WTNT42 KNHC 300852
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST TUE AUG 30 2011
 
THE CONVECTIVE PATTERN OF THE CYCLONE HAS IMPROVED OVERNIGHT...WITH
A LARGE AREA OF COLD CLOUD TOPS NOW SITUATED TO THE WEST AND
SOUTHWEST OF THE ESTIMATED CENTER LOCATION. THE 06Z DVORAK
INTENSITY ESTIMATES FROM TAFB AND SAB WERE BOTH 2.5/35 KT...AND ON
THIS BASIS THE CYCLONE IS UPGRADED TO A TROPICAL STORM. THE
STRUCTURE OF KATIA IS CONSISTENT WITH THE 15-20 KT OF
EAST-NORTHEASTERLY SHEAR OVER THE CYCLONE ANALYZED BY THE SHIPS
MODEL AND UW-CIMSS. THIS SHEAR SHOULD DECREASE IN THE NEXT 12 HOURS
OR SO...AND AFTER THAT TIME STEADY INTENSIFICATION SHOULD COMMENCE
AS THE CYCLONE MOVES OVER PROGRESSIVELY HIGHER OCEAN HEAT CONTENT.
MOST OF THE INTENSITY GUIDANCE HAS TRENDED UPWARD THIS CYCLE...AND
THE OFFICIAL FORECAST HAS AS WELL. KATIA IS EXPECTED TO BE NEAR
HURRICANE STRENGTH WITHIN 36 TO 48 HOURS WITH CONTINUED
STRENGTHENING TO NEAR MAJOR HURRICANE STATUS BY THE END OF THE
PERIOD. THE NHC FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS THAT
INCLUDES THE HFIP INTENSITY AIDS.
 
A TIMELY AMSR-E PASS FROM 0326Z WAS HELPFUL IN LOCATING THE CENTER
ON THE EASTERN EDGE OF THE DEEP CONVECTION...WHICH WAS A BIT NORTH
OF PREVIOUS ESTIMATES. THE INITIAL MOTION ESTIMATE IS 290/15...AS
KATIA CONTINUES TO BE STEERED WEST-NORTHWESTWARD BY THE SUBTROPICAL
RIDGE TO ITS NORTH. THE MODEL GUIDANCE IS IN GOOD AGREEMENT ON A
CONTINUATION OF THIS GENERAL MOTION THROUGH THE PERIOD AS THE
MID-LEVEL RIDGE BUILDS WESTWARD TO THE NORTH OF THE CYCLONE. AT
DAYS 4 AND 5...THE WESTERN EDGE OF THE RIDGE BEGINS TO WEAKEN AS A
MID-LEVEL TROUGH AMPLIFIES OVER THE WESTERN ATLANTIC...WHICH SHOULD
RESULT IN SOME DECREASE IN FORWARD SPEED. THE TRACK GUIDANCE
REMAINS TIGHTLY CLUSTERED BUT THERE ARE SOME FORWARD SPEED
DIFFERENCES...WITH THE UKMET AND GFDL MODELS ON THE FAST SIDE OF
THE GUIDANCE AND THE GFS CONTINUING TO BE A SLOW OUTLIER. FOR THIS
CYCLE THE MODELS HAVE TRENDED FASTER DURING THE FIRST 72 HOURS...
AND SO HAS THE OFFICIAL FORECAST. OTHERWISE...THE NHC FORECAST IS
VERY CLOSE TO THE PREVIOUS ONE AND LIES NEAR OR A LITTLE TO THE
RIGHT OF THE TVCA MULTI-MODEL CONSENSUS THROUGH THE PERIOD.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/0900Z 11.8N  31.7W   35 KT  40 MPH
 12H  30/1800Z 12.5N  33.7W   40 KT  45 MPH
 24H  31/0600Z 13.5N  36.8W   50 KT  60 MPH
 36H  31/1800Z 14.4N  40.2W   60 KT  70 MPH
 48H  01/0600Z 15.3N  43.7W   70 KT  80 MPH
 72H  02/0600Z 17.0N  49.5W   80 KT  90 MPH
 96H  03/0600Z 18.5N  54.0W   90 KT 105 MPH
120H  04/0600Z 20.5N  58.0W  100 KT 115 MPH
 
$$
FORECASTER BRENNAN
 

WTNT42 KNHC 301432
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST TUE AUG 30 2011
 
EAST-NORTHEASTERLY SHEAR OVER KATIA HAS DECREASED AND THE STORM
CONTINUES TO GRADUALLY BECOME BETTER ORGANIZED.  THE BANDING
FEATURES ARE BETTER DEFINED AND THE LOW-LEVEL CENTER HAS BECOME
EMBEDDED WITHIN A SMALL CENTRAL CONVECTIVE OVERCAST.  UPPER-LEVEL
OUTFLOW IS ALSO BECOMING MORE PROMINENT.  DVORAK INTENSITY
ESTIMATES RANGE FROM 35 TO 45 KT SO THE CURRENT WIND SPEED IS SET
AT 40 KT.  WITH WEAKENING SHEAR AND SEA SURFACE TEMPERATURES JUST
BELOW 28 DEG C...KATIA SHOULD CONTINUE TO STRENGTHEN AND WILL
LIKELY BECOME A HURRICANE IN 36 HOURS OR SO.  THE OFFICIAL
INTENSITY FORECAST IS CLOSE TO THE HFIP MODEL CONSENSUS...WHICH
SHOWS KATIA NEARING MAJOR HURRICANE STATUS BY THE END OF THE
FORECAST PERIOD.   

THE INITIAL MOTION IS A SLIGHTLY FASTER 285/16. NOT MUCH CHANGE HAS
BEEN MADE TO THE TRACK FORECAST.  KATIA IS EXPECTED TO CONTINUE
MOVING WEST-NORTHWESTWARD ON THE SOUTH SIDE OF THE SUBTROPICAL
RIDGE FOR THE NEXT COUPLE OF DAYS.  LATER IN THE FORECAST
PERIOD...THE TROPICAL CYCLONE IS EXPECTED TO BE APPROACHING A
WEAKNESS IN THE RIDGE CREATED BY A TROUGH OVER THE WESTERN
ATLANTIC.  THIS SHOULD CAUSE KATIA TO BEGIN TO TURN TOWARD THE
NORTHWEST WITH A DECREASE IN FORWARD SPEED.  THE OFFICIAL FORECAST
LIES A LITTLE NORTH OF THE DYNAMICAL MODEL CONSENSUS THROUGH 48
HOURS AND IS VERY CLOSE TO THE CONSENSUS FOR THE REMAINDER OF THE
FORECAST PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/1500Z 12.3N  33.4W   40 KT  45 MPH
 12H  31/0000Z 13.0N  35.7W   50 KT  60 MPH
 24H  31/1200Z 13.8N  39.0W   55 KT  65 MPH
 36H  01/0000Z 14.6N  42.4W   65 KT  75 MPH
 48H  01/1200Z 15.4N  45.7W   75 KT  85 MPH
 72H  02/1200Z 17.0N  51.5W   85 KT 100 MPH
 96H  03/1200Z 19.0N  55.5W   95 KT 110 MPH
120H  04/1200Z 21.5N  59.5W  100 KT 115 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 302040
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST TUE AUG 30 2011
 
KATIA CONTINUES TO LOOK MORE IMPRESSIVE ON SATELLITE IMAGES...WITH
INCREASING CENTRAL DEEP CONVECTION AND WELL-DEFINED BANDING
FEATURES.  UPPER-LEVEL OUTFLOW IS BECOMING WELL ESTABLISHED TO THE
NORTH...WEST...AND SOUTH OF THE STORM.  DVORAK INTENSITY ESTIMATES
HAVE INCREASED TO 45 KT AND 55 KT FROM SAB AND TAFB RESPECTIVELY...
AND THE ADVISORY INTENSITY IS SET AT 50 KT.  KATIA WILL BE MOVING
OVER SEA SURFACE TEMPERATURES NEAR 28 DEG C AND IN A LOW SHEAR
ENVIRONMENT FOR THE NEXT FEW DAYS...SO STEADY STRENGTHENING APPEARS
TO BE LIKELY.  THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE
STATISTICAL AND DYNAMICAL MODEL GUIDANCE.

THE INITIAL MOTION...285/17...IS ONLY A LITTLE FASTER THAN IN THE
PREVIOUS PACKAGE.  THE TRACK FORECAST AND FORECAST PHILOSOPHY ARE
BASICALLY UNCHANGED.  KATIA SHOULD CONTINUE TO MOVE
WEST-NORTHWESTWARD TO THE SOUTH OF THE SUBTROPICAL RIDGE FOR THE
NEXT SEVERAL DAYS.  NEAR THE END OF THE FORECAST PERIOD...A WEAKNESS
IN THE RIDGE PRODUCED BY A TROUGH OVER THE WESTERN ATLANTIC IS
EXPECTED TO INDUCE A GRADUAL TURN TO THE RIGHT WITH A DECREASE IN
FORWARD SPEED.  THE OFFICIAL TRACK FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS AND SOUTH OF THE LATEST ECMWF SOLUTION.

THE WIND RADII HAVE BEEN EXPANDED ON THE BASIS OF AN ASCAT PASS FROM
EARLIER TODAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 12.7N  35.4W   50 KT  60 MPH
 12H  31/0600Z 13.3N  37.9W   60 KT  70 MPH
 24H  31/1800Z 14.1N  41.1W   65 KT  75 MPH
 36H  01/0600Z 14.9N  44.4W   70 KT  80 MPH
 48H  01/1800Z 15.7N  47.5W   80 KT  90 MPH
 72H  02/1800Z 17.5N  52.5W   90 KT 105 MPH
 96H  03/1800Z 19.5N  56.5W  100 KT 115 MPH
120H  04/1800Z 21.5N  60.5W  105 KT 120 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 310238
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST TUE AUG 30 2011
 
A SERIES OF MICROWAVE IMAGES DURING THE LATE AFTERNOON SHOWED 
THAT THE CENTER OF KATIA WAS LOCATED NEAR THE NORTHWESTERN EDGE
OF A BAND OF DEEP CONVECTION.  SINCE THAT TIME...ANOTHER BAND OF
CONVECTION HAS DEVELOPED TO THE SOUTH AND WEST OF THE CENTER AND IT
APPEARS THAT THE CYCLONE IS GRADUALLY BECOMING BETTER ORGANIZED. 
HOWEVER...THE LATEST DVORAK INTENSITY ESTIMATES WERE UNCHANGED FROM
1800 UTC...AND THE INITIAL INTENSITY REMAINS 50 KT.  KATIA IS
FORECAST TO BE IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM
WATER AND VERY LOW SHEAR DURING THE NEXT SEVERAL DAYS.  STEADY
STRENGTHENING IS THEREFORE EXPECTED AND THE OFFICIAL FORECAST SHOWS
KATIA BECOMING A HURRICANE IN ABOUT 24 HOURS...AND A MAJOR
HURRICANE IN 2-3 DAYS.  THE NHC FORECAST IS A BLEND OF THE VARIOUS
INTENSITY AIDS THROUGH 72 HOURS...BUT IS CLOSER TO THE MORE
AGGRESSIVE HWRF/GFDL GUIDANCE AT 96 AND 120 HOURS.
 
KATIA IS MOVING BRISKLY WEST-NORTHWESTWARD OR 285/19 KT.  KATIA
SHOULD CONTINUE ON A WEST-NORTHWEST HEADING TO THE SOUTH OF THE
SUBTROPICAL RIDGE FOR THE NEXT SEVERAL DAYS.  LATE IN THE FORECAST
PERIOD...KATIA IS EXPECTED TO SLOW DOWN AND TURN TOWARD THE
NORTHWEST AS A TROUGH OVER THE WESTERN ATLANTIC INDUCES A WEAKNESS
IN THE RIDGE.  THE UPDATED FORECAST IS VERY SIMILAR TO THE PREVIOUS
NHC TRACK THROUGH 72 HOURS...BUT IT HAS BEEN ADJUSTED TO THE RIGHT
AT DAYS 4 AND 5 TO BE IN BETTER AGREEMENT WITH THE GFS AND ECMWF
MODELS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 13.3N  37.5W   50 KT  60 MPH
 12H  31/1200Z 14.0N  40.1W   60 KT  70 MPH
 24H  01/0000Z 14.8N  43.4W   70 KT  80 MPH
 36H  01/1200Z 15.5N  46.5W   80 KT  90 MPH
 48H  02/0000Z 16.5N  49.3W   90 KT 105 MPH
 72H  03/0000Z 18.5N  54.0W  100 KT 115 MPH
 96H  04/0000Z 20.5N  57.5W  110 KT 125 MPH
120H  05/0000Z 23.0N  60.5W  110 KT 125 MPH
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 310837
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST WED AUG 31 2011

SATELLITE IMAGERY THIS MORNING INDICATES THAT KATIA IS GRADUALLY
BECOMING BETTER ORGANIZED.  THE PRIMARY CONVECTIVE BAND HAS WRAPPED
FARTHER AROUND THE CENTER...AND THE CLOUD TOPS IN THE BAND HAVE
COOLED.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM SAB AND
TAFB...AND THAT IS THE INITIAL INTENSITY FOR THIS ADVISORY.  THE
CIRRUS OUTFLOW IS FAIR TO GOOD IN ALL DIRECTIONS.

THE INITIAL MOTION IS 285/18.  KATIA IS ON THE SOUTH SIDE OF A
DEEP-LAYER SUBTROPICAL RIDGE...WHILE WATER VAPOR IMAGERY SHOWS A
LARGE MID/UPPER-LEVEL LOW...A WEAKNESS IN THE RIDGE...CENTERED NEAR
30N54W AND MOVING WESTWARD.  THE TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT THAT KATIA SHOULD MOVE GENERALLY WEST-NORTHWARD FOR THE
NEXT 48 HR OR SO....THEN GRADUALLY TURN TOWARD THE NORTHWEST AT A
SLOWER FORWARD SPEED AS IT APPROACHES THE LOW OR ITS REMNANTS.  THE
GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE SOUTH DURING THE
FIRST 36 HR...AND SHIFTED A LITTLE TO THE NORTH AFTER THAT TIME. 
THE NEW FORECAST TRACK MAKES SIMILAR SMALL ADJUSTMENTS COMPARED TO
THE PREVIOUS FORECAST AND LIES NEAR THE VARIOUS CONSENSUS MODELS.
 
A COUPLE OF ISSUES HAVE APPEARED REGARDING THE INTENSITY FORECAST. 
FIRST...WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER
DATA SHOW DRY AIR NOT FAR TO THE NORTH AND EAST OF THE CORE OF
KATIA.  THIS HAS NOT YET AFFECTED DEVELOPMENT...AND THE NEW
INTENSITY FORECAST KEEPS THE TREND OF THE PREVIOUS FORECAST FOR THE
FIRST 36 HR.  HOWEVER...THERE IS A POSSIBILITY THAT INTENSIFICATION
COULD BE SLOWER THAN FORECAST IF THE DRY AIR REACHES THE CENTER. 
SECOND...THE DYNAMICAL MODELS DISAGREE ON THE UPPER-LEVEL WINDS
NEAR KATIA FROM 72-120 HR.  THE GFS...NOGAPS... AND CANADIAN MODELS
SHOW THE UPPER-LEVEL LOW TO THE NORTHWEST WEAKENING TO THE POINT
WHERE THE STORM REMAINS IN LIGHT VERTICAL WIND SHEAR CONDITIONS. 
THE ECMWF AND UKMET KEEP A STRONG ENOUGH UPPER-LEVEL TROUGH FOR
KATIA TO EXPERIENCE SIGNIFICANT SOUTHWESTERLY SHEAR.  THE FORECAST
INTENSITIES HAVE BEEN LOWERED SLIGHTLY AFTER 48 HR DUE TO THE
POSSIBILITY OF SHEAR DURING THAT TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0900Z 13.9N  39.1W   55 KT  65 MPH
 12H  31/1800Z 14.3N  41.7W   65 KT  75 MPH
 24H  01/0600Z 15.0N  44.9W   75 KT  85 MPH
 36H  01/1800Z 15.8N  47.7W   85 KT 100 MPH
 48H  02/0600Z 16.8N  50.2W   90 KT 105 MPH
 72H  03/0600Z 19.0N  54.0W   95 KT 110 MPH
 96H  04/0600Z 21.0N  57.0W  100 KT 115 MPH
120H  05/0600Z 23.0N  60.0W  105 KT 120 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 311435
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST WED AUG 31 2011
 
KATIA REMAINS A WELL-ORGANIZED TROPICAL CYCLONE WITH DISTINCT
BANDING FEATURES AND A DEVELOPING CENTRAL DENSE OVERCAST.  DVORAK
CLASSIFICATIONS ARE T3.5 FROM BOTH AGENCIES AND THE CURRENT
INTENSITY IS HELD AT 55 KT.  THE SYSTEM HAS A WELL-DEFINED
UPPER-LEVEL OUTFLOW PATTERN.  AT THE MOMENT...IT DOES NOT APPEAR
THAT THE DRY AIR ADJACENT TO THE STORM IS BEING ENTRAINED INTO THE
CIRCULATION.  THE SHIPS MODEL INDICATES THAT VERTICAL SHEAR WILL BE
WEAK FOR THE NEXT DAY OR TWO WHICH SHOULD FAVOR STRENGTHENING AT
LEAST FOR THE EARLIER PART OF THE FORECAST PERIOD.  A LARGE
UPPER-LEVEL LOW TO THE NORTHWEST OF KATIA COULD PLAY A ROLE IN THE
INTENSITY OF THE TROPICAL CYCLONE IN THE LATTER PART OF THE
FORECAST PERIOD.  AS NOTED EARLIER...SOME OF THE GLOBAL MODELS
SUGGEST THAT THIS LOW COULD PRODUCE INCREASING SOUTHWESTERLY SHEAR
IN 4 TO 5 DAYS WHICH WOULD INHIBIT INTENSIFICATION.  THE OFFICIAL
INTENSITY FORECAST IS THE SAME AS THAT FROM THE PREVIOUS ADVISORY
AND IS SLIGHTLY ABOVE THE NUMERICAL CONSENSUS.

KATIA CONTINUES TO MOVE SWIFTLY TOWARD THE WEST-NORTHWEST OR 285/18
TO THE SOUTH OF A MID-TROPOSPHERIC SUBTROPICAL ANTICYCLONE.  THE
DYNAMICAL GUIDANCE IS IN RATHER GOOD AGREEMENT ON A CONTINUATION OF
THIS WEST-NORTHWESTWARD TRACK FOR THE NEXT COUPLE OF DAYS WITH SOME
DECELERATION AS THE TROPICAL CYCLONE NEARS A WEAKNESS IN THE RIDGE. 
IN THE LATTER PART OF THE FORECAST PERIOD...MOST OF THE GUIDANCE
SHOWS A TURN TOWARD THE NORTHWEST AS KATIA APPROACHES THE SOUTHWEST
SIDE OF THE SUBTROPICAL ANTICYCLONE.  THE OFFICIAL TRACK FORECAST
FOR THIS ADVISORY PACKAGE IS AN UPDATE OF THE PREVIOUS ONE AND IS
CLOSE TO THE VARIOUS MODEL CONSENSUS TRACKS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/1500Z 14.2N  40.8W   55 KT  65 MPH
 12H  01/0000Z 14.7N  43.3W   65 KT  75 MPH
 24H  01/1200Z 15.4N  46.3W   75 KT  85 MPH
 36H  02/0000Z 16.2N  48.7W   85 KT 100 MPH
 48H  02/1200Z 17.3N  51.0W   90 KT 105 MPH
 72H  03/1200Z 19.5N  54.5W   95 KT 110 MPH
 96H  04/1200Z 21.5N  57.5W  100 KT 115 MPH
120H  05/1200Z 23.5N  60.5W  105 KT 120 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 312039
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST WED AUG 31 2011

KATIA IS NEAR THE THRESHOLD OF HURRICANE STATUS.  THE SYSTEM
CONTINUES TO EXHIBIT PROMINENT CURVED CONVECTIVE BANDS AND DEEP
CONVECTION IS BECOMING STRONGER OVER THE CENTER.  THE STORM ALSO
HAS A FAIRLY SYMMETRIC AND WELL-ESTABLISHED UPPER-LEVEL OUTFLOW
PATTERN.  DVORAK INTENSITY ESTIMATES FROM BOTH AGENCIES REMAIN AT
55 KT...BUT AMSU INTENSITY ESTIMATES FROM THE UNIVERSITY OF
WISCONSIN CIMSS ARE A LITTLE HIGHER.  THE INTENSITY IS SET AT 60 KT
FOR THIS ADVISORY.  WEAK VERTICAL SHEAR AND MODESTLY WARM WATERS
ARE LIKELY TO PREVAIL OVER THE NEXT FEW DAYS...SO CONTINUED
INTENSIFICATION IS FORECAST.  A LARGE UPPER-LEVEL LOW TO THE
NORTHWEST OF KATIA COULD CAUSE AN INCREASE IN SHEAR...AND INHIBIT
INTENSIFICATION...LATE IN THE FORECAST PERIOD.  HOWEVER SOME OF THE
GLOBAL MODELS...SUCH AS THE GFS...SUGGEST THAT THE OUTFLOW
ANTICYCLONE OF KATIA WILL DOMINATE THE UPPER-LEVEL WIND PATTERN AND
DISPLACE THE SHEARING FLOW ASSOCIATED WITH THE LOW.  IF THAT
OCCURS...KATIA WOULD LIKELY BECOME A MAJOR HURRICANE BY DAY 4 OR 5. 
THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND
SLIGHTLY HIGHER THAN THE STATISTICAL-DYNAMICAL GUIDANCE.

