ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM HURRICANE IGNACIO DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 PM PDT SUN AUG 24 2003 DESPITE A CONVECTIVE BURST OVER THE PAST HOUR OR SO...IGNACIO HAS WEAKEND SLIGHTLY BASED ON LONGER TERM...6 HOUR...TRENDS OBSERVED IN SATELLITE IMAGERY. THE SATELLITE INTENSITY ESTIMATE FROM TAFB IS STILL 90 KT...ALTHOUGH THE T NUMBER IS DOWN TO 4.0...65 KT. THE ESTIMATES FROM FROM SAB AND AFWA ARE 77 KT. THE INITIAL INTENSITY IS PARED DOWN TO 80 KNOTS FOR THIS ADVISORY...MAKING IGNACIO A CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON SCALE. IGNACIO HAS MOVED NORTH-NORTHWESTWARD OVER THE PAST 12 HOURS...WHILE THE SHORTER-TERM MOTION HAS BEEN MORE TOWARD THE NORTHWEST. WATER VAPOR IMAGERY DEPICTS A SMALL ANTICYCLONE AND RIDGING TO THE NORTH OF IGNACIO OVER THE SOUTHWESTERN UNITED STATES...PRODUCING WEAK STEERING CURRENTS. THERE HAS BEEN LITTLE CHANGE TO THE PREVIOUS ADVISORY OR FORECAST PHILOSOPHY...AND IN SPITE OF THE WEAK STEERING...MODEL GUIDANCE IS TIGHTLY CLUSTERED THROUGH 72 HOURS. AFTER THAT...THE GFS TURNS IGNACIO TOWARD MAINLAND MEXICO. ON THE OTHER HAND THE GUNS/GUNA ENSEMBLES BEND THE STORM SHARPLY WESTWARD AFTER 72 HOURS. THE SPLIT IN THE GUIDANCE SUGGESTS A PARTICULARLY WEAK STEERING CURRENT IN THE LONGER RANGE. THE OFFICIAL FORECAST INDICATES A VERY SLOW MOTION ON DAYS 4 AND 5. THE INTENSITY FORECAST...AS IN THE PREVIOUS ADVISORY...CALLS FOR A VERY SLOW WEAKENING THROUGH THE PERIOD...KEEPING IGNACIO A HURRICANE THROUGH 72 HOURS. BEYOND THAT...INCREASING INTERACTION WITH LAND WEAKENS THE CYCLONE FURTHER TO A TROPICAL STORM. THE SHIPS MODEL FORECASTS SOME INTENSIFICATION IN 24-36 HOURS AND FORECASTS A 90 KNOT HURRICANE AT 72 HOURS. THE VERY WARM SSTS AND LIGHT SHEAR ARE THE LARGEST CONTRIBUTORS TO THE SHIPS INTENSITY FORECASTS...AND SUCH A REINTENSIFICATION COULD OCCUR IF IGNACIO CAN GET FARTHER AWAY FROM LAND. FORECASTER COBB/FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 23.9N 109.3W 80 KT 12HR VT 25/1200Z 24.3N 109.7W 75 KT 24HR VT 26/0000Z 24.7N 110.2W 75 KT 36HR VT 26/1200Z 25.2N 110.6W 70 KT 48HR VT 27/0000Z 25.9N 111.1W 70 KT 72HR VT 28/0000Z 27.5N 112.0W 65 KT 96HR VT 29/0000Z 28.5N 112.5W 60 KT 120HR VT 30/0000Z 29.0N 113.0W 55 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:57 UTC