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| #540234 (Received by flhurricane at: 10:44 PM 04.Sep.2012) TCDAT2 TROPICAL STORM LESLIE DISCUSSION NUMBER 23 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012 1100 PM AST TUE SEP 04 2012 DEEP CONVECTION HAS BEEN BURSTING NEAR THE LOW-LEVEL CENTER OF LESLIE FOR THE PAST FEW HOURS. THE CONVECTION HAS TAKEN ON THE SHAPE OF A NASCENT CENTRAL DENSE OVERCAST...BUT WEST-NORTHWESTERLY SHEAR OF AROUND 20 KT CONTINUES TO PUSH THE MAIN CONVECTIVE MASS EASTWARD. TRMM AND SSM/IS IMAGES...FROM 2223 AND 0013 UTC RESPECTIVELY...SUGGEST SOME RECENT INCREASE IN ORGANIZATION AS EVIDENCED BY THE FORMATION OF A CLOSED MID-LEVEL EYE...BUT THIS FEATURE CONTINUES TO BE DISPLACED 20-30 N MI EAST OF THE LOW-LEVEL CENTER. THE INITIAL INTENSITY IS HELD AT 55 KT IN AGREEMENT WITH A 0000 UTC SATELLITE CLASSIFICATION FROM TAFB. GLOBAL MODELS FORECAST A SUBSTANTIAL DECREASE IN SHEAR IN ABOUT 24 HOURS AS A LARGE-SCALE ANTICYCLONE FORMS OVER LESLIE. THE DEEP OCEANIC MIXED LAYER ALONG THE TRACK OF THE SLOW-MOVING STORM SHOULD ALSO MINIMIZE THE EFFECTS OF UPWELLING. STRENGTHENING IS FORECAST TO BEGIN AROUND THE TIME THE SHEAR RELAXES...BUT THE RATE OF INTENSIFICATION COULD INITIALLY BE SLOW DUE TO THE LARGE SIZE OF THE CIRCULATION. THE NHC INTENSITY FORECAST IS NOT MUCH DIFFERENT THAN THE PREVIOUS ONE...AND IS IN GOOD AGREEMENT WITH THE LATEST SHIPS AND INTENSITY CONSENSUS AIDS. LESLIE APPEARS TO HAVE JOGGED A BIT TO THE LEFT TODAY...AND IS PLODDING ALONG TOWARD THE NORTH-NORTHWEST WITH AN INITIAL MOTION ESTIMATE OF 345/02. THE CYCLONE IS IN A WEAK STEERING ENVIRONMENT...SANDWICHED BETWEEN TWO WEAK MID-LEVEL ANTICYCLONES. WHILE THIS PATTERN SHOULD ALLOW A NET NORTHWARD STEERING FLOW OVER LESLIE DURING THE NEXT FEW DAYS...THE STORM IS LIKELY TO MAKE ONLY SLOW PROGRESS DUE TO A WEAK BLOCKING LOW- TO MID-LEVEL RIDGE SLIDING BY TO THE NORTH. AS THAT RIDGE SHIFTS AND BUILDS TO THE NORTHEAST IN 48-72 HOURS...LESLIE WILL BE DRAWN NORTHWARD MORE QUICKLY. THE FLOW BETWEEN THIS SAME RIDGE AND AN AMPLIFYING SHORTWAVE TROUGH APPROACHING THE UNITED STATES EAST COAST ON DAYS 4-5 WILL BEGIN TO EJECT LESLIE TOWARD THE NORTH OR NORTH-NORTHEAST BY THE END OF THE FORECAST PERIOD. THE NHC TRACK FORECAST IS BIT SLOWER THAN THE PREVIOUS ONE AFTER 48 HOURS IN DEFERENCE TO THE LATEST GFS RUN...BUT IS ADJUSTED A BIT TO THE EAST AT LATER TIMES. THIS IS CLOSE TO THE MULTI-MODEL TVCA CONSENSUS. LESLIE IS A LARGE TROPICAL CYCLONE AND IS FORECAST TO GROW FURTHER IN SIZE DURING THE NEXT SEVERAL DAYS. THE WIND FIELD OF THE CYCLONE...IN COMBINATION WITH ITS EXPECTED SLOW MOTION...WILL HELP TO GENERATE LARGE LONG-PERIOD SWELLS WHICH WILL PROPAGATE AWAY FROM THE TROPICAL CYCLONE TOWARD BERMUDA BERMUDA AND MUCH OF THE UNITED STATES EAST COAST FOR THE REMAINDER OF THIS WEEK. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 25.2N 62.8W 55 KT 65 MPH 12H 05/1200Z 25.6N 62.9W 55 KT 65 MPH 24H 06/0000Z 26.1N 63.0W 55 KT 65 MPH 36H 06/1200Z 26.5N 63.0W 60 KT 70 MPH 48H 07/0000Z 26.7N 63.0W 65 KT 75 MPH 72H 08/0000Z 27.5N 63.8W 75 KT 85 MPH 96H 09/0000Z 30.0N 65.0W 80 KT 90 MPH 120H 10/0000Z 35.0N 65.0W 90 KT 105 MPH $$ FORECASTER KIMBERLAIN |
