILL GAIN SOME STRENGTH DURING THE NEXT 12-24 HOURS AS IT
MOVES NORTHWARD PAST NEWFOUNDLAND BUT THEN ALL THE MODELS SHOW
GRADUAL WEAKENING AS IT MOVES NEAR GREENLAND.  THE OFFICIAL
INTENSITY FORECAST IS A BLEND OF THE MODEL GUIDANCE...AND GUIDANCE
PROVIDED BY THE NOAA OCEAN PREDICTION CENTER.

IGOR IS MOVING RAPIDLY NORTHEASTWARD AT 40 KT.  MODEL GUIDANCE IS IN
GOOD AGREEMENT THAT IGOR WILL BE TURNING NORTHWARD DURING THE NEXT
24 HOURS AS IT SWINGS AROUND NEWFOUNDLAND AND MOVES THROUGH THE
DAVIS STRAITS.  THE EXTRATROPICAL CYCLONE IS EXPECTED TO SLOW DOWN
MARKEDLY FROM 36-96 HOURS AS IT INTERACTS AND POSSIBLY MERGES WITH
ANOTHER AREA OF LOW PRESSURE OFF THE NORTHEASTERN COAST OF QUEBEC. 
THE OFFICIAL FORECAST IS JUST A LITTLE FASTER THAN THE PREVIOUS ONE
AND REMAINS RELATIVELY NEAR THE MODEL CONSENSUS TVCN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/1500Z 46.2N  52.8W    65 KT
 12HR VT     22/0000Z 50.2N  49.4W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/1200Z 55.3N  48.5W    70 KT...POST-TROP/EXTRATROP
 36HR VT     23/0000Z 59.8N  51.6W    65 KT...POST-TROP/EXTRATROP
 48HR VT     23/1200Z 62.7N  57.8W    50 KT...POST-TROP/EXTRATROP
 72HR VT     24/1200Z 63.5N  61.0W    40 KT...POST-TROP/EXTRATROP
 96HR VT     25/1200Z 62.0N  60.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     26/1200Z...DISSIPATED
 
$$
FORECASTER BERG/STEWART
 


WTNT41 KNHC 212032
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER  55
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST TUE SEP 21 2010
 
LAND AND BUOY OBSERVATIONS IN NEWFOUNDLAND AND THE ADJACENT WATERS
INDICATE THAT IGOR HAS BECOME FULLY EMBEDDED WITHIN A FRONTAL ZONE.
JUST AFTER THE CENTER OF IGOR PASSED OVER CANADIAN BUOY 44251 NEAR
CAPE RACE EARLIER IN THE DAY...THE TEMPERATURE DROPPED BY ABOUT 10
DEGREES F.  HOWEVER...THE CYCLONE IS STILL PRODUCING HURRICANE-
FORCE WINDS...AND THE INITIAL INTENSITY OF 70 KT IS BASED ON
REPORTED SUSTAINED WINDS OF 63 KT AT BONAVISTA NEWFOUNDLAND.  IGOR
IS EXPECTED TO CONTINUE TO PRODUCE HURRICANE-FORCE WINDS FOR
ANOTHER DAY OR SO...AND THEN SHOULD GRADUALLY WEAKEN AS IT MOVES
NORTHWARD INTO THE DAVIS STRAITS.
 
THE INITIAL MOTION IS ESTIMATED TO BE 25 DEGREES AT 34 KT.  THE
TRACK GUIDANCE CONTINUES TO BE IN RELATIVELY GOOD AGREEMENT IN
SHOWING IGOR TURNING NORTHWESTWARD TO THE WEST OF GREENLAND IN A
COUPLE OF DAYS AND INTERACTING WITH ANOTHER AREA OF LOW PRESSURE
NEAR NORTHERN QUEBEC.  THE MODELS DO SHOW VARYING SOLUTIONS...
HOWEVER...ON WHICH OF THESE TWO SYSTEMS WILL BECOME THE DOMINANT
ONE.  THE OFFICIAL FORECAST...IN ACCORDANCE WITH GUIDANCE
PROVIDED BY THE OCEAN PREDICTION CENTER...WILL KEEP IGOR AS A
DISTINCT CYCLONE THROUGH 96 HOURS.  THE OFFICIAL FORECAST INDICATES
VERY LITTLE MOTION FROM 72 TO 96 HOURS SINCE THE CYCLONE WILL BE
NORTH OF THE BELT OF STRONG WESTERLIES BY THEN.

THE 12-FT SEAS RADII PROVIDED BY THE OCEAN PREDICTION CENTER ARE 480
NE...900 SE...1320 SW...AND 380 NW.  RADII IN THE FORECAST/ADVISORY
ARE LIMITED TO 995 N MI...BUT 12-FT SEAS ARE ACTUALLY OCCURRING AT
A GREATER DISTANCE THAN THAT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/2100Z 49.3N  51.7W    70 KT...POST-TROP/EXTRATROP
 12HR VT     22/0600Z 53.0N  49.8W    70 KT...POST-TROP/EXTRATROP
 24HR VT     22/1800Z 57.2N  51.0W    70 KT...POST-TROP/EXTRATROP
 36HR VT     23/0600Z 61.6N  57.5W    55 KT...POST-TROP/EXTRATROP
 48HR VT     23/1800Z 62.5N  60.5W    45 KT...POST-TROP/EXTRATROP
 72HR VT     24/1800Z 62.0N  60.5W    40 KT...POST-TROP/EXTRATROP
 96HR VT     25/1800Z 61.5N  59.5W    40 KT...POST-TROP/EXTRATROP
120HR VT     26/1800Z...DISSIPATED
 
$$
FORECASTER BERG
 


