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| #538889 (Received by flhurricane at: 10:44 PM 30.Aug.2012) 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 |
