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| #541772 (Received by flhurricane at: 4:50 AM 10.Sep.2012) 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 |
