Tropical Storm ISIS

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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
 
 
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