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| #539455 (Received by flhurricane at: 10:56 PM 01.Sep.2012) 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 |
