ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ISABEL DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SUN SEP 07 2003 OVERNIGHT SATELLITE IMAGERY SHOWS THAT ISABEL CONTINUES TO EXHIBIT A WELL-DEFINED CURVED CONVECTIVE BAND...AND THE LAST FEW IMAGES SUGGEST THAT THE CONVECTION HAS BEGUN TO WRAP CLOSER TO THE CENTER. SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS 55 KT FROM TAFB...SAB...AND AFWA. THEREFORE...THE INITIAL INTENSITY IS RAISED TO 55 KT FOR THIS ADVISORY. GLOBAL MODELS SUGGEST THAT A MID/UPPER LEVEL RIDGE WILL REMAIN NORTH OF THE CYCLONE THROUGH THE FORECAST PERIOD...PROVIDING FAVORABLE CONDITIONS FOR STRENGTHENING. THE SHIPS MODEL TAKES ISABEL TO 85 KT IN 72 HOURS...AND THE GFDL BRINGS THE INTENSITY UP TO 95 KT IN 48 HOURS. THE INTENSITY FORECAST WILL BE RATHER CONSERVATIVE AND INDICATE GRADUAL STRENGTHENING OVER THE NEXT 2-3 DAYS...WITH THE INTENSITY LEVELING OFF AT 85 KT BY 72 HOURS WHICH IS IN GENERAL AGREEMENT WITH SHIPS. THE INITIAL MOTION IS 275/09...SLIGHTLY NORTH OF THE PREVIOUS ADVISORY. THE SYNOPTIC PATTERN REMAINS BASICALLY UNCHANGED FROM THE PREVIOUS FORECAST...WITH ISABEL BEING STEERED BY A MID/UPPER LEVEL RIDGE TO THE NORTH. WATER VAPOR IMAGERY INDICATES AN UPPER-LEVEL TROUGH ABOUT 900 NM NORTHWEST OF THE TROPICAL CYCLONE. LARGE-SCALE GLOBAL MODELS SUGGEST THAT THIS TROUGH WILL CREATE JUST ENOUGH OF A WEAKNESS IN THE RIDGE TO ALLOW FOR A MORE WEST-NORTHWEST MOTION BEYOND 12 HOURS...AND CONTINUE THAT MOTION THROUGH DAY 5. NHC TRACK GUIDANCE BASICALLY FOLLOWS THIS SCENARIO...WITH THE FORECAST TRACK ADJUSTED A TAD TO THE NORTH OF THE PREVIOUS TRACK AND REMAINING ON THE SOUTH SIDE OF THE GUIDANCE. FORECASTER MOLLEDA/LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 07/0900Z 13.7N 37.1W 55 KT 12HR VT 07/1800Z 13.8N 38.5W 60 KT 24HR VT 08/0600Z 14.8N 40.9W 65 KT 36HR VT 08/1800Z 15.6N 43.2W 70 KT 48HR VT 09/0600Z 16.5N 45.3W 75 KT 72HR VT 10/0600Z 18.0N 50.0W 85 KT 96HR VT 11/0600Z 18.5N 55.5W 85 KT 120HR VT 12/0600Z 19.0N 60.0W 85 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:58 UTC