Tropical Storm LESLIE

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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
 
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