ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 40 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT MON SEP 15 2003 THE DEEP CONVECTION HAS CONTINUED TO ERODE ON THE WEST SIDE OF ISABEL SINCE THE 18Z RECONNAISSANCE AIRCRAFT DATA INDICATED 110 KNOTS...SO THE ADVISORY INITIAL WIND SPEED IS REDUCED 5 KNOTS TO 105 KNOTS. THE SHIPS MODEL AS WELL AS SEVERAL OF THE GLOBAL MODELS INDICATE LITTLE CHANGE IN WIND SPEED BEFORE LANDFALL WHICH IS EXPECTED BETWEEN 48 AND 60 HOURS. THE SHIPS MODEL DIAGNOSES THE GFS VERTICAL SHEAR NEAR 30 KNOTS AT 48 HOURS SO IT IS DIFFICULT TO UNDERSTAND WHY THE GUIDANCE DOES NOT CALL FOR MORE WEAKENING BEFORE LANDFALL. PERHAPS IT IS THE PATH OVER THE GULFSTREAM THAT WILL KEEP THE WIND SPEED UP. ANYWAY THE OFFICIAL WIND SPEED IS REDUCED ONLY 5 MORE KNOTS BEFORE LANDFALL TO 100 KNOTS...STILL A CATEGORY THREE HURRICANE ON THE SAFFIR SIMPSON SCALE. THE FORECAST TRACK AND SCENARIO IS VERY SIMILAR TO THE PREVIOUS ADVISORY. THE INITIAL MOTION ESTIMATE IS 320/06. THE GUIDANCE IS TIGHTLY CLUSTERED ABOUT A NORTH-NORTHWESTWARD TRACK AT LESS THAN 10 KNOTS FORWARD SPEED FOR 48 HOURS AS THE HURRICANE MOVES AROUND THE WEST SIDE OF A DEEP-LAYER MEAN RIDGE WHILE BEING BYPASSED BY A SHORT-WAVE TROUGH. A SECOND SHORT-WAVE TROUGH WILL ACCELERATE THE TRACK NORTH-NORTHWESTWARD WITH THE CENTER INLAND IN 72 HOURS. FORECASTER LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 16/0300Z 26.1N 70.2W 105 KT 12HR VT 16/1200Z 26.9N 70.8W 105 KT 24HR VT 17/0000Z 28.4N 71.7W 100 KT 36HR VT 17/1200Z 29.8N 72.5W 100 KT 48HR VT 18/0000Z 31.5N 73.7W 100 KT 72HR VT 19/0000Z 37.2N 77.2W 60 KT...INLAND 96HR VT 20/0000Z 44.5N 79.5W 40 KT...INLAND...EXTRATROPICAL 120HR VT 21/0000Z 54.0N 78.5W 30 KT...INLAND...EXTRATROPICAL NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:58 UTC