WTNT42 KNHC 302036
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM EDT THU AUG 30 2012
 
LESLIE HAS QUICKLY ORGANIZED TODAY WITH PROMINENT BANDING FEATURES
AND INCREASED CONVECTION NEAR THE CENTER.  THE INITIAL INTENSITY IS
SET TO 40 KT AS A BLEND OF THE SUBJECTIVE AND MICROWAVE ESTIMATES.
GLOBAL MODELS ALL BUILD AN UPPER-LEVEL ANTICYCLONE NEAR THE STORM
FOR THE NEXT FEW DAYS...WHICH WOULD SEEM TO BE A FAVORABLE
ENVIRONMENT FOR FURTHER STRENGTHENING.  MOST OF THE GUIDANCE
SUGGESTS THAT LESLIE WILL BECOME A HURRICANE IN A DAY OR TWO...AND
THERE ARE EVEN A COUPLE MODELS THAT SHOW IT NEAR MAJOR HURRICANE
STRENGTH IN A FEW DAYS.  THE NHC FORECAST IS RAISED FROM THE
PREVIOUS ONE...AND IS A LITTLE BELOW THE ROBUST LGEM/SHIPS GUIDANCE
THROUGHOUT THE PERIOD.  WHILE THE TIMING IS IMPOSSIBLE TO
PINPOINT...IT WOULD NOT BE SURPRISING IF LESLIE BECAME STRONGER
THAN FORECAST IN THE THREE-TO-FIVE DAY PERIOD.  
 
THE INITIAL MOTION IS ABOUT 280/18.  LESLIE SHOULD TURN TOWARD THE
WEST-NORTHWEST IN THE NEXT 12 HOURS OR SO AS IT MOVES AROUND THE
SOUTHWESTERN SIDE OF THE SUBTROPICAL RIDGE.  A SERIES OF TROUGHS IS
EXPECTED TO DIG BETWEEN 60W-70W...WHICH SHOULD CAUSE THE STORM TO
MAKE A GRADUAL TURN TOWARD THE NORTHWEST AND NORTH IN A FEW DAYS.
MODEL GUIDANCE IS IN VERY GOOD AGREEMENT FOR THE FIRST THREE
DAYS...THEN SOME DIVERGENCE OCCURS ON WHICH TROUGH MIGHT RECURVE
THE CYCLONE.  AT THE END OF THE PERIOD...SPEED DIFFERENCES BECOME
VERY IMPORTANT ON WHETHER LESLIE MOVES QUICKLY OUT TO SEA...AS
SUGGESTED BY THE GFS...OR GETS STUCK UNDER A RIDGE...AS FORECAST BY
THE ECMWF.  THE NHC FORECAST IS BASICALLY AN UPDATE OF THE
PREVIOUS ONE...STILL A BIT FASTER AND WEST OF THE MODEL CONSENSUS.  
 
GLOBAL MODELS SHOW THIS SYSTEM BECOMING RATHER LARGE...SO THE WIND
RADII FORECAST HAS BEEN SIGNIFICANTLY EXPANDED.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 14.4N  45.3W   40 KT  45 MPH
 12H  31/0600Z 15.3N  47.6W   50 KT  60 MPH
 24H  31/1800Z 16.5N  50.6W   60 KT  70 MPH
 36H  01/0600Z 17.7N  53.6W   70 KT  80 MPH
 48H  01/1800Z 19.0N  56.1W   75 KT  85 MPH
 72H  02/1800Z 22.0N  59.5W   85 KT 100 MPH
 96H  03/1800Z 26.0N  61.0W   85 KT 100 MPH
120H  04/1800Z 28.5N  60.5W   85 KT 100 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 310241
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM EDT THU AUG 30 2012

CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY SHOW THAT THE CENTER OF
LESLIE IS LOCATED TO THE NORTHEAST OF THE MAIN CONVECTIVE
MASS...MOST LIKELY DUE TO LIGHT/MODERATE NORTHEASTERLY VERTICAL
WIND SHEAR.  SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND
SAB.  IN ADDITION...NOAA BUOY 41041 REPORTED 1004 MB AND
NORTHWESTERLY WINDS OF 20-25 KT AS THE CENTER PASSED TO THE NORTH. 
BASED ON THESE DATA...THE INITIAL INTENSITY IS INCREASED TO 45 KT.

THE INITIAL MOTION IS 280/16.  LESLIE IS CURRENTLY ON THE SOUTH SIDE
OF THE SUBTROPICAL RIDGE...WHICH SHOULD STEER THE SYSTEM GENERALLY
WEST-NORTHWESTWARD FOR THE NEXT 48 HR OR SO.  AFTER THAT...THE
GLOBAL MODELS ARE IN GOOD AGREEMENT THAT A MID-/UPPER-LEVEL
SHORTWAVE TROUGH...CURRENTLY SEEN IN WATER VAPOR IMAGERY MOVING OFF
OF THE COAST OF THE NORTHEASTERN UNITED STATES...SHOULD DEVELOP
INTO A CUT-OFF LOW BETWEEN BERMUDA AND THE BAHAMAS.  THIS LOW IS
FORECAST TO BREAK THE SUBTROPICAL RIDGE AT THE MID-/UPPER-LEVELS...
AND EXTEND FAR ENOUGH VERTICALLY DOWNWARD TO WEAKEN THE RIDGE AT
700-850 MB.  THIS EVOLUTION SHOULD CAUSE LESLIE TO GRADUALLY TURN
NORTHWARD ON THE EASTERN SIDE OF THE CUT-OFF LOW AFTER THE 48 HR
POINT.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT WITH THIS
SCENARIO...AND THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS
TRACK THROUGH 96 HR.  IT SHOULD BE NOTED THAT THE TRACK GUIDANCE
STARTS TO DIVERGE AT 120 HR REGARDING HOW QUICKLY LESLIE SHOULD
ENCOUNTER THE WESTERLIES...AND BASED ON THIS SPREAD...THE TRACK
FORECAST CALLS FOR A SLOWER AND MORE NORTHERLY MOTION NEAR THAT
TIME.

THE GLOBAL MODELS SUGGEST THAT LESLIE SHOULD REMAIN IN AN
ENVIRONMENT OF LIGHT/MODERATE EASTERLY SHEAR FOR THE NEXT 36-48
HR...WHICH SHOULD ALLOW FOR GRADUAL DEVELOPMENT.  AFTER THAT
TIME...THE CYCLONE IS FORECAST TO ENCOUNTER SIGNIFICANT
SOUTHWESTERLY UPPER-LEVEL WINDS ASSOCIATED WITH THE CUT-OFF
LOW...WHICH IS EXPECTED TO CAUSE ENOUGH SHEAR TO SLOW OR HALT
INTENSIFICATION.  THE INTENSITY GUIDANCE IS FORECASTING A LITTLE
LESS STRENGTHENING THAN FOR THE PREVIOUS ADVISORY...MOST NOTABLY
AFTER 48 HR.  THE NEW INTENSITY FORECAST IS A BLEND OF THE PREVIOUS
FORECAST AND THE CURRENT SHIPS MODEL...SHOWING LESLIE BECOMING A
HURRICANE BY 24 HR AND SHOWING LITTLE CHANGE IN STRENGTH FROM
72-120 HR.
 
THE GLOBAL MODELS SHOW THIS SYSTEM BECOMING VERY LARGE...WHICH IS
REFLECTED IN THE CURRENT WIND FIELD FORECAST.  AN ADDITIONAL
INCREASE IN SIZE APPEARS LIKELY AFTER 72 HR.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 14.7N  46.8W   45 KT  50 MPH
 12H  31/1200Z 15.5N  49.0W   55 KT  65 MPH
 24H  01/0000Z 16.7N  51.7W   65 KT  75 MPH
 36H  01/1200Z 17.9N  54.4W   75 KT  85 MPH
 48H  02/0000Z 19.3N  56.8W   80 KT  90 MPH
 72H  03/0000Z 22.5N  60.5W   85 KT 100 MPH
 96H  04/0000Z 26.5N  61.5W   85 KT 100 MPH
120H  05/0000Z 29.0N  61.5W   85 KT 100 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 310849
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST FRI AUG 31 2012
 
WATER VAPOR IMAGERY SUGGESTS THAT THE EASTERLY SHEAR THAT HAS BEEN
AFFECTING LESLIE IS GRADUALLY SUBSIDING.  THE STORM IS PRODUCING
GOOD OUTFLOW IN ALL QUADRANTS...AND IT APPEARS THAT THE LOW-LEVEL
CENTER HAS MIGRATED FARTHER INTO THE CONVECTIVE CANOPY.  DVORAK
ESTIMATES HAVE INCREASED TO T3.5 FROM BOTH TAFB AND SAB...AND THE
INITIAL INTENSITY IS RAISED TO 55 KT.
 
LESLIE IS CURRENTLY MOVING AT 285/14 KT...AND A WEST-NORTHWESTWARD
MOTION SHOULD CONTINUE AS THE CYCLONE APPROACHES A BREAK IN THE
SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC.  THE RIDGE IS FORECAST
TO NEARLY VANISH BY DAY 3 AS LESLIE BECOMES POSITIONED BETWEEN TWO
MID/UPPER-LEVEL LOWS AND WELL TO THE SOUTH OF THE MID-LATITUDE
WESTERLIES.  BECAUSE OF THE COLLAPSE IN THE STEERING FLOW...LESLIE
IS EXPECTED TO TURN NORTHWARD BUT SLOW DOWN CONSIDERABLY BY DAYS 4
AND 5.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO...
BUT THERE HAS BEEN A NOTICEABLE SOUTHWESTWARD SHIFT ON DAYS 4 AND
5.  THE NEW NHC FORECAST IS THEREFORE SLOWER AND FARTHER WEST OF
THE PREVIOUS FORECAST AT THE LATTER END OF THE FORECAST PERIOD...
BUT IT IS STILL EAST OF THE MODEL CONSENSUS TVCA ON DAY 5.
 
THE UPPER-LEVEL ENVIRONMENT AROUND LESLIE IS IMPROVING...AND THE
GLOBAL MODELS SUGGEST THAT THE STORM SHOULD HAVE AN OUTFLOW PATTERN
BENEFICIAL FOR STRENGTHENING FOR AT LEAST THE NEXT 3 DAYS.  THE
OFFICIAL FORECAST THEREFORE SHOWS STEADY INTENSIFICATION THROUGH 72
HOURS AND ACTUALLY ENDS UP A BIT HIGHER THAN THE INTENSITY
GUIDANCE.  THERE IS SOME DISAGREEMENT AMONG THE MODELS ON DAYS 4
AND 5...HOWEVER.  THE OPERATIONAL GFS MAINTAINS A GOOD UPPER-LEVEL
OUTFLOW PATTERN ON THOSE DAYS...WHILE THE ECMWF...UKMET...GFS
ENSEMBLE MEAN...AND ECMWF ENSEMBLE MEANS ALL SHOW AN INCREASE IN
SHEAR.  THE NHC FORECAST HEDGES ON THE SCENARIO SHOWN BY THE
MAJORITY OF THESE MODELS...AS WELL AS THE STATISTICAL-DYNAMICAL
GUIDANCE...AND INDICATES SOME POSSIBLE WEAKENING ON DAYS 4 AND 5.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0900Z 15.2N  47.8W   55 KT  65 MPH
 12H  31/1800Z 16.1N  50.0W   65 KT  75 MPH
 24H  01/0600Z 17.4N  52.7W   70 KT  80 MPH
 36H  01/1800Z 18.6N  55.2W   80 KT  90 MPH
 48H  02/0600Z 19.9N  57.4W   85 KT 100 MPH
 72H  03/0600Z 23.0N  60.5W   90 KT 105 MPH
 96H  04/0600Z 25.5N  62.0W   85 KT 100 MPH
120H  05/0600Z 27.0N  62.0W   80 KT  90 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 311443
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST FRI AUG 31 2012
 
LESLIE CONTINUES TO EXPERIENCE NORTHEASTERLY SHEAR...WHICH IS
CAUSING MOST OF THE CONVECTION TO BE LOCATED IN THE SOUTHWESTERN
QUADRANT OF THE STORM.  THIS STRUCTURE IS CONFIRMED BY RECENT
MICROWAVE PASSES AND VISIBLE SATELLITE IMAGERY THAT SHOW THE CENTER
EMBEDDED IN THE NORTHERN PORTION OF A SMALL CENTRAL DENSE OVERCAST
FEATURE.  THE INTENSITY ESTIMATES HAVE NOT CHANGED MUCH...SO THE
WIND SPEED IS KEPT AT 55 KT.  THE SHEAR HAS BEEN A LITTLE STRONGER
THAN PREVIOUSLY ANTICIPATED...AND MICROWAVE IMAGES SUGGEST THAT
LESLIE LACKS ANY CENTRAL CORE.  GIVEN THESE FACTORS...THE INTENSITY
FORECAST HAS BEEN REDUCED A BIT FROM THE PREVIOUS ONE IN THE SHORT
TERM.  WHILE THE GLOBAL MODELS ARE STILL SHOWING A LARGE UPPER-LEVEL
ANTICYCLONE NEAR LESLIE IN A FEW DAYS...THE POSITIONING OF LESLIE
WITHIN THAT ANTICYCLONE APPEARS LESS FAVORABLE THAN YESTERDAY...
WITH WESTERLY SHEAR POSSIBLE.  THE INTENSITY CONSENSUS IS QUITE A
BIT LOWER THAN A COUPLE MODEL CYCLES AGO...AND THIS TOOL HAS BEEN A
GOOD PERFORMER THIS YEAR.  THE NEW FORECAST IS A BLEND OF THE
PREVIOUS INTERPOLATED FORECAST AND THE INTENSITY CONSENSUS...AND
RESULTS IN A REDUCTION TO THE NHC WIND SPEED PREDICTION.

THE INITIAL MOTION ESTIMATE IS 295/15...A BIT FASTER AND TO THE
RIGHT OF THE PREVIOUS ONE.  LESLIE REMAINS BASICALLY ON TRACK AS IT
MOVES BENEATH A NARROW RIDGE TO THE SOUTH OF HURRICANE KIRK.  THE
RIDGE BREAKS BETWEEN 60W-65W...WHICH SHOULD CAUSE THE STORM TO TURN
TOWARD THE NORTHWEST AND NORTH WITH A LARGE DECREASE IN FORWARD
SPEED IN A FEW DAYS.  THE GLOBAL MODELS ARE WELL CLUSTERED ON THE
TRACK THROUGH THE FIRST 48 HOURS...AND ONLY SMALL CHANGES WERE MADE
TO THE NHC FORECAST UP TO THAT TIME.  IT NOW APPEARS THAT LESLIE
WILL MISS A TROUGH FORECAST TO DIVE OFFSHORE OF NORTH AMERICA...AND
WILL BE CAUGHT IN AN AREA OF LIGHT STEERING CURRENTS IN THE LONG
RANGE.  THE MODELS CONTINUE TO SLOW DOWN AT DAYS 4 AND 5...AND THE
NHC FORECAST IS SHIFTED SLIGHTLY TO THE SOUTH AND WEST AT THOSE
TIMES.  


 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/1500Z 16.2N  49.1W   55 KT  65 MPH
 12H  01/0000Z 17.2N  51.3W   60 KT  70 MPH
 24H  01/1200Z 18.5N  54.0W   65 KT  75 MPH
 36H  02/0000Z 19.6N  56.3W   70 KT  80 MPH
 48H  02/1200Z 20.9N  58.4W   75 KT  85 MPH
 72H  03/1200Z 23.8N  61.3W   80 KT  90 MPH
 96H  04/1200Z 25.9N  62.2W   75 KT  85 MPH
120H  05/1200Z 27.0N  62.5W   75 KT  85 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 312037
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST FRI AUG 31 2012
 
THE STORM LOOKS A LITTLE BETTER ORGANIZED ON VISIBLE IMAGERY THIS
AFTERNOON WITH AN INCREASE IN CONVECTION IN ADDITION TO MICROWAVE
OVERPASSES SHOWING THE CENTER BECOMING MORE EMBEDDED IN THE
OVERCAST.  INTENSITY ESTIMATES...HOWEVER...ARE UNCHANGED...SO THE
INITIAL WIND SPEED IS KEPT AT 55 KT.  WHILE THE VERTICAL SHEAR IS
EXPECTED TO REMAIN LIGHT-TO-MODERATE IN THE SHORT TERM...MOST OF
THE GLOBAL MODELS ARE NOW SHOWING AN INCREASINGLY HOSTILE
ENVIRONMENT AFTER THAT TIME.  THESE CONDITIONS ARE DUE TO AN
UPPER-LEVEL HIGH MOVING WEST OF THE CENTER...CAUSING AN INCREASE IN
NORTHWESTERLY SHEAR.  MOST OF THE INTENSITY GUIDANCE NOW SHOW
LESLIE ONLY AS A CATEGORY ONE HURRICANE IN A FEW DAYS TIME.  THE
OFFICIAL FORECAST IS REDUCED SLIGHTLY FROM THE PREVIOUS ONE...IN
BEST AGREEMENT WITH A BLEND OF THE INTENSITY CONSENSUS AND THE LGEM
MODEL.  THERE IS SOME CHANCE OF LESLIE FINDING A MORE FAVORABLE
ENVIRONMENT IN THE LONG TERM...BUT ITS LIKELY SLOW MOTION AT THAT
TIME COULD CAUSE UPWELLING UNDER THE STORM...SO THE NHC FORECAST
WILL STAY CONSERVATIVE.

A SERIES OF MICROWAVE PASSES GIVES A GOOD INITIAL MOTION ESTIMATE OF
295/16.  THERE HAS BEEN A SUBTLE WESTWARD SHIFT IN MOST OF THE
RELIABLE MODEL GUIDANCE DURING THE FORECAST PERIOD...PERHAPS
INITIALLY DUE TO THE RIDGE BETWEEN KIRK AND LESLIE BEING A BIT
STRONGER THAN EXPECTED.  THE GLOBAL MODELS ARE CONSISTENT IN
FORECASTING A BREAK IN THE SUBTROPICAL RIDGE IN A FEW DAYS
TIME...WHICH SHOULD CAUSE LESLIE TO TURN NORTHWESTWARD AND
NORTHWARD IN 3 TO 4 DAYS.  BY THE END OF THE FORECAST...LITTLE
MOTION IS EXPECTED AS THE CYCLONE IS CAUGHT IN LIGHT STEERING
CURRENTS TO THE SOUTHEAST OF BERMUDA.  THE OFFICIAL NHC PREDICTION
IS SHIFTED WESTWARD TO COME CLOSER TO THE DYNAMICAL MODEL
CONSENSUS... ALTHOUGH THE MODEL CONSENSUS IS STILL A BIT WEST OF
THE NEW FORECAST.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/2100Z 16.7N  51.0W   55 KT  65 MPH
 12H  01/0600Z 17.7N  53.2W   60 KT  70 MPH
 24H  01/1800Z 18.9N  55.9W   60 KT  70 MPH
 36H  02/0600Z 20.1N  58.1W   65 KT  75 MPH
 48H  02/1800Z 21.5N  60.0W   70 KT  80 MPH
 72H  03/1800Z 24.1N  62.0W   70 KT  80 MPH
 96H  04/1800Z 26.0N  62.5W   70 KT  80 MPH
120H  05/1800Z 27.0N  63.0W   75 KT  85 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 010244
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST FRI AUG 31 2012

LESLIE IS PRODUCING A LARGE CENTRAL AREA OF CONVECTION WITH CLOUD
TOPS COLDER THAN -80C.  HOWEVER...AN SSM/IS OVERPASS AT 2318 UTC
AND A TRMM OVERPASS AT 0030 UTC INDICATED THAT THE CENTER IS STILL
DISPLACED TO THE NORTH OF THE CONVECTION DUE TO CONTINUING
NORTHERLY VERTICAL WIND SHEAR.  SATELLITE INTENSITY ESTIMATES ARE
55 KT FROM TAFB AND 45 KT FROM SAB....AND THE INITIAL INTENSITY
REMAINS 55 KT.  ALTHOUGH SHEAR CONTINUES...THE CIRRUS OUTFLOW IS
GOOD IN ALL DIRECTIONS EXCEPT TO THE NORTH.

