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Tropical Storm ISIS (Text)

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TROPICAL STORM ISIS DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT TUE SEP 14 2004
 
SATELLITE IMAGERY TODAY SHOWS THAT THE OVERALL ORGANIZATION OF THE
CONVECTION OF ISIS HAS DECREASED A LITTLE DURING THE PAST 6 HR. 
SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND SAB...AND 35
KT FROM AFWA.  THE INITIAL INTENSITY REMAINS 45 KT...WHICH IS IN
AGREEMENT WITH A RECENT QUIKSCAT OVERPASS.  THE SHEAR REMAINS LIGHT
AND ISIS IS SHOWING POOR TO FAIR OUTFLOW IN ALL DIRECTIONS EXCEPT
TO THE SOUTH EAST...WHERE IT IS POOR.
 
THE INITIAL MOTION IS A RATHER UNCERTAIN 285/5.  ISIS IS SOUTH OF
LOW/MID-LEVEL RIDGE AND A DEVELOPING WEAKNESS IN A MID/UPPER-LEVEL
RIDGE TO THE NORTH.  LARGE-SCALE MODELS FORECAST THIS WEAKNESS TO
PERSIST...WHICH SHOULD PRODUCE A SLOW MOTION FOR THE NEXT 5 DAYS.
TRACK FORECAST GUIDANCE IS IN GOOD AGREEMENT ON A SLOW
WEST-NORTHWESTWARD MOTION FOR THE FIRST 36 HR...THEN SPREADS OUT
SIGNIFICANTLY WITH FORECAST TRACKS EVERYWHERE FROM WEST THROUGH
NORTH THROUGH EAST.  THIS GENERALLY MEANS THE MOTION WILL CONTINUE
TO BE SLOW...AND THE OFFICIAL FORECAST THUS CALLS FOR A SLOW
WEST-NORTHWESTWARD DRIFT ALONG THE LINES OF THAT OF THE PREVIOUS
FORECAST.  GIVEN THAT THE 120 HR TRACK GUIDANCE POSITIONS RANGE
BETWEEN 124W AND 141W...THIS IS A LOW CONFIDENCE FORECAST.
 
THE INTENSITY FORECAST WILL CONTINUE TO INCLUDE SOME MODEST
STRENGTHENING DURING THE NEXT 24 HR.  BEYOND THAT TIME...IF THE
STORM FOLLOWS THE FORECAST TRACK IT WILL BE NEAR OR OVER 26C SEA
SURFACE TEMPERATURES IN 48-72 HR AND OVER 25C BY 120 HR.  THIS
SHOULD RESULT IN SOME GRADUAL WEAKENING.  THE INTENSITY FORECAST IS
IN GENERAL AGREEMENT WITH SHIPS AND THE GFDL.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 17.1N 130.6W    45 KT
 12HR VT     15/0600Z 17.2N 131.1W    50 KT
 24HR VT     15/1800Z 17.4N 131.6W    50 KT
 36HR VT     16/0600Z 17.6N 132.0W    45 KT
 48HR VT     16/1800Z 17.8N 132.2W    45 KT
 72HR VT     17/1800Z 18.0N 132.5W    45 KT
 96HR VT     18/1800Z 18.0N 133.0W    40 KT
120HR VT     19/1800Z 18.0N 133.5W    35 KT
 
 
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