THE STORM CONTINUES TO MOVE WEST-NORTHWESTWARD ON THE SOUTH SIDE OF
A SUBTROPICAL ANTICYCLONE.  THE TRACK FORECAST AND REASONING ARE
ESSENTIALLY UNCHANGED.  AS KATIA NEARS THE SOUTHWEST SIDE OF THE
ANTICYCLONE...A GRADUAL TURN TOWARD THE NORTHWEST WITH DECREASING
FORWARD SPEED IS LIKELY.  THE CURRENT OFFICIAL TRACK FORECAST IS AN
UPDATE OF THE PREVIOUS ONE AND ABOUT IN THE MIDDLE OF THE GUIDANCE
ENVELOPE.  IT IS ALSO A LITTLE TO THE WEST OF THE GFS AND ECMWF
SOLUTIONS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/2100Z 14.6N  42.6W   60 KT  70 MPH
 12H  01/0600Z 15.1N  44.9W   65 KT  75 MPH
 24H  01/1800Z 15.8N  47.7W   75 KT  85 MPH
 36H  02/0600Z 16.6N  50.0W   85 KT 100 MPH
 48H  02/1800Z 17.7N  52.0W   90 KT 105 MPH
 72H  03/1800Z 20.0N  55.5W   95 KT 110 MPH
 96H  04/1800Z 22.0N  58.5W  100 KT 115 MPH
120H  05/1800Z 23.5N  61.0W  105 KT 120 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 010248
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST WED AUG 31 2011
 
THE CLOUD PATTERN ASSOCIATED WITH KATIA CONTINUES TO GRADUALLY
IMPROVE.  THE CENTER IS LOCATED NEAR THE MIDDLE OF AN EXPANDING
CENTRAL DENSE OVERCAST AND THERE IS A LARGE CURVED BAND OF DEEP
CONVECTION OVER THE SOUTHERN SEMICIRCLE OF THE CYCLONE.  RECENT
SSMIS MICROWAVE DATA SHOWED THE BEGINNINGS OF A BANDING EYE
FEATURE...HOWEVER THE CONVECTION OVER THE SOUTHERN PORTION OF THE
EYE IS STILL A BIT THIN.  SUBJECTIVE AND OBJECTIVE DVORAK SATELLITE
INTENSITY ESTIMATES HAVE INCREASED TO 65 KT...AND THE INITIAL
INTENSITY HAS BEEN RAISED ACCORDINGLY.  KATIA IS THE SECOND
HURRICANE OF THE 2011 ATLANTIC HURRICANE SEASON.

THE HURRICANE IS EXPECTED TO REMAIN IN A LOW SHEAR ENVIRONMENT
AND OVER WARM WATER DURING THE NEXT DAY OR SO...WHICH SHOULD FAVOR
ADDITIONAL STRENGTHENING.  AFTER THAT TIME...A MID- TO UPPER-LEVEL
TROUGH SEEN IN WATER VAPOR IMAGERY BETWEEN 50W AND 60W IS FORECAST
BY THE GLOBAL MODELS TO WEAKEN.  THIS SHOULD KEEP THE HURRICANE IN
A FAVORABLE UPPER-LEVEL WIND PATTERN AND KATIA IS FORECAST TO
BECOME A MAJOR HURRICANE WITHIN 72 HOURS.  THE NEW NHC INTENSITY
FORECAST SHOWS A SLIGHTLY FASTER RATE OF INTENSIFICATION DURING THE
FIRST 2-3 DAYS THAN INDICATED IN THE PREVIOUS ADVISORY...AND IS A
BLEND OF THE STATISTICAL AND DYNAMICAL GUIDANCE.

THE INITIAL MOTION ESTIMATE IS 285/17 KT.   THE HURRICANE IS
EXPECTED TO CONTINUE MOVING WEST-NORTHWESTWARD TO THE SOUTH OF A
SUBTROPICAL RIDGE DURING THE NEXT 2-3 DAYS.  AFTER 72 HOURS...
KATIA WILL BE NEARING THE SOUTHWESTERN PORTION OF THE RIDGE.  THIS
SHOULD RESULT IN A REDUCTION IN FORWARD SPEED AND A GRADUAL TURN
TOWARD THE NORTHWEST.  THE NEW TRACK FORECAST IS ESSENTIALLY AN
UPDATE OF THE PREVIOUS NHC FORECAST AND LIES BETWEEN THE
MULTI-MODEL CONSENSUS AND THE RELIABLE GFS AND ECMWF MODELS.

THE WIND RADII HAVE BEEN ADJUSTED SLIGHTLY ON THE BASIS OF RECENT
ASCAT DATA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0300Z 15.0N  44.4W   65 KT  75 MPH
 12H  01/1200Z 15.6N  46.7W   75 KT  85 MPH
 24H  02/0000Z 16.3N  49.1W   85 KT 100 MPH
 36H  02/1200Z 17.3N  51.3W   90 KT 105 MPH
 48H  03/0000Z 18.4N  53.1W   95 KT 110 MPH
 72H  04/0000Z 20.5N  56.0W  100 KT 115 MPH
 96H  05/0000Z 22.5N  59.0W  105 KT 120 MPH
120H  06/0000Z 24.0N  61.5W  105 KT 120 MPH
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 010837
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST THU SEP 01 2011

AN AMSR-E OVERPASS AT 0451 UTC RATHER UNEXPECTEDLY SHOWED A PARTLY
EXPOSED LOW-LEVEL CENTER WITH ONLY A FRAGMENT OF AN EYEWALL TO THE
NORTH AND NORTHEAST.  ANALYSES FROM CIMSS AT THE UNIVERSITY OF
WISCONSIN SHOW ABOUT 10 KT OF SOUTHERLY VERTICAL WIND SHEAR...BUT
THAT BY ITSELF DOES NOT ADEQUATELY EXPLAIN THE OBSERVED STRUCTURE.
IT MAY BE THAT DRY AIR PREVIOUSLY SEEN NEAR THE STORM HAS WORKED ITS
WAY INTO THE CORE AS HINTED AT IN AMSR-E TOTAL PRECIPITABLE WATER
DATA.  SATELLITE INTENSITY ESTIMATES ARE 77 KT FROM TAFB AND 65 KT
FROM SAB...AND THE INITIAL INTENSITY REMAINS 65 KT FOR THIS
ADVISORY.

THE INITIAL MOTION IS SLIGHTLY TO THE LEFT OF THE PREVIOUS
ADVISORY...280/17.  KATIA IS ON THE SOUTH SIDE OF A DEEP-LAYER
RIDGE OVER THE CENTRAL ATLANTIC.  WATER VAPOR IMAGERY SHOWS A
MID/UPPER-LEVEL LOW NEAR 29N55W WITH A TROUGH EXTENDING TO 15N60W...
AND A SECOND MID/UPPER-LEVEL LOW NEAR 34N71W.  THESE FEATURES HAVE
CREATED A SIZABLE WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE
WESTERN ATLANTIC...AND THE DYNAMICAL MODELS FORECAST KATIA TO MOVE
GENERALLY WEST-NORTHWESTWARD INTO THE WEAKNESS.  THERE IS SOME
SPREAD IN THE GUIDANCE...ESPECIALLY BY 120 HOURS.  THE GFDL...
UKMET...CANADIAN...AND NOGAPS MODELS ARE ON THE LEFT SIDE OF THE
GUIDANCE ENVELOPE...WHILE THE GFS AND ECMWF ARE ON THE RIGHT SIDE. 
THE NEW FORECAST TRACK IS ALONG THE LEFT SIDE OF THE GUIDANCE
ENVELOPE FOR THE FIRST 24 HOURS BASED ON THE CURRENT MOTION...THEN
THEREAFTER LIES IN THE CENTER OF THE ENVELOPE NEAR THE VARIOUS
CONSENSUS MODELS.  THE NEW TRACK IS A LITTLE TO THE WEST OF THE
PREVIOUS TRACK.
 
IT IS UNCLEAR WHETHER THE CURRENT CONVECTIVE TREND IS TEMPORARY OR A
SIGN OF ARRESTED DEVELOPMENT.  THE EARLY PART OF THE INTENSITY
FORECAST IS BASED ON THE FORMER POSSIBILITY AND SHOWS A SLOW
STRENGTHENING FOR THE FIRST 24-36 HR.  AFTER THAT TIME...THERE
REMAINS SOME UNCERTAINTY REGARDING THE UPPER-LEVEL WINDS NEAR
KATIA.  THE GFS...NOGAPS...AND CANADIAN MODELS SHOW A VERY
FAVORABLE PATTERN...WHILE THE UKMET AND ECMWF FORECAST SOME
SOUTHWESTERLY SHEAR.  DUE TO THE UNCERTAINTY...THE LATER PART OF
THE INTENSITY FORECAST IS THE SAME AS IN THE PREVIOUS ADVISORY. 
HOWEVER...THE GFDL AND GFDN MODELS BOTH FORECAST KATIA TO INTENSIFY
TO STRONGER THAN 120 KT...WHICH IS A POSSIBILITY IF THE MORE
FAVORABLE UPPER-LEVEL WINDS OCCUR.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0900Z 15.2N  45.9W   65 KT  75 MPH
 12H  01/1800Z 15.7N  48.1W   70 KT  80 MPH
 24H  02/0600Z 16.5N  50.5W   80 KT  90 MPH
 36H  02/1800Z 17.6N  52.4W   90 KT 105 MPH
 48H  03/0600Z 18.6N  54.1W   95 KT 110 MPH
 72H  04/0600Z 20.5N  57.0W  100 KT 115 MPH
 96H  05/0600Z 22.0N  60.0W  105 KT 120 MPH
120H  06/0600Z 23.5N  63.0W  105 KT 120 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 011450
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST THU SEP 01 2011
 
KATIA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS.
BASED ON MICROWAVE DATA...THE LOW-LEVEL CENTER IS LOCATED NEAR THE
WESTERN PERIPHERY OF THE CORE CONVECTION. A CURVED BAND STILL
EXISTS OVER THE SOUTHERN SEMICIRCLE OF THE STORM...BUT CLOUD TOPS
HAVE BEEN WARMING IN THIS BAND DURING THE PAST FEW HOURS. THE
INITIAL WIND SPEED REMAINS AT 65 KT FOR THIS ADVISORY...IN
AGREEMENT WITH THE LATEST SATELLITE CLASSIFICATIONS.

SOUTHWESTERLY SHEAR OF ABOUT 15 KT...AS ANALYZED BY UW-CIMSS...IS
CURRENTLY AFFECTING KATIA. THIS SHEAR IS ASSOCIATED WITH AN
UPPER-LEVEL LOW LOCATED TO THE NORTHWEST OF THE HURRICANE. THE
UPPER LOW IS EXPECTED TO CONTINUE TO IMPOSE MODERATE SHEAR OVER
KATIA FOR ANOTHER 24 TO 36 HOURS. IN ADDITION...SOME DRY AIR
APPEARS TO BE ENTRAINING INTO THE CIRCULATION OF KATIA AND
THIS...IN COMBINATION WITH THE AFOREMENTIONED SHEAR...COULD INHIBIT
SIGNIFICANT DEVELOPMENT IN THE SHORT-TERM. BEYOND 36 HOURS...THE
GLOBAL MODELS SHOW THE UPPER LOW LIFTING OUT...CREATING A MORE
FAVORABLE UPPER-LEVEL WIND PATTERN. THEREFORE...STEADY
STRENGTHENING IS FORECAST IN THE LONGER RANGE. THE OFFICIAL
FORECAST IS LOWERED SLIGHTLY FROM THE PREVIOUS ONE IN THE
SHORT-TERM...BUT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW
DAYS.

KATIA IS MOVING WESTWARD AT 16 KT TO THE SOUTH OF A SUBTROPICAL
HIGH. THE HURRICANE IS EXPECTED TO SLOW DOWN AND TURN TO THE
WEST-NORTHWEST DURING THE NEXT 12-24 HOURS AS IT APPROACHES A
WEAKNESS IN THE RIDGE. THE MODEL GUIDANCE BECOMES VERY DIVERGENT IN
4 TO 5 DAYS WITH THE UKMET...NOGAPS...AND GFDL MODELS ON THE SOUTH
SIDE OF THE ENVELOPE AND THE GFS...ECMWF...AND HWRF MODELS ON THE
NORTH SIDE. THIS SPREAD APPEARS TO BE ASSOCIATED WITH THE STRENGTH
OF A TROUGH MOVING OVER THE NORTHEASTERN UNITED STATES AND THE
POSITION OF THE SUBTROPICAL HIGH. THE OFFICIAL TRACK FORECAST IS
ONLY NUDGED A LITTLE TO THE LEFT...IN PART BECAUSE OF THE INITIAL
MOTION AND POSITION...AND IS VERY NEAR THE MULTI-MODEL CONSENSUS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/1500Z 15.5N  47.5W   65 KT  75 MPH
 12H  02/0000Z 16.1N  49.5W   70 KT  80 MPH
 24H  02/1200Z 17.0N  51.7W   75 KT  85 MPH
 36H  03/0000Z 18.0N  53.4W   85 KT 100 MPH
 48H  03/1200Z 19.0N  55.0W   95 KT 110 MPH
 72H  04/1200Z 20.8N  58.0W  100 KT 115 MPH
 96H  05/1200Z 22.3N  61.0W  105 KT 120 MPH
120H  06/1200Z 23.8N  64.0W  105 KT 120 MPH
 
$$
FORECASTER CANGIALOSI/ZELINSKY
 

WTNT42 KNHC 012031
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST THU SEP 01 2011

KATIA HAS TAKEN THE APPEARANCE OF A SHEARED TROPICAL CYCLONE.
VISIBLE AND MICROWAVE SATELLITE IMAGERY CONTINUE TO INDICATE THAT
THE LOW-LEVEL CENTER IS DISPLACED TO THE WEST OF THE CONVECTION.
THE CURVED BAND THAT WAS LOCATED SOUTH OF THE CENTER HAS
DISSIPATED...AND CONVECTION IS NOW LIMITED TO THE NORTHEAST
QUADRANT OF THE SYSTEM. BASED ON A BLEND OF DVORAK CI AND T NUMBERS
FROM SAB AND TAFB...THE INTENSITY HAS BEEN LOWERED TO 60 KT FOR
THIS ADVISORY.

UW-CIMMS SHEAR ANALYSIS CONTINUES TO INDICATE THAT SOUTHWESTERLY
SHEAR OF ABOUT 15 KT IS CURRENTLY IMPACTING KATIA. AN UPPER-LEVEL
LOW LOCATED TO THE NORTHWEST OF THE CYCLONE APPEARS TO BE THE
PRIMARY SOURCE OF THIS SHEAR. KATIA IS EXPECTED TO CONTINUE TO
INTERACT WITH THIS LOW FOR THE NEXT 24 TO 36 HOURS. AFTER
THAT...THE UPPER-LEVEL LOW IS EXPECTED TO LIFT TO THE
NORTH...RESULTING IN A MORE CONDUCIVE ENVIRONMENT FOR
INTENSIFICATION. THE OFFICIAL FORECAST HAS BEEN LOWERED SLIGHTLY
DUE TO THE MARGINAL ENVIRONMENTAL CONDITIONS IN THE SHORT
TERM...HOWEVER IT STILL BRINGS KATIA TO A MAJOR HURRICANE IN A FEW
DAYS.

KATIA CONTINUES TO MOVE TO THE WEST AT 16 KT. IT IS EXPECTED TO SLOW
DOWN AND BEGIN A GRADUAL TURN TO THE NORTHWEST AS IT APPROACHES A
WEAKNESS IN THE SUBTROPICAL RIDGE. THE GFS...ECMWF...AND HFIP
CONSENSUS MODELS ARE IN GOOD AGREEMENT FOR THE FIRST 3 DAYS. AFTER
THAT THERE IS MORE UNCERTAINTY IN THE FORECAST AS THE MODEL SPREAD
INCREASES. SOME MODELS SUGGEST A TURN TOWARD THE WEST AS THE
SUBTROPICAL RIDGE REBUILDS TO THE NORTH OF KATIA...WHILE OTHERS
SUGGEST THAT THE WEAKNESS WILL PERSIST...BRINGING THE CYCLONE
FARTHER NORTH. THE OFFICIAL FORECAST LIES BETWEEN THESE SCENARIOS
AND IS VERY CLOSE TO THE HFIP CONSENSUS. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 16.1N  49.2W   60 KT  70 MPH
 12H  02/0600Z 16.8N  51.0W   65 KT  75 MPH
 24H  02/1800Z 17.7N  52.9W   70 KT  80 MPH
 36H  03/0600Z 18.7N  54.6W   75 KT  85 MPH
 48H  03/1800Z 19.7N  56.1W   85 KT 100 MPH
 72H  04/1800Z 21.6N  59.0W   95 KT 110 MPH
 96H  05/1800Z 23.5N  62.0W  100 KT 115 MPH
120H  06/1800Z 25.5N  65.0W  105 KT 120 MPH
 
$$
FORECASTER ZELINSKY/CANGIALOSI
 

WTNT42 KNHC 020237
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST THU SEP 01 2011
 
MICROWAVE IMAGES AROUND 2245 UTC SHOWED THE CENTER OF KATIA ON THE
EDGE OF THE DEEP CONVECTION...BUT MORE RECENT SATELLITE IMAGES SHOW
AN INCREASE OF THE THUNDERSTORM ACTIVITY AND IT APPEARS THAT THE
CENTER IS AGAIN UNDER THE CANOPY. THE OUTFLOW HAS ALSO BECOME A
LITTLE BETTER DEFINED IN THE NORTHWEST QUADRANT. DVORAK T-NUMBERS
ONLY SUPPORT 55 KNOTS BUT GIVEN THAT THE CLOUD PATTERN IS A LITTLE
BETTER ORGANIZED THAN EARLIER THIS EVENING...THE INITIAL INTENSITY
IS KEPT AT 60 KNOTS.  WATER VAPOR IMAGES STILL SHOW A SHARP
UPPER-TROUGH WITH ITS AXIS ALONG 56 DEGREES WEST LONGITUDE INDUCING
STRONG SOUTHWESTERLY SHEAR OVER KATIA. GLOBAL MODELS...MAINLY THE
GFS AND EVENTUALLY THE ECMWF INSIST ON WEAKENING THIS TROUGH AND
FORECAST A MORE FAVORABLE ENVIRONMENT FOR INTENSIFICATION IN A DAY
OR SO. THERE ARE NO SIGNS THAT THE TROUGH IS WEAKENING YET...AND
GIVEN THE CURRENT SHEAR...NO CHANGE IN STRENGTH IS INDICATED IN THE
NEXT 12 TO 18 HOURS.  KATIA SHOULD BEGIN TO RE-INTENSIFY IN ABOUT 24
TO 36 HOURS AND BECOME A MAJOR HURRICANE IN A FEW DAYS ASSUMING
THAT THE ENVIRONMENT BECOMES LESS HOSTILE AS INDICATED BY GLOBAL
MODELS.  

KATIA HAS SLOWED DOWN A LITTLE BIT AND IT APPEARS TO BE MOVING
TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 14 KNOTS AROUND THE
PERIPHERY OF THE SUBTROPICAL RIDGE. A TROUGH CURRENTLY LOCATED OVER
THE WESTERN ATLANTIC IS ERODING THE WESTERN SIDE OF THE SUBTROPICAL
RIDGE AND THIS WILL INDUCE A NORTHWESTERLY MOTION DURING THE NEXT
TWO TO THREE DAYS. HOWEVER...IN THE LONG RANGE...A STRONG MID-LEVEL
TROUGH IS FORECAST TO DEVELOP OVER THE GULF OF MEXICO AS THE
ATLANTIC SUBTROPICAL RIDGE BUILDS WESTWARD. THIS PATTERN SHOULD
FORCE KATIA ON A MORE WEST-NORTHWESTWARD MOTION BY THE END OF THE
FORECAST PERIOD AS INDICATED BY THE ECMWF AND THE GFS. THIS SMALL
BEND TO THE WEST-NORTHWEST IS REFLECTED IN THE OFFICIAL FORECAST.  

ON THE FORECAST TRACK...KATIA WILL CONTINUE TO MOVE OVER OPEN WATER 
DURING THE NEXT FIVE DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0300Z 16.7N  50.6W   60 KT  70 MPH
 12H  02/1200Z 17.5N  52.5W   60 KT  70 MPH
 24H  03/0000Z 18.5N  54.0W   65 KT  75 MPH
 36H  03/1200Z 19.5N  55.5W   75 KT  85 MPH
 48H  04/0000Z 20.5N  57.0W   85 KT 100 MPH
 72H  05/0000Z 22.5N  60.0W   95 KT 110 MPH
 96H  06/0000Z 25.0N  63.5W  100 KT 115 MPH
120H  07/0000Z 26.5N  67.0W  105 KT 120 MPH
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 020848
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST FRI SEP 02 2011
 
ALTHOUGH KATIA HAS PRODUCED A RATHER LARGE AND INTENSE AREA OF
THUNDERSTORMS OVERNIGHT...ASCAT DATA FROM AROUND 0100 UTC SHOWED
THAT THE CENTER WAS NEAR THE SOUTHERN EDGE OF THE CONVECTION. THIS
STRUCTURE IS DUE TO SOUTHWESTERLY SHEAR...WHICH IS QUITE EVIDENT
FROM THE CIRRUS CLOUD MOTIONS MOVING DIRECTLY INTO THE CORE OF THE
CYCLONE. THE ASCAT PASS...HOWEVER...DID SUPPORT AN INTENSITY OF AT
LEAST 60 KT AFTER ACCOUNTING FOR THE LOW BIAS OF THE INSTRUMENT.
GIVEN THE STRUCTURE TONIGHT...AND SATELLITE CLASSIFICATIONS BELOW
HURRICANE FORCE...THE INITIAL WINDS ARE KEPT AT 60 KT.
 
