Tropical Storm LESLIE

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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
 
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