THE INITIAL MOTION IS 295/18.  THE SUBTROPICAL RIDGE NORTH AND
NORTHEAST OF THE STORM SHOULD STEER LESLIE WEST-NORTHWESTWARD FOR
THE NEXT 36 HR.  AFTER THAT...THE CYCLONE IS LIKELY TO TURN
NORTHWESTWARD AND THEN NORTHWARD DUE TO A BREAK IN THE RIDGE
CREATED BY A DEVELOPING MID/UPPER-LEVEL LEVEL LOW PRESSURE
SYSTEM...CURRENTLY SEEN IN WATER VAPOR IMAGERY BETWEEN BERMUDA AND
THE EASTERN UNITED STATES.  THE FORECAST TRACK THROUGH 72 HR IS AN
UPDATE OF THE PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE TRACK
GUIDANCE ENVELOPE.  THE GUIDANCE DIVERGES AFTER 72 HR AS LESLIE IS
EXPECTED TO MOVE INTO AN AREA OF LIGHT STEERING CURRENTS.  THE
GFS...GFDL...HWRF...AND CANADIAN MODELS SHOW A SLOW EASTWARD OR
NORTHEASTWARD MOTION DURING THIS PERIOD...WHILE THE ECMWF AND THE
FLORIDA STATE SUPERENSEMBLE SHOW A SLOW NORTHWESTWARD MOTION. 
OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE EAST
AFTER 72 HR.  AS A RESULT...THE NEW FORECAST TRACK IS ALSO NUDGED A
LITTLE TO THE EAST AND SHOWS A SLOW NORTHWARD MOTION BY 120 HR. 
HOWEVER...IT LIES ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE TO THE
WEST OF THE CONSENSUS MODELS.

THE GLOBAL MODELS SUGGEST THAT SOME NORTHERLY SHEAR SHOULD PERSIST
FOR THE NEXT 24-48 HR...AND IT IS UNCLEAR IF LESLIE WILL FIND A
REALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT DURING THIS TIME. 
FROM 48-96 HR...THE CYCLONE MOVES NORTH OF AN UPPER-LEVEL RIDGE AND
IS LIKELY TO ENCOUNTER MODERATE/STRONG WESTERLY SHEAR...WHICH AT
THE VERY LEAST SHOULD STOP DEVELOPMENT.  THE UPPER-LEVEL WINDS MAY
BECOME MORE FAVORABLE AFTER 96 HR...ALTHOUGH THE ECMWF STILL SHOWS
A RATHER HOSTILE ENVIRONMENT DURING THIS TIME.  THE NEW INTENSITY
FORECAST IS THE SAME AS THE PREVIOUS FORECAST...CALLING FOR SLOW
DEVELOPMENT THROUGH 48 HR...LITTLE CHANGE IN STRENGTH AT 72 AND 96
HR...AND SLIGHT STRENGTHENING FROM 96-120 HR.  THE FORECAST IS A
BLEND OF THE SHIPS MODEL AND THE INTENSITY CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0300Z 17.4N  52.8W   55 KT  65 MPH
 12H  01/1200Z 18.3N  54.8W   60 KT  70 MPH
 24H  02/0000Z 19.7N  57.4W   60 KT  70 MPH
 36H  02/1200Z 21.1N  59.4W   65 KT  75 MPH
 48H  03/0000Z 22.6N  60.9W   70 KT  80 MPH
 72H  04/0000Z 25.0N  62.0W   70 KT  80 MPH
 96H  05/0000Z 26.5N  62.5W   70 KT  80 MPH
120H  06/0000Z 28.0N  62.5W   75 KT  85 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 010846
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SAT SEP 01 2012
 
LESLIE CONTINUES TO PRODUCE A LARGE CENTRAL DENSE OVERCAST WITH A
BAND OF DEEP CONVECTION WRAPPING AROUND THE SOUTHERN AND WESTERN
SEMICIRCLES.  DURING THE PAST FEW HOURS...AN EYE-LIKE FEATURE WAS
OBSERVED IN INFRARED SATELLITE IMAGERY EMBEDDED IN THE CENTER OF
THE CDO.  HOWEVER...THERE HAVE BEEN NO TIMELY MICROWAVE PASSES...
AND IT IS UNCLEAR IF THIS FEATURE IS COINCIDENT WITH THE LOW-LEVEL
CENTER.  STILL...DVORAK ESTIMATES HAVE COME UP TO T4.0 FROM TAFB
AND T3.5 FROM SAB...AND THE INITIAL INTENSITY IS RAISED TO 60 KT.

DESPITE THE UNCERTAINTY IN THE CENTER LOCATION...THE INITIAL MOTION
APPEARS TO BE A LITTLE SLOWER THAN BEFORE AND IS ESTIMATED TO BE
295/15 KT.  A DIGGING SHORTWAVE TROUGH OVER THE WESTERN ATLANTIC IS
EXPECTED TO DEVELOP A CUT-OFF LOW DURING THE NEXT 24 HOURS...AND
THIS SHOULD CAUSE THE RIDGE TO THE NORTH OF LESLIE TO WEAKEN. 
LESLIE WILL RESPOND BY TURNING NORTHWESTWARD AND THEN NORTHWARD
DURING THE NEXT 5 DAYS...BUT THE CYCLONE WILL ALSO SLOW DOWN AS THE
STEERING FLOW AROUND IT COLLAPSES.  ALTHOUGH THERE IS SOME
DIVERGENCE IN THE TRACK GUIDANCE AFTER ABOUT 72 HOURS...THEY ALL
SHOW A SLOW MOTION TOWARD THE NORTH OR EVEN NORTH-NORTHEAST BY DAY
5.  THE NEW NHC FORECAST LIES ON THE WESTERN SIDE OF THE GUIDANCE
ENVELOPE...AND IS NUDGED SLIGHTLY EAST OF THE PREVIOUS FORECAST ON
DAYS 4 AND 5.

IF LESLIE IS GOING TO STRENGTHEN...IT PROBABLY HAS TO DO IT DURING
THE NEXT 24 TO 48 HOURS BEFORE IT ENCOUNTERS STRONG WESTERLY TO
NORTHWESTERLY SHEAR.  THE UPPER-LEVEL PATTERN COULD THEN BECOME
MORE FAVORABLE FOR STRENGTHENING BY DAY 5.  THE INTENSITY MODELS DO
NOT SUPPORT MUCH INTENSIFICATION DURING THE FORECAST PERIOD...AND
THE NEW NHC FORECAST IS LARGELY UNCHANGED FROM THE PREVIOUS ONE BY
INDICATING ONLY GRADUAL STRENGTHENING.  THIS FORECAST IS HIGHER
THAN THAT SHOWN BY THE STATISTICAL GUIDANCE...BUT NOT AS HIGH AS
THE INTENSITY CONSENSUS ICON AND HFIP CONSENSUS TV15.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0900Z 17.8N  53.5W   60 KT  70 MPH
 12H  01/1800Z 18.8N  55.5W   65 KT  75 MPH
 24H  02/0600Z 20.2N  57.7W   65 KT  75 MPH
 36H  02/1800Z 21.6N  59.5W   65 KT  75 MPH
 48H  03/0600Z 23.1N  60.8W   70 KT  80 MPH
 72H  04/0600Z 25.0N  61.5W   70 KT  80 MPH
 96H  05/0600Z 26.5N  61.5W   70 KT  80 MPH
120H  06/0600Z 28.5N  61.0W   75 KT  85 MPH
 
$$
FORECASTER BERG
 

WTNT42 KNHC 011452
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST SAT SEP 01 2012
 
VISIBLE SATELLITE IMAGES SHOW THAT LESLIE REMAINS A SHEARED CYCLONE 
WITH THE LOW-LEVEL CENTER DISPLACED TO THE NORTHWEST OF THE MAIN
CONVECTIVE BAND.  THE INITIAL WIND SPEED IS KEPT AT 60 KT AS A
COMPROMISE BETWEEN THE VARIOUS INTENSITY ESTIMATES.  IT SEEMS LIKE
THE WINDOW FOR LESLIE TO BECOME A HURRICANE IS CLOSING AS
NORTHWESTERLY SHEAR HAS INCREASED.  THIS SHEAR IS EVIDENT IN CIRRUS
CLOUD MOTIONS NEAR THE CENTER...ALONG WITH LARGE-SCALE ANALYSES
FROM THE SHIPS MODEL AND UW-CIMSS.  THE GLOBAL MODELS SUGGEST
THIS SHEAR WILL PERSIST OR EVEN INTENSIFY DURING THE NEXT COUPLE OF
DAYS AS LESLIE IS CAUGHT ON THE EASTERN SIDE OF AN UPPER-LEVEL
ANTICYCLONE.  THE NHC INTENSITY FORECAST IS REDUCED DURING THAT
TIME...AND IS IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS AND
THE FSU SUPERENSEMBLE.  THERE ARE SOME INDICATIONS THAT THE SHEAR
COULD RELAX IN A FEW DAYS...SO GRADUAL STRENGTHENING IS SHOWN IN
THE LONG RANGE...CONTINUING THE TREND OF THE PREVIOUS FORECAST.
 
MICROWAVE AND VISIBLE IMAGES REQUIRE A REPOSITIONING OF LESLIE ABOUT
30 N MI WEST OF THE PREVIOUS FIXES...GIVING A LONG-TERM MOTION OF
ABOUT 290/16.  THE CYCLONE SHOULD TURN TO THE NORTHWEST BY TOMORROW
AS IT MOVES AROUND A WEAKENING RIDGE OVER THE CENTRAL ATLANTIC
OCEAN...THEN TURN NORTHWARD IN A FEW DAYS AS IT NEARS A BREAK IN
THE RIDGE.  THE GLOBAL MODELS ARE A BIT FASTER IN GENERAL...SHOWING
ENOUGH RIDGING EAST OF LESLIE TO KEEP THE SYSTEM FROM TOTALLY
STALLING OUT AS SUGGESTED IN EARLIER MODEL CYCLES.  THE NEW NHC
FORECAST IS A BIT FASTER AND LEFT OF THE PREVIOUS ONE...MOSTLY DUE
TO THE CENTER REPOSITIONING.

THE INITIAL AND FORECAST WIND RADII WERE ADJUSTED BASED ON A 1244
UTC ASCAT PASS.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  01/1500Z 18.3N  55.7W   60 KT  70 MPH
 12H  02/0000Z 19.4N  57.6W   60 KT  70 MPH
 24H  02/1200Z 21.0N  59.8W   60 KT  70 MPH
 36H  03/0000Z 22.7N  61.2W   60 KT  70 MPH
 48H  03/1200Z 24.1N  62.1W   60 KT  70 MPH
 72H  04/1200Z 26.0N  62.5W   65 KT  75 MPH
 96H  05/1200Z 27.5N  62.0W   70 KT  80 MPH
120H  06/1200Z 29.0N  61.5W   75 KT  85 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 012040
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST SAT SEP 01 2012
 
SATELLITE IMAGES SHOW THAT THE CENTER OF LESLIE IS EXPOSED TO THE
NORTHWEST OF A WEAKENING CONVECTIVE CLUSTER.  INTENSITY ESTIMATES
ARE DROPPING...SO THE INITIAL WINDS ARE REDUCED TO 55 KT. 
NORTHWESTERLY SHEAR IS FORECAST TO PERSIST AND SOMEWHAT INCREASE
OVER THE NEXT COUPLE OF DAYS PRIMARILY DUE TO FLOW AROUND THE
EASTERN PORTION OF AN UPPER-LEVEL HIGH.  CURIOUSLY...THE MODELS DO
NOT WEAKEN THE SYSTEM MUCH MORE...PERHAPS BECAUSE LESLIE MOVES
THROUGH AN EXTREMELY UNSTABLE ENVIRONMENT AND WARM WATERS.  THE NHC
FORECAST IS REDUCED FROM THE PREVIOUS ONE...SHOWING A STEADY STATE
CYCLONE FOR THE NEXT COUPLE OF DAYS...BUT IT WOULD NOT BE
SURPRISING IF LESLIE WEAKENED SOMEWHAT DURING THAT TIME.  THE NEW
FORECAST STILL LEAVES OPEN THE CHANCE THAT CYCLONE WILL RECOVER IN
A FEW DAYS TIME DUE TO A POSSIBLE LESSENING OF THE SHEAR.  

VISIBLE FIXES GIVE A MOTION OF ABOUT 295/16.  THERE IS NO CHANGE TO
THE SYNOPTIC REASONING AS LESLIE SHOULD TURN TO THE NORTHWEST BY
LATE TOMORROW AS IT MOVES AROUND A WEAKENING RIDGE OVER THE CENTRAL
ATLANTIC OCEAN.  THE GLOBAL MOTION ARE THEN CONSISTENT ABOUT THE
CYCLONE TURNING BY EARLY TUESDAY DUE TO A BREAK IN THE RIDGE.  THE
NEW NHC FORECAST CONTINUES TO SHIFT THE TRACK A BIT FASTER AND LEFT
OF THE PREVIOUS ONE THROUGH THE FIRST FEW DAYS.  THE LONG RANGE
FORECAST IS UNCERTAIN BECAUSE IT INVOLVES THE INTERACTION OF MANY
FEATURES...INCLUDING THE REMNANTS OF ISAAC...A CUTOFF LOW OFFSHORE
OF FLORIDA...AND A WEAK RIDGE OVER THE CENTRAL ATLANTIC.  GIVEN THE
UNCERTAINTY...THE OFFICIAL FORECAST IS TRENDED TOWARD THE MODEL
CONSENSUS...WHICH ENDS UP BEING A BIT SLOWER AND WEST OF THE
PREVIOUS FORECAST.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/2100Z 19.2N  57.3W   55 KT  65 MPH
 12H  02/0600Z 20.3N  59.2W   55 KT  65 MPH
 24H  02/1800Z 21.9N  61.0W   55 KT  65 MPH
 36H  03/0600Z 23.6N  62.2W   55 KT  65 MPH
 48H  03/1800Z 24.9N  62.8W   55 KT  65 MPH
 72H  04/1800Z 26.3N  62.9W   60 KT  70 MPH
 96H  05/1800Z 27.5N  62.5W   65 KT  75 MPH
120H  06/1800Z 29.0N  62.5W   70 KT  80 MPH
 
$$
FORECASTER BLAKE
 

WTNT42 KNHC 020255
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SAT SEP 01 2012

THE CENTER OF LESLIE REMAINS EXPOSED TO THE NORTHWEST OF THE MAIN
CONVECTIVE MASS DUE TO 15-20 KT OF NORTHWESTERLY VERTICAL WIND
SHEAR.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND 45 KT
FROM SAB.  DATA FROM THE INDIAN OSCAT SCATTEROMETER NEAR 1630 UTC
SUGGESTED AN INTENSITY NEAR 55 KT.  SINCE THE SATELLITE APPEARANCE
HAS CHANGED LITTLE SINCE THAT TIME...THE INITIAL INTENSITY IS HELD
AT A POSSIBLY GENEROUS 55 KT.
 
LESLIE HAS TURNED NORTHWESTWARD DURING THE PAST SEVERAL HOURS WITH
AN INITIAL MOTION OF 305/16. THE CYCLONE SHOULD GRADUALLY TURN
NORTHWARD WITH A DECREASE IN FORWARD SPEED DURING THE NEXT 48 HR AS
IT MOVES INTO A BREAK IN THE SUBTROPICAL RIDGE CAUSED BY A
MID/UPPER-LEVEL LOW NEAR 28N72W AND A BROAD MID/UPPER-LEVEL TROUGH
NORTH OF 35N BETWEEN 55-75W. AFTER THAT...ALL OF THE GUIDANCE
AGREES THAT LESLIE SHOULD MOVE SLOWLY IN A GENERALLY NORTHWARD
DIRECTION AS IT INTERACTS WITH THE MID/UPPER-LEVEL LOW...THE
REMANTS OF ISAAC...THE SUBTROPICAL RIDGE TO THE EAST...AND A
SHORTWAVE RIDGE IN THE WESTERLIES PASSING NORTH OF THE STORM. THE
GUIDANCE HAS CHANGED LITTLE SINCE THE PREVIOUS ADVISORY...AND THE
NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS TRACK.
 
THE INTENSITY FORECAST IS PROBLEMATIC.  THE GLOBAL MODELS AGREE ON
FORECASTING INCREASING SHEAR OVER LESLIE DURING THE NEXT 48 HR...
AND THE SHIPS MODEL FORECASTS SHEAR IN EXCESS OF 25 KT.  DESPITE
THIS...MUCH OF THE INTENSITY GUIDANCE EITHER MAINTAINS THE
STRENGTH OF THE CYCLONE OR FORECASTS INTENSIFICATION DURING THIS
TIME.  BASED ON THE FORECAST SHEAR...THE NEW INTENSITY FORECAST NOW
CALLS FOR SLIGHT WEAKENING DURING THE FIRST 48 HR...WITH THE
FORECAST NEAR THE THE LOWER EDGE OF THE INTENSITY GUIDANCE.  THE
SHEAR MAY START TO SUBSIDE AFTER 48 HR...AND THE GLOBAL MODELS
FORECAST LESLIE TO GROW IN BOTH SIZE AND DEPTH DURING THAT TIME. 
THIS PORTION OF THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY...BUT IS WEAKER THAN THE INTENSITY CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0300Z 20.2N  58.4W   55 KT  65 MPH
 12H  02/1200Z 21.3N  60.1W   55 KT  65 MPH
 24H  03/0000Z 23.1N  61.6W   50 KT  60 MPH
 36H  03/1200Z 24.7N  62.5W   50 KT  60 MPH
 48H  04/0000Z 25.8N  62.7W   50 KT  60 MPH
 72H  05/0000Z 27.0N  62.5W   55 KT  65 MPH
 96H  06/0000Z 28.0N  62.5W   65 KT  75 MPH
120H  07/0000Z 29.5N  62.5W   70 KT  80 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 020858
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SUN SEP 02 2012
 
THE CENTER OF LESLIE REMAINS SHEARED TO THE NORTHWEST OF THE MAIN
CONVECTIVE CLOUD MASS. HOWEVER...CONVECTION HAS GRADUALLY BEEN
DEVELOPING CLOSER TO THE CENTER OVER THE PAST 6 HOURS...AND DVORAK
INTENSITY ESTIMATES FROM TAFB HAVE BEEN VARYING BETWEEN T3.0/45 KT
AND T3.5/55 KT. A 02/0134 UTC ASCAT OVERPASS INDICATED A PEAK WIND
VECTOR OF 51 KT SURROUNDED BY SEVERAL 50-KT VECTORS. ADJUSTING FOR
THE KNOWN LOW BIAS OF ASCAT WINDS YIELDS SURFACE WIND SPEEDS OF
NEAR 60 KT...AND THAT IS THE INTENSITY USED FOR THIS ADVISORY.

LESLIE IS MOVING NORTHWESTWARD...OR 310/13 KT. THE NHC MODEL
GUIDANCE REMAINS IN GOOD AGREEMENT ON LESLIE GRADUALLY TURNING
NORTHWARD AND ACCOMPANIED BY A DECREASE IN FORWARD SPEED DURING THE
NEXT 48 HOURS AS THE CYCLONE MOVES INTO A BREAK IN THE SUBTROPICAL
RIDGE BETWEEN 60-65W LONGITUDE. BY 72 HOURS...HOWEVER...THE BROAD
TROUGH/UPPER LOW CREATING THE BREAK IN THE RIDGE IS FORECAST TO
LIFT OUT TO THE NORTHEAST...WHICH WILL ALLOW A TRAILING SHORTWAVE
RIDGE TO BUILD IN TO THE NORTH OF LESLIE ON DAYS 4 AND 5. THIS
SHOULD RESULT IN A BLOCKING FLOW PATTERN DEVELOPING AROUND THE
CYCLONE THAT WILL CAUSE LESLIE TO SLOW DOWN TO LESS THAN 5 KT...AND
POSSIBLY EVEN BECOME STATIONARY DURING THE LATTER FORECAST PERIODS.
THE OFFICIAL FORECAST TRACK IS AN UPDATE OF THE PREVIOUS
TRACK...AND IS SIMILAR TO THE CONSENSUS MODELS TVCA AND TV15.
 
