000 WTNT43 KNHC 020859 TCDAT3 HURRICANE HANNA DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 500 AM EDT TUE SEP 02 2008 CONVENTIONAL AND PASSIVE MICROWAVE SATELLITE IMAGERY INDICATE HANNA HAS MOVED SOUTHWARD OVER THE PAST 6 HOURS WHILE MAINTAINING A PRONOUNCED EYE FEATURE IN A 02/203Z AMSU OVERPASS. SATELLITE INTENSITY ESTIMATES ARE T4.0/65 KT AND T4.5/77 KT FROM TAFB AND SAB...RESPECTIVELY. THEREFORE...THE INITIAL INTENSITY REMAINS UNCHANGED AT 70 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 270/02 KT. LATEST SATELLITE POSITION ESTIMATES SUGGEST THAT HANNA COULD STILL BE MOVING SOUTHWARD. HOWEVER...ALL OF THE GLOBAL MODELS ARE NOW IN EXCELLENT AGREEMENT THAT AN UPPER-LEVEL LOW WILL PINCH OFF TO THE SOUTH AND WEST OF HANNA DURING THE NEXT 24-36 HOURS...WHICH IS EXPECTED TO INDUCE A SLOW NORTH AND THEN NORTHWESTWARD MOTION ACROSS THE SOUTHEASTERN BAHAMAS. BY 48-72 HOURS...THE SUBTROPICAL RIDGE TO THE NORTHEAST OF HANNA IS FORECAST TO GRADUALLY BUILD WESTWARD THROUGH 96 HOURS...WHICH SHOULD INDUCE A FASTER FORWARD NORTHWESTWARD MOTION TOWARD THE SOUTHEASTERN UNITED STATES. THE RIDGE AXIS IS FORECAST BY ALL THE MODELS TO GENERALLY EXTEND EAST-WEST BETWEEN 32-24N LATITUDE...AND THE EXACT TRACK OF HANNA WILL DEPEND HEAVILY ON HOW FAR SOUTH AND WEST THE CYCLONE MOVES DURING THE NEXT 36 HOURS...AND ALSO HOW STRONG THE WESTERN PORTION OF THE RIDGE WILL BE. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS ADVISORY AND IS DOWN THE MIDDLE OF THE TIGHTLY CLUSTERED NHC MODEL GUIDANCE SUITE. HANNA IS FORECAST TO MOVE NORTHWESTWARD UNTIL IT REACHES THE COAST OF SOUTH CAROLINA...AFTER WHICH IT IS EXPECTED TO GRADUALLY RECURVE TO THE NORTHEAST. AN APPROXIMATE 84-HOUR POSITION WOULD BE NEAR 31.3N 80.2W. HANNA HAS MAINTAINED A WELL-DEFINED INNER-CORE STRUCTURE BASED ON THE 0202Z AMSU OVERPASS...AND ANOTHER CDO FEATURE WITH CLOUD TOPS AS COLD OF -80C TO -87C HAS REDEVELOPED OVER THE CENTER SIMILAR TO THE THIS TIME LAST NIGHT. THE CURRENT 30-KT NORTHERLY SHEAR PATTERN IS FORECAST BY ALL THE MODELS TO BEGIN TO WEAKEN TODAY AND CONTINUE TO WEAKEN DURING THE NEXT 48 HOURS...AND GRADUALLY SWITCH TO A SOUTHEASTERLY COMPONENT WITH LESS THAN 15 KT OF SHEAR AT 72-96 HOURS. GIVEN THE DEVELOPMENT OF A FAVORABLE UPPER-LEVEL OUTFLOW PATTERN AND SSTS OF AT LEAST 28C ALONG THE FORECAST TRACK UNTIL LANDFALL...STEADY INTENSIFICATION SEEMS QUITE REASONABLE. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY ...AND IS SIMILAR TO THE SHIPS MODEL. IT IS IMPORTANT TO NOTE THAT HANNA IS EXPECTED TO CONTINUE TO INTENSIFY...OR AT LEAST REMAIN STEADY...UNTIL LANDFALL OCCURS BETWEEN 84 AND 96 HOURS...RATHER THAN APPEAR TO BE WEAKENING LIKE SOME AUTOMATIC INTENSITY PLOTTING SOFTWARE MAY SHOW. IN FACT...BY 84 HOURS HANNA COULD BE A MAJOR HURRICANE. FORECAST POSITIONS AND MAX WINDS INITIAL 02/0900Z 21.3N 72.7W 70 KT 12HR VT 02/1800Z 21.4N 73.1W 70 KT 24HR VT 03/0600Z 22.0N 73.5W 75 KT 36HR VT 03/1800Z 23.0N 74.3W 80 KT 48HR VT 04/0600Z 24.4N 75.5W 85 KT 72HR VT 05/0600Z 28.7N 79.0W 90 KT 96HR VT 06/0600Z 34.7N 80.7W 55 KT...INLAND 120HR VT 07/0600Z 42.5N 74.0W 35 KT...EXTRATROPICAL INLAND $$ FORECASTER STEWART