THE INTENSITY FORECAST IS NOT AN EASY ONE THIS MORNING. A LARGE
MID/UPPER-LEVEL TROUGH TO THE NORTHWEST OF THE CYCLONE SHOULD
CONTINUE TO SHEAR KATIA FOR AT LEAST THE NEXT DAY OR SO. THE GLOBAL
MODELS ARE IN RATHER POOR AGREEMENT ON WHEN THIS SHEAR COULD
ABATE...WITH THE GFS SHOWING LIGHTER SHEAR BY LATE TOMORROW...WHILE
THE ECMWF KEEPS SOME SOUTHERLY SHEAR FOR THE NEXT SEVERAL DAYS. THE
MODELS HAVE GENERALLY UNDERDONE THE AMOUNT OF THE SHEAR FOR THIS
SYSTEM...SO THE NEW FORECAST WILL BE DECREASED FROM THE PREVIOUS
ONE AND PUTS MORE WEIGHT ON THE LOWER STATISTICAL GUIDANCE. THE
LARGE-SCALE ENVIRONMENT IS FORECAST BY MOST OF THE GUIDANCE TO
BECOME MORE FAVORABLE FOR STRENGTHENING BY EARLY NEXT WEEK...WHICH
WOULD SEEM TO BE THE BEST CHANCE OF KATIA BECOMING SIGNIFICANTLY
STRONGER. 

AN EXTRAPOLATION FROM THE PREVIOUS ADVISORY AND A TIMELY AMSR-E
MICROWAVE PASS AT 0533 UTC GIVES AN INITIAL MOTION IS 295/13. A
TURN TO THE NORTHWEST IS FORECAST BY MOST OF THE GLOBAL GUIDANCE
LATER TODAY AS KATIA ROUNDS THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE...WITH THAT TRACK GENERALLY CONTINUING FOR THE
NEXT SEVERAL DAYS. THE ONE NOTABLE OUTLIER TO THIS SOLUTION IS THE
UKMET MODEL...WHICH SHOWS A MUCH STRONGER RIDGE BUILDING OVER THE
WESTERN ATLANTIC OCEAN AND KEEPS A WEST-NORTHWESTWARD TRACK. THAT
MODEL HAS SHOWN A WESTWARD BIAS IN EARLIER SIMILAR SITUATIONS...SO
THE NHC FORECAST WILL DISREGARD THAT SOLUTION AND LEAN MORE CLOSELY
ON THE USUALLY RELIABLE ECMWF AND GFS MODELS. AT THE END OF THE
FORECAST PERIOD...ALL MODELS FORECAST A RIDGE TO BUILD IN OVER THE
WESTERN ATLANTIC...WHICH WOULD FORCE KATIA TO TURN TOWARD THE WEST
OR WEST-NORTHWEST. THE NEW FORECAST IS CLOSE TO THE PREVIOUS
ONE...BUT IS SHIFTED A BIT TO THE NORTH AT DAY 5.

 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0900Z 17.0N  51.8W   60 KT  70 MPH
 12H  02/1800Z 17.7N  53.1W   60 KT  70 MPH
 24H  03/0600Z 18.9N  54.8W   60 KT  70 MPH
 36H  03/1800Z 19.9N  56.2W   65 KT  75 MPH
 48H  04/0600Z 21.0N  57.6W   70 KT  80 MPH
 72H  05/0600Z 23.3N  60.6W   80 KT  90 MPH
 96H  06/0600Z 25.5N  63.5W   90 KT 105 MPH
120H  07/0600Z 27.0N  66.5W  100 KT 115 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 021454
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST FRI SEP 02 2011
 
THE CONVECTIVE DEPICTION OF KATIA HAS IMPROVED THIS MORNING AS BOTH
MICROWAVE IMAGERY FROM SSMIS AND CONVENTIONAL VISIBLE SATELLITE
IMAGERY INDICATE THAT AN EYE MAY BE FORMING.  BECAUSE OF THE
IMPROVED STRUCTURE...BOTH TAFB AND SAB DVORAK CLASSIFICATIONS CAME
IN AT A 4.0...OR 65 KT...AS DID A 1053Z CIMSS AMSU INTENSITY
ESTIMATE.  THUS KATIA HAS REGAINED HURRICANE STATUS.

THE HURRICANE IS MOVING TOWARD THE WEST-NORTHWEST AT ABOUT 12
KT...AS IT IS BEING ADVECTED AROUND THE SOUTHWEST PERIPHERY OF A
DEEP-LAYER RIDGE.  KATIA SHOULD MOVE TOWARD THE WEST-NORTHWEST OR
NORTHWEST FOR THE NEXT FEW DAYS AT A SLIGHTLY SLOWER RATE OF SPEED.  
ALL OF THE RELIABLE GUIDANCE...WITH THE EXCEPTION OF THE UKMET WHICH
HAS A MUCH MORE EQUATORWARD SOLUTION DUE TO A SHORT-WAVE TROUGH OFF
OF THE U.S. EAST COAST LIFTING OUT TO THE NORTHEAST MORE QUICKLY...
IS IN EXCELLENT AGREEMENT.  THE TRACK FORECAST IS VERY SIMILAR TO
THE PREVIOUS ADVISORY AND THE CONSENSUS OF THE GLOBAL AND HURRICANE
MODELS LESS THE UKMET MODEL.

DESPITE BECOMING A HURRICANE AGAIN...KATIA FACES A RELATIVELY
HOSTILE ENVIRONMENT WITH SOUTHWEST VERTICAL SHEAR OF 15-20 KT
SUGGESTED FOR THE NEXT DAY OR TWO.  BEYOND 48 HOURS...THE SHEAR
FROM THE GLOBAL MODELS IS ANTICIPATED TO DECREASE...BUT THE
THERMODYNAMICS MAY NOT BE IDEAL WITH LOW HUMIDITIES AND A MORE
STABLE ENVIRONMENT ANTICIPATED.  SOME OF THE UPPER-LEVEL
TEMPERATURE INCREASES ANALYZED IN THE SHIPS/LGEM STATISTICAL
MODELS...HOWEVER...MAY BE SPURIOUS...AS THE STRONGER VORTEX FROM
THE GFS MAY BE THE CAUSE OF THESE VALUES RATHER THAN THE
ENVIRONMENT.  THUS THE SHIPS/LGEM GUIDANCE MAY BE TOO LOW AT DAYS
THREE TO FIVE. THE INTENSITY PREDICTION IS SLIGHTLY LOWER THAN A
SHIPS/LGEM/HWRF BLEND BUT HIGHER THAN THE PREVIOUS ADVISORY DURING
THE NEXT TWO DAYS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  02/1500Z 17.5N  52.4W   65 KT  75 MPH
 12H  03/0000Z 18.6N  53.8W   65 KT  75 MPH
 24H  03/1200Z 19.6N  55.2W   70 KT  80 MPH
 36H  04/0000Z 20.6N  56.4W   75 KT  85 MPH
 48H  04/1200Z 21.7N  57.9W   80 KT  90 MPH
 72H  05/1200Z 24.0N  61.0W   90 KT 105 MPH
 96H  06/1200Z 26.0N  64.0W   95 KT 110 MPH
120H  07/1200Z 27.0N  67.0W  100 KT 115 MPH
 
$$
FORECASTER LANDSEA/STEWART
 

WTNT42 KNHC 022051
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST FRI SEP 02 2011
 
KATIA REMAINS A HURRICANE THIS AFTERNOON...BUT IS STRUGGLING WITH
MODERATE VERTICAL SHEAR.  A 1718Z TRMM SATELLITE PASS INDICATED
THAT THE SURFACE CENTER IS TILTED SOUTHWARD FROM THE MID-LEVEL
CIRCULATION. DATA-T NUMBERS FROM BOTH TAFB AND SAB DECREASED
TO 3.5...THOUGH THE CURRENT INTENSITY NUMBERS REMAIN AT 4.0 ON THE
DVORAK SCALE.  THE INITIAL INTENSITY IS KEPT AT 65 KT...A MINIMAL
HURRICANE...THOUGH IT IS QUITE POSSIBLE THAT KATIA IS SLIGHTLY
WEAKER.
 
THE HURRICANE IS MOVING TOWARD THE NORTHWEST AT ABOUT 10 KT...AS IT
IS BEING ADVECTED AROUND THE SOUTHWEST PERIPHERY OF A DEEP-LAYER
RIDGE. KATIA SHOULD MOVE TOWARD THE WEST-NORTHWEST OR
NORTHWEST FOR THE NEXT FEW DAYS AT ABOUT THE SAME RATE OF SPEED.
ALL OF THE RELIABLE GUIDANCE IS IN EXCELLENT AGREEMENT...WITH THE
EXCEPTION OF THE UKMET WHICH HAS A MUCH MORE EQUATORWARD SOLUTION
DUE TO A SHORT-WAVE TROUGH OFF OF THE U.S. EAST COAST LIFTING OUT
TO THE NORTHEAST MORE QUICKLY.  THE TRACK FORECAST IS SHIFTED
SLIGHTLY TO THE LEFT COMPARED TO THE PREVIOUS ADVISORY AND IS BASED
UPON THE CONSENSUS OF THE GLOBAL AND HURRICANE MODELS EXCEPT THE
UKMET MODEL. IT IS STILL TOO EARLY TO SAY WHETHER KATIA WILL
DIRECTLY IMPACT THE UNITED STATES.
 
THE HURRICANE FACES A RELATIVELY HOSTILE ENVIRONMENT WITH SOUTHWEST
VERTICAL SHEAR OF 15-20 KT LIKELY FOR THE NEXT DAY OR TWO.  BEYOND
48 HOURS...THE SHEAR AS SHOWN IN THE GLOBAL MODELS IS ANTICIPATED
TO DECREASE SOME.  HOWEVER...THE THERMODYNAMICS AT THAT TIME MAY
NOT BE IDEAL AS LOW HUMIDITIES AND A MORE STABLE ENVIRONMENT IS
ANTICIPATED.  THE INTENSITY PREDICTION IS MOST SIMILAR TO A BLEND
OF THE SHIPS/LGEM/HWRF MODELS AS WELL AS THE NEW IV15 INTENSITY
CONSENSUS FROM THE HURRICANE FORECAST IMPROVEMENT PROGRAM.
 
THE TROPICAL-STORM WIND RADII WERE ADJUSTED OUTWARD SOME BASED UPON
A 1334Z ASCAT PASS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/2100Z 18.4N  53.5W   65 KT  75 MPH
 12H  03/0600Z 19.0N  54.5W   65 KT  75 MPH
 24H  03/1800Z 19.9N  55.8W   70 KT  80 MPH
 36H  04/0600Z 20.9N  57.1W   75 KT  85 MPH
 48H  04/1800Z 21.9N  58.7W   80 KT  90 MPH
 72H  05/1800Z 24.0N  62.0W   90 KT 105 MPH
 96H  06/1800Z 26.0N  65.0W   95 KT 110 MPH
120H  07/1800Z 27.5N  68.0W   95 KT 110 MPH
 
$$
FORECASTER LANDSEA/STEWART
 

WTNT42 KNHC 030254
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST FRI SEP 02 2011
 
A SERIES OF MICROWAVE IMAGES DURING THE LATE AFTERNOON CLEARLY
SHOWED THE MID-LEVEL CENTER DISPLACED TO THE NORTH OF THE LOW-LEVEL
ONE. THIS MEANS THAT KATIA CONTINUES SUFFERING FROM SOUTHERLY SHEAR
AND HAS NOT INTENSIFIED. THE CLOUD PATTERN IS NOT VERY IMPRESSIVE
FOR A HURRICANE...BUT THE INITIAL INTENSITY IS CONSERVATIVELY KEPT
AT 65 KNOTS BASED ON T-NUMBERS FROM TAFB AND SAB. THERE IS A
SIGNIFICANT EXPANSION OF THE OUTFLOW IN THE WESTERN SEMICIRCLE
GIVING THE FALSE IMPRESSION THAT THE SHEAR IS WEAKENING. THIS IS
EXPECTED TO BE TRANSIENT SINCE WATER VAPOR IMAGES STILL SHOW THAT
THE UPPER-LEVEL TROUGH CAUSING THE SHEAR IS STILL THERE...AND
GLOBAL MODELS BASICALLY KEEP POSTPONING ITS WEAKENING.  ACTUALLY...
THE SHIPS MODEL INDICATE THAT UPPER-LEVEL WIND ENVIRONMENT WILL
REMAIN HOSTILE FOR 24 TO 36 HOURS...WHILE THE ECMWF KEEPS IT
HOSTILE EVEN LONGER. ON THIS BASIS...THE OFFICIAL FORECAST CALLS
FOR NO CHANGE IN INTENSITY FOR ABOUT TWO DAYS AND FOR STRENGTHENING
THEREAFTER.

KATIA IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 10 KNOTS.
GLOBAL MODELS UNANIMOUSLY BUILD THE SUBTROPICAL RIDGE WESTWARD AND
WEAKEN THE TROUGH OVER THE WESTERN ATLANTIC. THIS FORECAST PATTERN
CALLS FOR A GENERAL NORTHWEST TO WEST-NORTHWEST TRACK WITH NO
SIGNIFICANT CHANGE IN SPEED THROUGH FIVE DAYS AS INDICATED IN THE
NHC FORECAST. WITH THE EXCEPTION OF THE UK MODEL WHICH BUILDS A
STRONGER SUBTROPICAL RIDGE THAN THE OTHER MODELS AND KEEPS KATIA ON
A MORE WESTWARD TRACK...THE REST OF THE TRACK MODELS ARE IN GOOD
AGREEMENT. THE OFFICIAL FORECAST IS IN THE MIDDLE OF THE GUIDANCE
ENVELOPE AND IS VERY CLOSE TO THE ECMWF AND THE GFS GLOBAL MODELS.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0300Z 18.5N  54.3W   65 KT  75 MPH
 12H  03/1200Z 19.5N  55.4W   65 KT  75 MPH
 24H  04/0000Z 20.5N  57.0W   65 KT  75 MPH
 36H  04/1200Z 21.5N  59.0W   65 KT  75 MPH
 48H  05/0000Z 22.5N  60.5W   75 KT  85 MPH
 72H  06/0000Z 24.5N  63.5W   85 KT 100 MPH
 96H  07/0000Z 26.5N  66.5W   95 KT 110 MPH
120H  08/0000Z 28.0N  69.5W   95 KT 110 MPH
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 030900
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST SAT SEP 03 2011
 
KATIA CONTINUES TO STRUGGLE THIS MORNING WITH BURSTS OF CONVECTION
FORMING AN UNSHAPELY CENTRAL DENSE OVERCAST.  THE OVERALL PATTERN
IS NOT WELL ORGANIZED EITHER WITH THE HURRICANE HAVING TROUBLE
MAINTAINING BANDING FEATURES.  SATELLITE CLASSIFICATIONS ARE A
LITTLE LOWER THAN EARLIER...BUT STILL SUPPORT 65 KT ON THIS
ADVISORY. IT WOULD NOT BE SURPRISING IF IT WERE A LITTLE WEAKER
GIVEN THE RAGGED SATELLITE APPEARANCE.
 
SOUTHWESTERLY SHEAR AND SOME DRY AIR CONTINUE TO PREVENT SIGNIFICANT
STRENGTHENING OF THE TROPICAL CYCLONE.  THE UPPER-LEVEL TROUGH TO
THE NORTHWEST OF KATIA...HOWEVER...HAS BEEN WEAKENING...AND MOST OF
THE GLOBAL MODELS SUGGEST THE SHEAR WILL DECREASE STARTING ON
SUNDAY.  THUS SLOW INTENSIFICATION IS INDICATED AT THAT TIME IN THE
NHC FORECAST.  AFTERWARD...VERTICAL WIND SHEAR COULD BECOME RATHER
LOW BY DAY 4 AS AN UPPER-HIGH BUILDS CLOSER TO THE TROPICAL CYCLONE
WHILE KATIA MOVES OVER 29C WATER TEMPERATURES.  THE NHC FORECAST IS
SIMILAR TO THE PREVIOUS ONE EARLY ON...NEAREST THE LGEM/SHIPS
MODELS...BUT THEN IS BLENDED A LITTLE HIGHER AT THE END OF THE
FORECAST PERIOD WITH THE DYNAMICAL MODEL CONSENSUS.   BOTH THE HWRF
AND GFDL ARE SIGNIFICANTLY STRONGER THAN THE NHC FORECAST...BUT
THEY ARE PROBABLY NOT HANDLING THE MODERATE TO STRONG VERTICAL
SHEAR ENVIRONMENT CORRECTLY.
 
KATIA CONTINUES MOVING TOWARD THE NORTHWEST AT ABOUT 9 KT.  ALMOST
ALL OF THE GUIDANCE KEEP THIS GENERAL TRACK GOING FOR THE NEXT
SEVERAL DAYS AS THE CYCLONE APPROACHES THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE.  THE UKMET MODEL HAS BEEN STUBBORNLY FORECASTING
A MUCH STRONGER RIDGE...WHICH FORCES THE CYCLONE ON A WESTWARD
COURSE CLOSER TO THE BAHAMAS.  THIS WESTWARD TRACK SEEMS HIGHLY
UNLIKELY DUE TO A PRONOUNCED TROUGH OVER THE WESTERN ATLANTIC OCEAN
AND THE UKMET SOLUTION IS DISREGARDED FOR THIS FORECAST.  
OTHERWISE...THE MOST RELIABLE GUIDANCE HAS SHIFTED NORTHWARD
TONIGHT...PROBABLY DUE TO THE AFOREMENTIONED TROUGH OVER THE
WESTERN ATLANTIC BEING A BIT STRONGER THAN EARLIER ANTICIPATED. 
THE NHC FORECAST IS NEAR THE PREVIOUS ONE FOR THE FIRST COUPLE OF
DAYS...THEN IS SHIFTED TO THE NORTH...BUT NOT NEARLY AS FAR AS THE
MOST RECENT ECMWF/GFS/GFDL MODEL SOLUTIONS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0900Z 19.3N  55.1W   65 KT  75 MPH
 12H  03/1800Z 20.1N  56.3W   65 KT  75 MPH
 24H  04/0600Z 21.1N  57.9W   65 KT  75 MPH
 36H  04/1800Z 22.2N  59.7W   70 KT  80 MPH
 48H  05/0600Z 23.4N  61.5W   75 KT  85 MPH
 72H  06/0600Z 26.0N  64.5W   90 KT 105 MPH
 96H  07/0600Z 28.5N  67.5W  100 KT 115 MPH
120H  08/0600Z 31.0N  70.0W   95 KT 110 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 031452
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST SAT SEP 03 2011
 
SEVERAL MICROWAVE OVERPASSES FROM EARLIER THIS MORNING INDICATED
THAT KATIA IS TILTED...WITH A MID-LEVEL MICROWAVE EYE DISPLACED
ABOUT 20 N MI NORTH OF THE LOW-LEVEL CENTER. FINAL T-NUMBERS ARE
DOWN TO T3.5 FROM BOTH SAB AND TAFB...ALTHOUGH CI NUMBERS ARE STILL
HOLDING AT 4.0. UW-CIMSS ADT ESTIMATES HAVE BEEN DECREASING AND ARE
NOW T4.1. KATIA WILL BE KEPT AS A HURRICANE FOR NOW...BUT IF TRENDS
CONTINUE IT COULD ONCE AGAIN WEAKEN TO A TROPICAL STORM LATER
TODAY.

KATIA IS BEGINNING TO MOVE AROUND THE SOUTHWESTERN PERIPHERY OF A
MID-LEVEL HIGH LOCATED OVER THE CENTRAL ATLANTIC...AND TOWARDS A
DEEP-LAYER TROUGH OVER THE WESTERN ATLANTIC.  WITH THE EXCEPTION OF
THE UKMET...WHICH IS DISREGARDED IN THIS FORECAST...THE MODELS ARE
IN GOOD AGREEMENT ON MAINTAINING A MOTION OF ABOUT 305 DEGREES AT 9
TO 10 KT FOR THE NEXT 48 HOURS.  BEYOND 72 HOURS...THE TRACK
FORECAST BECOMES A LITTLE MORE COMPLEX AND PARTLY DEPENDS ON HOW
TROPICAL STORM LEE AND U.S. EAST COAST TROUGHING EVOLVE OVER THAT
TIME.  AS AN EXAMPLE...THE ECMWF DEVELOPS A DEEP-LAYER CLOSED LOW
OVER THE OHIO VALLEY BY DAY 5 WHILE THE GFS HAS A SHARP TROUGH
ALMOST READY TO CLOSE OFF OVER NEW YORK AND PENNSYLVANIA.  DESPITE
THESE DIFFERENCES...BOTH MODELS HAVE SHIFTED TO THE EAST...WITH THE
GFS BEING THE FASTEST DUE TO THE MORE PROGRESSIVE FLOW.  THE NHC
TRACK FORECAST IS ALSO SHIFTED TO THE EAST YET STILL LIES TO THE
WEST OF THOSE USUALLY RELIABLE MODELS.

STRONG SOUTHERLY SHEAR IS AFFECTING KATIA AND IS LIKELY ALLOWING DRY
AIR TO ERODE THE DEEP CONVECTION ON THE SOUTHERN SIDE.  THIS SHEAR
IS EXPECTED TO PERSIST FOR THE NEXT 24 HOURS OR SO...DURING WHICH
TIME NO STRENGTHENING IS INDICATED IN THE FORECAST.  THEREAFTER...
THE SHIPS MODEL SHOWS THAT UPPER-LEVEL WINDS COULD BECOME MORE
CONDUCIVE FOR STRENGTHENING...BUT THIS WILL ALL DEPEND ON THE
LOCATION OF KATIA RELATIVE TO THE DEEP-LAYER TROUGH OR CLOSED LOW
OVER THE EASTERN UNITED STATES.  THE NHC INTENSITY FORECAST WILL
CONTINUE TO INDICATE INTENSIFICATION BETWEEN DAYS 2 AND 4...AND IS
STILL ABOVE THE INTENSITY CONSENSUS AND STATISTICAL MODELS.

