Tropical Storm ISIS

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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
 
 
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