[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT41 KNHC 281444
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


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