ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE ISABEL DISCUSSION NUMBER 32 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SAT SEP 13 2003 SATELLITE IMAGES SHOW THAT CLOUD TOPS HAVE WARMED OVER THE PAST 6 HOURS AND ISABEL MAY HAVE WEAKENED A LITTLE. BUT SINCE THE PREVIOUS ADVISORY VALUE OF 140 KNOTS WAS BASED ON AIRCRAFT RECONNAISSANCE AND THE NEXT RECONNAISSANCE MISSION IS AT 06Z...THE OFFICIAL WIND SPEED IS KEPT THE SAME AS THE PREVIOUS ADVISORY VALUE OF 140 KNOTS. THE GLOBAL MODELS GENERALLY SHOW LITTLE CHANGE IN WIND SPEED FOR 5 DAYS BUT THE SHIPS STATISTICAL DYNAMICAL MODEL GRADUALLY WEAKENS ISABEL TO 70 KNOTS IN 5 DAYS...AS A RESULT OF INCREASING VERTICAL SHEAR AND CLIMATOLOGY AMONG OTHER FACTORS. THE OFFICIAL FORECAST IS FOR WEAKENING TO 100 KNOTS IN 5 DAYS...A COMPROMISE BETWEEN SHIPS AND THE GLOBAL MODELS. THE INITIAL MOTION IS 290/11 BASED ON THE PAST 12 HOURS OF MOTION. THE GLOBAL MODELS ARE IN GOOD AGREEMENT ABOUT A GRADUAL TURN TOWARD THE NORTHWEST TO NORTH-NORTHWEST OVER THE NEXT 5 DAYS. THE HURRICANE IS FORECAST TO MOVE AROUND THE PERIPHERY OF A DEEP-LAYER ANTICYCLONE CENTERED SOUTH OF NOVA SCOTIA. AN APPROACHING SHORT-WAVE TROUGH MOVING ACROSS THE EASTERN UNITED STATES IS FORECAST TO BYPASS ISABEL ON ABOUT DAY 3...BUT THE NEXT SHORT-WAVE TROUGH SHOULD PICK UP THE HURRICANE BY ABOUT DAY 5. THE OFFICIAL FORECAST TRACK IS ADJUSTED SLIGHTLY TO THE EAST OF THE PREVIOUS ADVISORY BUT IS STILL CLOSE TO THE WESTERN-MOST GUIDANCE WHICH IS THE GFS MODEL. THE OFFICIAL TRACK FORECAST SHOWS A DECREASE IN FORWARD SPEED FOR 3 DAYS FOLLOWED BY AN INCREASE IN FORWARD SPEED ON DAY 4 AND 5. NOTE THAT THE 5 DAY FORECAST POSITION IS RATHER CLOSE TO THE MID-ATLANTIC U.S. COAST. FORECASTER LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 14/0300Z 23.0N 63.7W 140 KT 12HR VT 14/1200Z 23.7N 65.4W 140 KT 24HR VT 15/0000Z 24.5N 67.3W 135 KT 36HR VT 15/1200Z 25.2N 68.7W 130 KT 48HR VT 16/0000Z 25.9N 69.8W 125 KT 72HR VT 17/0000Z 28.0N 71.6W 120 KT 96HR VT 18/0000Z 31.6N 73.4W 110 KT 120HR VT 19/0000Z 36.5N 75.0W 100 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:58 UTC