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| #210621 (Received by flhurricane at: 11:03 PM 25.Aug.2008) TCDAT2 TROPICAL STORM GUSTAV DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008 1100 PM EDT MON AUG 25 2008 THE CLOUD PATTERN HAS BECOME BETTER DEFINED OVER THE PAST FEW HOURS...WITH A WELL-DEFINED EYE AND A THICKENING EYEWALL. DVORAK CLASSIFICATIONS AT 00Z WERE T3.5 FROM BOTH TAFB AND SAB BUT THE STRUCTURE HAS IMPROVED SINCE THEN. THE INITIAL INTENSITY IS INCREASED TO 60 KT AND THE NEXT AIRCRAFT AT 06Z WILL MOST LIKELY FIND A HURRICANE. A MICROWAVE PASS AT 2243Z SHOWED A LOW-LEVEL EYEWALL. GIVEN THIS STRUCTURE...AND A SHIPS RI INDEX WELL ABOVE CLIMATOLOGY...SIGNIFICANT STRENGTHENING IS LIKELY PRIOR TO THE CENTER OF GUSTAV REACHING HAITI. AFTER THAT...THE INTENSITY OF GUSTAV WILL DEPEND LARGELY ON HOW MUCH THE CIRCULATION INTERACTS WITH THE LAND MASSES OF HAITI AND CUBA. GLOBAL MODELS FORECAST AN UPPER LEVEL PATTERN THAT...WHILE NOT ANTICYCLONIC...IS AT LEAST DIFLUENT AND OF LIGHT SHEAR. THE LATEST FORECAST TRACK INDICATES MORE TIME OVER WATER THAN THE PREVIOUS ADVISORY AND SO THE INTENSITY FORECAST HAS BEEN INCREASED TO REFLECT THAT. BOTH THE GFDL AND THE HWRF SHOW GUSTAV AVOIDING NEARLY ALL OF CUBA AND HAVE GUSTAV AS A MAJOR HURRICANE IN FIVE DAYS. THE INITIAL MOTION IS 310/10. A MID-TROPOSPHERIC ANTICYCLONE CENTERED IN THE NORTHWESTERN BAHAMAS IS FORECAST TO REMAIN LARGELY IN PLACE FOR THE NEXT THREE DAYS OR SO. THIS PATTERN SHOULD RESULT IN A SLOWING OF GUSTAV'S FORWARD SPEED AND A TURN TO THE LEFT. EXCEPT FOR THE NOGAPS...THE DYNAMICAL GUIDANCE MODELS KEEP GUSTAV SOUTH OF CENTRAL CUBA. THE OFFICIAL FORECAST IS ADJUSTED SOUTHWARD OF THE PREVIOUS ADVISORY BUT MOST OF THE PRIMARY GUIDANCE IS EVEN FARTHER SOUTH. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 16.6N 71.4W 60 KT 12HR VT 26/1200Z 17.5N 72.6W 65 KT 24HR VT 27/0000Z 18.5N 73.9W 80 KT...INLAND 36HR VT 27/1200Z 19.3N 75.1W 75 KT 48HR VT 28/0000Z 19.8N 76.2W 80 KT 72HR VT 29/0000Z 20.5N 78.0W 75 KT 96HR VT 30/0000Z 21.5N 80.5W 75 KT 120HR VT 31/0000Z 23.0N 83.5W 75 KT $$ FORECASTER FRANKLIN |
