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| #7200 (Received by flhurricane at: 11:07 PM 02.Sep.2004) 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 |