THE VERTICAL WIND SHEAR AFFECTING LESLIE IS EXPECTED TO BE MODERATE
FOR THE NEXT 24 HOURS OR SO...WHICH SHOULD CAP ANY SIGNIFICANT
INTENSIFICATION. AT 36 AND 48 HOURS...THE SHEAR IS FORECAST TO
INCREASE TO NEAR 30 KT...WHICH IS EXPECTED TO CAUSE THE CYCLONE TO
WEAKEN SOME. ASSUMING LESLIE SURVIVES THE DAY 2 HOSTILE SHEAR
CONDITIONS...THE UPPER-LEVEL WIND ENVIRONMENT IS FORECAST TO
IMPROVE AND BECOME CONDUCIVE FOR SIGNIFICANT STRENGTHENING TO
OCCUR. THE INTENSITY FORECAST REMAINS ON THE CONSERVATIVE SIDE AT
DAYS 4 AND 5 DUE TO THE UNCERTAINTY IN JUST HOW MUCH LESLIE WILL
WEAKEN OVER THE DAY 2-3 TIME PERIOD. THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND REMAINS ALONG
THE LOWER END OF THE GUIDANCE ENVELOPE NEAR THE SHIPS-LGEM
CONSENSUS.

THE INITIAL 34-KT AND 50-KT WIND RADII WERE INCREASED BASED ON WIND
DATA FROM THE AFOREMENTIONED ASCAT OVERPASS...WHICH CAPTURED THE
ENTIRE CIRCULATION OF LESLIE.

FORECAST POSITIONS AND MAX WINDS
 
INIT  02/0900Z 20.8N  59.5W   60 KT  70 MPH
 12H  02/1800Z 22.0N  60.9W   60 KT  70 MPH
 24H  03/0600Z 23.7N  62.1W   60 KT  70 MPH
 36H  03/1800Z 25.0N  62.6W   55 KT  65 MPH
 48H  04/0600Z 25.9N  62.7W   55 KT  65 MPH
 72H  05/0600Z 26.9N  62.4W   55 KT  65 MPH
 96H  06/0600Z 28.0N  62.5W   65 KT  75 MPH
120H  07/0600Z 29.2N  63.0W   70 KT  80 MPH
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 021458
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST SUN SEP 02 2012
 
LESLIE REMAINS A SHEARED TROPICAL CYCLONE.  THE LOW-LEVEL CENTER
BECAME WELL-SEPARATED FROM THE MAIN AREA OF SHOWERS AND
THUNDERSTORMS EARLY THIS MORNING...BUT WITHIN THE PAST HOUR OR TWO
A NEW BURST OF CONVECTION HAS DEVELOPED A LITTLE CLOSER TO THE
CENTER.  EARLIER ASCAT DATA INDICATED THAT THE AREA OF STRONGEST
WINDS WAS LOCATED WELL EAST OF THE CENTER AND THEY HAVE LIKELY
PASSED VERY CLOSE TO NOAA BUOY 41044 THIS MORNING.  THE BUOY HAS
REPORTED PEAK 1-MINUTE WINDS OF 43-47 KT DURING THE PAST SEVERAL
HOURS.  HOWEVER...SINCE STRONGER WINDS MAY BE OCCURRING IN THE
CONVECTION...THE INITIAL WIND SPEED IS SET AT 55 KT.
 
NORTHWESTERLY SHEAR IS EXPECTED TO CONTINUE PLAGUING LESLIE
DURING THE NEXT SEVERAL DAYS.  IN FACT...IT IS FORECAST TO BECOME
STRONGER BETWEEN 24 AND 60 HOURS...WHICH SHOULD CAUSE LESLIE TO
WEAKEN A LITTLE. DURING THIS TIME...THE NHC FORECAST FOLLOWS THE
LGEM GUIDANCE...WHICH TYPICALLY HANDLES THE INTENSITY OF TROPICAL
CYCLONES BETTER IN EVOLVING SHEAR CONDITIONS.  AT DAYS 4 AND
5...THE SHEAR IS FORECAST TO RELAX AND LESLIE IS EXPECTED TO BE IN
A MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING.  AS A RESULT...THE
NHC FORECAST CALLS FOR INTENSIFICATION LATE IN THE FORECAST PERIOD.
 
VISIBLE SATELLITE IMAGERY SHOWS THAT LESLIE WAS LOCATED A LITTLE
WEST OF THE PREVIOUS TRACK AND THAT IT HAS SLOWED DOWN DURING THE
PAST COUPLE OF HOURS.  HOWEVER...THE LONGER TERM MOTION ESTIMATE IS
NORTHWESTWARD OR 305 DEGREES AT 13 KT. THE TRACK GUIDANCE IS IN
GOOD AGREEMENT ON MOVING LESLIE NORTHWESTWARD...THEN TURNING IT
NORTHWARD IN 24-36 HOURS AS IT MOVES TOWARD A BREAK IN THE
SUBTROPICAL RIDGE.  AFTER THAT TIME...A MID-LATITUDE TROUGH IS
FORECAST TO BY-PASS LESLIE WHILE A MID-LEVEL RIDGE BUILDS OVER THE
WESTERN ATLANTIC.  THIS SHOULD CAUSE LESLIE TO MOVE VERY SLOWLY
NORTHWARD DURING THE REMAINDER OF THE FORECAST PERIOD.  THE NHC
TRACK HAS BEEN SHIFTED A LITTLE WESTWARD...PARTIALLY DUE TO THE
MORE WESTWARD INITIAL POSITION.  THE NEW TRACK IS NEAR THE MIDDLE
OF THE GUIDANCE ENVELOPE AND BETWEEN THE ECMWF AND GFS MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/1500Z 21.3N  61.1W   55 KT  65 MPH
 12H  03/0000Z 23.0N  62.5W   55 KT  65 MPH
 24H  03/1200Z 24.5N  63.4W   50 KT  60 MPH
 36H  04/0000Z 25.5N  63.6W   50 KT  60 MPH
 48H  04/1200Z 26.2N  63.6W   50 KT  60 MPH
 72H  05/1200Z 27.3N  63.5W   50 KT  60 MPH
 96H  06/1200Z 28.3N  63.5W   55 KT  65 MPH
120H  07/1200Z 29.5N  64.0W   65 KT  75 MPH
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 022047
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST SUN SEP 02 2012
 
THE OVERALL SATELLITE PRESENTATION OF LESLIE HAS CHANGED LITTLE
DURING THE DAY...AS THE CENTER REMAINS EXPOSED TO THE NORTHWEST OF
THE DEEP CONVECTION DUE TO MODERATE TO STRONG NORTHWESTERLY SHEAR.
AN ASCAT PASS THAT ARRIVED SHORTLY AFTER THE RELEASE OF THE
PREVIOUS ADVISORY SHOWED A LARGE AREA OF 40-45 KT WINDS WELL TO THE
NORTHEAST OF THE CENTER.  BASED ON ASCAT DATA...THE INTENSITY IS
REDUCED TO 50 KT.
 
THE NORTHWESTERLY SHEAR IS EXPECTED TO CONTINUE OVER THE CYCLONE
DURING THE NEXT COUPLE OF DAYS.  SINCE LESLIE HAS SUCH A LARGE
CIRCULATION AND WIND FIELD...IT IS LIKELY TO CHANGE LITTLE IN
INTENSITY DURING THAT TIME.  AFTER 48 HOURS...THE SHEAR IS
FORECAST TO GRADUALLY SUBSIDE...AND THE REMAINING ENVIRONMENT
CONDITIONS APPEAR FAVORABLE FOR STRENGTHENING.  THE GFDL AND HWRF
MODELS BRING LESLIE TO HURRICANE STRENGTH IN 3-4 DAYS AND THE
GLOBAL MODELS ALSO SHOW SIGNIFICANT DEEPING BY LATE IN THE PERIOD.
THE NHC FORECAST CALLS FOR GRADUAL INTENSIFICATION AFTER 48 HOURS
AND REMAINS SOMEWHAT CONSERVATIVE SINCE IT IS UNCLEAR HOW THE
STRUCTURE OF LESLIE WILL EVOLVE IN THE SHORT-TERM.  THE NHC
FORECAST IS CLOSEST THE LGEM GUIDANCE...WHICH IS HISTORICALLY
THE BEST PERFORMING INTENSITY MODEL.
 
AFTER HESITATING THIS MORNING...LESLIE HAS RESUMED A NORTHWESTWARD
MOTION AT AROUND 9 KT.  THE TROPICAL STORM SHOULD CONTINUE
NORTHWESTWARD TONIGHT...THEN TURN NORTHWARD IN 24-36 HOURS
AS IT MOVES TOWARD A BREAK IN THE SUBTROPICAL RIDGE.  AFTER THAT
TIME...LESLIE IS EXPECTED TO SLOW DOWN AS A MID-LEVEL RIDGE BUILDS
OVER THE WESTERN ATLANTIC.  THERE IS MORE SPREAD IN THE TRACK
GUIDANCE AFTER 48 HOURS THAN THERE WAS THIS MORNING.  THE ECMWF AND
GFS MODEL TRACKS ARE NOW SEVERAL HUNDRED MILES APART...WITH THE GFS
ALONG THE EAST SIDE OF THE GUIDANCE ENVELOPE...AND THE ECMWF THE
WESTERNMOST MODEL.  GIVEN THIS SPREAD...THE UPDATED TRACK IS
BETWEEN THE MULTI-MODEL CONSENSUS AND THE PREVIOUS NHC FORECAST.
BECAUSE OF THE INCREASED SPREAD...THERE IS A LITTLE LESS CONFIDENCE
IN THE TRACK FORECAST THAN BEFORE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  02/2100Z 22.4N  61.3W   50 KT  60 MPH
 12H  03/0600Z 23.3N  62.3W   50 KT  60 MPH
 24H  03/1800Z 24.6N  62.9W   50 KT  60 MPH
 36H  04/0600Z 25.5N  63.1W   50 KT  60 MPH
 48H  04/1800Z 26.0N  63.0W   50 KT  60 MPH
 72H  05/1800Z 26.9N  62.9W   60 KT  70 MPH
 96H  06/1800Z 28.0N  63.0W   65 KT  75 MPH
120H  07/1800Z 29.5N  63.5W   70 KT  80 MPH
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 030240
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SUN SEP 02 2012
 
LESLIE CONTINUES TO BE UNDER THE INFLUENCE OF STRONG NORTHWESTERLY
SHEAR.  ALTHOUGH THE CLOUD TOPS ARE QUITE COLD...SUGGESTING VIGOROUS
DEEP CONVECTION...THERE IS LITTLE EVIDENCE OF BANDING FEATURES AS
THE CLOUD PATTERN HAS THE APPEARANCE OF AN AMORPHOUS BLOB.  SINCE
THERE HAVE BEEN NO NOTABLE CHANGES IN THE APPEARANCE OF THE SYSTEM
OVER THE PAST SEVERAL HOURS...THE INTENSITY ESTIMATE IS HELD AT 50
KT FOR THIS ADVISORY.  THE SHEAR IS EXPECTED TO REMAIN PROHIBITIVE
FOR SIGNIFICANT STRENGTHENING DURING THE NEXT COUPLE OF DAYS. 
AFTERWARDS...DYNAMICAL MODELS PREDICT THAT THE UPPER-LEVEL WINDS
WILL BECOME MORE CONDUCIVE FOR INTENSIFICATION WITH INCREASING
UPPER-LEVEL ANTICYCLONIC OUTFLOW OVER THE SYSTEM.  THE OFFICIAL
WIND SPEED FORECAST IS THE SAME AS THE PREVIOUS ONE...AND IS IN
CLOSE AGREEMENT WITH THE LATEST LGEM GUIDANCE.

AN SSM/IS IMAGE FROM A FEW HOURS AGO INDICATED THAT THE CENTER WAS
LOCATED A LITTLE FARTHER NORTH OF THE PREVIOUS ESTIMATES...AND THE
WORKING BEST TRACK HAS BEEN ADJUSTED ACCORDINGLY.  EVEN WITH THE
SLIGHT NORTHWARD RELOCATION...THE INITIAL MOTION ESTIMATE...
325/9...IS NOT CHANGED MUCH FROM THE PREVIOUS ADVISORY.  LESLIE IS
MOVING TOWARD A BREAK IN THE SUBTROPICAL RIDGE...HOWEVER...THE
GLOBAL MODELS INDICATE THAT THE RIDGE WILL BUILD SOMEWHAT TO THE
NORTHWEST AND NORTH OF THE TROPICAL CYCLONE IN A FEW DAYS.  AS A
RESULT...THE FORWARD MOTION OF THE STORM IS LIKELY TO SLOW DURING
THE NEXT 48-72 HOURS.  THE OFFICIAL TRACK FORECAST IS NOT TOO
DIFFERENT FROM THE PREVIOUS ONE AND NOT FAR FROM THE MULTI-MODEL
CONSENSUS TVCA.  THIS IS BETWEEN THE LATEST GFS AND GFS ENSEMBLE
MEAN FORECASTS AND THE ECMWF TRACK...WITH THE LATTER MODEL BEING
FASTER THAN MOST OF THE OTHER GUIDANCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0300Z 23.4N  61.7W   50 KT  60 MPH
 12H  03/1200Z 24.4N  62.2W   50 KT  60 MPH
 24H  04/0000Z 25.4N  62.6W   50 KT  60 MPH
 36H  04/1200Z 26.0N  62.7W   50 KT  60 MPH
 48H  05/0000Z 26.6N  62.7W   50 KT  60 MPH
 72H  06/0000Z 27.5N  62.7W   60 KT  70 MPH
 96H  07/0000Z 28.5N  63.0W   65 KT  75 MPH
120H  08/0000Z 30.0N  63.5W   70 KT  80 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 030844
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST MON SEP 03 2012
 
A TREMENDOUS BURST OF DEEP CONVECTION CONTAINING CLOUD TOP
TEMPERATURES OF -84C TO -88C HAS PERSISTED NEAR THE CENTER AND OVER
THE SOUTHERN SEMICIRCLE FOR MORE THAN 6 HOURS. THE CLOUD CANOPY HAS
GRADUALLY BEEN EXPANDING NORTHWARD...WHICH SUGGESTS THAT THE
VERTICAL SHEAR IS NOT AS STRONG AS SOME OF THE MODELS HAVE BEEN
INDICATING. RECENT MICROWAVE FIXES SUGGEST THAT THE LOW-LEVEL
CIRCULATION CENTER IS LOCATED JUST INSIDE THE NORTHWESTERN PORTION
OF THE MASSIVE CONVECTIVE CLOUD SHIELD. SATELLITE INTENSITY
ESTIMATES USING A SHEAR PATTERN ARE T3.5/55 KT FROM TAFB AND
T3.0/45 KT FROM SAB...PLUS AN ADT ESTIMATE T3.2/49 KT. GIVEN THE
UNCERTAINTY IN THE EXACT LOCATION OF THE SURFACE CENTER...THE
INTENSITY WILL REMAIN 50 KT FOR THIS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 335/07 KT. OTHER THAN A FEW WOBBLES
HERE AND THERE...LESLIE HAS REMAINED BASICALLY ON TRACK. OVER THE
NEXT 48 HOURS...THE LATEST MODEL GUIDANCE CONTINUES TO INDICATE
THAT LESLIE WILL MOVE TOWARD A BREAK IN THE SUBTROPICAL RIDGE THAT
IS BEING INDUCED BY A SHORTWAVE TROUGH LOCATED ALONG 65W. AS THE
TROUGH CONTINUES TO MOVE EASTWARD...THE RIDGE WILL BUILD BACK IN TO
THE NORTH OF THE CYCLONE AND CAUSE IT TO SLOW DOWN CONSIDERABLY ON
DAYS 3 AND 4. HOWEVER...BY DAY 5...A SHORTWAVE TROUGH/UPPER-LOW
CURRENTLY LOCATED OVER THE BAHAMAS IS FORECAST TO MOVE EASTWARD AND
ACT TO LIFT LESLIE NORTHWARD OR NORTH-NORTHWESTWARD AT A FASTER
FORWARD SPEED. THE OFFICIAL FORECAST IS IN THE MIDDLE OF THE FAIRLY
TIGHT GUIDANCE ENVELOPE...AND LIES BETWEEN THE DYNAMICAL CONSENSUS
MODELS TVCA AND TV15.
 
THE GFS-BASED SHIPS MODEL IS CURRENTLY INDICATING MORE THAN 20 KT OF
WEST-NORTHWESTERLY VERTICAL SHEAR ON THE CYCLONE...WHICH APPEARS TO
BE OVERDONE DUE TO THE 500 KM RADIUS USED BY THAT MODEL TO COMPUTE
SHEAR. THE LATEST UW-CIMSS SHEAR ANALYSIS INDICATES ONLY ABOUT 15
KT OF SHEAR...WHICH SEEMS MORE REASONABLE GIVEN THE TREMENDOUS
AMOUNT OF DEEP CONVECTION THAT HAS PERSISTED SINCE THE PREVIOUS
ADVISORY. THE SHIPS MODEL IS FORECASTING THE SHEAR TO INCREASE TO
NEAR 30 KT FROM THE NORTHWEST OVER THE NEXT 24 HOURS. ALTHOUGH
THESE SHEAR VALUES MAY BE SOMEWHAT OVERDONE...EVEN AN INCREASE IN
TO AROUND 20 KT SHOULD BE ENOUGH TO HINDER THE INTENSIFICATION
PROCESS FOR THE NEXT 24-36 HOURS. AFTER THAT...HOWEVER...THE SHEAR
IS FORECAST TO GRADUALLY SUBSIDE AND ALL OF THE GLOBAL MODELS BUILD
AN UPPER-LEVEL RIDGE OVER LESLIE AS THE CYCLONE MOVES BETWEEN THE
UPPER-LEVEL LOW OVER THE BAHAMAS AND A DIGGING TROUGH ALONG 50W ON
DAYS 4 AND 5. THIS FLOW PATTERN SHOULD CREATE CONDITIONS MORE
CONDUCIVE FOR INTENSIFICATION.  THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY...EXCEPT AT DAY 5 WHERE THE
FORECAST IS HIGHER...BASED ON A BLEND OF THE SHIPS AND HWRF MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0900Z 23.8N  62.1W   50 KT  60 MPH
 12H  03/1800Z 24.7N  62.5W   50 KT  60 MPH
 24H  04/0600Z 25.5N  62.8W   50 KT  60 MPH
 36H  04/1800Z 26.1N  62.9W   50 KT  60 MPH
 48H  05/0600Z 26.6N  62.9W   55 KT  65 MPH
 72H  06/0600Z 27.6N  62.9W   60 KT  70 MPH
 96H  07/0600Z 28.7N  63.3W   70 KT  80 MPH
120H  08/0600Z 30.8N  64.1W   80 KT  90 MPH
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 031450
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST MON SEP 03 2012
 
LESLIE CONTINUES TO BE AFFECTED BY ABOUT 15 KT OF NORTHWESTERLY
SHEAR...ACCORDING TO ANALYSIS FROM UW-CIMSS. THIS SHEAR HAS CAUSED
THE CONVECTIVE PATTERN TO BE QUITE ASYMMETRIC WITH NEARLY ALL OF
THE COLD CLOUD TOPS CONFINED TO THE SOUTHEASTERN PORTION OF THE
CIRCULATION. THERE HAS BEEN LITTLE CHANGE IN THE DVORAK
CLASSIFICATIONS THIS CYCLE...SO THE INITIAL INTENSITY IS HELD AT 50
KT. THE SHIPS MODEL SHOWS THE SHEAR INCREASING A LITTLE OVER THE
NEXT 24 HOURS...WHICH SHOULD LIMIT THE STORM FROM STRENGTHENING
DURING THAT TIME PERIOD. AFTER THAT...HOWEVER...THE SHEAR IS
EXPECTED TO RELAX AND GIVEN THAT THE OTHER ATMOSPHERIC AND OCEANIC
CONDITIONS APPEAR FAVORABLE...LESLIE WILL LIKELY HAVE AN
OPPORTUNITY TO GAIN STRENGTH. THE OFFICIAL FORECAST IS SIMILAR TO
THE PREVIOUS ONE AND BASICALLY A BLEND OF THE SHIPS AND LGEM
GUIDANCE.
 
