ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 46 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT WED SEP 17 2003 ALTHOUGH PEAK FLIGHT-LEVEL WINDS REMAIN BETWEEN 100 AND 105 KT...WHICH WOULD NORMALLY SUPPORT SURFACE WINDS OF ABOUT 95 KT...DROPSONDE OBSERVATIONS INDICATE THAT A LESS THAN TYPICAL AMOUNT OF THIS WIND IS MAKING IT DOWN TO THE SURFACE LAYER. THIS IS CONSISTENT WITH THE RELATIVELY WEAK CONVECTION IN THE INNER CORE OF ISABEL. IN ALL LIKELIHOOD THE SURFACE WINDS ARE CLOSER TO 85 KT. I HAVE KEPT THE ADVISORY WINDS AT 95 KT FOR NOW...SINCE ANY INCREASE IN CONVECTION WOULD MORE EFFECTIVELY TRANSPORT THE MOMENTUM ALOFT DOWNWARD...BUT IF THE CONVECTION DOES NOT STRENGTHEN THE INTENSITY WILL LIKELY BE LOWERED A BIT THIS AFTERNOON. EITHER WAY ISABEL IS A CATEGORY TWO HURRICANE. THE INITIAL MOTION REMAINS 335/8. THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE OFFICIAL FORECAST TRACK...ALTHOUGH THE MODEL GUIDANCE HAS SHIFTED ITS LANDFALL POINT A FEW MILES TO THE WEST. THE GFDL ADJUSTMENT WAS THE LARGEST...ABOUT 30 MILES...AND IT IS RATHER AMAZING THAT THIS IS ABOUT THE BIGGEST ADJUSTMENT WE HAVE SEEN OVER THE PAST COUPLE OF DAYS. WHILE A MORE FAVORABLE UPPER PATTERN IS BEGINNING TO DEVELOP AS FORECAST BY THE GLOBAL MODELS...THE LOW-LEVEL ENVIRONMENTAL THERMODYNAMICS AND CURRENT STORM STRUCTURE ARE EXPECTED TO LIMIT THE ABILITY OF ISABEL TO RESPOND TO THE UPPER FORCING. LITTLE CHANGE IN STRENGTH IS EXPECTED PRIOR TO LANDFALL. HOWEVER... INTENSITY FORECASTS TEND TO BE LESS CERTAIN THAN TRACK FORECASTS... AND AN INTENSITY FORECAST ERROR OF ONE SAFFIR-SIMPSON CATEGORY...UP OR DOWN...WOULD BE ENTIRELY POSSIBLE. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 17/1500Z 30.0N 72.6W 95 KT 12HR VT 18/0000Z 31.4N 73.5W 95 KT 24HR VT 18/1200Z 33.6N 75.4W 95 KT 36HR VT 19/0000Z 36.0N 77.3W 70 KT...INLAND 48HR VT 19/1200Z 39.0N 79.0W 50 KT...INLAND 72HR VT 20/1200Z 49.0N 77.0W 30 KT...EXTRATROPICAL 96HR VT 21/1200Z 58.0N 70.0W 25 KT...EXTRATROPICAL 120HR VT 22/1200Z...ABSORBED BY EXTRATROPICAL LOW NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:59 UTC