ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT MON SEP 08 2003 ISABEL HAS CONTINUED ITS RAPID INTENSIFICATION TREND. THE INITIAL INTENSITY IS INCREASED TO 110 KT BASED ON SATELLITE INTENSITY ESTIMATES OF 115 KT FROM TAFB AND AFWA...102 KT FROM SAB...AND 113 KT/T5.9 3-HOUR OBJECTIVE DVORAK INTENSITY ESTIMATES. THE OUTFLOW REMAINS VERY IMPRESSIVE AND THE OVERALL CONVECTIVE PATTERN HAS ALSO CONTINUED TO IMPROVE. THE INITIAL MOTION ESTIMATE IS 295/12. THERE HAS BEEN SOME WOBBLING ALONG THE TRACK THE PAST 6 HOURS...WHICH IS TYPICAL OF INTENSE HURRICANES. THE NHC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON ISABEL MOVING WEST-NORTHWESTWARD FOR THE NEXT 36 HOURS OR SO...AND THEN TURNING MORE WESTWARD AFTER THAT. HOWEVER...THE GFS AND NOGAPS MODELS MAINTAIN A WEST-SOUTHWESTWARD MOTION AFTER 48-72 HOURS. THE REASON FOR THIS MORE SOUTHERLY TRACK IS NOT APPARENT IN THE MODEL FIELDS...SO I AM CONTINUING TO PLACE LESS WEIGHT ON THAT SCENARIO AT THIS TIME BASED ON THOSE MODELS HAVING A PREVIOUS LEFT-BIAS WITH FABIAN. THE OFFICIAL FORECAST TRACK IS NUDGED SLIGHTLY NORTH OF THE PREVIOUS TRACK THROUGH 36 HOURS...AND THEN COMES BACK ON TRACK AFTER THAT. THIS IS CONSISTENT WITH THE GLOBAL MODEL CONSENSUS. ISABEL IS 24 HOURS INTO A RAPID INTENSIFICATION CYCLE...BUT RARELY DUE SUCH TRENDS OCCUR FOR MORE THAN 30-36 HOURS. THEREFORE...THE CURRENT INTENSIFICATION TREND IS LEVELED OFF AFTER ABOUT 12 HOURS OR SO. HOWEVER...UPPER-LEVEL CONDITIONS ARE FORECAST TO REMAIN QUITE FAVORABLE THROUGHOUT THE FORECAST PERIOD...SO ISABEL COULD STILL REACH CATEGORY 4 INTENSITY DURING THE NEXT 12 HOURS OR SO. AFTER THAT...INNER-CORE CONVECTION AND EYEWALL DYNAMICS WILL DICTATE ANY FURTHER INTENSITY CHANGES. HOWEVER...THE INTENSITY FORECAST COULD EASILY BE TOO LOW GIVEN THAT THE OUTFLOW PATTERN IS EXPECTED TO CONTINUE TO IMPROVE...THE VERTICAL SHEAR IS FORECAST TO REMAIN LESS THAN 10 KT...AND ISABEL WILL BE MOVING OVER 28C AND WARMER SSTS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 08/2100Z 17.9N 43.7W 110 KT 12HR VT 09/0600Z 18.6N 45.6W 120 KT 24HR VT 09/1800Z 19.2N 47.9W 125 KT 36HR VT 10/0600Z 19.5N 50.0W 125 KT 48HR VT 10/1800Z 19.5N 52.0W 125 KT 72HR VT 11/1800Z 19.5N 55.5W 125 KT 96HR VT 12/1800Z 19.5N 59.0W 125 KT 120HR VT 13/1800Z 20.0N 63.0W 125 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:58 UTC