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| #6619 (Received by flhurricane at: 6:30 AM 30.Aug.2004) TCDAT1 HURRICANE FRANCES DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT MON AUG 30 2004 THE LATEST DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER MONITORING FRANCES INDICATES THAT THE CENTRAL PRESSURE HAS RISEN TO 958 MB AND THAT THE MAXIMUM 700 MB FLIGHT-LEVEL WINDS ARE 99 KT. THIS WOULD SUPPORT AN INTENSITY 90 KT. HOWEVER...THE LAST FEW SATELLITE IMAGES SHOW A BETTER ORGANIZED CYCLONE...AND SATELLITE INTENSITY ESTIMATES ARE 115 KT FROM TAFB AND 102 KT FROM SAB. THE INITIAL INTENSITY IS REDUCED TO 105 KT...AND FOR THE MOMENT THIS MAY BE GENEROUS. THE AIRCRAFT DATA ALSO INDICATES TWO WELL-DEFINED OUTER WIND MAXIMA. THE INITIAL MOTION IS 275/9. FRANCES REMAINS ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE AND SHOULD CONTINUE TO DO SO FOR ABOUT 72 HR. BEYOND THAT TIME...MOST LARGE-SCALE MODELS AGREE THAT THE RIDGE SHOULD WEAKEN. THIS PATTERN SHOULD MOVE FRANCES BASICALLY WESTWARD TO WEST-NORTHWESTWARD FOR 48-72 HR...FOLLOWED BY A GRADUAL NORTHWESTWARD TURN. THE SYNOPTIC SURVEILLANCE MISSION FLOWN EARLIER TONIGHT SEEMS TO HAVE HELPED THE MODELS COME INTO BETTER AGREEMENT...AS THE GFS AND UKMET HAVE SHIFTED SOMEWHAT TO THE RIGHT OF THEIR PREVIOUS TRACKS. THE OFFICIAL FORECAST IS A LITTLE SOUTH OF THE PREVIOUS TRACK FOR THE FIRST 36-48 HR AND ALONG THE SOUTHERN EDGE OF THE GUIDANCE...AS THE RIDGE TO THE NORTH MAY NOT ALLOW AS MUCH NORTHWARD MOTION EARLY ON AS INDICATED BY THE MODELS. AFTER 72 HR...THE TRACK IS DOWN THE CENTER OF THE MAIN DYNAMICAL MODEL GUIDANCE. IT SHOULD BE NOTED THAT THE CANADIAN MODEL STILL CALLS FOR A MORE WESTERLY TRACK TOWARD THE FLORIDA KEYS OR SOUTH FLORIDA. FRANCES MAY HAVE BEEN SUFFERING SOME SOUTHERLY SHEAR WHICH HAS RESULTED IN THE OBSERVED WEAKENING. THE SHIPS MODEL FORECASTS THE SHEAR TO WEAKEN DURING THE NEXT 36-48 HR...AND BOTH SHIPS AND THE GFDL FORECAST STRENGTHENING DURING THAT TIME. THE INTENSITY FORECAST FOLLOWS SUIT...AND IT WOULD NOT BE A BIG SURPRISE IF FRANCES GOT STRONGER THAN THE 115 KT OFFICIAL FORECAST OR THE 121 KT GFDL FORECAST. THE SHIPS MODEL SHOWS INCREASING SHEAR AT 72 HR AND FORECASTS WEAKENING. WHILE THIS IS POSSIBLE...THE INTENSITY FORECAST WILL NOT FOLLOW THIS UNTIL THERE IS A CLEARER SIGNAL. ONE FLY IN THE INTENSITY FORECAST OINTMENT IS THE PRESENCE OF THE OUTER WIND MAXIMA...WHICH SUGGESTS CONCENTRIC EYEWALL CYCLES COULD OCCUR AND THROW OFF THE INTENSITY FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 30/0900Z 19.0N 57.3W 105 KT 12HR VT 30/1800Z 19.1N 59.2W 105 KT 24HR VT 31/0600Z 19.6N 62.0W 110 KT 36HR VT 31/1800Z 20.2N 64.7W 115 KT 48HR VT 01/0600Z 21.0N 67.4W 115 KT 72HR VT 02/0600Z 22.5N 71.5W 115 KT 96HR VT 03/0600Z 24.5N 75.0W 115 KT 120HR VT 04/0600Z 27.0N 77.5W 115 KT |