RECENT MICROWAVE DATA AND VISIBLE SATELLITE IMAGES INDICATE THAT THE
CENTER OF LESLIE WAS LOCATED A LITTLE TO THE WEST OF THE PREVIOUS
TRACK. BLENDING THE MICROWAVE DATA WITH EARLIER SATELLITE FIXES
YIELDS AN INITIAL MOTION ESTIMATE OF 330/7. LESLIE IS CURRENTLY
MOVING TOWARD A DEEP-LAYER TROUGH TO ITS NORTH. THIS TROUGH IS
EXPECTED TO SHIFT TO THE EAST...CAUSING THE STEERING CURRENTS TO
WEAKEN DURING THE NEXT DAY OR SO. THEREFORE...LESLIE IS ONLY
EXPECTED TO DRIFT NORTHWARD DURING THE 24 TO 72 HOUR TIME PERIOD.
LATE IN THE WEEK...THE COMBINED INFLUENCES OF A MID- TO UPPER-LEVEL
LOW OFF THE SOUTHEAST U.S. COAST AND A RIDGE TO THE EAST OF LESLIE
SHOULD CAUSE THE CYCLONE TO MOVE NORTH-NORTHWESTWARD OR NORTHWARD
AT A FASTER PACE. THE OFFICIAL FORECAST IS ADJUSTED ABOUT 30 N MI
TO THE WEST OF THE PREVIOUS TRACK DUE TO THE MORE WESTWARD INITIAL
POSITION.
 
DUE TO THE LARGE SIZE OF THE CYCLONE AND EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL AFFECT
BERMUDA AND NEARLY ALL OF THE U.S. EAST COAST FOR MUCH OF THE WEEK.

FORECAST POSITIONS AND MAX WINDS
 
INIT  03/1500Z 24.4N  63.1W   50 KT  60 MPH
 12H  04/0000Z 25.2N  63.2W   50 KT  60 MPH
 24H  04/1200Z 25.8N  63.3W   50 KT  60 MPH
 36H  05/0000Z 26.3N  63.4W   55 KT  65 MPH
 48H  05/1200Z 26.8N  63.5W   55 KT  65 MPH
 72H  06/1200Z 27.7N  63.6W   65 KT  75 MPH
 96H  07/1200Z 29.0N  64.0W   75 KT  85 MPH
120H  08/1200Z 31.5N  64.5W   80 KT  90 MPH
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 032034
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST MON SEP 03 2012
 
SOME DEEP CONVECTION HAS DEVELOPED CLOSE TO THE LOW-LEVEL CENTER OF
LESLIE RECENTLY...BUT THE OVERALL CLOUD PATTERN IS STILL HIGHLY
ASYMMETRIC DUE TO WEST-NORTHWESTERLY SHEAR. SATELLITE INTENSITY
ESTIMATES FROM TAFB...SAB...AND UW-CIMSS SUPPORT MAINTAINING THE
INITIAL WIND SPEED AT 50 KT. THE SHEAR IS NOT EXPECTED TO LET UP
MUCH FOR THE NEXT 12 TO 18 HOURS...SO LESLIE IS EXPECTED TO CHANGE
LITTLE IN STRENGTH DURING THAT TIME. AFTER THAT...HOWEVER...THE
SHEAR IS FORECAST TO LESSEN AND THE GLOBAL MODELS SHOW AN
UPPER-LEVEL WIND PATTERN THAT IS QUITE FAVORABLE FOR THE CYCLONE TO
INTENSIFY. THE OFFICIAL WIND SPEED FORECAST IS AN UPDATE OF THE
PREVIOUS ONE AND CLOSE TO AN AVERAGE OF THE LATEST SHIPS AND LGEM
GUIDANCE. 

LESLIE HAS BEEN WOBBLING AROUND MOST OF THE DAY...AND THE LATEST
VISIBLE IMAGES INDICATE THAT THE CENTER IS LOCATED TO THE SOUTH OF
THE PREVIOUS ADVISORY POSITION. A LONGER-TERM MOTION ESTIMATE IS
330/3. A VERY SLOW NORTHWARD MOTION IS FORECAST FOR THE NEXT 3 TO 4
DAYS AS LESLIE REMAINS IN WEAK STEERING CURRENTS. BY THE END OF THE
WEEK...A RIDGE IS EXPECTED TO BUILD TO THE EAST OF THE TROPICAL
CYCLONE WHICH SHOULD STEER LESLIE TO THE NORTH-NORTHWEST AT A
FASTER PACE. THE 12Z ECMWF MODEL HAS SHIFTED WELL TO THE WEST AT
DAYS 4 AND 5...AND THERE IS NOW A WIDE SPREAD IN THE MODEL
GUIDANCE. THE OFFICIAL FORECAST IS SLOWER THAN THE PREVIOUS ONE AND
A LITTLE TO THE LEFT AT DAY 5. THIS FORECAST LIES FAIRLY CLOSE TO
THE CONSENSUS AIDS...TVCA AND TV15.
  
DUE TO THE LARGE SIZE OF THE CYCLONE AND EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL AFFECT
BERMUDA AND NEARLY ALL OF THE U.S. EAST COAST FOR MUCH OF THE WEEK.
 
THE 34-KT AND 50-KT WIND RADII WERE MODIFIED BASED ON A 1340 UTC
ASCAT PASS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 24.0N  63.1W   50 KT  60 MPH
 12H  04/0600Z 24.6N  63.2W   50 KT  60 MPH
 24H  04/1800Z 25.3N  63.2W   55 KT  65 MPH
 36H  05/0600Z 25.8N  63.2W   55 KT  65 MPH
 48H  05/1800Z 26.3N  63.2W   60 KT  70 MPH
 72H  06/1800Z 27.0N  63.3W   70 KT  80 MPH
 96H  07/1800Z 28.1N  63.8W   80 KT  90 MPH
120H  08/1800Z 30.5N  65.0W   85 KT 100 MPH
 
$$
FORECASTER CANGIALOSI
 

WTNT42 KNHC 040256
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST MON SEP 03 2012
 
WEST-NORTHWESTERLY SHEAR CONTINUES TO KEEP THE STORM FROM BECOMING
BETTER ORGANIZED...WITH THE MAIN MASS OF DEEP CONVECTION DISPLACED
TO THE SOUTHEAST OF THE ESTIMATED CENTER LOCATION.  HOWEVER...A
RECENT ASCAT OVERPASS INDICATES THAT SOME SLIGHT STRENGTHENING HAS
OCCURRED...AND BASED ON THE SCATTEROMETER DATA THE CURRENT
INTENSITY IS SET TO 55 KT.  THIS IS ALSO CONSISTENT WITH THE LATEST
DVORAK ESTIMATES FROM TAFB AND SAB.  NOT MUCH ADDITIONAL
INTENSIFICATION IS LIKELY IN THE SHORT TERM AS THE DYNAMICAL
GUIDANCE DOES NOT SHOW THE SHEAR RELAXING SIGNIFICANTLY FOR THE NEXT
24 TO 36 HOURS.  LATER ON...HOWEVER...THE GLOBAL MODELS ARE
INSISTENT THAT THE UPPER-LEVEL WIND PATTERN WILL BECOME MORE
CONDUCIVE FOR STRENGTHENING...AS THE GFS DEPICTS A WELL-DEFINED AND
SYMMETRICAL UPPER-TROPOSPHERIC ANTICYCLONE BECOMING ESTABLISHED
OVER LESLIE IN ABOUT 72 HOURS.  THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THAT FROM THE PREVIOUS ADVISORY...AND IS CLOSE TO A
BLEND OF THE LATEST LGEM AND SHIPS PREDICTIONS.
 
MICROWAVE AND GEOSTATIONARY SATELLITE FIXES INDICATE THAT THE STORM
HAS MOVED VERY LITTLE...IF AT ALL...SO THE INTIAL MOTION ESTIMATE
IS STATIONARY.  LESLIE IS EXPECTED TO MOVE QUITE SLOWLY IN A
GENERAL NORTHWARD DIRECTION WHILE IT REMAINS IN VERY WEAK STEERING
CURRENTS FOR A GOOD PART OF THE FORECAST PERIOD.  BY ABOUT 5
DAYS...THE FLOW BETWEEN A MID-TROPOSPHERIC TROUGH OVER THE EASTERN
U.S. AND AN ANTICYCLONE TO THE NORTHEAST OF THE TROPICAL CYCLONE
SHOULD INDUCE A SLIGHTLY FASTER NORTH-NORTHWESTWARD MOTION.  THE
OFFICIAL TRACK FORECAST IS ABOUT THE SAME AS THAT FROM THE PREVIOUS
ADVISORY AND REMAINS CLOSE TO THE MULTI-MODEL CONSENSUS TVCN.
 
BUOY OBSERVATIONS SHOW THAT WAVES GREATER THAN 12 FEET HIGH EXTEND
SOME 300-400 N MI FROM THE CENTER.  DUE TO THE LARGE SIZE OF THE
TROPICAL CYCLONE AND ITS EXPECTED SLOW MOTION...LARGE SWELLS
PROPAGATING AWAY FROM LESLIE WILL AFFECT BERMUDA AND NEARLY ALL OF
THE U.S. EAST COAST FOR MUCH OF THE WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0300Z 24.0N  63.1W   55 KT  65 MPH
 12H  04/1200Z 24.6N  63.2W   55 KT  65 MPH
 24H  05/0000Z 25.3N  63.2W   55 KT  65 MPH
 36H  05/1200Z 25.8N  63.2W   55 KT  65 MPH
 48H  06/0000Z 26.3N  63.2W   60 KT  70 MPH
 72H  07/0000Z 27.2N  63.5W   70 KT  80 MPH
 96H  08/0000Z 28.5N  64.0W   80 KT  90 MPH
120H  09/0000Z 31.0N  65.0W   85 KT 100 MPH
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 040839
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST TUE SEP 04 2012
 
AFTER AN EARLIER BURST OF DEEP CONVECTION SHORTLY AFTER THE PREVIOUS
ADVISORY...CLOUD TOPS HAVE WARMED CONSIDERABLY. ALTHOUGH THE
SHEARED CONVECTIVE CLOUD SHIELD HAS TAKEN ON A SMOOTHER
APPEARANCE...THE INTENSITY WILL REMAIN AT 55 KT BASED ON DVORAK
CI-VALUES OF T3.5/55 KT FROM BOTH TAFB AND SAB.

MICROWAVE FIXES THAT ARRIVED AFTER THE PREVIOUS ADVISORY SUGGEST
THAT LESLIE HAD...IN FACT...MOVED LITTLE...BUT WAS ALSO LOCATED A
LITTLE FARTHER TO THE EAST. THE GENERAL MOTION TREND OF THE OVERALL
CLOUD MASS NOW SUGGESTS THAT LESLIE HAS RESUMED A SLOW NORTHWARD
MOTION OF 360/03 KT. WATER VAPOR IMAGERY AND SATELLITE-DERIVED
WINDS INDICATE A DEEP-LAYER TROUGH NORTH-NORTHEAST OF LESLIE HAS
BYPASSED THE CYCLONE WHILE A SHORTWAVE RIDGE OFF THE CAROLINAS IS
BUILDING EASTWARD IN THE WAKE OF THE TROUGH. THE INCREASED RIDGING
TO THE NORTH OF LESLIE IS EXPECTED TO HINDER ANY SIGNIFICANT
FORWARD MOTION FOR THE NEXT 4 DAYS. BY DAY 5...HOWEVER...A LARGE
MID-TROPOSPHERIC TROUGH CURRENTLY OVER THE PACIFIC NORTHWEST IS
FORECAST TO DIG SOUTHEASTWARD INTO THE TENNESSEE VALLEY BY DAY 5
AND GRADUALLY BEGINS TO LIFT THE CYCLONE NORTH-NORTHWESTWARD. 
THE OFFICIAL TRACK FORECAST IS NUDGED SLIGHTLY TO THE EAST OF THE
PREVIOUS TRACK THROUGH DAY 3...AND THEN IS BACK ON TRACK AT DAYS 4
AND 5. THIS SCENARIO CLOSELY FOLLOWS THE CONSENSUS MODEL TVCN.

LITTLE OR NO INTENSIFICATION IS EXPECTED THROUGH 36 HOURS DUE TO
MODERATE WEST-NORTHWESTERLY VERTICAL WIND SHEAR IMPINGING ON THE
CYCLONE. HOWEVER...GRADUAL STRENGTHENING IS FORECAST AT 48 HOURS
AND BEYOND AS THE SHEAR DECREASES AND AN IMPRESSIVE UPPER-LEVEL
ANTICYCLONE BUILDS OVER LESLIE. AN UPPER-LEVEL TROUGH CURRENTLY
OVER THE NORTHWESTERN BAHAMAS...IN CONJUNCTION WITH ANOTHER
UPPER-LEVEL TROUGH FORECAST TO DEVELOP ALONG 50W LONGITUDE...IS
EXPECTED TO ENHANCE THE OUTFLOW OF LESLIE ON DAY 5. THE GFS-BASED
SHIPS AND LGEM MODELS APPEAR TO BE SUFFERING FROM NEGATIVE FEEDBACK
AT DAYS 4-5 CAUSED BY 200/250 MB WARMING DUE TO THE GFS MODEL
MAKING LESLIE A SIGNIFICANT TROPICAL CYCLONE BY THAT TIME. IN
FACT...THE ECMWF ALSO IS FORECASTING SIGNIFICANT DEVELOPMENT OF
LESLIE ON DAYS 4-5...AS INDICATED BY 130-KT 850 MB WINDS ON DAY 5.
THE GFS IS SIMILAR IN STRENGTH WITH 115-KT 850 MB WINDS ALSO ON DAY
5. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS 
ADVISORY...BUT SHOWS A SLIGHTLY HIGHER INTENSITY ON DAY 5...WHICH
IS CLOSER TO THE CONSENSUS INTENSITY MODEL ICON.
 
WIND RADII WERE ADJUSTED IN ALL QUADRANTS BASED ON A 04/0054 UTC
ASCAT OVERPASS AND A 37-KT WIND REPORT FROM SHIP DPJK...WHICH WAS
LOCATED ABOUT 180 NMI SOUTH OF THE CENTER. DUE TO THE LARGE SIZE OF
LESLIE AND ITS EXPECTED SLOW MOTION...LARGE SWELLS PROPAGATING AWAY
FROM THE TROPICAL CYCLONE WILL AFFECT BERMUDA AND NEARLY ALL OF
THE U.S. EAST COAST FOR MUCH OF THIS WEEK.

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0900Z 24.7N  62.5W   55 KT  65 MPH
 12H  04/1800Z 25.3N  62.5W   55 KT  65 MPH
 24H  05/0600Z 25.9N  62.6W   55 KT  65 MPH
 36H  05/1800Z 26.4N  62.6W   55 KT  65 MPH
 48H  06/0600Z 26.7N  62.6W   60 KT  70 MPH
 72H  07/0600Z 27.6N  63.1W   70 KT  80 MPH
 96H  08/0600Z 29.1N  64.1W   80 KT  90 MPH
120H  09/0600Z 32.0N  65.3W   90 KT 105 MPH
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 041442
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST TUE SEP 04 2012

DEEP CONVECTION HAS DECREASED NEAR THE CENTER OF LESLIE OVER THE
PAST FEW HOURS. ALTHOUGH THERE IS STILL EVIDENCE OF ABOUT 20 KT OF
NORTHWESTERLY SHEAR...THE CONVECTIVE CLOUD STRUCTURE NOW MORE
RESEMBLES A CURVED BAND PATTERN. RECENT MICROWAVE DATA AND VISIBLE
SATELLITE IMAGES INDICATE THAT THE SHEAR HAS CONTINUED TO CAUSE THE
CIRCULATION TO BE VERTICALLY TILTED AND THE LOW-LEVEL CENTER IS
DISPLACED ABOUT 30 N MI TO THE WEST OF THE MID-LEVEL CENTER. THE
INITIAL WIND SPEED IS HELD AT 55 KT...IN AGREEMENT WITH DVORAK
CI-NUMBERS FROM TAFB AND SAB...BUT THIS COULD BE GENEROUS. LITTLE
CHANGE IN STRENGTH IS FORECAST FOR THE NEXT 36 HOURS DUE TO THE
POOR VERTICAL ALIGNMENT OF LESLIE AND THE FORECAST SHEAR...WHICH IS
EXPECTED TO REMAIN HIGH DURING THAT TIME. IN A COUPLE OF DAYS...THE
SHEAR IS EXPECTED TO LESSEN AND THE NUMERICAL MODELS SHOW A MUCH
MORE FAVORABLE UPPER-LEVEL WIND PATTERN FOR LESLIE TO GAIN
STRENGTH. THEREFORE...THE OFFICIAL FORECAST REMAINS IN LINE WITH
THE PREVIOUS FORECAST AND IS BETWEEN LGEM AND HWRF GUIDANCE.

LESLIE IS MOVING VERY SLOWLY NORTHWARD AT ABOUT 3 KT AND IS LOCATED
IN WEAK STEERING CURRENTS. THE STEERING IS EXPECTED TO REMAIN WEAK
FOR THE NEXT COUPLE OF DAYS...THEREFORE LESLIE IS FORECAST TO
CONTINUE DRIFTING NORTHWARD DURING THAT TIME. BY THE END OF THE
WEEK...THE MODELS ARE IN FAIR AGREEMENT IN SHOWING A MID-LEVEL
RIDGE BUILDING TO THE NORTHEAST OF LESLIE. THIS SHOULD CAUSE THE
CYCLONE TO FIRST TURN NORTHWESTWARD AND THEN ACCELERATE
NORTH-NORTHWESTWARD IN 4 TO 5 DAYS AS IT MOVES ALONG THE WESTERN
PERIPHERY OF THE RIDGE. THE OFFICIAL FORECAST IS SIMILAR TO THE
PREVIOUS ONE AND CLOSE TO THE CONSENSUS AIDS...TV15 AND TVCA.

DUE TO THE LARGE SIZE OF LESLIE AND ITS EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL
CONTINUE TO AFFECT BERMUDA AND NEARLY ALL OF THE U.S. EAST
COAST FOR MUCH OF THIS WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 25.0N  62.5W   55 KT  65 MPH
 12H  05/0000Z 25.5N  62.5W   55 KT  65 MPH
 24H  05/1200Z 26.0N  62.5W   55 KT  65 MPH
 36H  06/0000Z 26.5N  62.5W   55 KT  65 MPH
 48H  06/1200Z 26.8N  62.6W   60 KT  70 MPH
 72H  07/1200Z 27.5N  63.3W   70 KT  80 MPH
 96H  08/1200Z 29.2N  64.6W   80 KT  90 MPH
120H  09/1200Z 33.0N  65.5W   90 KT 105 MPH
 
$$
FORECASTER CANGIALOSI/ZELINSKY
 

WTNT42 KNHC 042031
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST TUE SEP 04 2012
 
ALTHOUGH DEEP CONVECTION HAS REDEVELOPED NEAR THE CENTER OF LESLIE
DURING THE DAY...THE LOW-LEVEL CENTER IS STILL SOMEWHAT DISPLACED
TO THE WEST OF THE MID- AND UPPER-LEVEL CENTER. THE CI-NUMBERS FROM
TAFB AND SAB REMAIN 3.5 AND A RECENT ASCAT PASS SHOWED
BIAS-CORRECTED WINDS OF 50-55 KT...SO THE INITIAL INTENSITY IS HELD
AT 55 KT. 20 KT OF WEST-NORTHWESTERLY VERTICAL WIND SHEAR...AS
ANALYZED BY THE UW-CIMSS AND SHIPS SHEAR ANALYSIS...CONTINUES TO BE
THE PRIMARY INHIBITING FACTOR FOR DEVELOPMENT. THE SHEAR IS
FORECAST TO RELAX AFTER 36 HOURS...WHICH SHOULD ALLOW FOR
INTENSIFICATION. ADDITIONALLY...THE UNIVERSITY OF MIAMI-RSMAS OCEAN
ANALYSIS INDICATES THAT THE HEAT CONTENT OF THE OCEAN BELOW LESLIE
IS HIGH...WHICH MAY LIMIT THE IMPACTS OF COLD WATER UPWELLING FROM
THE SLOW-MOVING CYCLONE. THE FORECAST CALLS FOR STEADY
INTENSIFICATION AFTER 36 HOURS...AND IS CLOSE TO THE LGEM MODEL
FORECAST. BY DAY 5...THE OFFICIAL FORECAST IS HIGHER THAN MOST OF
THE NUMERICAL GUIDANCE...HOWEVER...GIVEN THE EXPECTED FAVORABLE
ENVIRONMENT AROUND THE CYCLONE...THE INTENSITY FORECAST HAS NOT
BEEN ADJUSTED DOWN AT THIS TIME.
 
