ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ISIS DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 AM PDT THU SEP 09 2004 AFTER MOST OF THE CONVECTION WAS SHEARED AWAY ABOUT 9-12 HOURS AGO...A TREMENDOUS BURST OF DEEP CONVECTION HAS SINCE RE-DEVELOPED OVER THE PREVIOUSLY EXPOSED TIGHT LOW-LEVEL CIRCULATION CENTER. THE INTENSITY ESTIMATE OF 45 KT IS BASED ON A DVORAK SATELLITE ESTIMATE OF T3.0...OR 45 KT...FROM TAFB USING A SHEAR PATTERN. A BANDING PATTERN...WHICH IS NOT APPLICABLE IN THIS SITUATION... YIELDS A LOWER INTENSITY OF T2.5...OR 35 KT. THE LOCATION OF THE CENTER WAS BASED ON A 09/0414Z SSMI IMAGE. THE INITIAL MOTION ESTIMATE IS 295/09. AFTER THE CONVECTION WEAKENED EARLIER...ISIS MADE A SHARP JOG TO THE NORTHWEST. HOWEVER...OVER THE PAST 6 HOURS...CONVENTIONAL AND MICROWAVE FIXES INDICATE THAT ISIS HAS TURNED BACK TOWARD THE WEST-NORTHWEST. ISIS IS EXPECTED TO REMAIN ON THE SOUTH SIDE OF THE STRONG SUBTROPICAL RIDGE LOCATED TO THE NORTH AND MOVE WEST-NORTHWESTWARD FOR THE NEXT 48-72 HOURS... AND THEN TURN MORE WESTWARD AFTER THAT. THIS TRACK IS CONSISTENT WITH THE CONSENSUS OF THE NHC MODEL GUIDANCE AND IS SOUTH OF THE PREVIOUS FORECAST TRACK...BUT ONLY DUE TO THE MORE SOUTHERLY INITIAL POSITION OF ISIS ON THIS ADVISORY. MODERATE EASTERLY SHEAR IS FORECAST TO CONTINUE TO AFFECT ISIS FOR THE NEXT 24 HOURS...SO THERE MAY BE PERIODIC FLUCTUATIONS IN THE INTENSITY AS THE DEEP CONVECTION WAXES AND WANES. HOWEVER...BY 36 HOURS...THE SHEAR IS FORECAST BY THE SHIPS INTENSITY MODEL TO WEAKEN TO 5-10 KT AND REMAIN THAT WAY THROUGH 120 HOURS. THE ONLY MODULATING EFFECT ON ISIS WILL BE THE COOLER SSTS...BELOW 26 C... THAT THE CYCLONE WILL BE CROSSING IN 72 HOURS. THE INTENSITY FORECAST IS SIMILAR TO THE SHIPS MODEL...WHICH BRINGS ISIS UP TO 62 KT AT 48 AND 60 HOURS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 16.7N 113.1W 45 KT 12HR VT 09/1800Z 17.3N 114.3W 50 KT 24HR VT 10/0600Z 17.9N 116.3W 55 KT 36HR VT 10/1800Z 18.5N 118.8W 60 KT 48HR VT 11/0600Z 19.1N 121.5W 65 KT 72HR VT 12/0600Z 19.8N 127.2W 55 KT 96HR VT 13/0600Z 20.0N 133.5W 45 KT 120HR VT 14/0600Z 20.0N 140.5W 35 KT $$ NNNN
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Page last modified: Thursday, 09-Sep-2004 08:24:30 UTC