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| #7045 (Received by flhurricane at: 10:35 PM 01.Sep.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 33 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT WED SEP 01 2004 RECON THIS AFTERNOON AND EVENING INDCIATED THE CENTRAL PRESSURE HAD DECREASED TO 939 MB. A DROPSONDE AT 01/1904Z INDICATED WINDS OF 154 KT...OR 177 MPH...AT THE 850 MB LEVEL. THE HIGHEST 700 MB RECON FLIGHT-LEVEL WIND AT 2210Z WAS 134 KT...EQUAL TO ABOUT A 121-KT SURFACE WIND. BASED ON THIS INFORMATION...FRANCES IS BEING HELD AT 120 KT...WHICH MAY BE A LITTLE CONSERVATIVE. THE INITIAL MOTION IS 295/12. HOWEVER...THERE HAS BEEN CONSIDERBALE WOBBLE IN THE TRACK THE PAST 12 HOURS DUE TO THE EYEWALL REPLACEMENT CYCLES THAT HAVE BEEN OCCURRING. FRANCES HAS BEEN MOVING WEST-NORTHWESTWARD FOR THE PAST 24 HOURS UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE TO THE NORTH...WHICH IS EXPECTED TO REMAIN INTACT THROUGH AT LEAST 48 HOURS. THE GULFSTREAM-IV JET AND AN AFRES C-130 HAVE BEEN RELEASING DROPSONDES AROUND THE PERIPHERY OF FRANCES. THE SONDE DATA HAS PRODUCED SOME INTERESTING AND DISTURBING RESULTS. THE HEIGHT DATA FOR THE VARIOUS PRESSURE LEVELS...COMPARED TO 18Z SURROUNDING UPPER-AIR DATA...APPEAR TO BE AT LEAST 20 METERS TOO LOW. HOWEVER...THE WIND DATA CLEARLY INDICATE A MID-TROPOSPHERIC HIGH PRESSURE CENTER NEAR 30N 75W...OR ABOUT 500 NMI NORTHWEST OF FRANCES WITH A RIDGE AXIS EXTENDING WEST-SOUTHWESTWARD ACROSS NORTH FLORIDA AND INTO THE NORTHEAST GULF OF MEXICO. IN THE SHORT TERM... THIS WOULD SUGGEST THAT FRANCES SHOULD CONTINUE MOVING AT 295 OR EVEN 290 DEGREES MOTION FOR THE NEXT 24 HOURS OR SO. ALSO...00Z UPPER-AIR DATA INDICATE THAT THE 18Z NOGAPS AND 12Z UKMET MODELS HAVE VERIFIED THE 00Z 500 MB RIDGE AND HEIGHTS THE BEST...WHILE THE 18Z GFS AND GFDL MODELS WERE MUCH TOO WEAK...AT LEAST 20 METERS TOO LOW...WITH THE STRENGTH OF THE RIDGE. SINCE THE 00Z MODEL RUNS WILL HAVE THE NEW GPS DROPSONDE DATA INCLUDED IN THOSE RUNS FOR THE 06Z ADVISORY...NO SIGNIFICANT CHANGE IS BEING MADE TO THE PREVIOUS FORECAST TRACK. HOWEVER...WITH HIGH PRESSURE LOCATED TO THE NORTHWEST OF FRANCES...I WOULD NOT BE SURPRISED TO THE 00Z MODEL TRACKS SHIFT A LITTLE MORE WESTWARD. FRANCES IS EXPECTED TO MOVE OVER WARMER WATER NEAR AND WITHIN THE BAHAMA ISLANDS CHAIN IN 24-48 HOURS. GIVEN THE ALREADY IMPRESSIVE OUTFLOW PATTERN...SOME ADDITIONAL STRENGTHENING SEEMS PLAUSIBLE. ALSO...THE VERY DRY MID-LEVEL AIR...30-40 PERCENT HUMIDITY...THAT FRANCES HAS BEEN TRAVERSING THROUGH AND INGESTING OVER THE PAST 5 DAYS IS FORECAST TO INCREASE TO MORE THAN 60 PERCENT IN 36-60HR... WHICH MAY ALSO HELP WITH THE INTENSIFICATION PROCESS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 02/0300Z 22.6N 72.0W 120 KT 12HR VT 02/1200Z 23.5N 73.7W 120 KT 24HR VT 03/0000Z 24.7N 75.6W 125 KT 36HR VT 03/1200Z 25.8N 77.3W 125 KT 48HR VT 04/0000Z 26.6N 78.5W 125 KT 72HR VT 05/0000Z 28.0N 81.0W 105 KT...INLAND 96HR VT 06/0000Z 30.0N 83.0W 35 KT...INLAND 120HR VT 07/0000Z 33.5N 85.0W 25 KT...INLAND |