WHILE THE CENTER HAS WOBBLED SLIGHTLY TO THE WEST DURING THE
DAY...LESLIE CONTINUES TO DRIFT GENERALLY NORTHWARD AND THE LONG-
TERM INITIAL MOTION IS ESTIMATED AT 360/3. THIS TRACK IS EXPECTED
TO CONTINUE FOR THE NEXT COUPLE OF DAYS UNTIL A RIDGE BEGINS TO
BUILD TO THE NORTHEAST OF THE TROPICAL CYCLONE...IMPARTING A MORE
NORTHWESTERLY MOTION. LESLIE SHOULD FINALLY BEGIN TO ACCELERATE AS
IT MOVES AROUND THIS RIDGE ON DAYS 4 AND 5. THE GLOBAL AND REGIONAL
DYNAMICAL MODELS ARE SHOWING A SLIGHTLY SLOWER AND WESTWARD TRACK
THIS CYCLE AND THE OFFICIAL FORECAST HAS BEEN NUDGED ACCORDINGLY.

THE 34- AND 50-KT WIND RADII WERE MODIFIED BASED ON A 1320 UTC ASCAT
PASS.
 
DUE TO THE LARGE SIZE OF LESLIE AND ITS EXPECTED SLOW MOTION...
LARGE SWELLS PROPAGATING AWAY FROM THE TROPICAL CYCLONE WILL
CONTINUE TO AFFECT BERMUDA AND NEARLY ALL OF THE U.S. EAST
COAST FOR MUCH OF THIS WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/2100Z 25.3N  62.6W   55 KT  65 MPH
 12H  05/0600Z 25.7N  62.7W   55 KT  65 MPH
 24H  05/1800Z 26.1N  62.7W   55 KT  65 MPH
 36H  06/0600Z 26.5N  62.7W   55 KT  65 MPH
 48H  06/1800Z 26.9N  62.8W   60 KT  70 MPH
 72H  07/1800Z 27.5N  63.5W   70 KT  80 MPH
 96H  08/1800Z 29.5N  65.0W   80 KT  90 MPH
120H  09/1800Z 34.0N  65.5W   90 KT 105 MPH
 
$$
FORECASTER ZELINSKY/CANGIALOSI
 

WTNT42 KNHC 050243
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST TUE SEP 04 2012
 
DEEP CONVECTION HAS BEEN BURSTING NEAR THE LOW-LEVEL CENTER OF
LESLIE FOR THE PAST FEW HOURS.  THE CONVECTION HAS TAKEN ON THE
SHAPE OF A NASCENT CENTRAL DENSE OVERCAST...BUT WEST-NORTHWESTERLY
SHEAR OF AROUND 20 KT CONTINUES TO PUSH THE MAIN CONVECTIVE MASS
EASTWARD.  TRMM AND SSM/IS IMAGES...FROM 2223 AND 0013 UTC
RESPECTIVELY...SUGGEST SOME RECENT INCREASE IN ORGANIZATION AS
EVIDENCED BY THE FORMATION OF A CLOSED MID-LEVEL EYE...BUT THIS
FEATURE CONTINUES TO BE DISPLACED 20-30 N MI EAST OF THE LOW-LEVEL
CENTER.  THE INITIAL INTENSITY IS HELD AT 55 KT IN AGREEMENT WITH A
0000 UTC SATELLITE CLASSIFICATION FROM TAFB. GLOBAL MODELS FORECAST
A SUBSTANTIAL DECREASE IN SHEAR IN ABOUT 24 HOURS AS A LARGE-SCALE
ANTICYCLONE FORMS OVER LESLIE. THE DEEP OCEANIC MIXED LAYER ALONG
THE TRACK OF THE SLOW-MOVING STORM SHOULD ALSO MINIMIZE THE EFFECTS
OF UPWELLING.  STRENGTHENING IS FORECAST TO BEGIN AROUND THE TIME
THE SHEAR RELAXES...BUT THE RATE OF INTENSIFICATION COULD INITIALLY
BE SLOW DUE TO THE LARGE SIZE OF THE CIRCULATION. THE NHC INTENSITY
FORECAST IS NOT MUCH DIFFERENT THAN THE PREVIOUS ONE...AND IS IN
GOOD AGREEMENT WITH THE LATEST SHIPS AND INTENSITY CONSENSUS AIDS.
 
LESLIE APPEARS TO HAVE JOGGED A BIT TO THE LEFT TODAY...AND IS
PLODDING ALONG TOWARD THE NORTH-NORTHWEST WITH AN INITIAL MOTION
ESTIMATE OF 345/02.  THE CYCLONE IS IN A WEAK STEERING
ENVIRONMENT...SANDWICHED BETWEEN TWO WEAK MID-LEVEL ANTICYCLONES. 
WHILE THIS PATTERN SHOULD ALLOW A NET NORTHWARD STEERING FLOW OVER
LESLIE DURING THE NEXT FEW DAYS...THE STORM IS LIKELY TO MAKE ONLY
SLOW PROGRESS DUE TO A WEAK BLOCKING LOW- TO MID-LEVEL RIDGE
SLIDING BY TO THE NORTH.  AS THAT RIDGE SHIFTS AND BUILDS TO THE
NORTHEAST IN 48-72 HOURS...LESLIE WILL BE DRAWN NORTHWARD MORE
QUICKLY.  THE FLOW BETWEEN THIS SAME RIDGE AND AN AMPLIFYING
SHORTWAVE TROUGH APPROACHING THE UNITED STATES EAST COAST ON DAYS
4-5 WILL BEGIN TO EJECT LESLIE TOWARD THE NORTH OR NORTH-NORTHEAST
BY THE END OF THE FORECAST PERIOD.  THE NHC TRACK FORECAST IS BIT
SLOWER THAN THE PREVIOUS ONE AFTER 48 HOURS IN DEFERENCE TO THE
LATEST GFS RUN...BUT IS ADJUSTED A BIT TO THE EAST AT LATER TIMES. 
THIS IS CLOSE TO THE MULTI-MODEL TVCA CONSENSUS.
 
LESLIE IS A LARGE TROPICAL CYCLONE AND IS FORECAST TO GROW FURTHER
IN SIZE DURING THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE
CYCLONE...IN COMBINATION WITH ITS EXPECTED SLOW MOTION...WILL HELP
TO GENERATE LARGE LONG-PERIOD SWELLS WHICH WILL PROPAGATE AWAY FROM
THE TROPICAL CYCLONE TOWARD BERMUDA BERMUDA AND MUCH OF THE UNITED
STATES EAST COAST FOR THE REMAINDER OF THIS WEEK.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0300Z 25.2N  62.8W   55 KT  65 MPH
 12H  05/1200Z 25.6N  62.9W   55 KT  65 MPH
 24H  06/0000Z 26.1N  63.0W   55 KT  65 MPH
 36H  06/1200Z 26.5N  63.0W   60 KT  70 MPH
 48H  07/0000Z 26.7N  63.0W   65 KT  75 MPH
 72H  08/0000Z 27.5N  63.8W   75 KT  85 MPH
 96H  09/0000Z 30.0N  65.0W   80 KT  90 MPH
120H  10/0000Z 35.0N  65.0W   90 KT 105 MPH
 
$$
FORECASTER KIMBERLAIN
 

WTNT42 KNHC 050859
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST WED SEP 05 2012
 
AFTER DEVELOPING A CDO-LIKE FEATURE EARLIER...THE DEEP CONVECTION IS
NOW DISPLACED TO THE EAST OF THE ESTIMATED CENTER LOCATION...LIKELY
DUE TO CONTINUED WEST-NORTHWESTERLY SHEAR OF AROUND 20 KT. THE
INITIAL INTENSITY REMAINS 55 KT BASED ON THE LATEST DVORAK ESTIMATE
FROM TAFB. ONLY GRADUAL STRENGTHENING IS EXPECTED FOR THE NEXT DAY
OR SO UNTIL THE SHEAR RELAXES...AND THE NHC INTENSITY FORECAST IS
BELOW THE INTENSITY CONSENSUS FOR THE FIRST 48 HOURS. CONDITIONS
APPEAR FAVORABLE FOR STEADIER INTENSIFICATION AFTER THAT TIME...AND
THE NHC FORECAST AT DAYS 3 THROUGH 5 IS CLOSE TO THE LATEST IVCN
CONSENSUS.
 
IT STILL APPEARS THAT THE LOW-LEVEL CENTER IS DISPLACED A BIT TO THE
WEST OF THE MID-LEVEL ROTATION SEEN IN SATELLITE IMAGERY...BUT THE
INITIAL POSITION AND MOTION OF 340/02 IS UNCERTAIN GIVEN A LACK OF
RECENT MICROWAVE IMAGERY. OVERALL THE SYNOPTIC REASONING REMAINS
UNCHANGED FOR THE TRACK FORECAST. LESLIE IS CAUGHT IN A REGION OF
WEAK STEERING BETWEEN TWO WEAK MID-LEVEL ANTICYCLONES...WHICH
SHOULD RESULT IN A SLOW NORTH-NORTHWESTWARD TO NORTHWARD MOTION FOR
THE NEXT 48 HOURS. BY 72 HOURS...A TROUGH BEGINS TO AMPLIFY OVER
EASTERN NORTH AMERICA WHILE A MID-LEVEL RIDGE BUILDS TO THE EAST OF
LESLIE...WHICH SHOULD RESULT IN A NORTHWARD ACCELERATION. WHILE
THERE IS STILL SOME SPREAD IN THE GUIDANCE REGARDING THE FORWARD
SPEED AND HEADING LATE IN THE PERIOD...THE MODELS HAVE TRENDED
TOWARD A MORE PROGRESSIVE SOLUTION WITH THE TROUGH MOVING OFF THE
U.S. EAST COAST. THIS SHOULD RESULT IN LESLIE TURNING A LITTLE TO
THE EAST OF DUE NORTH BY DAY 5 WITH AN INCREASE IN FORWARD SPEED.
THE NEW NHC TRACK IS LARGELY AN UPDATE OF THE PREVIOUS ONE BUT IS A
LITTLE FASTER AND FARTHER TO THE RIGHT AT DAY 5. THE NHC FORECAST
IS CLOSE TO THE LATEST TVCA CONSENSUS AND LIES ROUGHLY BETWEEN THE
ECMWF AND GEFS ENSEMBLE MEAN.

LESLIE IS A LARGE TROPICAL CYCLONE AND IS FORECAST TO GROW IN SIZE
DURING THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE CYCLONE...
COMBINED WITH ITS EXPECTED SLOW MOTION...WILL HELP TO GENERATE
LARGE LONG-PERIOD SWELLS THAT WILL PROPAGATE AWAY FROM THE TROPICAL
CYCLONE TOWARD BERMUDA AND MUCH OF THE U.S. EAST COAST FOR THE
REMAINDER OF THIS WEEK.
 
THE 34-KT WIND RADII WERE EXPANDED IN THE NORTHWEST QUADRANT BASED
ON OBSERVATIONS FROM NOAA BUOY 41049. 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 25.4N  62.9W   55 KT  65 MPH
 12H  05/1800Z 25.8N  63.0W   55 KT  65 MPH
 24H  06/0600Z 26.2N  63.1W   60 KT  70 MPH
 36H  06/1800Z 26.6N  63.1W   65 KT  75 MPH
 48H  07/0600Z 26.9N  63.3W   70 KT  80 MPH
 72H  08/0600Z 28.2N  64.2W   80 KT  90 MPH
 96H  09/0600Z 31.5N  65.0W   85 KT 100 MPH
120H  10/0600Z 37.5N  64.0W   90 KT 105 MPH
 
$$
FORECASTER BRENNAN
 

WTNT42 KNHC 062037
TCDAT2
 
HURRICANE LESLIE DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST THU SEP 06 2012
 
THERE HAS NOT BEEN A SIGNIFICANT CHANGE IN THE SATELLITE
PRESENTATION DURING THE DAY WITH THE EXCEPTION THAT THE OVERALL
CLOUD PATTERN IS A LITTLE SMALLER. THERE IS A CONVECTIVE BAND
WRAPPING AROUND A SMALL CENTRAL DENSE OVERCAST...WHICH GIVES THE
APPEARANCE OF BETTER ORGANIZATION. HOWEVER...MICROWAVE DATA DOES NOT
SHOW A WELL-DEFINED INNER CORE AT THIS TIME. DVORAK T-NUMBERS FROM
BOTH TAFB AND SAB SUPPORT KEEPING AN INITIAL INTENSITY OF 65 KNOTS.
SINCE LESLIE HAS BEEN MOVING LITTLE...IT IS PRODUCING UPWELLING
RESULTING IN LOWER SEA SURFACE TEMPERATURES IN THE AREA. THE
UPWELLING IN COMBINATION WITH THE SHEAR WOULD NOT FAVOR ANY
SIGNIFICANT STRENGTHENING UNTIL LESLIE BEGINS TO MOVE NORTHWARD OVER
UNDISTURBED WARMER WATERS IN A DAY OR TWO. THE NHC FORECAST CALLS
FOR A MODEST STRENGTHENING BEGINNING IN 24 HOURS.
 
LESLIE CONTINUES TO BE EMBEDDED WITHIN VERY LIGHT STEERING
CURRENTS...AND CONSEQUENTLY IT HAS REMAINED PRACTICALLY STATIONARY
ALL DAY. THERE ARE NO INDICATIONS FROM GLOBAL MODELS OR OTHER
GUIDANCE THAT LESLIE WILL BEGIN TO MOVE FASTER ANY TIME SOON. IN
FACT...THE NHC FORECAST MOVES LESLIE NORTHWARD ONLY 120 NAUTICAL
MILES IN TWO DAYS.  BEYOND 48 HOURS...THE SUBTROPICAL RIDGE IS
FORECAST TO BUILD TO THE EAST OF LESLIE...AND THIS FEATURE IN
COMBINATION WITH AN APPROACHING MID-LEVEL TROUGH WILL FORCE THE
HURRICANE ON A NORTHWARD TRACK...AND THEN NORTHEASTWARD WITH A
GRADUAL INCREASE IN FORWARD SPEED. THE NHC FORECAST CONTINUES TO BE
VERY CLOSE TO THE CONSENSUS AND BETWEEN THE GFS AND THE ECMWF
GLOBAL MODELS. IT IS INTERESTING TO NOTE THAT THE WHOLE GUIDANCE
ENVELOPE SHIFTED A LITTLE BIT EASTWARD AWAY FROM BERMUDA THIS
AFTERNOON...BUT THE NHC FORECAST PREFERS TO MAKE THAT EASTWARD
ADJUSTMENT MORE GRADUALLY.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST FOR THE REMAINDER OF THIS WEEK.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  06/2100Z 26.5N  62.2W   65 KT  75 MPH
 12H  07/0600Z 26.6N  62.2W   65 KT  75 MPH
 24H  07/1800Z 27.0N  62.4W   70 KT  80 MPH
 36H  08/0600Z 27.5N  62.5W   75 KT  85 MPH
 48H  08/1800Z 28.5N  62.6W   85 KT 100 MPH
 72H  09/1800Z 32.0N  62.2W   90 KT 105 MPH
 96H  10/1800Z 35.5N  60.0W   80 KT  90 MPH
120H  11/1800Z 41.5N  56.0W   70 KT  80 MPH
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 070234
TCDAT2
 
HURRICANE LESLIE DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST THU SEP 06 2012

THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE SATELLITE APPEARANCE OF
LESLIE DURING THE PAST SEVERAL HOURS...WITH THE SYSTEM CONTINUING
TO FEATURE A CENTRAL DENSE OVERCAST WITH CLOUD TOPS COLDER
THAN -70C.  HOWEVER...MICROWAVE IMAGES PRIOR TO 0000 UTC DID NOT
SHOW A WELL-DEFINED EYE OR EYEWALL.  SATELLITE INTENSITY ESTIMATES
FROM TAFB AND SAB ARE 65 KT...WHILE SATELLITE CONSENSUS INTENSITY
ESTIMATES FROM CIMSS ARE 60-65 KT.  THE INITIAL INTENSITY REMAINS
65 KT FOR THIS ADVISORY.  THE CIRRUS OUTFLOW IS GOOD IN THE EASTERN
SEMICIRCLE AND IMPROVING IN THE WESTERN SEMICIRCLE.

LESLIE HAS MOVED LITTLE DURING THE PAST SEVERAL HOURS AS IT REMAINS
IN AN AREA OF LIGHT-TO-NON-EXISTENT STEERING CURRENTS.  WATER VAPOR
IMAGERY SHOWS A SHORTWAVE RIDGE IN THE WESTERLIES NORTH OF THE
HURRICANE.  THIS FEATURE IS EXPECTED TO MOVE EAST DURING THE NEXT
12-24 HR AND ALLOW LESLIE TO BEGIN A SLOW NORTHWARD MOTION.  IN THE
LONGER TERM...THE GLOBAL MODELS FORECAST A DEEP-LAYER TROUGH AND
ASSOCIATED SURFACE FRONTAL SYSTEM TO MOVE EASTWARD THROUGH THE
EASTERN UNITED STATES AND REACH THE WESTERN ATLANTIC BY 72 HR. 
THIS SYSTEM SHOULD STEER LESLIE NORTHWARD AND THEN EVENTUALLY
NORTH-NORTHEASTWARD.  HOWEVER...THERE IS SOME SPREAD IN THE
GUIDANCE IN THE FORWARD SPEED...WITH THE CANADIAN MODEL NOTABLY
FASTER THAN THE OTHER GUIDANCE...AND THE GFS SOMEWHAT SLOWER THAN
THE OTHER GUIDANCE.  THE FORECAST TRACK AFTER 36 HR COMPROMISES
BETWEEN THESE EXTREMES AND LIES NEAR THE VARIOUS CONSENSUS MODELS. 
THE GUIDANCE ENVELOPE HAS CHANGED LITTLE SINCE THE LAST ADVISORY...
AND THUS THE NEW FORECAST TRACK IS CLOSE TO THE PREVIOUS FORECAST.

LESLIE HAS MOVED SLOWLY ENOUGH FOR THE PAST TWO DAYS TO HAVE
UPWELLED COLD OCEAN WATER TO THE SURFACE.  REPORTS FROM NOAA BUOY
41049 INDICATE THAT THE SEA SURFACE TEMPERATURE HAS DECREASED FROM
29C TO 26C-27C...WHILE MICROWAVE-BASED SEA SURFACE TEMPERATURE
ESTIMATES SUGGEST TEMPERATURES OF 24C-25C UNDER THE CORE OF THE
HURRICANE.  AT BEST...LITTLE INTENSIFICATION SHOULD OCCUR UNTIL
LESLIE MOVES NORTH OF THE COLD WATER...AND SOME WEAKENING IS
POSSIBLE.  THE NEW INTENSITY FORECAST FROM 12-36 HR IS REDUCED FROM
THAT OF THE PREVIOUS ADVISORY BASED ON THE PRESENCE OF THE COLD
WATER.  FROM 36-72 HR...LESLIE SHOULD MOVE OVER WARMER WATERS AND
STRENGTHEN...AND THE NEW FORECAST IS SIMILAR TO THE PREVIOUS
FORECAST DURING THIS TIME.  INCREASING SHEAR AND THE START OF
EXTRATROPICAL TRANSITION SHOULD LEAD TO WEAKENING AFTER THE 72 HR
POINT.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST FOR THE REMAINDER OF THIS WEEK.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0300Z 26.5N  62.2W   65 KT  75 MPH
 12H  07/1200Z 26.8N  62.2W   65 KT  75 MPH
 24H  08/0000Z 27.2N  62.4W   65 KT  75 MPH
 36H  08/1200Z 28.0N  62.6W   70 KT  80 MPH
 48H  09/0000Z 29.3N  62.6W   80 KT  90 MPH
 72H  10/0000Z 33.0N  61.5W   90 KT 105 MPH
 96H  11/0000Z 37.0N  59.0W   80 KT  90 MPH
120H  12/0000Z 43.0N  55.5W   70 KT  80 MPH
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 070841
TCDAT2
 
HURRICANE LESLIE DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST FRI SEP 07 2012
 
THE SATELLITE PRESENTATION OF LESLIE HAS DEGRADED SOMEWHAT OVER THE
PAST FEW HOURS. THE EARLIER CDO FEATURE HAS LARGELY DISSIPATED AND
MOST OF THE REMAINING COLD CLOUD TOPS ARE DISPLACED TO THE EAST OF
THE CENTER IN SOME RAGGED BANDS. THE INITIAL INTENSITY REMAINS 65
KT BASED ON THE LATEST DVORAK ESTIMATES FROM TAFB AND SAB. A NOAA
HURRICANE HUNTER AIRCRAFT WILL BE INVESTIGATING LESLIE LATER THIS
MORNING AND PROVIDE VALUABLE DATA ON THE INTENSITY AND STRUCTURE OF
THE CYCLONE. 

