[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT41 KNHC 030300
TCDAT1
HURRICANE FRANCES DISCUSSION NUMBER  37
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU SEP 02 2004

FRANCES HAS WEAKENED SOME THIS EVENING BASED ON RECONNAISSANCE
REPORTS AND SATELLITE DATA. THE INTENSITY IS BEING DECREASED TO 110
KT BASED ON 948-950 MB PRESSURE REPORTS. SINCE THE LAST RECON
REPORTS...SATELLITE IMAGERY INDICATES THE DEEP CONVECTION AROUND
THE EYE HAS BECOME CIRCULAR AND TOPS HAVE COOLED. THUS...THIS MAY
ONLY BE A TEMPORARY WEAKENING PHASE.

THE MOTION OVER THE PAST 12 HOURS HAS BEEN 300/09. UNLIKE THE PAST
SEVERAL DAYS...THE MODEL GUIDANCE IS STRONGLY CONVERGENT ON A
GENERAL WEST-NORTHWESTWARD MOTION THROUGH THE NEXT 72 HOURS...WITH
A GRADUAL DECREASE IN FORWARD SPEED. THE 18Z MODEL GUIDANCE HAS
MADE A SLIGHT SHIFT TO THE RIGHT...BUT THIS IS LIKELY DUE TO THE
MODELS HAVING TOO WEAK OF A RIDGE TO THE NORTH. 18Z UPPER-AIR AND
SYNOPTIC SURVEILLANCE DROPSONDE DATA INDICATE A STRONGER 700-400
RIDGE BY ABOUT 20 METERS. A SMALL HIGH PRESSURE CELL THAT WAS NEAR
30N 75W THIS TIME LAST NIGHT HAS NOW MOVED WESTWARD TO NEAR
JACKSONVILLE FLORIDA...WITH A RIDGE AXIS EXTENDING EASTWARD TO THE
NORTH OF FRANCES...AND SOUTHWESTWARD OVER THE NORTHEAST AND CENTRAL
GULF OF MEXICO. THIS WRAPAROUND-TYPE RIDGE PATTERN IS INDICATIVE OF
A SLOWING OF THE FORWARD SPEED...AND ALL OF THE MODELS APPEAR TO
HAVE PICKED UP REASONABLY WELL ON THIS FEATURE. UNFORTUNATELY...
THAT TYPE OF RIDGE PATTERN WITH FORWARD SPEEDS AS LOW AS 6-8 KT
ALSO FAVORS ERRATIC MOTION AND WOBBLES ALONG THE TRACK. THE SLOW
FORWARD SPEED WILL ALSO PROLONG ADVERSE AND HAZARDOUS CONDITIONS.
THE FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK...ONLY
SLIGHTLY SLOWER...AND IS A LITTLE LEFT OF THE GUNA CONSENSUS MODEL.

THE DROPSONDE SURVEILLANCE WIND DATA ALSO INDICATED THAT THE 300 MB
WIND FLOW IS FROM THE SOUTH-SOUTHEAST AND IS UNDERCUTTING THE VERY
IMPRESSIVE OUTFLOW LAYER. THIS HAS LIKELY BEEN DISRUPTING THE EYE
SINCE THE BLOCKING RIDGE TO THE NORTH HAS BEEN TRYING TO PUSH
FRANCES WESTWARD. THIS MID-TO UPPER-LEVEL SHEAR PATTERN IS NOT
FORECAST BY THE MODELS TO ABATE UNTIL ABOUT 24-26 HOURS. AT THAT
TIME...SOME STRENGTHENING MAY OCCUR AS FRANCES PASSES SLOWLY OVER
THE VERY WARM GULFSTREAM.

AT THIS TIME...CHANGES IN THE WARNINGS AND WATCHES ARE NOT
NECESSARY.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      03/0300Z 24.5N  75.4W   110 KT
 12HR VT     03/1200Z 25.2N  76.5W   110 KT
 24HR VT     04/0000Z 26.1N  77.9W   115 KT
 36HR VT     04/1200Z 26.8N  79.1W   120 KT
 48HR VT     05/0000Z 27.6N  80.6W   105 KT...INLAND
 72HR VT     06/0000Z 28.4N  83.0W    45 KT...OVER GULF OF MEXICO
 96HR VT     07/0000Z 31.5N  85.5W    30 KT...INLAND
120HR VT     08/0000Z 35.0N  86.5W    25 KT...INLAND


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