IT IS ADVISABLE NOT TO FOCUS ON SLIGHT FORECAST INTENSITY CHANGES
NEAR THE MAJOR HURRICANE THRESHOLD OF 100 KT SINCE THERE IS VERY
LITTLE DIFFERENCE BETWEEN A 95- AND 100-KT HURRICANE.  BASED ON THE
CURRENT FORECAST AND RECENT NHC INTENSITY ERRORS...AT THIS TIME
THERE IS ROUGHLY A 50/50 CHANCE OF KATIA STILL BECOMING A MAJOR
HURRICANE DURING THE NEXT 5 DAYS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  03/1500Z 19.6N  55.8W   65 KT  75 MPH
 12H  04/0000Z 20.3N  57.0W   65 KT  75 MPH
 24H  04/1200Z 21.3N  58.7W   65 KT  75 MPH
 36H  05/0000Z 22.5N  60.4W   70 KT  80 MPH
 48H  05/1200Z 23.7N  62.1W   75 KT  85 MPH
 72H  06/1200Z 26.5N  65.0W   85 KT 100 MPH
 96H  07/1200Z 29.5N  67.5W   95 KT 110 MPH
120H  08/1200Z 32.0N  69.5W   90 KT 105 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 032052
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST SAT SEP 03 2011
 
DVORAK INTENSITY ESTIMATES HAVE FALLEN THROUGH THE DAY AND ARE NOW
T3.0/4.0 FROM TAFB AND T3.5/3.5 FROM SAB.  BASED ON THE STRUCTURE
NOTED IN EARLIER MICROWAVE DATA...IT APPEARS THAT KATIA HAS
WEAKENED SOME AND AGAIN IS A TROPICAL STORM.  FLUCTUATIONS IN
INTENSITY BY 5 TO 10 KT ARE POSSIBLE OVER THE NEXT DAY OR SO...BUT
THIS FACT WILL ONLY BE MORE APPARENT THAN USUAL SINCE THE INTENSITY
WOULD BE OSCILLATING AROUND THE 65-KT HURRICANE THRESHOLD.

IT CANNOT BE STRESSED ENOUGH THAT THERE IS CONSIDERABLE UNCERTAINTY
IN THE TRACK FORECAST...WHICH IS EXTREMELY SENSITIVE TO THE
EVOLUTION OF TROPICAL STORM LEE AND ITS INTERACTION WITH A MID-
TO UPPER-LEVEL LOW OVER THE EASTERN UNITED STATES.  THE MODEL
GUIDANCE IS IN PRETTY GOOD AGREEMENT DURING THE FIRST 36 HOURS OR
SO...BUT THE DIVERGENCE ONLY GROWS FROM THERE.  COMPARED TO THE
PREVIOUS FORECAST CYCLE...THE UKMET HAS SHIFTED TO THE NORTH AND
THE GFS HAS SLOWED DOWN...WHICH NORMALLY WOULD HAVE INCREASED
CONFIDENCE IN THE FORECAST.  FURTHERMORE...THE ECMWF...WHICH IS
NORMALLY RELIABLE...SWUNG FROM THE NORTH AND EAST SIDE OF THE
GUIDANCE TO THE SOUTH AND WEST SIDE...SHOWING A MORE WESTWARD
MOTION BY DAY 5.  THE OFFICIAL TRACK FORECAST HAS BEEN NUDGED A BIT
TO THE WEST TOWARDS THE VARIOUS CONSENSUS MODELS...BUT WE WOULD
RATHER SEE SOME STABILITY IN THE MODELS BEFORE MAKING A LARGER
SHIFT.

NEEDLESS TO SAY...THE INTENSITY FORECAST IS ALSO COMPLEX.  KATIA HAS
NOT BEEN STRENGTHENING AS ANTICIPATED...AND UPPER-LEVEL WINDS DO
NOT APPEAR AS THOUGH THEY WILL BE CONDUCIVE FOR SIGNIFICANT
INTENSIFICATION FOR THE NEXT 24 TO 48 HOURS.  THE UPPER-LEVEL
ENVIRONMENT AROUND KATIA BECOMES MORE UNCERTAIN AFTER
THAT TIME DEPENDING ON THE POSITIONING OF THE EASTERN U.S.
MID-/UPPER-LEVEL LOW.  THE STATISTICAL SHIPS AND LGEM MODELS DO NOT
STRENGTHEN KATIA BEYOND CATEGORY 1 STATUS WHEREAS THE GFDL AND HWRF
STILL SHOW THE STORM REACHING MAJOR HURRICANE STRENGTH.  THE
OFFICIAL INTENSITY FORECAST IS STILL NEAR OR JUST ABOVE THE
INTENSITY CONSENSUS...ESPECIALLY AT DAYS 4 AND 5.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 19.9N  56.8W   60 KT  70 MPH
 12H  04/0600Z 20.7N  58.1W   65 KT  75 MPH
 24H  04/1800Z 21.8N  59.8W   65 KT  75 MPH
 36H  05/0600Z 23.1N  61.5W   70 KT  80 MPH
 48H  05/1800Z 24.3N  63.2W   75 KT  85 MPH
 72H  06/1800Z 27.0N  66.0W   85 KT 100 MPH
 96H  07/1800Z 29.5N  69.0W   90 KT 105 MPH
120H  08/1800Z 31.5N  70.5W   85 KT 100 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 040250
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST SAT SEP 03 2011
 
ONCE AGAIN TONIGHT...THERE IS AN INCREASE IN ORGANIZATION OF THE
CLOUD PATTERN WITH THE FORMATION OF A ROUND CENTRAL DENSE OVERCAST
AND A BETTER DEFINED OUTFLOW IN CONVENTIONAL IR IMAGES. I HAVE BEEN
LUCKY ENOUGH TO HAVE SEVERAL MICROWAVE PASSES OVER KATIA TONIGHT. 
THESE DATA SHOW A MUCH BETTER ORGANIZED INNER CORE STRUCTURE THAN
IN EARLIER PASSES...BUT THE CIRCULAR RING OF CONVECTION
REPRESENTING THE MID-LEVEL EYE FEATURE CONTINUES TO BE DISPLACED TO
THE NORTH OF THE LOW-LEVEL CENTER DUE TO SHEAR. THIS SUGGESTS THAT
THE CYCLONE MIGHT NOT BE AS WELL ORGANIZED AS IT SEEMS IN
CONVENTIONAL IMAGERY.  HAVING SAID THAT...THE INITIAL INTENSITY HAS
BEEN KEPT AT 60 KNOTS BASED ON A BLEND OF THE LATEST DVORAK
T-NUMBERS.  AS STATED IN THE PREVIOUS ADVISORY...KATIA COULD REACH
HURRICANE STATUS AGAIN AT ANY TIME...AND SINCE THE SHEAR SHOULD
BEGIN TO RELAX IN ABOUT 12 TO 24 HOURS ACCORDING TO THE SHIPS
MODEL...A GRADUAL INTENSIFICATION IS INDICATED IN THE OFFICIAL
FORECAST.  

SINCE THE OVERALL STEERING PATTERN HAS NOT CHANGED...THERE IS NOT
TOO MUCH TO ADD TO THE DISCUSSION.  KATIA CONTINUES TO MOVE TOWARD
THE NORTHWEST OR 305 DEGREES AT 9 KNOTS AROUND THE SOUTHERN EDGE OF
THE SUBTROPICAL RIDGE. GUIDANCE HAS BEEN SHIFTING SLIGHTLY EASTWARD
OR WESTWARD DEPENDING ON HOW EACH MODEL REPRESENTS THE MID-LEVEL
TROUGH OVER THE EASTERN UNITED STATES IN EACH RUN.  IT INTERESTING
TO NOTE THAT TONIGHT...THE GFS DEFINES THE EASTERN SIDE OF THE
GUIDANCE ENVELOPE AND THE ECMWF THE WESTERN EDGE. THE OFFICIAL
FORECAST IS A THE MIDDLE OF THESE TWO EXTREME SOLUTIONS. IN
GENERAL...MODEL SOLUTIONS ARE TO KEEP KATIA ON A TRACK BETWEEN THE
WEST-NORTHWEST AND NORTHWEST FOR THE NEXT 3 TO 4 DAYS AND THEN TURN
THE CYCLONE MORE TO THE NORTH THEREAFTER. 

NOAA BUOY 41044...LOCATED A LITTLE MORE THAN 100 N MI TO THE
NORTHWEST OF KATIA RECENTLY REPORTED WINDS OF 33 KNOTS AND 18-FOOT
WAVES. 
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0300Z 20.3N  57.4W   60 KT  70 MPH
 12H  04/1200Z 21.0N  58.6W   65 KT  75 MPH
 24H  05/0000Z 22.3N  60.3W   65 KT  75 MPH
 36H  05/1200Z 23.5N  62.0W   70 KT  80 MPH
 48H  06/0000Z 24.5N  63.5W   75 KT  85 MPH
 72H  07/0000Z 27.0N  67.0W   85 KT 100 MPH
 96H  08/0000Z 29.1N  70.0W   90 KT 105 MPH
120H  09/0000Z 32.0N  71.0W   85 KT 100 MPH
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 040852
TCDAT2
 
TROPICAL STORM KATIA DISCUSSION NUMBER  25
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST SUN SEP 04 2011
 
KATIA REMAINS IN A NEARLY STEADY STATE. THE CLOUD PATTERN CONTINUES
TO CONSIST OF A RATHER INDISTINCT CENTRAL DENSE OVERCAST WHICH HAS
BEEN PULSATING SOMEWHAT FREQUENTLY. A COUPLE OF MICROWAVE PASSES
SHOWED THE EXISTENCE OF A MID-LEVEL EYE THAT HAS BEEN LESS DEFINED
IN THE LOW-LEVELS. WITH ESSENTIALLY NO STRUCTURAL CHANGES TO REPORT
AND DVORAK T-NUMBERS THE SAME AS AT 0000 UTC...THE INITIAL
INTENSITY IS HELD AT 60 KT. CIRRUS CLOUD MOTIONS AND UW-CIMSS
ANALYSES SUGGEST A SOUTHWESTERLY FLOW UNDERCUTTING THE OUTFLOW
LAYER...WHICH MAY HAVE BEEN STALLING THE INTENSIFICATION PROCESS.
GLOBAL MODELS CONTINUE TO INSIST ON A MORE CONDUCIVE UPPER AIR
FORECAST AHEAD OF KATIA THAT WOULD FAVOR INTENSIFICATION BEGINNING
IN A COUPLE OF DAYS. THEN AGAIN...THE FORECAST REDUCTION IN SHEAR
BY THIS TIME HAS NOT MATERIALIZED AND IT WOULD SEEM THAT THE MODELS
HAVE CONTINUALLY UNDERFORECAST THE AMOUNT OF SHEAR. THE OFFICIAL
FORECAST WILL KEEP THIS IN MIND AND REPRESENT A MEASURED
APPROACH...BLENDING THE MORE RELIABLE STATISTICAL MODELS INDICATING
MODEST STRENGTHENING AND DYNAMICAL GUIDANCE WHICH STILL FORECASTS
KATIA TO BECOME A MAJOR HURRICANE.
 
LOCATING THE CENTER HAS BEEN DIFFICULT IN CONVENTIONAL SATELLITE
IMAGERY...BUT A TIMELY AMSR-E PASS HELPED TO ESTABLISH THE INITIAL
MOTION ESTIMATE OF 305/10.  WATER VAPOR IMAGERY SHOWS KATIA HEADING
NORTHWESTWARD TOWARD A MID- TO UPPER-LEVEL IMPULSE LOCATED OVER THE
WESTERN ATLANTIC.  ALTHOUGH THE LARGE-SCALE MODELS FORECAST THIS
FEATURE TO LIFT OUT DURING THE NEXT DAY OR TWO...THEY ALSO FORECAST
A WEAKNESS OVER THIS REGION TO REMAIN IN PLACE WHICH SHOULD CAUSE
KATIA TO CONTINUE ON A NORTHWESTWARD COURSE AND SLOW DURING THE
NEXT SEVERAL DAYS.  THE LONGER-TERM TRACK OF KATIA SEEMS DEPENDENT
ON THE TROUGH ASSOCIATED WITH THE REMNANTS OF LEE AND A PROCESSION
OF SHORTWAVE TROUGHS MOVING THROUGH THE NORTHEASTERN UNITED
STATES...BOTH OF WHICH THE MODELS ARE HANDLING DIFFERENTLY TO
VARYING DEGREES.  THERE HAS BEEN A SIGNIFICANT WESTWARD SHIFT IN
THE GUIDANCE THIS CYCLE...ALONG WITH A NOTABLE INCREASE IN THE
SPREAD.  THE OFFICIAL TRACK AT THIS LONGER RANGE IS OF SOMEWHAT
LOWER CONFIDENCE...GIVEN THE SPREAD...AND IS ADJUSTED TO THE
LEFT...BUT NOT AS FAR LEFT AS THE LATEST MULTI-MODEL CONSENSUS.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0900Z 21.4N  58.5W   60 KT  70 MPH
 12H  04/1800Z 22.3N  59.8W   65 KT  75 MPH
 24H  05/0600Z 23.5N  61.6W   70 KT  80 MPH
 36H  05/1800Z 24.7N  63.5W   75 KT  85 MPH
 48H  06/0600Z 25.8N  65.0W   80 KT  90 MPH
 72H  07/0600Z 27.7N  68.0W   85 KT 100 MPH
 96H  08/0600Z 30.0N  71.0W   90 KT 105 MPH
120H  09/0600Z 32.5N  72.0W   85 KT 100 MPH
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 041454
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST SUN SEP 04 2011
 
EARLIER THIS MORNING...THE CENTER OF KATIA MOVED JUST TO THE SOUTH
OF NOAA BUOY 41044...WHICH MEASURED A PEAK 1-MINUTE WIND OF 78
KT...A GUST TO 93 KT...AND A MINIMUM PRESSURE OF 968.3 MB.
SUBJECTIVE DVORAK INTENSITY ESTIMATES HAVE RISEN TO BETWEEN 65 AND
77 KT FROM TAFB AND SAB...BUT THE LATEST UW-CIMSS ADT ESTIMATES
HAVE BEEN HOVERING AROUND 85 KT.  BASED ON THESE DATA...KATIA IS
INITIALIZED AS AN 85-KT HURRICANE.  AN EYE IS BECOMING APPARENT IN
VISIBLE SATELLITE IMAGERY...YET THE INFRARED IMAGERY DOES NOT SHOW
THE DEEP CONVECTION VERY SYMMETRICAL.
 
KATIA APPEARS TO BE ON TRACK WITH AN INITIAL MOTION OF 305/10 KT.
ALTHOUGH A LOT OF UNCERTAINTY REMAINS IN THE 3 TO 5 DAY FORECAST
PERIOD...LITTLE CHANGE WAS MADE ON THIS FORECAST RELATIVE TO THE
PREVIOUS ONE.  THE ECMWF...UKMET...AND HWRF MODELS REMAIN ON THE
SOUTHWESTERN SIDE OF THE GUIDANCE WHILE THE GFS AND GFDL ARE A
LITTLE FASTER AND FARTHER NORTH BY DAY 5.  MUCH OF THIS DIFFERENCE
APPEARS TO BE DUE TO THE POSITIONING OF THE CLOSED MID- TO
UPPER-LEVEL LOW FORECAST TO DEVELOP OVER THE EASTERN UNITED STATES
IN 4-5 DAYS...WHICH THE GFS SHOWS ABOUT 300 N MI FARTHER TO THE
EAST AND DEEPER THAN IN THE ECMWF AND UKMET AT DAY 5.  THE OFFICIAL
FORECAST IS VERY CLOSE TO THE MULTI-MODEL CONSENSUS AND STILL KEEPS
THE HURRICANE AT OR EAST OF 72W.
 
DESPITE THE QUICK STRENGTHENING OVER THE PAST 6 TO 12 HOURS...ADT
ESTIMATES HAVE LEVELED OFF AT 85 KT...AND IT IS HARD TO TELL IF THE
CYCLE OF RAPID INTENSIFICATION IS GOING TO CONTINUE DURING THE DAY.
THE SHIPS MODEL IS STILL DIAGNOSING ABOUT 15 KT OF SOUTH TO
SOUTHWESTERLY VERTICAL SHEAR OVER KATIA...BUT THE HURRICANE MAY BE
BENEFITING FROM UPPER-LEVEL DIVERGENCE ASSOCIATED WITH OUTFLOW
JETS TO ITS NORTH AND NORTHEAST.  THE OFFICIAL INTENSITY FORECAST
IS AT THE HIGHER RANGE OF THE INTENSITY GUIDANCE...FOLLOWING CLOSE
TO THE GFDL AND HWRF MODELS.  HOWEVER...THE ENVIRONMENT APPEARS
SUFFICIENTLY CONDUCIVE FOR INTENSIFICATION...AND KATIA COULD STILL
STRENGTHEN MORE THAN INDICATED HERE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 21.9N  59.2W   85 KT 100 MPH
 12H  05/0000Z 22.9N  60.6W   95 KT 110 MPH
 24H  05/1200Z 24.1N  62.4W  100 KT 115 MPH
 36H  06/0000Z 25.2N  64.0W  100 KT 115 MPH
 48H  06/1200Z 26.2N  65.6W  105 KT 120 MPH
 72H  07/1200Z 28.0N  68.5W  105 KT 120 MPH
 96H  08/1200Z 30.0N  71.5W  105 KT 120 MPH
120H  09/1200Z 33.0N  72.0W   95 KT 110 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 042048
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  27
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST SUN SEP 04 2011
 
WHILE KATIA HAS HAD A FAIRLY WELL-DEFINED EYE IN VISIBLE SATELLITE
IMAGERY...THE INFRARED REPRESENTATION OF THE EYE HAS COME AND GONE
OVER THE PAST FEW HOURS.  DVORAK INTENSITY ESTIMATES AT 1800 UTC
WERE A UNANIMOUS T5.0 FROM TAFB...SAB...AND THE UW-CIMSS ADT...SO
THE INITIAL INTENSITY IS RAISED TO 90 KT FOR THIS ADVISORY.

KATIA HAS TURNED JUST A BIT TO THE RIGHT WITH AN INITIAL MOTION OF
310/10 KT.  COMPARED TO THE PREVIOUS FEW FORECAST CYCLES...THERE IS
CONSIDERABLY MORE AGREEMENT IN THE TRACK MODEL GUIDANCE FOR THIS
PACKAGE.  FOR THE FIRST 48 HOURS...THE GUIDANCE IS TIGHTLY CLUSTERED
AND AGREES ON MAINTAINING KATIA ON A HEADING OF 310 DEGREES WITH
SOME DECELERATION.  THEREAFTER...THERE IS SOME DIVERGENCE BUT NOT
AS MUCH AS THERE WAS EARLIER.  ACTUALLY...THE GFS...ECWMF...AND
UKMET MODELS ARE ALL SHOWING A MID- TO UPPER-LEVEL CLOSED LOW
DEVELOPING OVER THE EASTERN UNITED STATES AND HAVE THE POSITION OF
THE LOW WITHIN 200 N MI OF EACH OTHER BY DAY 5.  THIS CONFIGURATION
SHOULD CAUSE KATIA TO MAKE A TURN TOWARD THE NORTH BY THE END OF
THE FORECAST PERIOD.  THE USUALLY RELIABLE ECMWF HAS SHIFTED A BIT
TO THE EAST AND IS NOW VERY CLOSE TO THE PREVIOUS OFFICIAL
FORECAST.  THEREFORE...LITTLE CHANGE WAS MADE TO THE TRACK FORECAST
FOR THIS CYCLE.

THE PERIOD OF RAPID INTENSIFICATION MAY HAVE LEVELED OFF A BIT...BUT
ENVIRONMENTAL CONDITIONS STILL APPEAR FAVORABLE FOR ADDITIONAL
STRENGTHENING.  THE ONLY APPARENT NEGATIVE FACTORS FOR THIS ARE
RELATIVELY WARM UPPER-TROPOSPHERIC TEMPERATURES AND LOWER OCEANIC
HEAT CONTENT VALUES ALONG THE FORECAST PATH...ESPECIALLY FROM DAYS
3 THROUGH 5.  THE OFFICIAL FORECAST IS STILL AT THE UPPER END OF
THE RANGE OF GUIDANCE VALUES...CLOSE TO THE DYNAMICAL HURRICANE
MODELS...AND INDICATES GRADUAL STRENGTHENING OVER THE NEXT 48
HOURS...FOLLOWED BY GRADUAL WEAKENING ON DAYS 4 AND 5.

LONG-PERIOD SWELLS ASSOCIATED WITH KATIA ARE ALREADY APPROACHING
PARTS OF THE EAST COAST OF THE UNITED STATES.  EVEN IF KATIA DOES
NOT DIRECTLY IMPACT THE UNITED STATES...THE THREAT FOR HIGH SURF
AND RIP CURRENTS ALONG EAST COAST BEACHES IS EXPECTED TO INCREASE
OVER THE NEXT FEW DAYS.  PLEASE CONSULT PRODUCTS ISSUED BY LOCAL
NATIONAL WEATHER SERVICE OFFICES FOR MORE INFORMATION.

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 22.7N  60.1W   90 KT 105 MPH
 12H  05/0600Z 23.7N  61.5W   95 KT 110 MPH
 24H  05/1800Z 25.0N  63.2W  100 KT 115 MPH
 36H  06/0600Z 26.1N  64.7W  100 KT 115 MPH
 48H  06/1800Z 27.1N  66.1W  105 KT 120 MPH
 72H  07/1800Z 29.0N  69.0W  105 KT 120 MPH
 96H  08/1800Z 31.5N  71.5W  100 KT 115 MPH
120H  09/1800Z 34.5N  71.5W   90 KT 105 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 050236
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  28
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST SUN SEP 04 2011
 
AFTER KATIA STRENGTHENED STEADILY EARLIER TODAY...THE
INTENSIFICATION PROCESS APPEARS TO HAVE STOPPED FOR NOW. THE
CONVECTIVE PATTERN HAS BECOME A LITTLE LESS SYMMETRIC SINCE THE
LAST ADVISORY...WITH THE COLDEST CLOUD TOPS LOCATED OVER THE
SOUTHERN HALF OF THE CIRCULATION. ALTHOUGH AN EYE IS EASILY SEEN IN
MULTI-CHANNEL NIGHT VISIBLE IMAGERY...IT IS ONLY OCCASIONALLY
EVIDENT IN INFRARED IMAGES. DVORAK CURRENT INTENSITY ESTIMATES FROM
TAFB AND SAB REMAIN 90 KT...AND THE INITIAL WIND SPEED IS HELD AT
THAT VALUE.

