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| #6698 (Received by flhurricane at: 4:35 PM 30.Aug.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 24 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT MON AUG 30 2004 REPORTS FROM A NOAA P-3 HURRICANE HUNTER PLANE INDICATE THAT THE CENTRAL PRESSURE HAS DROPPED TO 948 MB AND THERE WAS A FLIGHT LEVEL...700 MB...WIND OF 122 KT JUST EAST-SOUTHEAST OF THE CENTER. BASED ON THESE DATA THE CURRENT INTENSITY IS INCREASED TO 110 KT. THERE IS STRONG UPPER-LEVEL OUTFLOW AND VERTICAL SHEAR IS EXPECTED TO REMAIN LOW. THERE WILL PROBABLY BE SOME FLUCTUATIONS IN INTENSITY DUE TO INNER CORE PROCESSES...SUCH AS THE CONCENTRIC EYEWALLS THAT WERE OBSERVED BY THE HURRICANE HUNTERS AND ALSO SEEN IN TRMM AND SSM/I DATA. HOWEVER...ADDITIONAL STRENGTHENING IS CERTAINLY POSSIBLE AND THE OFFICIAL WIND SPEED FORECAST IS PROBABLY CONSERVATIVE. THE WIND RADII HAVE BEEN ADJUSTED A LITTLE BASED ON OBSERVATIONS FROM THE STEPPED-FREQUENCY MICROWAVE RADIOMETER...SFMR...ON BOARD THE NOAA AIRCRAFT. THE HURRICANE REMAINS ON TRACK...275/12. A DEEP-LAYER SUBTROPICAL RIDGE IS LIKELY TO PREVAIL TO THE NORTH OF FRANCES OVER THE NEXT SEVERAL DAYS. BEYOND 72 HOURS...SOME WEAKENING OF THIS RIDGE IS INDICATED BY THE GLOBAL MODELS. THE BAD NEWS FOR THE BAHAMAS AND FLORIDA PENINSULA IS THAT THERE IS NO SIGNIFICANT MID-LATITUDE TROUGH IN THE CURRENT MODEL FORECASTS THROUGH 5 DAYS THAT COULD SUBSTANTIALLY WEAKEN THIS RIDGE. THE OFFICIAL FORECAST SHOWS SOME SLOWING AND A SLIGHT BENDING OF THE TRACK TOWARD THE NORTHWEST BEYOND 72 HOURS...BUT THIS FORECAST HAS BEEN SHIFTED A LITTLE LEFT IN COMPARISON TO THE PREVIOUS ONE. THIS IS IN GOOD AGREEMENT WITH THE CONSENSUS OF THE DYNAMICAL MODELS. ONCE AGAIN...IT IS EXTREMELY IMPORTANT NOT TO FOCUS ON THE EXACT TRACK...ESPECIALLY AT 96 AND 120 HOURS...BECAUSE THE HURRICANE IS NOT A POINT...ESPECIALLY A HURRICANE AS LARGE AS FRANCES...AND FORECASTS AT THESE EXTENDED TIME RANGES CAN EASILY HAVE ERRORS OF SEVERAL HUNDRED MILES. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 30/2100Z 19.5N 60.0W 110 KT 12HR VT 31/0600Z 19.7N 62.1W 115 KT 24HR VT 31/1800Z 20.2N 64.8W 115 KT 36HR VT 01/0600Z 21.0N 67.4W 115 KT 48HR VT 01/1800Z 22.0N 70.0W 115 KT 72HR VT 02/1800Z 24.0N 74.0W 120 KT 96HR VT 03/1800Z 25.5N 77.0W 120 KT 120HR VT 04/1800Z 27.5N 80.0W 120 KT |
