[South Florida DX Association] HURRICANE FRANCES DISCUSSION NUMBER 33

[Bill Marx]

From: <k4pg at adelphia.net>


> 000
> WTNT41 KNHC 020225
> 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