THE HURRICANE CONTINUES NORTHWESTWARD AT 11 KT ON THE SOUTHWESTERN
PERIPHERY OF A SUBTROPICAL HIGH LOCATED OVER THE CENTRAL ATLANTIC. 
DURING THE NEXT TWO TO THREE DAYS...THE HIGH IS EXPECTED TO BUILD
WESTWARD AS A TROUGH BETWEEN BERMUDA AND THE UNITED STATES WEAKENS.
THIS PATTERN WILL ALLOW KATIA TO CONTINUE ON THE SAME GENERAL TRACK
WITH A SLIGHT DECREASE IN FORWARD SPEED. BEYOND THREE DAYS...KATIA
IS FORECAST TO TURN TOWARD THE NORTH AS IT BECOMES EMBEDDED IN THE
FLOW BETWEEN THE AFOREMENTIONED HIGH AND A LARGE CUTOFF LOW OVER
THE EASTERN UNITED STATES. GLOBAL MODELS SHOW A SERIES OF
SHORTWAVES MOVING ACROSS NEW ENGLAND AND ATLANTIC CANADA IN FOUR TO
FIVE DAYS...AND THAT COULD CAUSE THE HURRICANE TO TURN
NORTHEASTWARD AT THE END OF THE FORECAST PERIOD. THE OFFICIAL
FORECAST IS ADJUSTED TO THE EAST THIS CYCLE...ESPECIALLY AT 120
HOURS...BUT LIES WEST OF THE MULTI-MODEL CONSENSUS. IF THE CURRENT
TREND TOWARD A FASTER NORTHEASTWARD MOTION CONTINUES IN THE
GUIDANCE...FURTHER ADJUSTMENTS IN THAT DIRECTION WOULD BE REQUIRED.

ALTHOUGH THE INTENSITY OF KATIA HAS LEVELED OFF THIS EVENING...THE
HURRICANE IS FORECAST TO STRENGTHEN SOME DURING THE NEXT COUPLE OF
DAYS AS IT REMAINS IN FAVORABLE ATMOSPHERIC AND OCEANIC
ENVIRONMENTS.  SOME WEAKENING IS FORECAST IN THE THREE TO FIVE DAY
RANGE AS THE HURRICANE MOVES INTO A REGION WITH LOWER VALUES OF
OCEANIC HEAT CONTENT AND PERHAPS INTO A MORE STABLE ENVIRONMENT. 
THE OFFICIAL FORECAST FOLLOWS THE TREND IN THE GUIDANCE AND IS NEAR
A BLEND OF THE STATISTICAL AND DYNAMICAL MODELS. 

LONG-PERIOD SWELLS ASSOCIATED WITH KATIA ARE ALREADY APPROACHING
PARTS OF THE EAST COAST OF THE UNITED STATES. EVEN IF KATIA DOES
NOT DIRECTLY IMPACT THE UNITED STATES...THE THREAT FOR HIGH SURF
AND RIP CURRENTS ALONG EAST COAST BEACHES IS EXPECTED TO INCREASE
OVER THE NEXT FEW DAYS. PLEASE CONSULT PRODUCTS ISSUED BY LOCAL
NATIONAL WEATHER SERVICE OFFICES FOR MORE INFORMATION.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0300Z 23.4N  61.0W   90 KT 105 MPH
 12H  05/1200Z 24.4N  62.4W   95 KT 110 MPH
 24H  06/0000Z 25.7N  64.0W  100 KT 115 MPH
 36H  06/1200Z 26.9N  65.5W  100 KT 115 MPH
 48H  07/0000Z 28.0N  66.9W  105 KT 120 MPH
 72H  08/0000Z 30.3N  69.8W  100 KT 115 MPH
 96H  09/0000Z 33.5N  71.0W   95 KT 110 MPH
120H  10/0000Z 36.0N  69.0W   85 KT 100 MPH
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 050853
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST MON SEP 05 2011
 
THE INNER CORE CONVECTIVE STRUCTURE OF KATIA APPEARS TO HAVE GONE
THROUGH ANOTHER ROUND OF CHANGES...WITH A NET DECREASE IN
ORGANIZATION NOTED DURING THE PAST SEVERAL HOURS.  AN EYE THAT WAS
EVIDENT EARLIER IS NO LONGER APPARENT...AND THERE ARE SIGNS THAT
DRY AIR HAS BEEN ROTATING AROUND THE CIRCULATION. UPPER-LEVEL
OUTFLOW IS GOOD TO EXCELLENT...WITH A FAVORABLE OUTFLOW SINK TO THE
NORTHEAST.  A BLEND OF DVORAK T AND CI NUMBERS FROM TAFB AND SAB IS
LOWER THAN 6 HOURS AGO...SO THE CURRENT INTENSITY ESTIMATE IS
LOWERED TO 85 KT.
 
THE CENTER OF KATIA HAS BEEN WOBBLING. SMOOTHING OF RECENT FIXES
YIELDS AN INITIAL MOTION ESTIMATE OF 305/10. LARGE-SCALE MODELS
SHOW KATIA ROUNDING THE SOUTHWEST PERIPHERY OF A MID-LEVEL RIDGE
EAST OF BERMUDA...HEADING TOWARD A WEAKNESS OVER THE WESTERN
ATLANTIC. THIS SYNOPTIC PATTERN SHOULD STEER THE HURRICANE ON A
GENERAL NORTHWESTWARD COURSE WITH SOME DECELERATION OVER THE NEXT
FEW DAYS. LATER IN THE FORECAST PERIOD...FURTHER WESTWARD PROGRESS
IS LIKELY TO BE BLOCKED AS KATIA IS CAUGHT UP IN DEEP-LAYER
SOUTHERLY FLOW IN BETWEEN A LARGE CUT-OFF LOW OVER THE EASTERN
UNITED STATES AND THE RIDGE TO THE EAST. ONCE KATIA GAINS ENOUGH
LATITUDE...GLOBAL MODELS SHOW THE HURRICANE BECOMING EMBEDDED IN 
STRONG MID-LATITUDE WESTERLY FLOW AND ACCELERATING NORTHEASTWARD.
THE SPREAD IN THE TRACK GUIDANCE HAS DECREASED SUBSTANTIALLY SINCE
YESTERDAY AND NOW FAVORS A RECURVATURE SCENARIO ROUGHLY ALONG
70W...WITH EVEN THE LEFT-LEANING UKMET/ECMWF MODELS NOW SHIFTING
SIGNIFICANTLY TO THE EAST. THE MAIN FORECAST CHALLENGE IS HOW
QUICKLY KATIA WILL TURN NORTHWARD AND THEN NORTHEASTWARD...WITH
MAJOR TIMING DIFFERENCES NOTED AMONGST THE VARIOUS MODELS. THE
OFFICIAL TRACK IS NEARLY IDENTICAL TO THE PREVIOUS ONE THROUGH 72
HOURS BUT IS ADJUSTED TO THE RIGHT AND IS MUCH FASTER TOWARD THE
END OF THE PERIOD BUT NOT AS FAST AS THE MULTI-MODEL CONSENSUS.
 
ACCORDING TO THE GLOBAL MODELS...KATIA WILL BE MOVING THROUGH AN
ENVIRONMENT CHARACTERIZED BY ANTICYCLONIC UPPER-LEVEL FLOW AND WEAK
VERTICAL SHEAR THROUGH AT LEAST 72 HOURS. THE PRIMARY NEGATIVE
FACTORS THAT COULD INHIBIT THE INTENSIFICATION PROCESS DURING THIS
TIME ARE LOW MID-LEVEL RELATIVE HUMIDITY VALUES...A LOWERING OF THE
OCEANIC HEAT CONTENT ALONG THE FORECAST TRACK...AND THE POSSIBILITY
OF A MORE STABLE ENVIRONMENT DUE TO WARMING ALOFT.  AFTER 96
HOURS...INCREASING SHEAR AND THE PROXIMITY OF KATIA TO A STRONG
GRADIENT OF SEA SURFACE TEMPERATURES WILL LIKELY CONTRIBUTE TO
WEAKENING. THE OFFICIAL INTENSITY FORECAST HAS BEEN LOWERED EARLY
IN THE FORECAST PERIOD BASED ON CURRENT TRENDS AND ALSO AT THE END
OF THE PERIOD AS A RESULT OF ADJUSTMENTS TO THE TRACK FORECAST. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 23.9N  62.0W   85 KT 100 MPH
 12H  05/1800Z 25.0N  63.2W   90 KT 105 MPH
 24H  06/0600Z 26.3N  64.8W   95 KT 110 MPH
 36H  06/1800Z 27.5N  66.2W  100 KT 115 MPH
 48H  07/0600Z 28.6N  67.6W  105 KT 120 MPH
 72H  08/0600Z 31.4N  70.1W  100 KT 115 MPH
 96H  09/0600Z 35.5N  69.5W   90 KT 105 MPH
120H  10/0600Z 38.5N  64.0W   75 KT  85 MPH
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 051447
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST MON SEP 05 2011
 
KATIA APPEARS TO HAVE GONE THROUGH AN EYEWALL REPLACEMENT AND NOW
HAS A 30 N MI WIDE EYE SURROUNDED BY A RELATIVELY NARROW BAND OF
THE COLDEST CLOUD TOPS.  DVORAK INTENSITY ESTIMATES HAVE RISEN TO
T5.0 FROM TAFB AND SAB...AND THE OBJECTIVE NUMBERS ARE AT T5.5. 
THE INITIAL INTENSITY IS THEREFORE BEING RAISED TO 95 KT.

THE EYE HAS BEEN WOBBLING A BIT...BUT THE 12-HOUR SMOOTHED MOTION IS
310/11 KT.  KATIA IS MOVING AROUND THE SOUTHWESTERN PERIPHERY OF A
CENTRAL ATLANTIC MID-LEVEL ANTICYCLONE AND TOWARDS DEEP-LAYER
TROUGHING OVER THE EASTERN UNITED STATES AND WESTERN ATLANTIC.  THE
TRACK GUIDANCE IS IN GOOD AGREEMENT IN MAINTAINING A NORTHWESTWARD
HEADING WITH SOME DECREASE IN FORWARD SPEED DURING THE FIRST 48
HOURS.  ALTHOUGH ALL THE GUIDANCE SHOWS SHARP RE-CURVATURE BETWEEN
BERMUDA AND THE U.S. EAST COAST IN ABOUT 3 DAYS...THERE IS STILL A
LARGE DIVERGENCE IN FORWARD SPEED WITH GREATER-THAN-NORMAL SPREAD
AT DAYS 4 AND 5.  FOR THIS CYCLE...THE GUIDANCE IS BOUNDED BY THE
SLOWER-MOVING ECMWF AND UKMET...AND THE FASTER-MOVING GFS. IF
TRENDS FROM THE PAST FEW DAYS CONTINUE TODAY...I WOULD EXPECT
THE 12Z GUIDANCE TO SHOW LESS SPREAD AND FOR NOW WILL MAINTAIN THE
OFFICIAL FORECAST AS BEING SLOWER THAN THE CONSENSUS MODELS.

THE UPPER-LEVEL ENVIRONMENT NEAR KATIA APPEARS CONDUCIVE FOR FURTHER
STRENGTHENING OVER THE NEXT SEVERAL DAYS.  HOWEVER...WITHIN THE NEXT
24 HOURS OR SO...THE HURRICANE WILL BE MOVING OVER OCEAN HEAT
CONTENT VALUES THAT DO NOT NORMALLY SUPPORT SIGNIFICANT
INTENSIFICATION.  THE OFFICIAL FORECAST THEREFORE INDICATES GRADUAL
STRENGTHENING OVER THE NEXT 24 HOURS AND THEN MAINTAINS THE
INTENSITY THROUGH DAYS 2 AND 3.  WEAKENING IS FORECAST ON DAYS 4
AND 5 AS VERTICAL SHEAR INCREASES...AND AS KATIA MOVES OVER EVEN
LESS CONDUCIVE OCEAN WATERS.  THE OFFICIAL INTENSITY FORECAST IS AT
THE UPPER END OF THE GUIDANCE FOR MOST OF THE FORECAST PERIOD.

DUE TO THE EYEWALL REPLACEMENT...IT APPEARS THAT THE WIND FIELD HAS
EXPANDED A BIT...AND THIS IS REFLECTED IN THE ANALYSIS AND FORECAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 24.6N  63.3W   95 KT 110 MPH
 12H  06/0000Z 25.6N  64.2W  100 KT 115 MPH
 24H  06/1200Z 26.9N  65.7W  105 KT 120 MPH
 36H  07/0000Z 28.1N  67.3W  105 KT 120 MPH
 48H  07/1200Z 29.2N  68.7W  100 KT 115 MPH
 72H  08/1200Z 32.5N  70.5W   95 KT 110 MPH
 96H  09/1200Z 37.0N  67.5W   80 KT  90 MPH
120H  10/1200Z 40.0N  60.0W   70 KT  80 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 052039
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST MON SEP 05 2011
 
VISIBLE SATELLITE IMAGERY SHOWS THAT KATIA HAS BECOME MORE ORGANIZED
THROUGH THE DAY WITH A WELL-DEFINED EYE AND EXCELLENT UPPER-LEVEL
OUTFLOW...ESPECIALLY OVER THE SOUTHERN SEMICIRCLE.  HOWEVER...THE
INFRARED PRESENTATION IS LAGGING A BIT AND SHOWS A THINNING OF THE
DEEP CONVECTION OVER THE NORTHEASTERN QUADRANT.  DVORAK ESTIMATES
FROM TAFB AND SAB ARE T5.5...AND THE INITIAL INTENSITY IS THEREFORE
RAISED TO 100 KT.  OBJECTIVE DVORAK NUMBERS HAVE BEEN RUNNING
HIGHER...BUT WITH THE CONVECTION LACKING SYMMETRY AND A COOLING EYE
IN THE LAST FEW IMAGES...I WOULD RATHER WAIT TO RAISE THE INTENSITY
ANY HIGHER.
 
THE 12-HOUR SMOOTHED MOTION IS ABOUT 310/10 KT...AND KATIA IS
EXPECTED TO CONTINUE ON ITS NEARLY STRAIGHT TRACK FOR THE NEXT 48
HOURS AS IT MOVES AROUND A CENTRAL ATLANTIC MID-LEVEL ANTICYCLONE. 
FAIRLY SHARP RE-CURVATURE IS SHOWN BY MOST OF THE MODELS AROUND DAY
3...AND THEY ARE TIGHTLY CLUSTERED WITH A TRACK THAT TAKES THE
CENTER ALMOST MIDWAY BETWEEN BERMUDA AND THE U.S. EAST COAST.  AS
WAS THE CASE EARLIER TODAY...THERE IS STILL GREATER-THAN-NORMAL
SPREAD IN THE GUIDANCE AT 96 AND 120 HOURS DUE TO A LACK OF
AGREEMENT ON WHEN KATIA WILL BE SCOOPED UP BY STRONG MID-LATITUDE
WESTERLIES TO THE NORTH.  HOWEVER...THE ECMWF AND UKMET HAVE SPED
UP A BIT AND THE GFS HAS SLOWED DOWN...SO THE UNCERTAINTY HAS
DECREASED SOMEWHAT.  THE MOST SIGNIFICANT CHANGE TO THE NEW
FORECAST IS A SLIGHT NORTHWESTWARD SHIFT OF THE 96-HOUR POINT TOWARD
THE MULTI-MODEL CONSENSUS.

THE OFFICIAL FORECAST IS LARGELY UNCHANGED AND STILL LIES NEAR THE
UPPER END OF THE GUIDANCE.  ONLY MODEST ADDITIONAL STRENGTHENING IS
FORECAST WITH KATIA EXPECTED TO MOVE OVER INCREASINGLY LESS
FAVORABLE OCEANIC CONDITIONS OVER THE NEXT SEVERAL DAYS.  IN
ADDITION...THE SHIPS GUIDANCE IS INDICATING THAT VERTICAL SHEAR
COULD BE A LITTLE HIGHER BETWEEN 24 AND 72 HOURS THAN WAS
PREVIOUSLY SHOWN...AND THIS COULD ALSO LIMIT STRENGTHENING. 
WEAKENING IS EXPECTED DURING THE LATTER PART OF THE FORECAST
PERIOD.  THE GFS IS SHOWING KATIA BECOMING EXTRATROPICAL BY DAY
5...BUT SINCE IT IS THE FASTEST OF THE MODELS IT IS PROBABLY
SHOWING THIS A LITTLE TOO SOON.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/2100Z 25.2N  63.9W  100 KT 115 MPH
 12H  06/0600Z 26.1N  64.9W  105 KT 120 MPH
 24H  06/1800Z 27.3N  66.3W  105 KT 120 MPH
 36H  07/0600Z 28.5N  67.8W  100 KT 115 MPH
 48H  07/1800Z 29.7N  69.1W  100 KT 115 MPH
 72H  08/1800Z 33.5N  70.5W   90 KT 105 MPH
 96H  09/1800Z 38.5N  66.5W   75 KT  85 MPH
120H  10/1800Z 42.0N  54.0W   65 KT  75 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 060241
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST MON SEP 05 2011
 
SATELLITE IMAGES INDICATE THAT KATIA HAS STRENGTHENED CONSIDERABLY
DURING THE PAST SEVERAL HOURS. AS THE ASSOCIATED DEEP CONVECTION
BECAME MUCH MORE SYMMETRIC AND THE EYE WARMED DURING THE EVENING
HOURS...DVORAK CLASSIFICATIONS FROM TAFB AND SAB INCREASED TO
6.0/115 KT AT 0000 UTC. DESPITE SOME FLUCTUATIONS IN THE APPEARANCE
OF THE EYE OVER THE LAST HOUR OR TWO...ADT ESTIMATES FROM UW-CIMSS
ARE STILL 6.2/122 KT...SO THE INITIAL INTENSITY IS INCREASED TO 115
KT...MAKING KATIA A CATEGORY FOUR HURRICANE.
 
THE LATEST 12-HOUR INITIAL MOTION ESTIMATE IS 315/9...A TOUCH SLOWER
THAN NOTED IN THE PREVIOUS PACKAGE. THE TRACK FORECAST REASONING IS
UNCHANGED. KATIA IS EXPECTED TO CONTINUE MOVING NORTHWESTWARD FOR
THE NEXT 36 HOURS AS IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE. A TURN TOWARD THE NORTH IS FORECAST IN 48 TO
72 HOURS AS THE HURRICANE BECOMES EMBEDDED IN SOUTHERLY FLOW
BETWEEN THE RIDGE AND A LARGE CUTOFF LOW OVER THE EASTERN UNITED
STATES. THIS STEERING PATTERN WILL ALLOW KATIA TO MOVE BETWEEN
BERMUDA AND THE UNITED STATES EAST COAST DURING THAT TIME PERIOD.
AFTER THAT...A SHARP NORTHEASTWARD AND EAST-NORTHEASTWARD TURN WITH
AN INCREASE IN FORWARD SPEED IS FORECAST AS KATIA GETS CAUGHT IN
THE MID-LATITUDE WESTERLIES. THE MODEL SOLUTIONS HAVE BEEN
CONVERGING DURING THE PAST FEW CYCLES AND ARE NOW IN RELATIVELY
GOOD AGREEMENT...INCREASING CONFIDENCE IN THE TRACK FORECAST. THE
OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND NEAR THE
MIDDLE OF THE GUIDANCE ENVELOPE.
 
FLUCTUATIONS IN THE INTENSITY OF KATIA ARE LIKELY DURING THE NEXT 12
TO 24 HOURS...PERHAPS DUE TO EYEWALL REPLACEMENT CYCLES...AS THE
MAJOR HURRICANE REMAINS IN A FAVORABLE ENVIRONMENT. SLOW WEAKENING
IS EXPECTED BEYOND THAT TIME AS KATIA MOVES INTO AN ENVIRONMENT OF
MODERATE SHEAR AND SLIGHTLY COOLER WATERS. THE NEW NHC INTENSITY
FORECAST HAS BEEN ADJUSTED UPWARD THROUGH 36 HOURS BASED ON THE
OBSERVED STRENGTHENING AND IS NEAR THE MODEL CONSENSUS. KATIA IS
NOW FORECAST TO BE A POST-TROPICAL CYCLONE BY DAY 5...AS IT IS
EXPECTED TO BE WELL-EMBEDDED IN THE WESTERLIES AND OVER 20-21C
WATERS BY THAT TIME.
 
DRIFTING BUOY 41855...WHICH WAS LOCATED ABOUT 20 N MI NORTHEAST OF
THE EYE OF KATIA AT 0000 UTC...REPORTED A MINIMUM PRESSURE OF 952
MB.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/0300Z 25.8N  64.4W  115 KT 135 MPH
 12H  06/1200Z 26.9N  65.5W  115 KT 135 MPH
 24H  07/0000Z 28.1N  66.9W  115 KT 135 MPH
 36H  07/1200Z 29.4N  68.3W  110 KT 125 MPH
 48H  08/0000Z 30.9N  69.5W  100 KT 115 MPH
 72H  09/0000Z 35.4N  69.7W   90 KT 105 MPH
 96H  10/0000Z 39.5N  63.5W   75 KT  85 MPH
120H  11/0000Z 42.5N  48.0W   65 KT  75 MPH
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 060337
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  32...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST MON SEP 05 2011

CORRECTED FOR STATUS AT 120 HOUR FORECAST IN TABLE
 
SATELLITE IMAGES INDICATE THAT KATIA HAS STRENGTHENED CONSIDERABLY
DURING THE PAST SEVERAL HOURS. AS THE ASSOCIATED DEEP CONVECTION
BECAME MUCH MORE SYMMETRIC AND THE EYE WARMED DURING THE EVENING
HOURS...DVORAK CLASSIFICATIONS FROM TAFB AND SAB INCREASED TO
6.0/115 KT AT 0000 UTC. DESPITE SOME FLUCTUATIONS IN THE APPEARANCE
OF THE EYE OVER THE LAST HOUR OR TWO...ADT ESTIMATES FROM UW-CIMSS
ARE STILL 6.2/122 KT...SO THE INITIAL INTENSITY IS INCREASED TO 115
KT...MAKING KATIA A CATEGORY FOUR HURRICANE.
 
