455 
 WTPZ42 KNHC 090817
 TCDEP2
 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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