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| #6307 (Received by flhurricane at: 10:58 AM 28.Aug.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT SAT AUG 28 2004 BASED ON SSMI AND AMSU MICROWAVE AND VISIBLE SATELLITE DATA THIS MORNING...IT APPEARS THAT FRANCES HAS COMPLETED AN EYEWALL REPLACEMENT CYCLE. THE EYE HAS CLEARED OUT NOW AND HAS INCREASED TO AT LEAST A 20 NMI DIAMETER. THE INITIAL INTENSITY HAS BEEN INCREASED SLIGHTLY TO 105 KT BASED ON A DVORAK INTENSITY ESTIMATE OF T5.5...OR 102 KT FROM TAFB FOR THE PAST 18 HR...A 3-HR ODT AVERAGE OF T5.6...OR 105 KT...AND THE IMPROVED EYE APPEARANCE. THE INITIAL MOTION IS 310/08. FRANCES REMAINS ON TRACK AND IS EXPECTED TO RESUME A MORE WEST-NORTHWESTWARD MOTION AT A SLIGHTLY FASTER SPEED LATER TODAY. NHC MODEL GUIDANCE IS IN STRONG AGREEMENT THROUGH 72 HOURS ON FRANCES TAKING A WEST-NORTHWESTWARD TRACK THROUGH 48 HOURS AND THEN BENDING MORE WESTWARD IN 48-72HR. HOWEVER ...THE MODELS DIVERGE DUE TO THE WAY THEY HANDLE NOW TROPICAL STORM GASTON OFF THE SOUTH CAROLINA COAST. THE GFS...UKMET...AND THE CANADIAN MODELS LIFT GASTON SLOWLY NORTHWARD THROUGH 48 HR...AND THEN RAPIDLY NORTHEASTWARD BY 96 HR AND HAS GASTON OUT OF THE PICTURE BY 120 HR. THE SUBTROPICAL RIDGE THEN BUILDS IN BETWEEN GASTON AND FRANCES...WHICH WOULD HELP TO KEEP FRANCES ON A WEST-NORTHWEST TO WESTWARD TRACK. IN CONTRAST...THE GFDL AND NOGAPS MODELS LEAVE A WEAK MID-LEVEL TROUGH BEHIND ALONG THE SOUTHEASTERN U.S. COAST IN THE WAKE OF GASTON. THIS ALLOWS FRANCES TO TURN NORTHWESTWARD BY 96HR WELL EAST OF THE BAHAMAS. THE OFFICIAL FORECAST TRACK LEANS CLOSELY TOWARD THE GFS-UKMET-CANADIAN SOLUTION GIVEN THAT THE MID- AND UPPER-LEVEL FLOW PATTERN IS FORECAST TO BECOME HIGHLY ZONAL ACROSS THE NORTHERN U.S...WHICH SHOULD ALLOW THE SUBTROPICAL RIDGE TO BUILD WESTWARD ACROSS THE SOUTHEASTERN U.S. AND EASTERN ATLANTIC TO THE NORTH OF FRANCES THROUGHOUT THE PERIOD. NOW THAT FRANCES HAS COMPLETED AN EYEWALL REPLACEMENT CYCLE...AT LEAST STEADY INTENSIFICATION SHOULD RESUME SINCE THE UPPER-LEVEL OUTFLOW HAS CONTINUED TO EXPAND AND BECOME MORE CIRCULAR. A POLEWARD OUTFLOW CHANNEL HAS ALSO DEVELOPED TO THE NORTH. THE FAVORABLE UPPER-LEVEL ENVIRONMENT COMBINED WITH ONLY WARM WATER... UP TO 29C SST...AHEAD OF FRANCES SHOULD ALLOW THE HURRICANE TO REACH AT LEAST CATEGORY 4 STRENGTH IN THE NEXT 24 HOURS OR SO. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 28/1500Z 17.4N 51.9W 105 KT 12HR VT 29/0000Z 18.3N 53.3W 110 KT 24HR VT 29/1200Z 19.3N 55.3W 115 KT 36HR VT 30/0000Z 20.1N 57.4W 120 KT 48HR VT 30/1200Z 20.5N 59.7W 120 KT 72HR VT 31/1200Z 21.3N 64.6W 120 KT 96HR VT 01/1200Z 22.0N 69.0W 120 KT 120HR VT 02/1200Z 23.0N 73.0W 120 KT |