THE LATEST 12-HOUR INITIAL MOTION ESTIMATE IS 315/9...A TOUCH SLOWER
THAN NOTED IN THE PREVIOUS PACKAGE. THE TRACK FORECAST REASONING IS
UNCHANGED. KATIA IS EXPECTED TO CONTINUE MOVING NORTHWESTWARD FOR
THE NEXT 36 HOURS AS IT REMAINS ON THE SOUTHWESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE. A TURN TOWARD THE NORTH IS FORECAST IN 48 TO
72 HOURS AS THE HURRICANE BECOMES EMBEDDED IN SOUTHERLY FLOW
BETWEEN THE RIDGE AND A LARGE CUTOFF LOW OVER THE EASTERN UNITED
STATES. THIS STEERING PATTERN WILL ALLOW KATIA TO MOVE BETWEEN
BERMUDA AND THE UNITED STATES EAST COAST DURING THAT TIME PERIOD.
AFTER THAT...A SHARP NORTHEASTWARD AND EAST-NORTHEASTWARD TURN WITH
AN INCREASE IN FORWARD SPEED IS FORECAST AS KATIA GETS CAUGHT IN
THE MID-LATITUDE WESTERLIES. THE MODEL SOLUTIONS HAVE BEEN
CONVERGING DURING THE PAST FEW CYCLES AND ARE NOW IN RELATIVELY
GOOD AGREEMENT...INCREASING CONFIDENCE IN THE TRACK FORECAST. THE
OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND NEAR THE
MIDDLE OF THE GUIDANCE ENVELOPE.
 
FLUCTUATIONS IN THE INTENSITY OF KATIA ARE LIKELY DURING THE NEXT 12
TO 24 HOURS...PERHAPS DUE TO EYEWALL REPLACEMENT CYCLES...AS THE
MAJOR HURRICANE REMAINS IN A FAVORABLE ENVIRONMENT. SLOW WEAKENING
IS EXPECTED BEYOND THAT TIME AS KATIA MOVES INTO AN ENVIRONMENT OF
MODERATE SHEAR AND SLIGHTLY COOLER WATERS. THE NEW NHC INTENSITY
FORECAST HAS BEEN ADJUSTED UPWARD THROUGH 36 HOURS BASED ON THE
OBSERVED STRENGTHENING AND IS NEAR THE MODEL CONSENSUS. KATIA IS
NOW FORECAST TO BE A POST-TROPICAL CYCLONE BY DAY 5...AS IT IS
EXPECTED TO BE WELL-EMBEDDED IN THE WESTERLIES AND OVER 20-21C
WATERS BY THAT TIME.
 
DRIFTING BUOY 41855...WHICH WAS LOCATED ABOUT 20 N MI NORTHEAST OF
THE EYE OF KATIA AT 0000 UTC...REPORTED A MINIMUM PRESSURE OF 952
MB.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/0300Z 25.8N  64.4W  115 KT 135 MPH
 12H  06/1200Z 26.9N  65.5W  115 KT 135 MPH
 24H  07/0000Z 28.1N  66.9W  115 KT 135 MPH
 36H  07/1200Z 29.4N  68.3W  110 KT 125 MPH
 48H  08/0000Z 30.9N  69.5W  100 KT 115 MPH
 72H  09/0000Z 35.4N  69.7W   90 KT 105 MPH
 96H  10/0000Z 39.5N  63.5W   75 KT  85 MPH
120H  11/0000Z 42.5N  48.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 060847
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  33
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST TUE SEP 06 2011
 
THE SATELLITE SIGNATURE OF KATIA HAS DECREASED SLIGHTLY IN
ORGANIZATION DURING THE LAST SEVERAL HOURS...WITH THE CLOUD PATTERN
BECOMING LESS SYMMETRIC AND THE EYE LESS DISTINCT AND COOLER. A
TIMELY AMSU-B IMAGE FROM 0544 UTC INDICATED A DOUBLE EYEWALL
STRUCTURE...SUGGESTING THAT KATIA IS AGAIN IN THE MIDST OF ANOTHER
EYEWALL REPLACEMENT. SUBJECTIVE DVORAK INTENSITY ESTIMATES HAVE
DECREASED SOMEWHAT SINCE 0000 UTC.  A BLEND OF THESE AND THE LATEST
ADT VALUES IS THE BASIS FOR THE CURRENT INTENSITY ESTIMATE OF 110
KT.  DURING THE NEXT DAY OR SO...THE LARGE-SCALE ATMOSPHERIC AND
OCEANIC ENVIRONMENT ARE LIKELY TO REMAIN CONDUCIVE FOR KATIA TO
MAINTAIN MAJOR HURRICANE STATUS. HOWEVER...FLUCTUATIONS IN STRENGTH
DUE TO A DIFFICULT-TO-FORECAST INNER CORE EVOLUTION ARE PROBABLE
DURING THIS TIME.  AFTER 48 HOURS...THE HURRICANE WILL BE
ENCOUNTERING AN ENVIRONMENT OF GRADUALLY INCREASING VERTICAL SHEAR
AND LOWER OCEANIC HEAT CONTENT...AND WEAKENING SHOULD COMMENCE.
LATER IN THE FORECAST PERIOD...KATIA SHOULD MOVING NEARLY PARALLEL
TO A STRONG GRADIENT OF SEA SURFACE TEMPERATURE AND WILL BECOME
EMBEDDED IN AN INCREASINGLY BAROCLINIC ENVIRONMENT AS IT NEARS A
MID-LATITUDE JET...BOTH OF WHICH SHOULD PROMOTE ITS TRANSITION TO
AN EXTRATROPICAL CYCLONE. THE OFFICIAL NHC INTENSITY FORECAST IS
CLOSE TO THE PREVIOUS ONE AND SHOWS KATIA AS STRONG CYCLONE THROUGH
EXTRATROPICAL TRANSITION.
 
KATIA APPEARS TO BE EXHIBITING A TROCHOIDAL MOTION...WITH A
SMOOTHING OF RECENT FIXES YIELDING AN INITIAL MOTION ESTIMATE OF
315/9.  VERY LITTLE CHANGE HAS BEEN MADE TO THE NHC FORECAST TRACK
ON THIS PACKAGE.  GLOBAL MODELS SHOW KATIA BEING STEERED AROUND THE
SOUTHWEST SIDE OF A MID-LEVEL RIDGE EAST OF BERMUDA AND TOWARD A
INTO A WEAKNESS OVER THE WESTERN ATLANTIC DURING THE NEXT COUPLE OF
DAYS.  BY 48 HOURS...KATIA SHOULD TURN NORTHWARD ROUGHLY ALONG 70W
IN BETWEEN A LARGE CUT-OFF LOW OVER THE EASTERN UNITED STATES AND
THE RIDGE TO THE EAST.  THE HURRICANE SHOULD THEN ACCELERATE
NORTHEASTWARD AND THEN EAST-NORTHEASTWARD AS IT BECOMES EMBEDDED IN
A FAST AND NEARLY ZONAL FLOW ON THE SOUTH SIDE OF A BROAD TROUGH
COVERING THE FAR NORTH ATLANTIC. THE NEW NHC TRACK FORECAST IS DOWN
THE CENTER OF THE GUIDANCE ENVELOPE THROUGH 72 HOURS AND A BIT TO
THE EAST OF THE MULTI-MODEL CONSENSUS AT LATER TIMES.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/0900Z 26.5N  65.1W  110 KT 125 MPH
 12H  06/1800Z 27.4N  66.2W  115 KT 135 MPH
 24H  07/0600Z 28.6N  67.6W  110 KT 125 MPH
 36H  07/1800Z 30.2N  69.0W  105 KT 120 MPH
 48H  08/0600Z 32.0N  69.8W   90 KT 105 MPH
 72H  09/0600Z 36.2N  68.5W   80 KT  90 MPH
 96H  10/0600Z 40.0N  60.0W   75 KT  85 MPH
120H  11/0600Z 44.0N  41.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 061445
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  34
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST TUE SEP 06 2011
 
MICROWAVE IMAGERY FROM OVERNIGHT INDICATES THAT KATIA HAS GONE
THROUGH A CLASSIC EYEWALL REPLACEMENT WITH A WIDE RING OF DEEP
CONVECTION ENCLOSING A SMALLER AND ERODING INNER EYEWALL.  AS WOULD
BE EXPECTED IN A CASE LIKE THIS...DVORAK FINAL T-NUMBERS HAVE
DECREASED TO BETWEEN 5.0 AND 5.5...AND CI NUMBERS REMAIN AT 6.0. 
THE INITIAL INTENSITY IS BEING SET AT 105 KT BASED ON A BLEND OF
THESE NUMBERS.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS
SCHEDULED TO INVESTIGATE KATIA THIS AFTERNOON.

ALTHOUGH THE CENTER OF KATIA CONTINUES TO WOBBLE...THE SMOOTHED
INITIAL MOTION IS 310/9 KT.  THERE HAS BEEN LITTLE CHANGE IN THE
TRACK FORECAST OR THE REASONING BEHIND IT.  THE HURRICANE IS STILL
EXPECTED TO MAKE A TURN TOWARD THE NORTH-NORTHWEST AND NORTH OVER
THE NEXT 2 DAYS AS IT IS STEERED BETWEEN THE BERMUDA HIGH AND A
CLOSED MID- TO UPPER-LEVEL LOW OVER THE TENNESSEE AND OHIO VALLEYS. 
THE GUIDANCE HAS SHIFTED SOMEWHAT TO THE NORTHWEST AT 72 HOURS...
SUGGESTING THAT THE RE-CURVATURE MAY NOT BE QUITE AS SHARP AS
PREVIOUSLY SHOWN.  THE OFFICIAL FORECAST HAS BEEN NUDGED IN THAT
DIRECTION BUT LIES TO THE SOUTHEAST OF THE TVCA AND EXPERIMENTAL
TV15 CONSENSUS MODELS.  AFTER 72 HOURS...KATIA IS EXPECTED TO
BECOME EMBEDDED IN THE MID-LATITUDE WESTERLIES.  THE MODELS ARE
STILL SHOWING SOME DIVERGENCE IN SPEED AT 96 AND 120 HOURS...BUT
THE SPREAD IS NOT AS LARGE AS IT HAS BEEN IN PREVIOUS DAYS.  ONLY A
SLIGHT NORTHWARD ADJUSTMENT WAS REQUIRED AT DAY 5.

SINCE KATIA IS GOING THROUGH AN EYEWALL REPLACEMENT AND WILL BE LEFT
WITH A LARGE RADIUS OF MAXIMUM WINDS...THE MOST LIKELY SCENARIO
WOULD BE FOR THE HURRICANE TO CHANGE LITTLE IN STRENGTH IN THE
SHORT TERM.  GRADUAL WEAKENING SHOULD COMMENCE BY 36 HOURS AS KATIA
IS EXPECTED TO BE MOVING OVER WATERS OF LOWER OCEANIC HEAT CONTENT
OVER THE WESTERN ATLANTIC...AND POSSIBLY BE AFFECTED BY STRONGER
SHEAR.  BY DAYS 4 AND 5...BAROCLINIC FORCING SHOULD PREVENT KATIA
FROM WEAKENING TOO MUCH...EVEN OVER COLDER WATERS...AND THE CYCLONE
IS FORECAST TO BE A POWERFUL EXTRATROPICAL STORM OVER THE NORTH
ATLANTIC.  THE INTENSITY GUIDANCE IS IN FAIRLY GOOD AGREEMENT...AND
THE OFFICIAL FORECAST IS MAINLY JUST AN UPDATE OF THE PREVIOUS
FORECAST.

FORECAST POSITIONS AND MAX WINDS
 
INIT  06/1500Z 27.0N  65.9W  105 KT 120 MPH
 12H  07/0000Z 27.9N  67.0W  105 KT 120 MPH
 24H  07/1200Z 29.2N  68.5W  105 KT 120 MPH
 36H  08/0000Z 30.9N  69.6W   95 KT 110 MPH
 48H  08/1200Z 32.9N  70.1W   85 KT 100 MPH
 72H  09/1200Z 37.5N  67.5W   75 KT  85 MPH
 96H  10/1200Z 41.5N  56.0W   70 KT  80 MPH
120H  11/1200Z 49.0N  35.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG/AVILA
 

WTNT42 KNHC 062048
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST TUE SEP 06 2011
 
A 1509 UTC TRMM PASS INDICATES THAT THE INNER EYEWALL OF KATIA IS
DECAYING WITHIN A LARGER EYEWALL...SUGGESTING THAT THE HURRICANE IS
NEARING THE END OF ITS EYEWALL REPLACEMENT.  AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT MADE TWO PASSES THROUGH THE STORM AND
MEASURED A MAXIMUM 700-MB FLIGHT-LEVEL WIND OF 114 KT AND A PEAK
SURFACE WIND OF 81 KT FROM THE SFMR. THE PLANE ALSO REPORTED THAT
THE NEW RADIUS OF MAXIMUM WINDS IS ABOUT 55 N MI...AND THE 64- AND
50-KT RADII HAVE EXPANDED. BASED ON THE EXPANSION OF THE WIND
FIELD...IT IS ASSUMED THAT THE STANDARD FLIGHT-LEVEL TO SURFACE
WIND RELATIONSHIP MAY BE TOO HIGH...AND THE INITIAL INTENSITY IS
THEREFORE SET AT 90 KT.
 
KATIA CONTINUES TO MOVE ON TRACK WITH A MOTION OF 310/9 KT.  THE
HURRICANE WILL BE MOVING AROUND THE SOUTHWESTERN PERIPHERY OF A
CENTRAL ATLANTIC MID-LEVEL HIGH IN THE SHORT-TERM...AND IT SHOULD
BEGIN TO TURN TOWARD THE NORTH-NORTHWEST AND NORTH OVER THE NEXT 48
HOURS.  AFTER 48 HOURS...THE MODEL GUIDANCE CONTINUES TO TREND
TOWARD A DELAY IN PICKING UP THE HURRICANE BY THE FAST MID-LATITUDE
WESTERLIES...AND THIS HAS RESULTED IN ANOTHER SLIGHT NORTHWESTWARD
SHIFT OF THE GUIDANCE ENVELOPE AT 72 HOURS.  THE OFFICIAL FORECAST
HAS ALSO BEEN NUDGED IN THAT DIRECTION...ENDING UP ON THE
SOUTHEASTERN SIDE OF THE GUIDANCE.  THE MODEL SPREAD APPEARS TO BE
DECREASING AT THE 96- AND 120-HOUR POINTS AS ALL THE MODELS HAVE
KATIA ACCELERATING IN THE WESTERLIES...AND LITTLE CHANGE TO THE
OFFICIAL FORECAST WAS REQUIRED AT THOSE TIMES.
 
THE EXPANDING WIND FIELD OF KATIA SUGGESTS THAT LITTLE CHANGE IN
INTENSITY SHOULD OCCUR OVER THE NEXT DAY OR SO.  THE HURRICANE
COULD BE AFFECTED BY SOME SHEAR OVER THE NEXT FEW DAYS...AND IT IS
ALREADY MOVING OVER WATERS THAT ARE BECOMING GRADUALLY LESS
CONDUCIVE FOR RE-STRENGTHENING.  GRADUAL WEAKENING IS INDICATED IN
THE OFFICIAL FORECAST FROM 24 TO 72 HOURS.  THEREAFTER...THE
VARIOUS GLOBAL MODEL FIELDS ARE IN AGREEMENT SHOWING KATIA BECOMING
ENTANGLED WITHIN A FRONTAL ZONE BY 96 HOURS.  THE CYCLONE IS
THEREFORE FORECAST TO BE EXTRATROPICAL AT THAT TIME...BUT THERE
SHOULD BE ENOUGH BAROCLINIC FORCING TO MAINTAIN IT AS A POWERFUL
HURRICANE-FORCE LOW PRESSURE SYSTEM.  THE OFFICIAL FORECAST AT THE
END OF THE FORECAST PERIOD IS BASED ON GUIDANCE FROM THE OCEAN
PREDICTION CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/2100Z 27.6N  66.7W   90 KT 105 MPH
 12H  07/0600Z 28.5N  67.8W   90 KT 105 MPH
 24H  07/1800Z 29.9N  69.2W   90 KT 105 MPH
 36H  08/0600Z 31.7N  70.0W   85 KT 100 MPH
 48H  08/1800Z 34.0N  69.9W   85 KT 100 MPH
 72H  09/1800Z 39.0N  66.0W   75 KT  85 MPH
 96H  10/1800Z 44.0N  50.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
120H  11/1800Z 53.0N  29.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG/BRENNAN
 

WTNT42 KNHC 070237
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  36
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST TUE SEP 06 2011
 
SINCE THE AIRCRAFT DEPARTED KATIA THIS AFTERNOON THE SATELLITE
PRESENTATION HAS IMPROVED SLIGHTLY. ALTHOUGH THE CONVECTIVE PATTERN
HAS GAINED CURVATURE...THUNDERSTORM ACTIVITY IS QUITE THIN OVER THE
WESTERN SEMICIRCLE...AS SEEN IN THE LAST FEW MICROWAVE OVERPASSES.
THIS ASYMMETRIC PATTERN IS LIKELY DUE TO SOME WESTERLY SHEAR AND
DRY AIR ENTRAINMENT. THE INITIAL WIND SPEED IS HELD AT 90 KT FOR
THIS ADVISORY...WHICH IS IN AGREEMENT WITH AN AVERAGE OF THE DVORAK
T AND CI NUMBERS.

KATIA IS STILL MOVING NORTHWESTWARD AT ABOUT 8 KT...BUT IS EXPECTED
TO TURN TOWARD THE NORTH WITH AN INCREASE IN FORWARD SPEED DURING
THE NEXT 24 TO 36 HOURS AS THE HURRICANE BECOMES EMBEDDED IN THE
FLOW BETWEEN THE SUBTROPICAL RIDGE AND A LARGE UPPER-LEVEL CUTOFF
LOW OVER THE OHIO VALLEY OF THE UNITED STATES. KATIA IS EXPECTED TO
ACCELERATE TO THE NORTHEAST AND EAST-NORTHEAST IN TWO TO THREE DAYS
AS THE CYCLONE GETS SWEPT UP IN THE STRONG MID-LATITUDE FLOW. THE
MODELS REMAIN IN GOOD AGREEMENT ON THE FUTURE TRACK OF KATIA...AND
THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE. THE 96- AND
120-HOUR FORECAST POINTS ARE LARGELY BASED ON GUIDANCE FROM THE
OCEAN PREDICTION CENTER.

LITTLE CHANGE IN STRENGTH OR GRADUAL WEAKENING IS LIKELY DURING THE
NEXT 24 TO 48 HOURS. BEYOND THAT TIME...KATIA WILL BE MOVING OVER
COOLER WATERS AND IS EXPECTED TO ENCOUNTER STRONGER SOUTHWESTERLY
SHEAR. THESE FACTORS SHOULD LEAD TO EXTRATROPICAL TRANSITION...
WHICH IS LIKELY TO OCCUR IN THREE TO FOUR DAYS. ALL OF THE GLOBAL
MODELS SHOW KATIA BECOMING A LARGE AND POWERFUL POST-TROPICAL
CYCLONE OVER THE NORTH ATLANTIC.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0300Z 28.1N  67.2W   90 KT 105 MPH
 12H  07/1200Z 29.0N  68.3W   85 KT 100 MPH
 24H  08/0000Z 30.6N  69.5W   85 KT 100 MPH
 36H  08/1200Z 32.7N  69.9W   80 KT  90 MPH
 48H  09/0000Z 35.2N  69.2W   80 KT  90 MPH
 72H  10/0000Z 40.0N  62.5W   75 KT  85 MPH
 96H  11/0000Z 45.0N  44.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
120H  12/0000Z 55.0N  25.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER CANGIALOSI/BRENNAN
 

WTNT42 KNHC 070849
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST WED SEP 07 2011
 
THE CLOUD PATTERN OF KATIA HAS BECOME A LITTLE LESS ORGANIZED
OVERNIGHT. CLOUD TOP TEMPERATURES HAVE GENERALLY BEEN WARMING AND
DRY AIR APPEARS TO WRAPPING AROUND THE WESTERN SEMICIRCLE OF THE
CIRCULATION...THE LATTER GIVING THE CYCLONE A SOMEWHAT HOLLOW
APPEARANCE. IN ADDITION...THERE APPEARS TO BE NORTHWESTERLY SHEAR
OVER THE HURRICANE...AS EVIDENCED BY CIRRUS CLOUD MOTIONS AND
CONFIRMED BY UW-CIMSS ANALYSES. DVORAK T- AND CI-NUMBERS FROM TAFB
AND SAB ARE LOWER...AND A REASONABLE BLEND OF THESE DATA GIVES AN
INTENSITY ESTIMATE OF 80 KT. AN EYEWALL REPLACEMENT CYCLE THAT
BEGAN 24-36 HOURS APPEARS TO HAVE BEEN INTERRUPTED...WITH EARLIER
MICROWAVE IMAGERY SHOWING AN OUTER EYEWALL AT LARGE RADIUS THAT WAS
NOT CONTRACTING MUCH. THIS STRUCTURE...ALONG WITH THE MODERATE
SHEAR...SUGGESTS NOT MUCH CHANGE IN STRENGTH...FOLLOWED BY ONLY A
SLOW WEAKENING DURING THE NEXT FEW DAYS AS KATIA REMAINS OVER
RELATIVELY WARM WATERS. AFTER 72 HOURS...KATIA WILL QUICKLY MOVE
ALONG A STRONG GRADIENT OF SSTS AND ENCOUNTER AN INCREASINGLY
BAROCLINIC ENVIRONMENT...BOTH OF WHICH SHOULD RESULT IN A RAPID
TRANSITION TO AN INTENSE EXTRATROPICAL CYCLONE. POST-TROPICAL
CYCLONE KATIA IS EXPECTED TO BE A SIGNIFICANT WEATHER SYSTEM OVER
THE FAR NORTH ATLANTIC FOR AT LEAST A COUPLE OF DAYS. THE OFFICIAL
NHC WIND SPEED FORECAST IS LOWERED IN ACCORDANCE WITH THE LATEST
INTENSITY GUIDANCE AND IS IN BEST AGREEMENT WITH THE MODEL
CONSENSUS.
 
