438 
 WTPZ42 KNHC 120240
 TCDEP2
 TROPICAL STORM ISIS DISCUSSION NUMBER  16
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 8 PM PDT SAT SEP 11 2004
  
 VISIBLE AND ENHANCED INFRARED IMAGERY INDICATE A DEVELOPING BAND OF
 CONVECTION WEST AND SOUTH OF THE LOW-LEVEL CIRCULATION CENTER. 
 THIS BANDING FEATURE CONTAINS A DEEP CONVECTIVE BURST ON THE SOUTH
 SIDE...AND CONTINUES TO BECOME BETTER ORGANIZED.  DVORAK DATA
 T-NUMBERS ARE 35 KT FROM TAFB AND SAB AND 30KT FROM AFWA.  BASED ON
 THE PERSISTENCE OF THE DEVELOPING BANDING FEATURE AND 35 KT
 SATELLITE ESTIMATES FROM TWO AGENCIES...ISIS HAS BEEN RE-UPGRADED
 TO A TROPICAL STORM. THE SHIPS GUIDANCE CONTINUES TO SHOW A GRADUAL
 INTENSIFICATION TO 55 KT IN 72 HOURS WHILE THE GFDL MODEL MAINTAINS
 ISIS AS ONLY A TROPICAL DEPRESSION.  SINCE SATELLITE IMAGERY IS
 ALREADY SUGGESTING THE SHEAR TO BE WEAKENING...THE INTENSITY
 FORECAST IS A BLEND OF THE TWO MODELS AND TAKES ISIS TO 45 KT IN 48
 HOURS. 
  
 THE INITIAL MOTION IS WESTWARD OR 270/9. DYNAMICAL TRACK GUIDANCE 
 REMAINS CLUSTERED ON A CONTINUED WESTWARD TRACK THROUGH THE
 PERIOD...AS A RESULT OF A PERSISTENCE MID-UPPER RIDGE EXTENDING
 WESTWARD FROM MEXICO/BAJA.  THE CURRENT OFFICIAL TRACK FORECAST IS
 BASICALLY AN UPDATE OF THE PREVIOUS ONE WITH A REDUCTION IN FORWARD
 SPEED AFTER 72 HOURS. 
 
 FORECASTER MAINELLI/JARVINEN
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      12/0300Z 17.4N 122.1W    35 KT
  12HR VT     12/1200Z 17.4N 123.5W    35 KT
  24HR VT     13/0000Z 17.4N 125.3W    40 KT
  36HR VT     13/1200Z 17.4N 127.1W    40 KT
  48HR VT     14/0000Z 17.5N 128.8W    45 KT
  72HR VT     15/0000Z 17.5N 131.0W    45 KT
  96HR VT     16/0000Z 17.5N 132.5W    40 KT
 120HR VT     17/0000Z 17.5N 134.0W    40 KT
  
  
 $$