SATELLITE WINDS AND ANALYSES FROM UW-CIMSS SUGGEST THAT SOME LIGHT
TO MODERATE WEST-SOUTHWESTERLY SHEAR IS IMPACTING THE CYCLONE. THE 
SHEAR ALONG WITH THE DISORGANIZED STATE OF THE INNER CORE AND
COOLING SSTS DUE TO UPWELLING SHOULD RESULT IN LITTLE CHANGE IN
INTENSITY DURING THE NEXT 24 HOURS. AFTER THAT TIME...AS LESLIE
BEGINS TO MOVE NORTHWARD TOWARD WARMER WATERS...THE SHEAR IS
EXPECTED TO DIMINISH AND SOME STRENGTHENING IS FORECAST. WEAKENING
IS EXPECTED LATE IN THE PERIOD AS THE CYCLONE ENCOUNTERS COOLER
WATERS AND INCREASING SHEAR DURING EXTRATROPICAL TRANSITION. THE
NEW NHC INTENSITY FORECAST IS A BIT LOWER THAN THE PREVIOUS ONE AT
48 AND 72 HOURS AND IS CLOSE TO THE LATEST IVCN CONSENSUS. 

SATELLITE FIXES AND WIND OBSERVATIONS FROM NOAA BUOY 41049 SUGGEST
THAT LESLIE IS DRIFTING SLOWLY NORTHWARD. A STEADIER NORTHWARD
MOTION SHOULD BEGIN BY 24 HOURS AS THE RIDGE NORTH OF LESLIE BEGINS
TO MOVE EASTWARD AND AMPLIFY. AFTER 48 HOURS...AN ACCELERATION
TOWARD THE NORTH AND NORTH-NORTHEAST IS EXPECTED AS LESLIE
INTERACTS WITH A COMPLEX MID/UPPER-LEVEL TROUGH MOVING FROM THE
EASTERN UNITED STATES TO THE CANADIAN MARITIMES. THE TRACK MODEL
GUIDANCE STILL SHOWS SOME SPREAD IN FORWARD SPEED AND HEADING...
ESPECIALLY LATE IN THE PERIOD. THE ECMWF IS ALONG THE LEFT SIDE OF
THE GUIDANCE ENVELOPE WITH THE GFDL...WHILE THE LATEST GFS RUN HAS
TRENDED FASTER AND LEFT TOWARD THE REST OF THE GUIDANCE. THE END
RESULT IS THAT THE LATEST TVCA MULTI-MODEL CONSENSUS IS VERY CLOSE
TO THE PREVIOUS NHC FORECAST...AND THE NEW NHC TRACK IS BASICALLY
AN UPDATE OF THE PREVIOUS ONE. AT DAYS 3 THROUGH 5 THE NHC FORECAST
IS VERY CLOSE TO THE FSU SUPERENSEMBLE AND A BLEND OF THE ECMWF AND
GFS MODELS. 

THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 26.7N  62.2W   65 KT  75 MPH
 12H  07/1800Z 26.9N  62.3W   65 KT  75 MPH
 24H  08/0600Z 27.6N  62.4W   65 KT  75 MPH
 36H  08/1800Z 28.6N  62.4W   70 KT  80 MPH
 48H  09/0600Z 30.1N  62.2W   75 KT  85 MPH
 72H  10/0600Z 33.7N  61.0W   85 KT 100 MPH
 96H  11/0600Z 38.5N  58.0W   80 KT  90 MPH
120H  12/0600Z 46.0N  54.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT42 KNHC 071451
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  33
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST FRI SEP 07 2012
 
LESLIE HAS BEEN NEARLY STATIONARY TOO LONG AND THE OCEAN BENEATH HAS
COOLED SIGNIFICANTLY. IN FACT...ONE OF THE AXBT SONDES LAUNCHED FROM
THE NOAA PLANE CURRENTLY IN LESLIE MEASURED A SEA SURFACE
TEMPERATURE OF 24.5 DEGREES CELSIUS. CONSEQUENTLY...THE CONVECTION
HAS DIMINISHED AND THE CLOUD PATTERN HAS BECOME LESS ORGANIZED. THE
NOAA HURRICANE HUNTER AIRCRAFT ALSO MEASURED A MINIMUM PRESSURE OF
981 MB...BUT BOTH SFMR AND FLIGHT LEVEL WINDS ONLY SUPPORT AN
INITIAL INTENSITY OF 60 KNOTS.  ONCE LESLIE MOVES AWAY FROM THE
COOL POOL IT HAS CREATED FOR ITSELF...THE CYCLONE WILL HAVE THE
OPPORTUNITY TO REGAIN HURRICANE STATUS SINCE THE SHEAR IS EXPECTED
TO BE LOW.  BY THE END OF THE FORECAST PERIOD...LESLIE SHOULD HAVE
LOST TROPICAL CHARACTERISTICS AND BECOME A STRONG POST-TROPICAL 
CYCLONE.
 
THE STEERING CURRENTS COLLAPSED A COUPLE OF DAYS AGO RESULTING IN
LESLIE BEING NEARLY STATIONARY. GLOBAL MODELS ARE SHOWING A LARGE
MID-LEVEL TROUGH MOVING EASTWARD ACROSS THE EASTERN UNITED STATES
AND CANADA. THIS TROUGH SHOULD ACCELERATE THE SOUTHERLY FLOW THAT
EVENTUALLY WILL FORCE LESLIE TO MOVE NORTHWARD AND THEN
NORTH-NORTHEASTWARD WITH AN INCREASING FORWARD SPEED DURING THE
NEXT FEW DAYS. THE TRACK GUIDANCE IS MORE CONSISTENT WITH THIS
SOLUTION PRIMARILY IN THE FIRST 3 DAYS.  THE NHC FORECAST IS VERY
CLOSE TO THE MODEL CONSENSUS AND IS A BLEND OF THE GFS AND THE
ECMWF.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 26.8N  62.2W   60 KT  70 MPH
 12H  08/0000Z 27.1N  62.2W   60 KT  70 MPH
 24H  08/1200Z 28.0N  62.2W   60 KT  70 MPH
 36H  09/0000Z 29.0N  62.2W   70 KT  80 MPH
 48H  09/1200Z 30.5N  61.9W   80 KT  90 MPH
 72H  10/1200Z 33.3N  60.8W   85 KT 100 MPH
 96H  11/1200Z 39.0N  57.0W   75 KT  85 MPH
120H  12/1200Z 45.5N  53.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 072031
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  34
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST FRI SEP 07 2012
 
THE ONLY SIGNIFICANT CHANGE THIS AFTERNOON IS THAT LESLIE HAS BEGUN
TO MOVE SLOWLY NORTHWARD AT ABOUT 4 KNOTS AND MAXIMUM WINDS ARE
ESTIMATED TO BE AT 55 KNOTS. 

THE CENTER IS PASSING JUST EAST OF NOAA BUOY 41049 WHICH REPORTED
NORTHERLY WINDS OF 40 TO 45 KNOTS AND A MINIMUM PRESSURE OF 989 MB.
VISIBLE SATELLITE IMAGES CLEARLY SHOW A LARGE CENTER OF CIRCULATION
WITH MOST OF THE CONVECTION TO NORTH AND EAST OF THE CENTER...
SUGGESTING THAT LESLIE STILL LACKS AN INNER CORE.  SHIP AND BUOY
OBSERVATIONS...AS WELL AS SST MICROWAVE DATA...ARE INDICATING SEA
SURFACE TEMPERATURES OF 28 AND 29 DEGREES CELSIUS TO THE NORTH OF
LESLIE. SINCE THE SHEAR HAS DECREASED...ONCE LESLIE MOVES OVER
THESE WARMER WATERS IN A DAY OR SO...THERE IS A STRONG LIKELIHOOD
THAT IT WILL REGAIN HURRICANE STRENGTH. IN FACT...MOST OF THE
CYCLONES IN THE ATLANTIC THIS YEAR THAT HAVE REACHED HURRICANE
INTENSITY HAVE DONE SO AS THEY APPROACH 30 DEGREES NORTH AND NOT IN
THE DEEP TROPICS.            

STEERING CURRENTS ARE FORECAST TO BECOME BETTER ESTABLISHED AS A
LARGE MID-LEVEL TROUGH MOVES EASTWARD ACROSS THE EASTERN UNITED
STATES AND CANADA. THIS TROUGH SHOULD ACCELERATE THE SOUTHERLY FLOW
THAT EVENTUALLY WILL FORCE LESLIE TO MOVE NORTHWARD AND THEN
NORTH-NORTHEASTWARD WITH AN INCREASING FORWARD SPEED DURING THE
NEXT FEW DAYS. THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST
SINCE THE GUIDANCE IS REMARKABLY IN GOOD AGREEMENT DURING THE NEXT 3
DAYS. THE NHC FORECAST CLOSELY FOLLOWS THE MODEL CONSENSUS.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 27.4N  62.2W   55 KT  65 MPH
 12H  08/0600Z 28.0N  62.2W   60 KT  70 MPH
 24H  08/1800Z 28.8N  62.2W   60 KT  70 MPH
 36H  09/0600Z 30.2N  62.0W   70 KT  80 MPH
 48H  09/1800Z 31.8N  61.6W   80 KT  90 MPH
 72H  10/1800Z 35.0N  60.0W   80 KT  90 MPH
 96H  11/1800Z 41.0N  56.0W   70 KT  80 MPH
120H  12/1800Z 47.0N  52.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 080244
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST FRI SEP 07 2012

SATELLITE IMAGERY AND REPORTS FROM NOAA P-3 AND G-IV HURRICANE
HUNTER AIRCRAFT SHOW CHANGES IN THE STRUCTURE OF LESLIE THIS
EVENING.  THE STORM CURRENTLY LACKS AN INNER CORE...AS THE RADIUS
OF MAXIMUM WINDS IS NOW ON THE ORDER OF 75 N MI.  IN ADDITION...
INFRARED AND MICROWAVE SATELLITE IMAGERY SHOW WELL-DEFINED CURVED
CONVECTIVE BANDS OVER THE NORTHERN SEMICIRCLE AT A LARGE DISTANCE
FROM THE CENTER.  DROPSONDE DATA AND SFMR SURFACE WIND ESTIMATES
SUPPORT AN INITIAL INTENSITY OF 55 KT...WHICH IS IN GOOD AGREEMENT
WITH THE SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB.  THE
CENTRAL PRESSURE OF 983 MB IS BASED ON A COMBINATION OF AIRCRAFT
AND NOAA BUOY DATA.  

THE INITIAL MOTION IS 350/3.  LESLIE IS STILL EMBEDDED IN AN AREA OF
WEAK STEERING CURRENTS IN THE MIDDLE OF THE SUBTROPICAL RIDGE.  THE
GLOBAL MODELS FORECAST THE RIDGE WEST OF LESLIE TO BREAK DOWN AS A
LARGE DEEP-LAYER TROUGH AND ASSOCIATED SURFACE COLD FRONT MOVE
ACROSS THE EASTERN UNITED STATES INTO THE WESTERN ATLANTIC.  THE
TRACK GUIDANCE IS IN GOOD AGREEMENT THAT DURING THE NEXT 48-72 HR
LESLIE SHOULD GRADUALLY ACCELERATE NORTHWARD TO NORTH-
NORTHEASTWARD...WITH THE CENTER PASSING EAST OF BERMUDA BETWEEN
36-48 HR.  AFTER THAT...THE GUIDANCE IS IN GOOD AGREEMENT THAT
LESLIE SHOULD CONTINUE NORTH-NORTHEASTWARD...BUT THERE IS SOME
SPREAD IN THE FORWARD SPEED.  THE ECMWF AND GFS MODELS SHOW LESLIE
SLOWING AS IT GETS CAUGHT UP IN AN UPPER-LEVEL LOW NEAR
NEWFOUNDLAND...WHILE THE CANADIAN AND UKMET MODELS SHOW A FASTER
MOTION.  THE LATTER PART OF THE NEW FORECAST TRACK COMPROMISES
BETWEEN THESE EXTREMES AND IS NEAR THE CONSENSUS MODELS.  IT IS
SIMILAR TO THE PREVIOUS FORECAST THROUGH 72 HR AND A LITTLE LEFT OF
THE PREVIOUS FORECAST AFTER THAT.

THE INTENSITY FORECAST REMAINS COMPLICATED.  ON THE PLUS SIDE...
LESLIE SHOULD BE MOVING AWAY FROM THE COLD WATER IT HAS UPWELLED...
AND THE VERTICAL WIND SHEAR IS FORECAST TO BE GENERALLY LIGHT
THROUGH 72 HR.  ON THE MINUS SIDE...THE CURRENT STRUCTURE IS LIKELY
NOT CONDUCIVE FOR RAPID DEVELOPMENT...AND WATER VAPOR IMAGERY SHOWS
THAT LESLIE WILL CONTINUE TO HAVE ISSUES WITH DRY AIR ENTRAINMENT. 
THE NEW INTENSITY FORECAST SHOW A SLOWER RATE OF DEVELOPMENT TO THE
PEAK INTENSITY IN 72 HR THAN THE PREVIOUS FORECAST...CLOSE TO THE
SHIPS MODEL AND BELOW THE INTENSITY CONSENSUS.  AFTER 72 HR...
INCREASING SHEAR AND THE ONSET OF EXTRATROPICAL TRANSITION SHOULD
CAUSE WEAKENING.  EXTRATROPICAL TRANSITION IS FORECAST TO BE
COMPLETE BY 120 HR.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 27.6N  62.3W   55 KT  65 MPH
 12H  08/1200Z 28.2N  62.3W   55 KT  65 MPH
 24H  09/0000Z 29.5N  62.2W   60 KT  70 MPH
 36H  09/1200Z 31.0N  61.9W   65 KT  75 MPH
 48H  10/0000Z 32.7N  61.3W   75 KT  85 MPH
 72H  11/0000Z 37.0N  59.0W   80 KT  90 MPH
 96H  12/0000Z 43.0N  55.0W   70 KT  80 MPH
120H  13/0000Z 48.0N  52.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 080846
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  36
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SAT SEP 08 2012
 
LESLIE SHOWED SOME SIGNS OF PERHAPS GETTING BETTER ORGANIZED EARLIER
TONIGHT...WITH CONVECTIVE BANDS TRYING TO WRAP AROUND THE SOUTH
SIDE OF THE CENTER. HOWEVER...THE CLOUD PATTERN HAS RECENTLY BECOME
MORE RAGGED AND THE COLDEST TOPS ARE DISPLACED WEST AND NORTH OF
THE CENTER LOCATION. DROPSONDE DATA FROM THE AIRCRAFT MISSIONS LAST
NIGHT AND SATELLITE IMAGERY SHOW SOME DRY AIR WRAPPING INTO THE
SOUTHERN PORTION OF THE CIRCULATION...WHICH IS LIKELY HINDERING
INTENSIFICATION FOR THE TIME BEING. THE INITIAL INTENSITY REMAINS
55 KT IN AGREEMENT WITH THE LATEST DVORAK ESTIMATE FROM TAFB.
 
THE INTENSITY FORECAST REASONING REMAINS UNCHANGED...AS DRY AIR AND
RELATIVELY COOL WATERS SHOULD LEAD TO ONLY GRADUAL STRENGTHENING IN
THE NEXT DAY OR SO. AFTER THAT TIME...AS LESLIE MOVES OVER WARMER
WATERS...STEADIER INTENSIFICATION IS EXPECTED THROUGH 72 HOURS. AT
DAYS 4 AND 5 LESLIE SHOULD WEAKEN AS THE SHEAR INCREASES WHILE THE
CYCLONE MOVES NORTH OF THE GULF STREAM AND UNDERGOES EXTRATROPICAL
TRANSITION. THE NHC FORECAST IS CLOSE TO OR A LITTLE ABOVE THE
INTENSITY CONSENSUS AFTER 12 HOURS AND IS SIMILAR TO THE PREVIOUS
ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 360/04. THE MID-LEVEL RIDGE NORTH OF
LESLIE IS EXPECTED TO WEAKEN DURING THE NEXT DAY OR TWO AS A
LONGWAVE TROUGH MOVES INTO EASTERN NORTH AMERICA. LESLIE SHOULD
BEGIN TO ACCELERATE NORTHWARD AND THEN NORTH-NORTHEASTWARD THROUGH
THE PERIOD AS IT INTERACTS WITH THE TROUGH. THE NHC TRACK FORECAST
THROUGH 48 HOURS IS LARGELY AN UPDATE OF THE PREVIOUS ONE AND IS
NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. AT 72 HOURS AND BEYOND...
THE NHC FORECAST HAS BEEN SHIFTED TO THE LEFT WITH A SLIGHTLY
SLOWER FORWARD SPEED. THIS REPRESENTS A TREND TOWARD THE LATEST
TRACK GUIDANCE...WHICH FOR THIS CYCLE GENERALLY SHOWS MORE
INTERACTION BETWEEN LESLIE AND A SHORTWAVE TROUGH THAT TRIES TO CUT
OFF EAST OF NEW ENGLAND IN 3 TO 4 DAYS. HOWEVER...THE NEW NHC TRACK
IS STILL A LITTLE EAST OF THE TVCA CONSENSUS AND LIES ALONG THE
EASTERN EDGE OF THE GUIDANCE ENVELOPE LATE IN THE PERIOD. 
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE WAVES AND
LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE U.S.
EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 28.1N  62.3W   55 KT  65 MPH
 12H  08/1800Z 28.9N  62.2W   55 KT  65 MPH
 24H  09/0600Z 30.3N  62.0W   60 KT  70 MPH
 36H  09/1800Z 31.9N  61.6W   65 KT  75 MPH
 48H  10/0600Z 33.6N  61.0W   75 KT  85 MPH
 72H  11/0600Z 38.5N  58.5W   80 KT  90 MPH
 96H  12/0600Z 44.5N  55.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
120H  13/0600Z 48.0N  53.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT42 KNHC 081452
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST SAT SEP 08 2012
 
THE SATELLITE PRESENTATION HAS NOT CHANGED SIGNIFICANTLY DURING THE
PAST SEVERAL HOURS. LESLIE DOES NOT HAVE AN INNER CORE AND MOST OF
THE STRONGEST WINDS ARE OCCURRING WITHIN CONVECTIVE BANDS REMOVED
FROM THE CENTER. A NOAA HURRICANE HUNTER AIRCRAFT HAS
BEEN TRAVERSING THE CYCLONE THIS MORNING AND REPORTED THAT THE
MAXIMUM SURFACE WINDS ARE ABOUT 55 KNOTS...AND THE PRESSURE HAS
RISEN TO
988 MB. SINCE LESLIE IS STILL FEELING THE INFLUENCE OF COLD SEA
SURFACE TEMPERATURES...THE CONVECTION IS NOT VERY DEEP AND NO
SIGNIFICANT CHANGE IN INTENSITY IS FORECAST FOR TODAY.
HOWEVER...THERE IS PLENTY OF WARM WATER AHEAD OF LESLIE...AND AS
SOON AS THE CIRCULATION MOVES OVER THESE WATERS...THE POTENTIAL FOR
LESLIE TO REGAIN HURRICANE STATUS WILL INCREASE. LESLIE IS EXPECTED
TO LOSE TROPICAL CHARACTERISTICS BY THE END OF THE FORECAST PERIOD.
 
