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| #386234 (Received by flhurricane at: 10:38 AM 29.Oct.2010) TCDAT5 TROPICAL STORM SHARY DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL202010 1100 AM AST FRI OCT 29 2010 SATELLITE IMAGERY INDICATES SHARY HAS SLOWED DOWN CONSIDERABLY DURING THE PAST FEW HOURS AS A SMALL UPPER-LEVEL LOW HAS DROPPED TO THE SOUTH AND SOUTHEAST OF THE CYCLONE. THIS HAS RESULTED IN THE VERTICAL SHEAR SHIFTING FROM AN EASTERLY TO NORTHERLY DIRECTION... CAUSING THE INNER-CORE CONVECTION TO SHIFT TO THE SOUTH SIDE OF THE CIRCULATION CENTER. DRY AIR NOTED IN WATER VAPOR IMAGERY HAS ALSO WRAPPED INTO THE EASTERN AND NORTHERN QUADRANTS...RESULTING IN EROSION OF CONVECTION IN THOSE AREAS. THE INITIAL ESTIMATE REMAINS AT 35 KT FOR THIS BASED ON SHEAR-PATTERN SATELLITE INTENSITY ESTIMATES OF T2.5/35 KT FROM TAFB AND T3.0/45 KT FROM SAB. THE INITIAL MOTION ESTIMATE IS 360/04. SHARY IS POSSIBLY PREPARING TO MAKE A SHARP CUSP IN THE TRACK...AND A TURN TO THE NORTH AND NORTHEAST IS EXPECTED WITHIN THE NEXT 12 HOURS OR SO AS THE SMALL UPPER-LEVEL LOW THAT HAS BEEN INFLUENCING THE SHORT TERM MOTION WEAKENS AND/OR DISSIPATES. AFTER THAT...AN EASTWARD-MOVING MID-/UPPER-LEVEL TROUGH CURRENTLY LOCATED JUST OFF THE U.S. EAST COAST AND EXTENDING ACROSS FLORIDA IS FORECAST TO CAPTURE THE CYCLONE BY 24 HOURS...AND ACCELERATE SHARY RAPIDLY TO THE NORTHEAST. NHC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS TRACK SCENARIO...EXCEPT FOR JUST MINOR DIFFERENCES IN THE FORWARD SPEED. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE MULTI-MODEL CONSENSUS...TVCN. THE VERTICAL SHEAR IS FORECAST TO WEAKEN SOME AND REMAIN BELOW 10 KT FOR THE NEXT 12-18 HOURS WHILE SHARY REMAINS OVER MARGINAL SSTS NEAR 26C. THE LOW SHEAR AND COOLER-THAN-NORMAL TEMPERATURES ALOFT...AS NOTED IN THE 11Z BERMUDA UPPER-AIR SOUNDING...SHOULD ALLOW FOR DEEP CONVECTION TO RE-DEVELOP NEAR THE CENTER...RESULTING IN SOME SLIGHT STRENGTHENING. BY 24 HOURS AND BEYOND...HOWEVER... STRONG VERTICAL SHEAR IN EXCESS OF 30 KT SHOULD KICK IN AND HELP THE CYCLONE TO TRANSITION INTO A POST-TROPICAL LOW PRESSURE SYSTEM AS THE CYCLONE MOVES OVER MUCH COOLER WATER TEMPERATURES. THE GFDL AND HWRF MODELS MAKE SHARY A HURRICANE IN ABOUT 36 HOURS...WHICH SEEMS EXCESSIVE GIVEN THE VERY COOL SSTS THAT THE CYCLONE WILL BE PASSING OVER AT THAT TIME. AS A RESULT...THOSE INTENSITY FORECAST SCENARIOS HAVE BEEN DISCOUNTED. THE NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A BLEND OF THE SHIPS/LGEM MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 29/1500Z 29.6N 66.2W 35 KT 12HR VT 30/0000Z 32.2N 64.5W 40 KT 24HR VT 30/1200Z 35.6N 60.0W 45 KT 36HR VT 31/0000Z 39.9N 52.9W 45 KT...POST-TROP/EXTRATROP 48HR VT 31/1200Z 45.0N 43.5W 40 KT...POST-TROP/EXTRATROP 72HR VT 01/1200Z...DISSIPATED $$ FORECASTER STEWART |
