ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 43 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT TUE SEP 16 2003 RECENT FIXES FROM NOAA AND AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE WEAKENING TREND HAS ENDED...AT LEAST FOR THE TIME BEING. THE MOST RECENT PEAK FLIGHT-LEVEL WIND REPORTED BY THE AIR FORCE AIRCRAFT WAS 111 KT OVER A VERY SMALL AREA IN THE NORTHEAST QUADRANT...AND THE CREW INDICATED AN IMPROVED RADAR PRESENTATION. BEFORE INCREASING THE ADVISORY INTENSITY...WE WOULD LIKE TO MAKE SURE THESE WINDS ARE REPRESENTATIVE. WHILE THE OUTFLOW PATTERN HAS BEEN IMPROVING TODAY...THE CORE CONVECTION IS STILL RATHER THIN. THE INITIAL MOTION REMAINS 330/7. THERE CONTINUES TO BE NO SIGNIFICANT CHANGE TO THE TRACK FORECAST. ISABEL IS ON THE WEST SIDE OF A DEEP-LAYER RIDGE EXTENDING FROM THE CANADIAN MARITIMES SOUTH-SOUTHEASTWARD TO EAST OF THE HURRICANE. A BROAD AREA OF WESTERLY FLOW IS OVER THE CENTRAL AND EASTERN UNITED STATES...WITH A SHORTWAVE TROUGH LIFTING NORTHEASTWARD FROM THE GREAT LAKES. LARGE-SCALE MODELS INDICATE THAT THE RIDGE SHOULD BUILD WESTWARD AS THE SHORTWAVE LIFTS OUT. THIS COULD CAUSE THE TRACK TO BEND SLIGHTLY TO THE LEFT OF THE CURRENT HEADING...AND THIS IS REFLECTED IN THE OFFICIAL FORECAST. MOST OF THE DYNAMICAL MODELS CONTINUE TO FORECAST THE DEVELOPMENT OF A MORE FAVORABLE UPPER-LEVEL ANTICYCLONIC OUTFLOW PATTERN AS ISABEL APPROACHES THE COAST. WATER-VAPOR IMAGERY SHOWS A SHORT WAVE TROUGH EXTENDING INTO THE GULF OF MEXICO ALONG 90W. THE MODELS DIG THIS SHORT WAVE TO THE SOUTHWEST OF ISABEL...CREATING AN OUTFLOW CHANNEL OVER THE WESTERN PERIPHERY OF THE HURRICANE. THE EXPLICIT INTENSITY GUIDANCE...THE SHIPS AND GFDL MODELS...NOW SHOW SOME REINTENSIFICATION. WIND RADII HAVE BEEN EXPANDED BASED ON DATA FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER ONBOARD THE NOAA P-3 AIRCRAFT. NOTE...THE HURRICANE HUNTER AIRCRAFT RECENTLY REPORTED A PRESSURE OF 958 MB. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 16/2100Z 27.8N 71.4W 90 KT 12HR VT 17/0600Z 28.6N 71.9W 90 KT 24HR VT 17/1800Z 30.5N 73.0W 90 KT 36HR VT 18/0600Z 32.7N 74.6W 90 KT 48HR VT 18/1800Z 35.0N 76.7W 95 KT...INLAND 72HR VT 19/1800Z 41.5N 79.5W 30 KT...INLAND 96HR VT 20/1800Z 50.0N 76.5W 30 KT...EXTRATROPICAL 120HR VT 21/1800Z...ABSORBED BY EXTRATROPICAL LOW NNNN
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