FIXES FROM THE AIRCRAFT INDICATE THAT LESLIE HAS BEEN MOVING
NORTHWARD AT 5 TO 7 KNOTS. A MID-LEVEL TROUGH IS EXPECTED TO BE
APPROACHING THE WESTERN ATLANTIC IN A DAY OR SO...AND THE
SOUTHWESTERLY FLOW AHEAD OF THE TROUGH WILL FORCE LESLIE TO RECURVE
AND INCREASE IN FORWARD SPEED. THE WESTERN EDGE OF THE GUIDANCE
ENVELOPE...WHICH IN FACT IS VERY TIGHT...REMAINS WELL EAST OF
BERMUDA.  THE NHC FORECAST IS BASICALLY ON TOP OF THE CONSENSUS AND
THERE IS HIGH CONFIDENCE IN THE TRACK FORECAST.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL CONTINUE TO GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE
WAVES AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH
OF THE U.S. EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 28.6N  62.5W   55 KT  65 MPH
 12H  09/0000Z 29.5N  62.5W   55 KT  65 MPH
 24H  09/1200Z 31.2N  62.2W   60 KT  70 MPH
 36H  10/0000Z 32.8N  61.8W   65 KT  75 MPH
 48H  10/1200Z 34.5N  61.0W   75 KT  85 MPH
 72H  11/1200Z 40.5N  58.0W   80 KT  90 MPH
 96H  12/1200Z 45.0N  55.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  13/1200Z 47.0N  51.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 082032
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  38
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST SAT SEP 08 2012
 
VISIBLE SATELLITE IMAGES REVEAL THAT THE CLOUD PATTERN HAS BECOME
SYMMETRIC AROUND A LARGE CLOUDLESS CENTER OF CIRCULATION...
COMMONLY REFERRED TO AS A TRUCK TIRE/DOUGHNUT-TYPE PATTERN. SINCE
THE CONVECTION IS NOT VERY DEEP AND DVORAK T-NUMBERS HAVE NOT
INCREASED YET...THE INITIAL INTENSITY IS KEPT AT 55 KNOTS.
GIVEN THAT THE UPPER-LEVEL OUTFLOW IS PERFECTLY ESTABLISHED IN ALL
QUADRANTS...AND THAT LESLIE IS BEGINNING TO MOVE OVER WARM
WATERS...THE NHC FORECAST CALLS FOR LESLIE TO REGAIN HURRICANE
STATUS IN A DAY OR SO.  EXTRATROPICAL TRANSITION SHOULD OCCUR BY
DAY 4 WHEN LESLIE IS NEAR NEWFOUNDLAND.

LESLIE IS MOVING TOWARD THE NORTH AT ABOUT 7 KNOTS. A LARGE
MID-LEVEL TROUGH IS RAPIDLY AMPLIFYING OVER THE EASTERN UNITED
STATES...AND THIS PATTERN WILL FORCE LESLIE TO RECURVE AND INCREASE
IN FORWARD SPEED.  TRACK GUIDANCE CONTINUES TO BE IN VERY GOOD
AGREEMENT IN THE NEXT 3 DAYS...BUT DIFFERS SIGNIFICANTLY IN SPEED
BY 96 HOURS WHEN LESLIE IS ABOUT TO LOSE TROPICAL CHARACTERISTICS.
THE OFFICIAL FORECAST FOLLOWS THE CONSENSUS DURING THE FIRST THREE
DAYS...AND THEN LEANS TOWARD THE GFS AND OCEAN PREDICTION CENTER
GUIDANCE.
 
THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL CONTINUE TO GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE
WAVES AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH
OF THE U.S. EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 29.4N  62.5W   55 KT  65 MPH
 12H  09/0600Z 30.4N  62.3W   60 KT  70 MPH
 24H  09/1800Z 32.2N  62.0W   65 KT  75 MPH
 36H  10/0600Z 34.0N  61.5W   75 KT  85 MPH
 48H  10/1800Z 36.0N  60.5W   80 KT  90 MPH
 72H  11/1800Z 44.0N  56.5W   70 KT  80 MPH
 96H  12/1800Z 46.0N  52.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  13/1800Z 48.0N  46.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 090235
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  39
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SAT SEP 08 2012

INFRARED SATELLITE IMAGERY SHOWS THAT THE CONVECTION ASSOCIATED WITH
LESLIE HAS AGAIN BECOME ASYMMETRIC...WITH MOST OF THE CONVECTION
CURRENTLY IN THE WESTERN SEMICIRCLE.  SATELLITE INTENSITY ESTIMATES
FROM TAFB AND SAB ARE 55 KT...AND A RECENT CIMSS SATELLITE
CONSENSUS ESTIMATE WAS 58 KT.  BASED ON THESE DATA...THE INITIAL
INTENSITY REMAINS 55 KT.

THE INITIAL MOTION IS 360/7.  A LARGE DEEP-LAYER TROUGH AND
ASSOCIATED SURFACE COLD FRONT ARE MOVING FROM THE EASTERN UNITED
STATES INTO THE NORTHWESTERN ATLANTIC.  INCREASING SOUTHERLY AND
SOUTHWESTERLY FLOW AHEAD OF THIS SYSTEM SHOULD STEER LESLIE TO THE
NORTH AND NORTH-NORTHEAST AT AN INCREASING FORWARD SPEED.  THE NEW
TRACK FORECAST IS SIMILAR TO THE PREVIOUS FORECAST THROUGH 48
HOURS.  AFTER THAT TIME...THE GLOBAL MODELS ARE NOW SHOWING A MUCH
FASTER NORTHWARD AND NORTHEASTWARD MOTION AS LESLIE UNDERGOES
EXTRATROPICAL TRANSITION.  THE GUIDANCE HAS SHIFTED ENOUGH THAT IT
IS IMPOSSIBLE TO FOLLOW IT AND MAINTAIN ANY CONTINUITY WITH THE
PREVIOUS FORECAST.  THUS...THE 72-120 HR FORECAST IS A COMPROMISE
BETWEEN THE SLOWER PREVIOUS FORECAST AND THE MUCH FASTER MODEL
GUIDANCE.  ADDITIONAL ADJUSTMENTS OF THIS PART OF THE FORECAST
TRACK MAY BE NECESSARY IF THE CURRENT MODEL TRENDS CONTINUE.

LESLIE CURRENTLY HAS A VERY IMPRESSIVE CIRRUS OUTFLOW PATTERN...AND
IT SHOULD ENCOUNTER A WARM WATER/LIGHT WIND SHEAR ENVIRONMENT FOR
THE NEXT 36-48 HR.  THIS SHOULD ALLOW SOME STRENGTHENING...
ALTHOUGH THE CURRENT STORM STRUCTURE AND ISSUES WITH DRY AIR
ENTRAINMENT ARGUE AGAINST RAPID DEVELOPMENT.  THE INTENSITY
GUIDANCE SHOWS A LITTLE LESS STRENGTHENING THAN 6 HR AGO...SO THE
NEW INTENSITY FORECAST IS REDUCED SLIGHTLY TO A PEAK INTENSITY OF
75 KT IN 48 HR.  THIS PART OF THE INTENSITY FORECAST IS A LITTLE
STRONGER THAN THE SHIPS MODEL AND THE INTENSITY CONSENSUS. 
EXTRATROPICAL TRANSITION SHOULD BEGIN AFTER 48 HR AND BE COMPLETE
BY 72-96 HR...WITH LESLIE FORECAST TO WEAKEN DURING THIS PROCESS.

THE WIND FIELD OF LESLIE...COMBINED WITH ITS EXPECTED SLOW MOTION...
WILL CONTINUE TO GENERATE LONG-PERIOD SWELLS THAT WILL PRODUCE LARGE
WAVES AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH
OF THE U.S. EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 30.1N  62.6W   55 KT  65 MPH
 12H  09/1200Z 31.3N  62.4W   60 KT  70 MPH
 24H  10/0000Z 33.2N  61.9W   65 KT  75 MPH
 36H  10/1200Z 35.3N  60.9W   70 KT  80 MPH
 48H  11/0000Z 38.5N  59.3W   75 KT  85 MPH
 72H  12/0000Z 46.0N  54.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  13/0000Z 49.0N  48.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  14/0000Z 51.5N  40.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT42 KNHC 090851
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  40
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST SUN SEP 09 2012
 
DEEP CONVECTION ASSOCIATED WITH LESLIE DECREASED IN COVERAGE LATE
IN THE EVENING...HOWEVER A NEW BURST OF THUNDERSTORMS HAS FORMED
JUST NORTH OF THE CENTER...AND IT IS NOW WRAPPING AROUND THE 
WESTERN PORTION OF THE CIRCULATION.  THE LATEST DVORAK INTENSITY
ESTIMATES RANGE FROM 45 TO 55 KT AND AN EARLIER ASCAT PASS SHOWED 
A LARGE AREA OF 40-45 KT WINDS.  THE INITIAL INTENSITY IS MAINTAINED
AT 55 KT...WHICH COULD BE A LITTLE GENEROUS.

AS LESLIE MOVES NORTHWARD IT SHOULD FINALLY LEAVE THE AREA OF COOLER
WATERS CAUSED BY UPWELLING DURING THE PAST SEVERAL DAYS.  AS THIS
OCCURS THE CYCLONE IS FORECAST TO BE IN A FAVORABLE UPPER-AIR
ENVIRONMENT.  THESE CONDITIONS FAVOR INTENSIFICATION...HOWEVER
GIVEN THE CURRENT STRUCTURE OF THE CYCLONE AND ISSUES WITH DRY 
AIR ENTRAINMENT...LESLIE MAY HAVE SOME DIFFICULTY IN STRENGTHENING. 
THE NEW NHC FORECAST CALLS SOME INCREASE IN WIND SPEED...BUT LESS
THAN IN THE PREVIOUS ADVISORY.  LESLIE IS FORECAST TO BEGIN
INTERACTING WITH A FRONTAL ZONE WITHIN 48 HOURS AND THE CYCLONE IS
EXPECTED TO BECOME EXTRATROPICAL EARLY TUESDAY. THE EXTRATROPICAL
LOW IS PREDICTED TO MAINTAIN ITS INTENSITY FOR A DAY OR SO BEFORE
GRADUALLY WEAKENING OVER THE NORTH ATLANTIC. 

THE INITIAL MOTION IS 360 DEGREES AT 8 KT.  LESLIE IS FORECAST TO
BEGIN MOVING FASTER TOWARD THE NORTH AND NORTH-NORTHEAST AS A LARGE
DEEP-LAYER TROUGH MOVES EASTWARD OFF THE EAST COAST OF THE UNITED
STATES.  THE TRACK MODEL GUIDANCE IS TIGHTLY CLUSTERED DURING THE
FIRST 48 HOURS AND THE NHC TRACK IS NEAR THE MIDDLE OF THE GUIDANCE
ENVELOPE.  THE GLOBAL MODEL GUIDANCE HAS ONCE AGAIN TRENDED TOWARD
A FASTER SOLUTION FOR THE 3 TO 5 DAY FORECAST PERIODS.  THIS HAS
RESULTED IN A SIGNIFICANT ADJUSTMENT TO THE TRACK FORECAST AT 72
THROUGH 120 H.  HOWEVER...THE TRACK FORECAST FOR THE EXTRATROPICAL
PORTION IS STILL SLOWER THAN THE MODEL CONSENSUS IN ORDER TO
MAINTAIN SOME CONTINUITY WITH THE PREVIOUS ADVISORY. 
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 30.8N  62.5W   55 KT  65 MPH
 12H  09/1800Z 32.4N  62.3W   55 KT  65 MPH
 24H  10/0600Z 34.5N  61.5W   60 KT  70 MPH
 36H  10/1800Z 37.5N  60.2W   65 KT  75 MPH
 48H  11/0600Z 42.0N  58.0W   65 KT  75 MPH
 72H  12/0600Z 52.0N  50.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  13/0600Z 59.5N  35.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  14/0600Z 61.0N  15.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 091435
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  41
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST SUN SEP 09 2012
 
LESLIE HAS A VERY BROAD EYE AS EVIDENCED BY BERMUDA RADAR
OBSERVATIONS AND SATELLITE IMAGES.  A RECENT ASCAT PASS OVER THE
TROPICAL CYCLONE SHOWED 40-45 KT WINDS...AND ENHANCED IR DATA SHOWED
SOME INCREASE IN THE DEEP CONVECTION IN CLUSTERS SURROUNDING THE
CENTER.  THE CURRENT INTENSITY IS HELD AT 50 KT FOR THIS ADVISORY. 
SINCE LESLIE LACKS A WELL-DEFINED INNER CORE...IT MAY HAVE
DIFFICULTY RE-INTENSIFYING AS IT MOVES FARTHER AWAY FROM THE COOLER
WATERS IT UPWELLED.  HOWEVER...UPPER-TROPOSPHERIC WINDS ARE
FORECAST TO BE FAVORABLE FOR STRENGTHENING DURING THE NEXT DAY OR
SO...AND THE OFFICIAL WIND SPEED FORECAST SHOWS THE CYCLONE
REGAINING HURRICANE STATUS AS IN THE PREVIOUS ADVISORY.  THIS IS
ALSO IN GOOD AGREEMENT WITH THE LATEST LGEM GUIDANCE.  BEYOND 48
HOURS...THE GLOBAL MODELS DEPICT LESLIE TO BE QUITE DEEP BUT
BECOMING EMBEDDED WITHIN A FRONTAL ZONE...SO THE SYSTEM IS FORECAST
TO BECOME A VIGOROUS EXTRATROPICAL CYCLONE IN 2-3 DAYS AS IT MOVES
OVER THE ATLANTIC.  BY DAY 5 THE SYSTEM IS LIKELY TO MERGE WITH A
LARGE LOW TO THE NORTHWEST OF SCANDANAVIA.

LESLIE IS BEGINNING TO INCREASE ITS FORWARD SPEED...AND THE INTIAL
MOTION IS ESTIMATED TO BE 010/9.  AS A MID-TROPOSPHERIC TROUGH
MOVES OFF THE NORTHEAST U.S. COAST...THE CYCLONE IS EXPECTED TO
ACCELERATE NORTH-NORTHEASTWARD IN THE FLOW ON THE EAST SIDE OF THE
TROUGH OVER THE NEXT COUPLE OF DAYS.  IN 3-4 DAYS...THE POST-
TROPICAL CYCLONE SHOULD TURN EAST-NORTHEASTWARD IN THE HIGHER
LATITUDE WESTERLIES.  THE OFFICIAL TRACK FORECAST IS SOMEWHAT
FASTER THAN THE PREVIOUS ONE IN THE LATTER PART OF THE FORECAST
PERIOD...BUT NOT AS FAST AS THE LATEST GFS SOLUTION.   
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 32.0N  62.4W   50 KT  60 MPH
 12H  10/0000Z 33.6N  62.0W   55 KT  65 MPH
 24H  10/1200Z 36.3N  60.9W   60 KT  70 MPH
 36H  11/0000Z 40.2N  59.0W   65 KT  75 MPH
 48H  11/1200Z 46.5N  55.5W   65 KT  75 MPH
 72H  12/1200Z 58.0N  42.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  13/1200Z 62.0N  20.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  14/1200Z...MERGED
 
$$
FORECASTER PASCH
 

WTNT42 KNHC 092033
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  42
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST SUN SEP 09 2012
 
ALTHOUGH DVORAK CLASSIFICATIONS FROM TAFB AND SAB WERE T3.5 AT
18Z...SINCE THEN THE COLD CLOUD TOPS HAVE WARMED A BIT AND THE
BANDING HAS BECOME LESS SOLID.  THE ADVISORY INTENSITY WILL REMAIN
50 KT.  LESLIE CONTINUES TO LACK A WELL-DEFINED INNER CORE...WHICH
SHOULD MITIGATE AGAINST OTHERWISE FAVORABLE ENVIRONMENTAL
CONDITIONS FOR THE NEXT 36 HOURS OR SO.  BOTH THE TROPICAL AND
GLOBAL GUIDANCE INDICATE THAT LESLIE WILL BE AT OR AT LEAST NEAR
HURRICANE STRENGTH ON ITS APPROACH TO NEWFOUNDLAND.  AFTER 36
HOURS...SSTS COOL AND SOUTHWESTERLY SHEAR INCREASES MARKEDLY...BUT
THE GLOBAL GUIDANCE SUGGESTS THAT LESLIE WILL CONTINUE TO BE A
VIGOROUS EXTRATROPICAL CYCLONE FOR AT LEAST THE NEXT THREE DAYS. 
BASED ON THE GFS AND ECMWF FIELDS...LESLIE WILL BE MERGING WITH A
FRONTAL SYSTEM ABOUT THE TIME IT REACHES NEWFOUNDLAND.  

THE INITIAL MOTION IS 010/12. THERE HAS BEEN NO CHANGE TO THE TRACK
FORECAST PHILOSOPHY WITH THIS ADVISORY...ALTHOUGH THE CURRENT
FORECAST IS A LITTLE FASTER THAN THE PREVIOUS ONE.  AS A
MID-TROPOSPHERIC TROUGH MOVES OFF THE NORTHEAST U.S. COAST...THE
CYCLONE IS EXPECTED TO ACCELERATE NORTH-NORTHEASTWARD IN THE FLOW
ON THE EAST SIDE OF THE TROUGH OVER THE NEXT COUPLE OF DAYS. IN 3-4
DAYS...THE POST-TROPICAL CYCLONE SHOULD TURN EAST-NORTHEASTWARD IN
THE HIGHER LATITUDE WESTERLIES.  
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT COUPLE OF DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 33.4N  62.1W   50 KT  60 MPH
 12H  10/0600Z 35.1N  61.6W   55 KT  65 MPH
 24H  10/1800Z 38.5N  60.0W   60 KT  70 MPH
 36H  11/0600Z 44.1N  56.7W   65 KT  75 MPH
 48H  11/1800Z 51.0N  51.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  12/1800Z 60.0N  32.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  13/1800Z 63.5N   9.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  14/1800Z...ABSORBED
 
$$
FORECASTER FRANKLIN
 

WTNT42 KNHC 100300
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  43
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SUN SEP 09 2012
 
THE CONVECTIVE CLOUD PATTERN OF LESLIE HAS CONTINUED TO SLOWLY ERODE
AND CLOUD TOPS HAVE ALSO CONTINUED TO WARM SINCE THE PREVIOUS
ADVISORY. THE INITIAL INTENSITY REMAINS AT 50 KT BASED ON A BLEND
OF DVORAK SATELLITE INTENSITY ESTIMATES OF T3.0/45 KT AND T3.5/55
KT FROM TAFB AND SAB...RESPECTIVELY. 
 
THE INITIAL MOTION ESTIMATE IS 015/14. THERE REMAINS NO SIGNIFICANT
CHANGE TO THE PREVIOUS TRACK FORECAST AND REASONING. LESLIE IS
EXPECTED TO CONTINUE MOVING NORTH-NORTHEASTWARD FOR THE NEXT 12
HOURS OR SO AS THE CYCLONE ROUNDS THE WESTERN PERIPHERY OF A
DEEP-LAYER RIDGE LOCATED TO ITS EAST. BY 24 HOURS...LESLIE IS
FORECAST TO ACCELERATE TO THE NORTHEAST BETWEEN INCREASING
SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING DEEP-LAYER TROUGH FROM
THE WEST AND THE AFOREMENTIONED RIDGE TO THE EAST. BY DAYS 3-4...
LESLIE WILL BE INTERACTING WITH A FRONTAL SYSTEM...AND THE
POST-TROPICAL CYCLONE IS EXPECTED TURN EAST-NORTHEASTWARD AND
EASTWARD IN THE HIGH-LATITUDE WESTERLY FLOW. ABSORPTION BY A LARGER
EXTRATROPICAL LOW IS FORECAST TO OCCUR BY DAY 5 OVER THE NORTH SEA.
THE OFFICIAL FORECAST TRACK IS CLOSE TO THE MIDDLE OF THE TIGHTLY
PACKED NHC MODEL GUIDANCE.