THE INITIAL MOTION IS A FAIRLY SLOW 315/08. GLOBAL MODELS SHOW KATIA
GRADUALLY TURNING FROM NORTHWESTWARD TO NORTHWARD INTO A WEAKNESS
IN THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC DURING THE NEXT
24-36 HOURS. AFTER THAT...THE HURRICANE IS EXPECTED TO GRADUALLY
RECURVE INTO THE WESTERLIES AND ACCELERATE NORTHEASTWARD ON THE
SOUTH SIDE OF A BROAD TROUGH COVERING THE FAR NORTH ATLANTIC. THE
TRACK GUIDANCE HAS CONSISTENTLY BEEN HANDLING THE STEERING FLOW
AROUND THE STORM WELL FOR SEVERAL FORECAST CYCLES AND IS TIGHTLY
CLUSTERED...GIVING HIGH CONFIDENCE TO THE FORECAST. ONLY MINOR
CHANGES WERE MADE TO THE PREVIOUS FORECAST TRACK...WITH THE CURRENT
NHC TRACK AGAIN CLOSE TO THE MULTI-MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 28.7N  67.9W   80 KT  90 MPH
 12H  07/1800Z 29.8N  69.0W   80 KT  90 MPH
 24H  08/0600Z 31.7N  69.6W   75 KT  85 MPH
 36H  08/1800Z 34.0N  69.5W   75 KT  85 MPH
 48H  09/0600Z 36.4N  67.9W   70 KT  80 MPH
 72H  10/0600Z 40.9N  58.2W   65 KT  75 MPH
 96H  11/0600Z 47.0N  38.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  12/0600Z 59.0N  17.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT42 KNHC 071448
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  38
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST WED SEP 07 2011
 
THE CLOUD PATTERN OF KATIA HAS CHANGED LITTLE SINCE EARLY
THIS MORNING. RECENT MICROWAVE IMAGES SHOW THE REMAINING
FRAGMENTS OF AN INNER EYE WALL WITH A COUPLE OF CONVECTIVE BANDS
OVER THE NORTHEASTERN SEMICIRCLE.  IT APPEARS THAT DRY AIR HAS
WRAPPED AROUND THE SOUTHWESTERN SIDE OF THE CIRCULATION WITH DEEP
CONVECTION NON EXISTENT OVER THAT PORTION OF THE CYCLONE.  THE
DVORAK T- AND CI-NUMBERS FROM TAFB HAVE DECREASED AND CI-NUMBERS
FROM BOTH AGENCIES ARE NOW T4.5.  THIS SUPPORTS LOWERING THE
INITIAL INTENSITY TO 75 KT.  GIVEN THE MODERATE WESTERLY SHEAR AND
THE LACK OF A TIGHT-INNER CORE...SOME SLIGHT WEAKENING IS
ANTICIPATED DURING THE NEXT 24 HOURS.  AS KATIA BEGINS MOVING
NORTH-NORTHEASTWARD IN A DAY OR SO...THE SHIPS GUIDANCE SHOWS THAT
THE SHEAR WILL DECREASE...HOWEVER THE HURRICANE WILL BE MOVING OVER
COOLER SSTS...WHICH SHOULD NEGATE THE SLIGHTLY MORE FAVORABLE
ATMOSPHERIC ENVIRONMENT.  THE OFFICIAL FORECAST CALLS FOR VERY
LITTLE CHANGE IN INTENSITY UNTIL THE SYSTEM BECOMES AN
EXTRATROPICAL CYCLONE IN 3-4 DAYS.
 
THE INITIAL MOTION ESTIMATE IS 315/9.  THE MODELS ARE IN EXCELLENT
AGREEMENT SHOWING A TURN TOWARD THE NORTH DURING THE NEXT 24
HOURS...FOLLOWED BY A TURN TOWARD THE NORTHEAST IN A COUPLE OF
DAYS.  AFTER THAT TIME...THE CYCLONE IS EXPECTED TO ACCELERATE
INTO THE WESTERLIES AHEAD OF A TROUGH THAT MOVES OVER THE CANADIAN
MARITIMES IN 3-4 DAYS.  THE GFS AND ECMWF ARE IN VERY GOOD
AGREEMENT EVEN DURING THE EXTRATROPICAL PORTION OF THE TRACK.  THE
NEW NHC FORECAST IS CLOSE TO THESE RELIABLE MODELS AND ONLY SLIGHT
ADJUSTMENTS WERE MADE TO THE PREVIOUS FORECAST.
 
THE WIND RADII OVER THE NORTHWEST QUADRANT OF THE HURRICANE WERE
EXPANDED OUTWARD BASED ON DATA FROM NOAA BUOY 41048.  THE CENTER OF
KATIA IS FORECAST TO PASS VERY NEAR THAT BUOY TONIGHT.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 29.2N  68.8W   75 KT  85 MPH
 12H  08/0000Z 30.6N  69.6W   70 KT  80 MPH
 24H  08/1200Z 32.8N  69.8W   70 KT  80 MPH
 36H  09/0000Z 35.4N  69.0W   70 KT  80 MPH
 48H  09/1200Z 38.1N  66.6W   70 KT  80 MPH
 72H  10/1200Z 42.5N  52.5W   65 KT  75 MPH
 96H  11/1200Z 51.0N  29.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  12/1200Z 60.0N   8.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 072051
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  39
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST WED SEP 07 2011
 
THE CLOUD TOPS ASSOCIATED WITH KATIA WARMED DURING THE EARLY
AFTERNOON...BUT SINCE THAT TIME A NEW BURST OF DEEP CONVECTION
HAS FORMED TO THE NORTHEAST OF THE CENTER.  AN EARLIER TRMM PASS
ONCE AGAIN SHOWED A SMALL REMNANT OF THE INNER EYEWALL WITH A LARGE
BAND OF CONVECTION OVER THE NORTH AND EAST SEMICIRCLES OF THE
CIRCULATION.  SUBJECTIVE AND OBJECTIVE DVORAK T- AND CI-NUMBERS
CONTINUE TO SLOWLY DECREASE...THEREFORE THE INITIAL INTENSITY IS
LOWERED TO 70 KT.  THERE HAS BEEN LITTLE CHANGE TO THE INTENSITY
FORECAST REASONING.  MODERATE WESTERLY SHEAR CURRENTLY OVER THE
SYSTEM IS FORECAST TO DECREASE ON THURSDAY...HOWEVER THIS IS LIKELY
TO BE NEGATED BY SLIGHTLY COOLER SSTS THAT THE HURRICANE WILL BE
MOVING OVER.  OVERALL...LITTLE CHANGE IN STRENGTH IS FORECAST
DURING THE NEXT COUPLE OF DAYS.  KATIA IS EXPECTED TO BECOME A
LARGE AND POWERFUL EXTRATROPICAL CYCLONE IN ABOUT 72 HOURS.
 
THE INITIAL MOTION ESTIMATE IS 320/9.  THE MODELS REMAIN IN VERY
GOOD AGREEMENT MOVING KATIA AROUND THE WEST SIDE OF A
MID/UPPER-LEVEL RIDGE OVER THE CENTRAL ATLANTIC DURING THE NEXT
24-36 HOURS.  AFTER 48 HOURS...THE CYCLONE IS EXPECTED TO
ACCELERATE NORTHEASTWARD AHEAD OF A BROAD TROUGH MOVING ACROSS
THE CANADIAN MARITIMES.  THE GFS AND ECMWF MODELS ARE STILL IN
REMARKABLY GOOD AGREEMENT ON THE EXTRATROPICAL PORTION OF THE
TRACK.  THE OFFICIAL FORECAST HAS BEEN NUDGED NORTHWARD AT 36 HOURS
AND BEYOND AND IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 29.9N  69.7W   70 KT  80 MPH
 12H  08/0600Z 31.3N  70.1W   70 KT  80 MPH
 24H  08/1800Z 33.8N  70.0W   70 KT  80 MPH
 36H  09/0600Z 36.6N  68.5W   70 KT  80 MPH
 48H  09/1800Z 39.2N  64.5W   70 KT  80 MPH
 72H  10/1800Z 44.5N  46.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  11/1800Z 53.0N  26.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  12/1800Z 60.0N   7.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 080254
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  40
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST WED SEP 07 2011
 
CONVENTIONAL SATELLITE AND MICROWAVE IMAGES INDICATE THAT KATIA IS
AN ASYMMETRIC HURRICANE.  DEEP CONVECTION IS LIMITED TO THE EASTERN
HALF OF THE CIRCULATION...WITH THE LOW-LEVEL CENTER ESTIMATED TO BE
ON THE WESTERN EDGE OF THE INNER-MOST CONVECTIVE BAND.  THIS
PATTERN IS THE RESULT OF MODERATE WESTERLY SHEAR AND DRY AIR
ENTRAINING INTO THE CIRCULATION.  NOAA BUOY 41048...LOCATED ABOUT
90 N MI NORTH OF THE CENTER OF KATIA...RECENTLY REPORTED A MAXIMUM
1-MINUTE WIND OF 58 KT WITH A GUST TO 72 KT.  ALTHOUGH THE LATEST
DVORAK CLASSIFICATIONS SUGGEST THAT KATIA MAY HAVE WEAKENED A
LITTLE...I PREFER TO KEEP THE INITIAL INTENSITY AT 70 KT GIVEN THE
BUOY OBSERVATION.  LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE
NEXT SEVERAL DAYS...AND ALL OF THE GLOBAL MODELS SHOW KATIA
BECOMING A LARGE EXTRATROPICAL STORM OVER THE NORTH ATLANTIC.
 
KATIA IS NOW BEGINNING THE ANTICIPATED NORTHWARD TURN AS IT MOVES
BETWEEN THE SUBTROPICAL RIDGE AND A LARGE MID- TO UPPER-LEVEL LOW
OVER THE OHIO VALLEY OF THE UNITED STATES.  A PRONOUNCED INCREASE
IN FORWARD SPEED AND A TURN TO THE NORTHEAST AND EAST-NORTHEAST IS
FORECAST TO OCCUR ON FRIDAY AS THE CYCLONE BECOMES EMBEDDED IN THE
MID-LATITUDE FLOW.  THE MODELS REMAIN IN VERY GOOD AGREEMENT...AND
THE OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS ONE.  THE
EXTRATROPICAL FORECAST POINTS ARE VERY CLOSE TO THE GUIDANCE
PROVIDED BY THE OCEAN PREDICTION CENTER.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 30.8N  70.0W   70 KT  80 MPH
 12H  08/1200Z 32.5N  70.2W   70 KT  80 MPH
 24H  09/0000Z 35.2N  69.5W   70 KT  80 MPH
 36H  09/1200Z 37.9N  67.0W   70 KT  80 MPH
 48H  10/0000Z 40.4N  61.0W   70 KT  80 MPH
 72H  11/0000Z 46.6N  40.6W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  12/0000Z 55.0N  22.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  13/0000Z 60.0N   6.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER CANGIALOSI/BEVEN
 

WTNT42 KNHC 080859
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  40
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST WED SEP 07 2011
 
NOAA BUOY 41048 HAS PROVIDED VERY VALUABLE DATA IN ESTIMATING THE
INITIAL INTENSITY OF KATIA.  AS THE CENTER OF THE HURRICANE
APPROACHED...THIS DATA BUOY REPORTED PEAK SUSTAINED WINDS OF 76 KT. 
THEREFORE THE CURRENT INTENSITY ESTIMATE IS INCREASED TO 80 KT. 
THE MINIMUM CENTRAL PRESSURE WAS REDUCED TO 970 MB...ALSO BASED ON
OBSERVATIONS FROM THIS BUOY.

NUMERICAL GUIDANCE INDICATES THAT KATIA WILL REMAIN AN INTENSE
CYCLONE...OR WEAKEN ONLY SLIGHTLY...FOR MOST OF THE FORECAST
PERIOD. THE GLOBAL MODELS DEPICT THE SYSTEM AS A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC OVER THE NEXT SEVERAL
DAYS.

THE HURRICANE HAS TURNED NORTHWARD...350/12...AS IT MOVES ON THE
WESTERN SIDE OF A SUBTROPICAL CYCLONE AND TO THE EAST OF A
MID-TROPOSPHERIC TROUGH OVER THE OHIO VALLEY.  THERE IS LITTLE
CHANGE TO EITHER THE TRACK FORECAST OR THE REASONING BEHIND IT.  A
SUBSTANTIAL INCREASE IN FORWARD SPEED IS FORECAST AS KATIA OR ITS
POST-TROPICAL COUNTERPART BECOMES ENTRAINED INTO THE MID-LATITUDE
WESTERLIES.  INDEED...BY THE END OF THE FORECAST PERIOD THE SYSTEM
IS FORECAST TO BE NEARING THE NORTHERN UNITED KINGDOM.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 30.8N  70.0W   70 KT  80 MPH
 12H  08/1200Z 32.5N  70.2W   70 KT  80 MPH
 24H  09/0000Z 35.2N  69.5W   70 KT  80 MPH
 36H  09/1200Z 37.9N  67.0W   70 KT  80 MPH
 48H  10/0000Z 40.4N  61.0W   70 KT  80 MPH
 72H  11/0000Z 46.6N  40.6W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  12/0000Z 55.0N  22.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  13/0000Z 60.0N   6.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER CANGIALOSI/PASCH
 

WTNT42 KNHC 081046
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  41...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST THU SEP 08 2011
 
...CORRECTED FOR TIME 

NOAA BUOY 41048 HAS PROVIDED VERY VALUABLE DATA IN ESTIMATING THE
INITIAL INTENSITY OF KATIA.  AS THE CENTER OF THE HURRICANE
APPROACHED...THIS DATA BUOY REPORTED PEAK SUSTAINED WINDS OF 76 KT.
THEREFORE THE CURRENT INTENSITY ESTIMATE IS INCREASED TO 80 KT.
THE MINIMUM CENTRAL PRESSURE WAS REDUCED TO 970 MB...ALSO BASED ON
OBSERVATIONS FROM THIS BUOY.
 
NUMERICAL GUIDANCE INDICATES THAT KATIA WILL REMAIN AN INTENSE
CYCLONE...OR WEAKEN ONLY SLIGHTLY...FOR MOST OF THE FORECAST
PERIOD. THE GLOBAL MODELS DEPICT THE SYSTEM AS A LARGE AND POWERFUL
EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC OVER THE NEXT SEVERAL
DAYS.
 
THE HURRICANE HAS TURNED NORTHWARD...350/12...AS IT MOVES ON THE
WESTERN SIDE OF A SUBTROPICAL CYCLONE AND TO THE EAST OF A
MID-TROPOSPHERIC TROUGH OVER THE OHIO VALLEY.  THERE IS LITTLE
CHANGE TO EITHER THE TRACK FORECAST OR THE REASONING BEHIND IT.  A
SUBSTANTIAL INCREASE IN FORWARD SPEED IS FORECAST AS KATIA OR ITS
POST-TROPICAL COUNTERPART BECOMES ENTRAINED INTO THE MID-LATITUDE
WESTERLIES.  INDEED...BY THE END OF THE FORECAST PERIOD THE SYSTEM
IS FORECAST TO BE NEARING THE NORTHERN UNITED KINGDOM.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 32.0N  70.2W   80 KT  90 MPH
 12H  08/1800Z 33.9N  70.0W   80 KT  90 MPH
 24H  09/0600Z 36.6N  68.5W   80 KT  90 MPH
 36H  09/1800Z 39.2N  64.5W   80 KT  90 MPH
 48H  10/0600Z 41.5N  57.6W   75 KT  85 MPH
 72H  11/0600Z 48.5N  36.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  12/0600Z 56.0N  19.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  13/0600Z 60.0N   5.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER CANGIALOSI/PASCH
 

WTNT42 KNHC 081507
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  42
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST THU SEP 08 2011
 

THE CLOUD PATTERN ASSOCIATED WITH KATIA HAS NOT CHANGED MUCH IN THE
PAST SEVERAL HOURS SINCE IT PASSED VERY CLOSE TO A NOAA BUOY. MOST
OF THE CONVECTION REMAINS NORTH AND EAST OF THE CENTER...CONSISTENT
WITH SOME WESTERLY SHEAR AFFECTING THE STORM. THE CURRENT INTENSITY
IS HELD AT 80 KT BASED ON THE PRIOR BUOY OBSERVATION AND CONTINUITY
OF THE CLOUD PATTERN...WITH MINIMUM CENTRAL PRESSURE ALSO HELD AT
970 MB. 

KATIA CONTINUES TO MOVE NORTHWARD...SLIGHTLY FASTER AT 360/15...AND
RELIABLE NUMERICAL GUIDANCE SUGGESTS THAT KATIA WILL GRADUALLY TURN
NORTHEASTWARD AND CONTINUE TO ACCELERATE OVER THE NORTH ATLANTIC
OVER THE NEXT DAY OR SO. THERE IS VERY LITTLE CHANGE TO THE TRACK
FORECAST...WHICH IS CLOSE TO THE MULTI-MODEL CONSENSUS. THE
FORECAST TAKES THE REMNANTS OF KATIA NORTH OF THE BRITISH ISLES IN
ABOUT FOUR DAYS.  THE GLOBAL MODELS INDICATE THAT KATIA WILL REMAIN
A POWERFUL CYCLONE EVEN AS IT INTERACTS WITH A MID-TROPOSPHERIC
TROUGH AND ASSOCIATED STRONG WESTERLIES.  THE GFS INDICATES THAT
EXTRATROPICAL TRANSITION COULD OCCUR A LITTLE SOONER THAN SHOWN
BELOW.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 33.6N  70.1W   80 KT  90 MPH
 12H  09/0000Z 35.6N  69.4W   80 KT  90 MPH
 24H  09/1200Z 38.3N  66.8W   80 KT  90 MPH
 36H  10/0000Z 40.7N  61.8W   75 KT  85 MPH
 48H  10/1200Z 43.2N  53.0W   70 KT  80 MPH
 72H  11/1200Z 50.0N  31.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  12/1200Z 59.0N   9.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  13/1200Z 62.0N   2.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER HOGSETT/FRANKLIN
 

WTNT42 KNHC 082054
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  43
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST THU SEP 08 2011
 

CONVECTION PERSISTS NEAR THE CENTER OF KATIA AND CLOUD BANDS HAVE
INCREASED IN ORGANIZATION...PARTICULARLY IN THE SOUTHWEST QUADRANT
THAT WAS PREVIOUSLY DEVOID OF CONVECTION. HOWEVER...A RECENT ASCAT
PASS AND TAFB/SAB SATELLITE ESTIMATES SUGGEST THAT THE MAXIMUM
WINDS HAVE DECREASED SLIGHTLY. THE TAFB/SAB ESTIMATES ARE THE BASIS
FOR A SLIGHT DECREASE IN THE INITIAL INTENSITY...TO 75 KT. 

KATIA IS MOVING SLIGHTLY EAST OF NORTH...WITH AN INITIAL MOTION OF
005/14. RELIABLE NUMERICAL GUIDANCE SUGGESTS THAT KATIA WILL
CONTINUE TO TURN AND ACCELERATE NORTHEASTWARD OVER THE NEXT SEVERAL
DAYS...AND BECOME EXTRATROPICAL WITHIN TWO TO THREE DAYS. THE
EXTRATROPICAL STORM SHOULD PASS NEAR THE BRITISH ISLES IN ABOUT
FIVE DAYS. GUIDANCE HAS BEEN CONSISTENT AND IN GOOD AGREEMENT ON
THE TRACK OF KATIA...AND THE TRACK FORECAST IS VERY CLOSE TO THE
PREVIOUS ADVISORY. 

RELIABLE INTENSITY GUIDANCE SUGGESTS THAT KATIA WILL WEAKEN RATHER
SLOWLY DURING THE NEXT SEVERAL DAYS...AND THE GLOBAL MODELS SUGGEST
THAT THE CYCLONE WILL REMAIN LARGE AND POWERFUL AFTER EXTRATROPICAL
TRANSITION AS IT TRAVERSES THE NORTH ATLANTIC. INITIAL WIND RADII
ARE ADJUSTED OUTWARD IN THE SOUTHWEST QUADRANT BASED ON THE RECENT
ASCAT PASS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 34.9N  69.6W   75 KT  85 MPH
 12H  09/0600Z 36.9N  68.4W   75 KT  85 MPH
 24H  09/1800Z 39.3N  64.6W   75 KT  85 MPH
 36H  10/0600Z 41.6N  57.7W   70 KT  80 MPH
 48H  10/1800Z 44.2N  47.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  11/1800Z 52.2N  23.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  12/1800Z 59.4N   6.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  13/1800Z 62.2N   2.2E   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER HOGSETT/FRANKLIN
 

WTNT42 KNHC 082119
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  43...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST THU SEP 08 2011
 
CORRECTED 120 HOUR POINT

CONVECTION PERSISTS NEAR THE CENTER OF KATIA AND CLOUD BANDS HAVE
INCREASED IN ORGANIZATION...PARTICULARLY IN THE SOUTHWEST QUADRANT
THAT WAS PREVIOUSLY DEVOID OF CONVECTION. HOWEVER...A RECENT ASCAT
PASS AND TAFB/SAB SATELLITE ESTIMATES SUGGEST THAT THE MAXIMUM
WINDS HAVE DECREASED SLIGHTLY. THE TAFB/SAB ESTIMATES ARE THE BASIS
FOR A SLIGHT DECREASE IN THE INITIAL INTENSITY...TO 75 KT.
 
