ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ISIS DISCUSSION NUMBER 31 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 PM PDT WED SEP 15 2004 THE EYE STRUCTURE SEEN EARLIER HAS COLLAPSED COMPLETELY DURING THE AFTERNOON...WITH DEEP CONVECTION NOW CONFINED TO A RELATIVELY SMALL AREA IN THE NORTHEASTERN SEMICIRCLE. SATELLITE INTENSITY ESTIMATES ARE 65 KT FROM TAFB AND SAB...AND 55 KT FROM AFWA. IN VIEW OF THE DEGENERATION...THE INITIAL INTENSITY IS DECREASED TO 60 KT...AND THIS MAY BE GENEROUS. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 310/4. ISIS IS EMBEDDED IN WEAK STEERING CURRENTS AND WILL GO NOWHERE FAST DURING THE NEXT FIVE DAYS. MOST DYNAMICAL GUIDANCE CALLS FOR A SLOW WESTWARD TO WEST-NORTHWESTWARD DRIFT...AND THE OFFICIAL FORECAST TRACK WILL FOLLOW THAT SCENARIO. THE MORE NORTHERLY POSITION HAS PROBABLY BROUGHT ISIS OVER COOLER WATER...AND THIS IS LIKELY PLAYING A ROLE IN THE CURRENT WEAKENING. BETWEEN THE COOL WATER AND STRATOCUMULUS ENTRAINMENT CURRENLY SEEN IN VISIBLE IMAGERY...ISIS SHOULD SLOWLY WEAKEN THROUGH THE FORECAST PERIOD. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 15/2100Z 18.2N 132.1W 60 KT 12HR VT 16/0600Z 18.3N 132.4W 55 KT 24HR VT 16/1800Z 18.4N 132.7W 55 KT 36HR VT 17/0600Z 18.5N 133.0W 50 KT 48HR VT 17/1800Z 18.5N 133.5W 45 KT 72HR VT 18/1800Z 18.5N 134.0W 40 KT 96HR VT 19/1800Z 18.5N 134.5W 35 KT 120HR VT 20/1800Z 18.5N 135.0W 30 KT $$ NNNN
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Page last modified: Wednesday, 15-Sep-2004 20:45:57 UTC