LESLIE CONTINUES TO LACK ANY INNER-CORE DEEP CONVECTION AND ALSO HAS
A BROAD INNER-CORE WIND FIELD...WHICH SHOULD INHIBIT ANY
SIGNIFICANT STRENGTHENING IN THE SHORT TERM. HOWEVER...AS THE
CYCLONE BEGINS TO ACCELERATE RAPIDLY NORTHEASTWARD...THE ADDITIONAL
FORWARD SPEED COMPONENT SHOULD INCREASE THE WIND SPEEDS IN THE
EASTERN SEMICIRCLE. SINCE LESLIE IS FORECAST TO BE MOVING AT NEARLY
35 KT BY 36 HOURS...THIS COULD ALLOW THE CYCLONE TO ACHIEVE
HURRICANE STATUS AGAIN BEFORE THE CYCLONE AFFECTS SOUTHEASTERN
NEWFOUNDLAND. AFTER 36 HOURS...THE GLOBAL MODELS INDICATE THAT
LESLIE WILL TRANSITION INTO A VIGOROUS EXTRATROPICAL CYCLONE AFTER
IT MERGES WITH A STRONG FRONTAL SYSTEM BY DAY 2. LESLIE WILL REMAIN
A POWERFUL EXTRATROPICAL CYCLONE UNTIL IT IS ABSORBED BY A LARGER
EXTRATROPICAL LOW PRESSURE SYSTEM ON DAY 5.
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT COUPLE OF DAYS. OWING TO THE INCREASING
FORWARD SPEED OF LESLIE FOR THE NEXT 36 HOURS...A HURRICANE WATCH
WILL LIKELY REQUIRED EARLY FRIDAY MORNING FOR PORTIONS OF
SOUTHEASTERN NEWFOUNDLAND...INCLUDING THE AVALON PENINSULA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 34.4N  61.8W   50 KT  60 MPH
 12H  10/1200Z 36.8N  60.8W   55 KT  65 MPH
 24H  11/0000Z 41.3N  58.2W   60 KT  70 MPH
 36H  11/1200Z 47.5N  53.9W   65 KT  75 MPH...INLAND
 48H  12/0000Z 54.1N  46.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/0000Z 62.5N  25.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  14/0000Z 62.5N   3.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  15/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 100342
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  43
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST SUN SEP 09 2012

CORRECTED FRIDAY TO MONDAY IN LAST PARAGRAPH 
 
THE CONVECTIVE CLOUD PATTERN OF LESLIE HAS CONTINUED TO SLOWLY ERODE
AND CLOUD TOPS HAVE ALSO CONTINUED TO WARM SINCE THE PREVIOUS
ADVISORY. THE INITIAL INTENSITY REMAINS AT 50 KT BASED ON A BLEND
OF DVORAK SATELLITE INTENSITY ESTIMATES OF T3.0/45 KT AND T3.5/55
KT FROM TAFB AND SAB...RESPECTIVELY. 
 
THE INITIAL MOTION ESTIMATE IS 015/14. THERE REMAINS NO SIGNIFICANT
CHANGE TO THE PREVIOUS TRACK FORECAST AND REASONING. LESLIE IS
EXPECTED TO CONTINUE MOVING NORTH-NORTHEASTWARD FOR THE NEXT 12
HOURS OR SO AS THE CYCLONE ROUNDS THE WESTERN PERIPHERY OF A
DEEP-LAYER RIDGE LOCATED TO ITS EAST. BY 24 HOURS...LESLIE IS
FORECAST TO ACCELERATE TO THE NORTHEAST BETWEEN INCREASING
SOUTHWESTERLY FLOW AHEAD OF AN APPROACHING DEEP-LAYER TROUGH FROM
THE WEST AND THE AFOREMENTIONED RIDGE TO THE EAST. BY DAYS 3-4...
LESLIE WILL BE INTERACTING WITH A FRONTAL SYSTEM...AND THE
POST-TROPICAL CYCLONE IS EXPECTED TURN EAST-NORTHEASTWARD AND
EASTWARD IN THE HIGH-LATITUDE WESTERLY FLOW. ABSORPTION BY A LARGER
EXTRATROPICAL LOW IS FORECAST TO OCCUR BY DAY 5 OVER THE NORTH SEA.
THE OFFICIAL FORECAST TRACK IS CLOSE TO THE MIDDLE OF THE TIGHTLY
PACKED NHC MODEL GUIDANCE.

LESLIE CONTINUES TO LACK ANY INNER-CORE DEEP CONVECTION AND ALSO HAS
A BROAD INNER-CORE WIND FIELD...WHICH SHOULD INHIBIT ANY
SIGNIFICANT STRENGTHENING IN THE SHORT TERM. HOWEVER...AS THE
CYCLONE BEGINS TO ACCELERATE RAPIDLY NORTHEASTWARD...THE ADDITIONAL
FORWARD SPEED COMPONENT SHOULD INCREASE THE WIND SPEEDS IN THE
EASTERN SEMICIRCLE. SINCE LESLIE IS FORECAST TO BE MOVING AT NEARLY
35 KT BY 36 HOURS...THIS COULD ALLOW THE CYCLONE TO ACHIEVE
HURRICANE STATUS AGAIN BEFORE THE CYCLONE AFFECTS SOUTHEASTERN
NEWFOUNDLAND. AFTER 36 HOURS...THE GLOBAL MODELS INDICATE THAT
LESLIE WILL TRANSITION INTO A VIGOROUS EXTRATROPICAL CYCLONE AFTER
IT MERGES WITH A STRONG FRONTAL SYSTEM BY DAY 2. LESLIE WILL REMAIN
A POWERFUL EXTRATROPICAL CYCLONE UNTIL IT IS ABSORBED BY A LARGER
EXTRATROPICAL LOW PRESSURE SYSTEM ON DAY 5.
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT COUPLE OF DAYS. OWING TO THE INCREASING
FORWARD SPEED OF LESLIE FOR THE NEXT 36 HOURS...A HURRICANE WATCH
WILL LIKELY REQUIRED EARLY MONDAY MORNING FOR PORTIONS OF
SOUTHEASTERN NEWFOUNDLAND...INCLUDING THE AVALON PENINSULA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 34.4N  61.8W   50 KT  60 MPH
 12H  10/1200Z 36.8N  60.8W   55 KT  65 MPH
 24H  11/0000Z 41.3N  58.2W   60 KT  70 MPH
 36H  11/1200Z 47.5N  53.9W   65 KT  75 MPH...INLAND
 48H  12/0000Z 54.1N  46.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/0000Z 62.5N  25.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  14/0000Z 62.5N   3.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  15/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 100848
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  44
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST MON SEP 10 2012
 
THE CLOUD TOPS ASSOCIATED WITH LESLIE HAVE CONTINUED TO WARM DURING
THE PAST SIX HOURS AND THE CYCLONE NOW HAS ONE PRIMARY BAND OF
CONVECTION OVER THE NORTHEASTERN PORTION OF THE CIRCULATION. RECENT
ASCAT DATA AND DVORAK SATELLITE INTENSITY ESTIMATES SUPPORT KEEPING
THE INITIAL WIND SPEED AT 50 KT. LESLIE HAS ABOUT 12-18 HOURS OVER
WARM WATERS AND IN FAVORABLE SHEAR CONDITIONS IN WHICH TO
STRENGTHEN AS A TROPICAL CYCLONE...HOWEVER...THE LARGE SIZE OF THE
WIND FIELD AND LACK OF AN INNER CORE SHOULD PRECLUDE SIGNIFICANT
INTENSIFICATION. LATER TODAY...LESLIE IS EXPECTED TO BEGIN ITS
TRANSITION TO AN EXTRATROPICAL CYCLONE AND THE GLOBAL MODEL
GUIDANCE SUGGEST THAT LESLIE COULD GAIN STRENGTH FROM BAROCLINIC
PROCESSES. THE NHC FORECAST...THEREFORE...CALLS FOR SOME
STRENGTHENING DURING THE NEXT 24 TO 36 HOURS...AND ALTHOUGH NOT
EXPLICITLY SHOWN...THE CYCLONE COULD REACH HURRICANE INTENSITY
BEFORE IT NEARS NEWFOUNDLAND. IT IS AROUND THAT TIME THAT LESLIE
IS FORECAST TO COMPLETE EXTRATROPICAL TRANSITION...AND THE SYSTEM
IS EXPECTED TO REMAIN A STRONG EXTRATROPICAL CYCLONE OVER THE NORTH
ATLANTIC.
 
THE INITIAL MOTION IS NORTH-NORTHEASTWARD AT 14 KT. INCREASING
SOUTHWESTERLY FLOW AHEAD OF A LARGE MID-LATITUDE TROUGH NEARING THE
EAST COAST OF THE UNITED STATES SHOULD CAUSE LESLIE TO ACCELERATE
NORTH-NORTHEASTWARD DURING THE NEXT DAY OR SO. IN A COUPLE OF
DAYS...THE EXTRATROPICAL CYCLONE SHOULD TURN EASTWARD IN STRONG
WESTERLY FLOW OVER THE NORTHERN LATITUDES.
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR ANOTHER DAY OR SO.
 
THE CANADIAN HURRICANE CENTER HAS ISSUED HURRICANE AND TROPICAL
STORM WATCHES FOR PORTIONS OF NEWFOUNDLAND.  WARNINGS MAY BE
REQUIRED LATER THIS MORNING.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 35.7N  61.2W   50 KT  60 MPH
 12H  10/1800Z 38.8N  59.8W   55 KT  65 MPH
 24H  11/0600Z 44.5N  56.8W   60 KT  70 MPH
 36H  11/1800Z 51.9N  50.9W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  12/0600Z 58.5N  42.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/0600Z 63.0N  20.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  14/0600Z...ABSORBED
 
$$
FORECASTER BROWN
 

WTNT42 KNHC 101456
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  45
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 AM AST MON SEP 10 2012
 
LESLIE NEVER DEVELOPED AN INNER CORE...AND CONTINUES AS A LARGE
SPRAWLING CYCLONE WITH MOST OT THE TROPICAL-STORM-FORCE WINDS
WITHIN A RELATIVELY WEAK CONVECTIVE BAND TO THE NORTH AND EAST OF
THE CENTER.  GIVEN THE SATELLITE PRESENTATION AND DVORAK
ESTIMATES...THE INITIAL INTENSITY IS KEPT AT 50 KNOTS.
LESLIE NEVER INTENSIFIED AS SUGGESTED BY GLOBAL MODELS A FEW DAYS
AGO...AND THERE IS LITTLE TIME REMAINING FOR LESLIE TO INTENSIFY AS
A TROPICAL CYCLONE SINCE IT IS ALREADY REACHING COOL WATERS. THE
OFFICIAL FORECAST INCREASES THE WINDS BY 10 KNOTS...BUT THIS
INTENSIFICATION...IF IT OCCURS...WILL BE ASSOCIATED WITH THE
EXTRATROPICAL TRANSITION.
 
SATELLITE FIXES YIELD AN INITIAL MOTION OF 030 DEGREES AT 15 KNOTS. 
SINCE LESLIE IS WELL EMBEDDED WITHIN THE FAST SOUTHWESTERLY
FLOW AHEAD OF THE WESTERN ATLANTIC TROUGH...THIS GENERAL TRACK
SHOULD CONTINUE WITH A SIGNIFICANT INCREASE IN FORWARD SPEED.  MOST
OF THE MODELS ARE IN GOOD AGREEMENT BRINGING THE CENTER OF LESLIE
ACROSS SOUTHEASTERN NEWFOUNDLAND IN ABOUT 24 HOURS.  IT IS AROUND
THAT TIME THAT LESLIE IS FORECAST TO COMPLETE EXTRATROPICAL
TRANSITION...AND THEN REMAIN A STRONG EXTRATROPICAL CYCLONE OVER
THE NORTH ATLANTIC FOR A COUPLE OF DAYS.
 
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR ANOTHER DAY OR SO.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 37.0N  60.2W   50 KT  60 MPH
 12H  11/0000Z 41.4N  58.5W   60 KT  70 MPH
 24H  11/1200Z 48.0N  54.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  12/0000Z 55.0N  47.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  12/1200Z 60.5N  38.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  13/1200Z...ABSORBED

$$
FORECASTER AVILA
 

WTNT42 KNHC 102033
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  46
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 PM AST MON SEP 10 2012
 
ALTHOUGH THE CLOUD PATTERN AND DVORAK T-NUMBERS HAVE NOT CHANGED
VERY MUCH...A RECENT ASCAT OVERPASS AND A NEARBY SHIP REPORT
INDICATE THAT LESLIE HAS WINDS OF 60 KNOTS WITHIN THE CONVECTIVE
BAND TO THE NORTH AND EAST OF THE CENTER. ASCAT DATA ALSO SHOW THAT
THE WINDS ARE DECREASING IN THE WESTERN SEMICIRCLE. THE ASYMMETRY
OF THE WINDS AND THE RAIN SHIELD SUGGEST THAT LESLIE IS BEGINNING
TO SLOWLY LOSE TROPICAL CHARACTERISTICS. ONLY SMALL CHANGES IN
INTENSITY ARE ANTICIPATED BEFORE LESLIE REACHES SOUTHEASTERN
NEWFOUNDLAND EARLY TUESDAY. ONCE LESLIE BECOMES POST-TROPICAL...
IT WILL REMAIN A VERY STRONG EXTRATROPICAL CYCLONE FOR THE NEXT 
FEW DAYS.
 
LESLIE HAS ACCELERATED AND IS NOW MOVING TOWARD THE NORTH-NORTHEAST
AT ABOUT 30 KNOTS...EMBEDDED IN THE MID-LEVEL JET EAST OF THE TROUGH
CURRENTLY MOVING OVER THE WESTERN ATLANTIC. AN ADDITIONAL INCREASE
IN FORWARD SPEED IS ANTICIPATED...AND THE CENTER IS FORECAST TO
CROSS SOUTHEASTERN NEWFOUNDLAND BETWEEN 12 AND 24 HOURS. THIS IS
CONSISTENT WITH MOST OF THE TRACK GUIDANCE.
 
LONG-PERIOD SWELLS FROM LESLIE ARE STILL EXPECTED TO PRODUCE ROUGH
SURF AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF
THE U.S. EAST COAST...THE CANADIAN ATLANTIC PROVINCES.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/2100Z 40.0N  59.1W   60 KT  70 MPH
 12H  11/0600Z 44.4N  56.8W   60 KT  70 MPH
 24H  11/1800Z 51.5N  51.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  12/0600Z 58.0N  42.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  12/1800Z 62.5N  34.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  13/1800Z 62.5N  17.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  14/1800Z...ABSORBED
 
$$
FORECASTER AVILA
 

WTNT42 KNHC 110258
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  47
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
1100 PM AST MON SEP 10 2012
 
THE OVERALL CLOUD PATTERN HAS NOT CHANGED MUCH SINCE THE PREVIOUS
ADVISORY OTHER THAN CLOUD TOPS HAVE COOLED SLIGHTLY TO THE NORTH
AND EAST OF THE CENTER. AN EARLIER ASCAT OVERPASS INDICATED THAT
LESLIE HAS WINDS OF AT LEAST 60 KT TO THE NORTH AND NORTHEAST OF
THE CENTER. HOWEVER...RECENT DATA FROM CANADIAN BUOY 44139 LOCATED
ABOUT 100 NMI NORTH-NORTHEAST OF THE CENTER SUGGEST THAT THE
MAXIMUM WINDS ASSOCIATED WITH LESLIE HAVE LIKELY SHIFTED TO THE
EAST AND SOUTHEAST OF THE CENTER SINCE THE WINDS AT THAT BUOY HAVE
NOT INCREASED TO MORE THAN 25 KT. THE ASYMMETRY OF THE WINDFIELD
AND THE CONVECTIVE PATTERN IS MORE INDICATIVE OF AN EXTRATROPICAL
RATHER THAN A TROPICAL CYCLONE DUE TO A STRONG COLD FRONTAL SYSTEM
NOW LOCATED ONLY ABOUT 100 NMI WEST OF THE CENTER. IT IS QUITE
POSSIBLE THAT THE FRONTAL SYSTEM WILL CATCH UP TO AND MERGE WITH
THE CIRCULATION CENTER BEFORE LESLIE REACHES NEWFOUNDLAND.
REGARDLESS OF THE STATUS OF THE CYCLONE AT LANDFALL TUESDAY
MORNING...IT WILL STILL BE A POWERFUL LOW PRESSURE SYSTEM.
ONCE LESLIE BECOMES POST-TROPICAL...IT WILL REMAIN A VERY STRONG
EXTRATROPICAL CYCLONE FOR THE NEXT FEW DAYS OVER THE COLD WATERS OF
THE FAR NORTH ATLANTIC.
 
LESLIE HAS CONTINUED TO ACCELERATE AND IS NOW MOVING TOWARD THE
NORTH-NORTHEAST AT ABOUT 35 KT. THE CYCLONE IS EMBEDDED IN STRONG
SOUTH-SOUTHWESTERLY DEEP-LAYER FLOW AHEAD OF A VIGOROUS NEGATIVELY
TILTED MID-LATITUDE TROUGH THAT IS ORIENTED NORTHWEST-TO-SOUTHEAST
ACROSS MAINE AND THE CANADIAN MARITIMES. AN ADDITIONAL INCREASE
IN FORWARD SPEED IS ANTICIPATED AS THE TROUGH LIFTS OUT TO THE
NORTHEAST...AND THE CENTER OF LESLIE IS FORECAST TO MAKE LANDFALL
OVER SOUTHEASTERN NEWFOUNDLAND IN ABOUT 12 HOURS OR SO. THE OFFICIAL
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY...AND LIES CLOSE
TO THE DYNAMICAL CONSENSUS MODELS TVCN AND TV15.
 
LONG-PERIOD SWELLS FROM LESLIE ARE STILL EXPECTED TO PRODUCE ROUGH
SURF AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF
THE U.S. EAST COAST...AND THE CANADIAN ATLANTIC PROVINCES.

FORECAST POSITIONS AND MAX WINDS
 
INIT  11/0300Z 42.7N  57.5W   60 KT  70 MPH
 12H  11/1200Z 47.6N  54.1W   60 KT  70 MPH...INLAND
 24H  12/0000Z 54.2N  47.2W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  12/1200Z 59.8N  38.6W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  13/0000Z 62.5N  29.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  14/0000Z 62.5N  10.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  15/0000Z...ABSORBED BY LARGER EXTRATROPICAL LOW
 
$$
FORECASTER STEWART
 

WTNT42 KNHC 110856
TCDAT2
 
TROPICAL STORM LESLIE DISCUSSION NUMBER  48
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122012
500 AM AST TUE SEP 11 2012
 
LESLIE IS RAPIDLY TRANSFORMING INTO AN EXTRATROPICAL CYCLONE AS 
THE COLDEST CLOUD TOPS ARE NOW LOCATED TO THE NORTH AND NORTHWEST
OF THE CENTER...AND COLD AIR IS BEGINNING TO WRAP AROUND THE
SOUTHWESTERN SIDE OF THE SYSTEM.  DATA FROM CANADIAN BUOY 44139
HAVE BEEN VERY HELPFUL IN LOCATING THE CENTER AND DETERMING THAT
THE MINIMUM PRESSURE IS SIGNIFICANTLY LOWER THAN PREVIOUSLY
ESTIMATED.  THE BUOY REPORTED SUSTAINED WINDS OF 47 KT WITH A GUST
TO 60 KT AROUND 0600 UTC...AND A MINIMUM PRESSURE OF 971.5 MB ABOUT
AN HOUR LATER.  THE BUOY REPORTS INDICATE THAT LESLIE IS ALSO
LOCATED SLIGHTLY WEST OF THE EARLIER POSITION ESTIMATES.  THE
INITIAL INTENSITY REMAINS 60 KT AND IS BASED ON ASCAT DATA
THAT SHOWED A LARGE AREA OF 50 TO 55 KT WINDS. 

LESLIE IS MOVING NORTH-NORTHEAST AT 35 KT...AND WILL CONTINUE TO
ACCELERATE TODAY.  THE CENTER WILL BE PASSING OVER EASTERN
NEWFOUNDLAND VERY SOON AND WINDS ARE ALREADY INCREASING ALONG THE
COAST.  THE NHC TRACK FORECAST HAS BEEN SHIFTED WEST OF THE PREVIOUS
ADVISORY DURING THE FIRST 12 TO 24 HOURS TO ACCOUNT FOR THE MORE
WESTWARD INITIAL POSTION.  

LESLIE SHOULD COMPLETE ITS TRANSITION TO AN EXTRATROPICAL CYCLONE
THIS MORNING AND IS FORECAST TO REMAIN A LARGE AND POWERFUL
CYCLONE OVER THE NORTH ATLANTIC FOR THE NEXT TWO TO THREE DAYS. 
THE EXTRATROPICAL LOW SHOULD TURN EAST-NORTHEASTWARD...THEN EASTWARD
DURING THE NEXT COUPLE OF DAYS.  THE GLOBAL MODELS SHOW THE
EXTRATROPICAL CYCLONE BEING ABSORBED BY ANOTHER LOW OVER THE
NORTHEASTERN ATLANTIC IN JUST OVER 72 HOURS.

THE INITIAL WIND RADII HAVE BEEN ADJUSTED OUTWARD BASED ON RECENT
ASCAT AND SURFACE DATA. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  11/0900Z 45.7N  56.4W   60 KT  70 MPH
 12H  11/1800Z 51.0N  52.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 24H  12/0600Z 57.5N  43.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  12/1800Z 61.5N  33.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  13/0600Z 63.5N  25.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  14/0600Z 61.5N   9.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  15/0600Z...ABSORBED
 
$$
FORECASTER BROWN
 