KATIA IS MOVING SLIGHTLY EAST OF NORTH...WITH AN INITIAL MOTION OF
005/14. RELIABLE NUMERICAL GUIDANCE SUGGESTS THAT KATIA WILL
CONTINUE TO TURN AND ACCELERATE NORTHEASTWARD OVER THE NEXT SEVERAL
DAYS...AND BECOME EXTRATROPICAL WITHIN TWO TO THREE DAYS. THE
EXTRATROPICAL STORM SHOULD PASS NEAR THE BRITISH ISLES IN ABOUT
FIVE DAYS. GUIDANCE HAS BEEN CONSISTENT AND IN GOOD AGREEMENT ON
THE TRACK OF KATIA...AND THE TRACK FORECAST IS VERY CLOSE TO THE
PREVIOUS ADVISORY.
 
RELIABLE INTENSITY GUIDANCE SUGGESTS THAT KATIA WILL WEAKEN RATHER
SLOWLY DURING THE NEXT SEVERAL DAYS...AND THE GLOBAL MODELS SUGGEST
THAT THE CYCLONE WILL REMAIN LARGE AND POWERFUL AFTER EXTRATROPICAL
TRANSITION AS IT TRAVERSES THE NORTH ATLANTIC. INITIAL WIND RADII
ARE ADJUSTED OUTWARD IN THE SOUTHWEST QUADRANT BASED ON THE RECENT
ASCAT PASS.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 34.9N  69.6W   75 KT  85 MPH
 12H  09/0600Z 36.9N  68.4W   75 KT  85 MPH
 24H  09/1800Z 39.3N  64.6W   75 KT  85 MPH
 36H  10/0600Z 41.6N  57.7W   70 KT  80 MPH
 48H  10/1800Z 44.2N  47.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  11/1800Z 52.2N  23.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  12/1800Z 59.4N   6.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  13/1800Z...ABSORBED
 
$$
FORECASTER HOGSETT/FRANKLIN
 

WTNT42 KNHC 090244
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  44
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST THU SEP 08 2011

THE CONVECTIVE PATTERN OF KATIA HAS IMPROVED SIGNIFICANTLY DURING
THE PAST 6 HOURS...AND AN EYE HAS BECOME APPARENT AND EMBEDDED
WITHIN A SHIELD OF CLOUD TOPS OF -60C AND COLDER. NHC AODT
SATELLITE INTENSITY ESTIMATES FOR A LARGE RAGGED EYE FEATURE ARE
75-80 KT. GIVEN THAT THE OVERALL STRUCTURE IS BETTER NOW THAN IT
WAS ON THE PREVIOUS ADVISORY...THE INITIAL INTENSITY WILL BE
MAINTAINED AT 75 KT FOR THIS ADVISORY...WHICH MIGHT BE A LITTLE
CONSERVATIVE. UPPER-LEVEL OUTFLOW IS EXCELLENT IN ALL QUADRANTS.
 
KATIA IS MOVING TO THE NORTHEAST NOW...AND THE INITIAL MOTION
ESTIMATE IS 035/18. KATIA HAS ROUNDED THE WESTERN PERIPHERY OF A
LARGE SUBTROPICAL RIDGE ORIENTED EAST-WEST ALONG 33N LATITUDE AND
IS BEGINNING TO ACCELERATE. ALL OF THE NHC MODEL GUIDANCE IS IN
VERY GOOD AGREEMENT THAT KATIA WILL CONTINUE TO MOVE NORTHEASTWARD
WITH A GRADUAL INCREASE IN FORWARD SPEED FOR THE NEXT 24-36 HOURS.
ONCE THE CYCLONE PASSES NORTH OF 40N LATITUDE...IT IS EXPECTED TO
GET CAUGHT UP IN VERY FAST WESTERLIES FOR THIS TIME OF THE YEAR AND
ACCELERATE TO THE EAST-NORTHEAST AND EAST AT FORWARD SPEEDS OF NEAR
50 KT. ONCE KATIA MOVES OVER MUCH COLDER WATER BY 36 HOURS... THE
COMBINATION OF THE FAST MID-LATITUDE FLOW AND SSTS LESS THAN 21C
ARE EXPECTED TO RESULT IN THE TROPICAL CYCLONE MAKING THE
TRANSITION INTO A POWERFUL EXTRATROPICAL CYCLONE. THE OFFICIAL
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY...AND CLOSELY
FOLLOWS THE NHC CONSENSUS MODELS TVCN AND TVCA.
 
NOW THAT KATIA HAS TURNED TO THE NORTHEAST...THE VERTICAL SHEAR HAS
DECREASED AND IT IS EXPECTED TO REMAIN LESS THAN 10 KT FOR THE NEXT
24 HOURS OR SO. THIS SHOULD ALLOW KATIA TO AT LEAST MAINTAIN ITS
CURRENT INTENSITY...ESPECIALLY SINCE DOWNSTREAM BUOYS AHEAD OF THE
CYCLONE ARE INDICATING SSTS OF 27-28C SOUTH OF 40N LATITUDE. BY 36
HOURS...EXTRATROPICAL TRANSITION IS EXPECTED...BUT KATIA IS STILL
FORECAST TO HAVE HURRICANE-FORCE WINDS...WHICH WILL BE AIDED BY
UNUSUALLY FAST FORWARD SPEEDS ABOVE 35 KT BEYOND 36 HOURS.

ALTHOUGH KATIA IS FORECAST TO EVENTUALLY LOSE ITS TROPICAL
CHARACTERISTICS...THIS CYCLONE IS EXPECTED TO REMAIN A VERY
POWERFUL EXTRATROPICAL LOW PRESSURE SYSTEM THAT COULD BRING VERY
STRONG WINDS TO THE BRITISH ISLES BY MONDAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 36.3N  68.8W   75 KT  85 MPH
 12H  09/1200Z 38.1N  66.5W   75 KT  85 MPH
 24H  10/0000Z 40.5N  61.1W   70 KT  80 MPH
 36H  10/1200Z 42.9N  52.6W   70 KT  80 MPH...POST-TROP/EXTRATROP
 48H  11/0000Z 46.4N  39.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  12/0000Z 54.1N  16.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  13/0000Z 61.0N   4.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  14/0000Z...ABSORBED
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 090901
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  45
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST FRI SEP 09 2011
 
THE CLOUD PATTERN CONTINUES WELL ORGANIZED AND IN FACT A DRIFTING
BUOY NEAR THE CENTER OF THE HURRICANE RECENTLY REPORTED A MINIMUM
PRESSURE OF 968 MB. THE INITIAL INTENSITY IS KEPT AT 75 KNOTS.
HOWEVER WEAKENING IS INDICATED SINCE THE HURRICANE IS ALREADY
REACHING COOLER WATERS AND KATIA IS FORECAST TO BECOME
POST-TROPICAL IN ABOUT 36 HOURS.

THE HURICANE IS MOVING TOWARD THE NORTHEAST OR 050 DEGREES AT 21
KNOTS. SINCE THE HURRICANE IS ALREADY EMBEDDED WITHIN THE
MID-LATITUDE WESTERLIES....IT SHOULD CONTINUE ON THIS GENERAL TRACK
WITH AN INCREASE IN FORWARD SPEED FOR THE NEXT FEW DAYS.

NO 96-HOUR POINT IS BEING GIVEN BECAUSE FORECAST POINTS IN THE
EASTERN HEMISPHERE BREAK A LOT OF SOFTWARE.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 37.6N  67.5W   75 KT  85 MPH
 12H  09/1800Z 39.5N  64.5W   75 KT  85 MPH
 24H  10/0600Z 42.0N  55.5W   70 KT  80 MPH
 36H  10/1800Z 45.5N  43.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  11/0600Z 49.5N  30.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  12/0600Z 56.5N  10.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 091436
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  46
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 AM AST FRI SEP 09 2011
 
KATIA HAS MAINTAINED A RAGGED EYE FEATURE IN BOTH CONVENTIONAL AND
MICROWAVE SATELLITE IMAGERY DURING THE PAST 6 HOURS...SO THE
INTENSITY WILL REMAIN AT 75 KT...WHICH IS CONSISTENT WITH NHC AODT
AND SAB INTENSITY ESTIMATES. DESPITE THE HIGH LATITUDE OF THE
CYCLONE...KATIA CONTINUES TO HAVE A WELL-DEFINED UPPER-LEVEL
OUTFLOW PATTERN.

THE INITIAL MOTION ESTIMATE IS 050/25 KT. KATIA IS WELL NORTH OF THE
SUBTROPICAL RIDGE AXIS ORIENTED ALONG 33N LATITUDE...AND WATER
VAPOR IMAGERY INDICATES THAT THE CYCLONE IS NOW ENTERING THE FAST
WESTERLY FLOW REGIME THAT LIES NORTH OF 40N LATITUDE. AS A
RESULT...KATIA IS EXPECTED TO ACCELERATE NORTHEASTWARD THROUGH THE
REMAINDER OF THE FORECAST PERIOD. THE HURRICANE SHOULD PASS OVER
MUCH COLDER WATER BY 24 HOURS AND BECOME A POWERFUL EXTRATROPICAL
CYCLONE. THE FORECAST TRACK IS DOWN THE MIDDLE OF THE TIGHTLY
PACKED MODEL GUIDANCE...AND LIES CLOSE TO THE NHC CONSENSUS MODEL
TVCN.

KATIA WILL BE MOVING OVER WATER TEMPERATURES LESS THAN 26C BY 12
HOURS...AND OVER SSTS LESS THAN 20C BY 24 HOURS. THEREFORE...A
FAIRLY QUICK TRANSITION TO AN EXTRATROPICAL CYCLONE IS EXPECTED BY
24 HOURS WHEN THE SYSTEM WILL ALSO BE MERGING WITH AN APPROACHING
FRONTAL ZONE. ALTHOUGH KATIA IS FORECAST TO WEAKEN BELOW HURRICANE
FORCE BY 36 HOURS...THE LARGE EXTRATROPICAL LOW PRESSURE SYSTEM IS
EXPECTED TO CONTAIN STORM-FORCE WINDS WHEN IT APPROACHES THE
BRITISH ISLES IN 3 DAYS.

NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO COMPUTATIONAL
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 39.3N  65.8W   75 KT  85 MPH
 12H  10/0000Z 41.1N  60.4W   70 KT  80 MPH
 24H  10/1200Z 44.1N  49.9W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/0000Z 47.8N  37.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  11/1200Z 51.5N  26.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/1200Z 58.5N   7.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 092042
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  47
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST FRI SEP 09 2011
 
DESPITE ITS HIGH LATITUDE LOCATION...KATIA HAS MAINTAINED A LARGE
RAGGED EYE FEATURE IN BOTH CONVENTIONAL AND MICROWAVE SATELLITE
IMAGERY. THE INITIAL INTENSITY REMAINS 75 KT BASED ON CONSENSUS
SATELLITE CURRENT INTENSITY ESTIMATES OF T4.5/77 KT FROM TAFB AND
SAB...AND NHC AODT INTENSITY ESTIMATES.
 
THE INITIAL MOTION ESTIMATE IS 060/33 KT. KATIA IS NOW EMBEDDED
WITHIN DEEP-LAYER WEST-SOUTHWESTERLY FLOW AHEAD OF A SHARP
MID-UPPER-LEVEL TROUGH AND ASSOCIATED COLD FRONT MOVING QUICKLY
SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA. THE LARGE HURRICANE IS
EXPECTED TO CONTINUE TO ACCELERATE TOWARD THE EAST-NORTHEAST
THROUGH THE REMAINDER OF THE FORECAST PERIOD. KATIA IS MOVING OVER
COOLER WATER AND IN 18-24 HOURS AND IT IS EXPECTED TO BECOME A
POWERFUL EXTRATROPICAL CYCLONE OVER THE FAR NORTH ATLANTIC. THE
FORECAST TRACK IS DOWN THE MIDDLE OF THE TIGHTLY PACKED NHC MODEL
GUIDANCE...AND LIES CLOSE TO THE CONSENSUS TRACK MODEL TVCN.
 
KATIA WILL BE MOVING OVER WATER TEMPERATURES LESS THAN 22C BY 12
HOURS...AND THE CYCLONE COULD BECOME EXTRATROPICAL AT THAT TIME.
HOWEVER...THE LARGE CIRCULATION IS EXPECTED TO TRANSPORT WARM
UNSTABLE AIR SOUTH OF 40N LATITUDE NORTHWARD INTO THE EASTERN
SEMICIRCLE...WHICH COULD HELP MAINTAIN CONVECTION A LITTLE LONGER
THAN USUAL FOR SYSTEMS AT SUCH A HIGH LATITUDE. REGARDLESS...
TRANSITION TO AN EXTRATROPICAL CYCLONE SHOULD BE COMPLETED BY
24 HOURS WHEN THE SYSTEM WILL HAVE MERGED WITH THE AFOREMENTIONED
COLD FRONT AND BE OVER SSTS LESS THAN 20C. ALTHOUGH KATIA IS
FORECAST TO WEAKEN BELOW HURRICANE FORCE BY 36 HOURS...THE LARGE
EXTRATROPICAL LOW PRESSURE SYSTEM IS EXPECTED TO CONTAIN
STORM-FORCE WINDS WHEN IT APPROACHES THE BRITISH ISLES IN 3 DAYS.
INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN EUROPE
SHOULD MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT
WWW.METOFFICE.GOV.UK/WEATHER/.
 
NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 40.6N  62.7W   75 KT  85 MPH
 12H  10/0600Z 42.6N  55.9W   70 KT  80 MPH
 24H  10/1800Z 46.0N  44.9W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/0600Z 49.6N  33.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  11/1800Z 53.2N  22.9W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/1800Z 60.1N   4.6W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  13/1800Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 100256
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  48
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
1100 PM AST FRI SEP 09 2011
 
KATIA HAS MOVED NORTH OF 40N AND OVER COOLER WATERS...YET IT STILL
MAINTAINS A RING OF DEEP CONVECTION THAT HAS NOT CHANGED MUCH SINCE
THE PREVIOUS ADVISORY. THE INITIAL INTENSITY IS HELD AT 75
KT...SUPPORTED BY A TAFB SATELLITE INTENSITY ESTIMATE OF T4.5 AND
CONTINUITY OF THE CONVECTIVE PATTERN.

THE CURRENT MOTION ESTIMATE IS 075/32...10 KT FASTER THAN THE
PREVIOUS ADVISORY. AN SSMIS MICROWAVE PASS AT 2045 UTC SUGGESTS
THAT THE CIRCULATION OF KATIA IS TILTED TO THE NORTHEAST...
INDICATING THAT SOUTHWESTERLY SHEAR ASSOCIATED WITH A TROUGH TO THE
NORTHWEST IS IMPACTING THE HURRICANE. AS KATIA CONTINUES TO
INTERACT WITH THE TROUGH...IT SHOULD FURTHER ACCELERATE TO THE
NORTHEAST AND BECOME AN EXTRATROPICAL CYCLONE DURING THE NEXT DAY
OR SO. THE FORECAST TRACK IS NEAR THE CENTER OF THE TIGHTLY PACKED
MODEL GUIDANCE...CLOSE TO THE GFS AND THE TRACK CONSENSUS TVCN.

RELIABLE INTENSITY GUIDANCE SUGGESTS THAT KATIA WILL WEAKEN BELOW
HURRICANE STRENGTH LATER SATURDAY. DESPITE THE EXTRATROPICAL
TRANSITION OF KATIA...IT WILL REMAIN A POWERFUL CYCLONE AS IT
TRAVERSES THE FAR NORTH ATLANTIC. THE STORM-FORCE WIND FIELD IS
FORECAST TO REMAIN LARGE AS KATIA APPROACHES THE BRITISH ISLES BY
48 HOURS. INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN
EUROPE SHOULD MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT
WWW.METOFFICE.GOV.UK/WEATHER/  .
 
NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 41.3N  58.0W   75 KT  85 MPH
 12H  10/1200Z 43.5N  50.3W   70 KT  80 MPH
 24H  11/0000Z 47.3N  37.2W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/1200Z 51.1N  25.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  12/0000Z 55.6N  15.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  13/0000Z 61.6N   1.1W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  14/0000Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER HOGSETT/BLAKE
 

WTNT42 KNHC 100849
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  49
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST SAT SEP 10 2011
 
KATIA APPEARS TO BE GRADUALLY LOSING ITS TROPICAL CHARACTERISTICS.
THE ASSOCIATED CLOUD PATTERN IS BECOMING INCREASINGLY ELONGATED...
WITH THE LOW-LEVEL CENTER ON THE SOUTHERN EDGE OF THE 
CONVECTION. THE LATEST SATELLITE CLASSIFICATIONS SUGGEST THAT KATIA
HAS WEAKENED A LITTLE...AND THAT IS THE BASIS FOR THE SLIGHTLY
LOWER INITIAL INTENSITY OF 70 KT. STRONG SOUTHWESTERLY SHEAR
ASSOCIATED WITH A DEEP-LAYER TROUGH AND SEA SURFACE TEMPERATURES
COLDER THAN 20C...SHOULD CAUSE KATIA TO BECOME EXTRATROPICAL IN
ABOUT 12 HOURS. HOWEVER...THE CYCLONE IS EXPECTED TO REMAIN QUITE
STRONG AS AN EXTRATROPICAL SYSTEM WHILE MOVING QUICKLY ACROSS THE
FAR NORTH ATLANTIC....APPROACHING THE BRITISH ISLES AND NORTHERN
EUROPE IN A COUPLE OF DAYS.
  
THE HURRICANE IS EMBEDDED IN THE STRONG MID-LATITUDE WESTERLIES...
AND THE LATEST INITIAL MOTION ESTIMATE IS 060/38. THE CYCLONE IS
EXPECTED TO ACCELERATE DURING THE NEXT 12 TO 24 HOURS WITHIN THE
STRONG FLOW TO THE EAST OF A HIGH LATITUDE DEEP-LAYER TROUGH. THE
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE
GUIDANCE PROVIDED BY THE OCEAN PREDICTION CENTER.
 
INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN EUROPE SHOULD
MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT
WWW.METOFFICE.GOV.UK/WEATHER
 
NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE. THE 34- AND
50-KT WIND RADII WERE EXPANDED OUTWARD OVER THE WESTERN SEMICIRCLE
BASED ON A 0144 UTC ASCAT PASS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 43.3N  53.4W   70 KT  80 MPH
 12H  10/1800Z 46.0N  44.7W   65 KT  75 MPH
 24H  11/0600Z 50.2N  32.2W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/1800Z 53.9N  21.6W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  12/0600Z 57.3N  13.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/0600Z 61.3N   1.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  14/0600Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 101023
TCDAT2
 
HURRICANE KATIA DISCUSSION NUMBER  49...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 AM AST SAT SEP 10 2011
 
CORRECTED STATUS IN TABLE AT 12-HOUR FORECAST TIME

KATIA APPEARS TO BE GRADUALLY LOSING ITS TROPICAL CHARACTERISTICS.
THE ASSOCIATED CLOUD PATTERN IS BECOMING INCREASINGLY ELONGATED...
WITH THE LOW-LEVEL CENTER ON THE SOUTHERN EDGE OF THE 
CONVECTION. THE LATEST SATELLITE CLASSIFICATIONS SUGGEST THAT KATIA
HAS WEAKENED A LITTLE...AND THAT IS THE BASIS FOR THE SLIGHTLY
LOWER INITIAL INTENSITY OF 70 KT. STRONG SOUTHWESTERLY SHEAR
ASSOCIATED WITH A DEEP-LAYER TROUGH AND SEA SURFACE TEMPERATURES
COLDER THAN 20C...SHOULD CAUSE KATIA TO BECOME EXTRATROPICAL IN
ABOUT 12 HOURS. HOWEVER...THE CYCLONE IS EXPECTED TO REMAIN QUITE
STRONG AS AN EXTRATROPICAL SYSTEM WHILE MOVING QUICKLY ACROSS THE
FAR NORTH ATLANTIC....APPROACHING THE BRITISH ISLES AND NORTHERN
EUROPE IN A COUPLE OF DAYS.
  
THE HURRICANE IS EMBEDDED IN THE STRONG MID-LATITUDE WESTERLIES...
AND THE LATEST INITIAL MOTION ESTIMATE IS 060/38. THE CYCLONE IS
EXPECTED TO ACCELERATE DURING THE NEXT 12 TO 24 HOURS WITHIN THE
STRONG FLOW TO THE EAST OF A HIGH LATITUDE DEEP-LAYER TROUGH. THE
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE
GUIDANCE PROVIDED BY THE OCEAN PREDICTION CENTER.
 
INTERESTS IN AND AROUND THE BRITISH ISLES AND NORTHERN EUROPE SHOULD
MONITOR PRODUCTS ISSUED BY THE UKMET OFFICE AT
WWW.METOFFICE.GOV.UK/WEATHER
 
NO 96-HOUR FORECAST POINT HAS BEEN PROVIDED DUE TO SOFTWARE
ISSUES WHEN SYSTEMS MOVE EAST OF ZERO DEGREES LONGITUDE. THE 34- AND
50-KT WIND RADII WERE EXPANDED OUTWARD OVER THE WESTERN SEMICIRCLE
BASED ON A 0144 UTC ASCAT PASS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 43.3N  53.4W   70 KT  80 MPH
 12H  10/1800Z 46.0N  44.7W   65 KT  75 MPH...POST-TROP/EXTRATROP
 24H  11/0600Z 50.2N  32.2W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  11/1800Z 53.9N  21.6W   65 KT  75 MPH...POST-TROP/EXTRATROP
 48H  12/0600Z 57.3N  13.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/0600Z 61.3N   1.3W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  14/0600Z...EAST OF ZERO DEGREES LONGITUDE
 
$$
FORECASTER CANGIALOSI
 

