Tropical Storm ISABEL

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TROPICAL STORM ISABEL DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SAT SEP 06 2003
 
SATELLITE IMAGES DURING THE DAY INDICATE THAT ISABEL HAS CONTINUED
TO BECOME BETTER ORGANIZED. THE TROPICAL STORM HAS A LARGE ENVELOPE
DEFINED BY LOW CLOUDS ON SATELLITE...CONVECTIVE CURVED BANDS AND AN
EXPANDING CENTRAL DENSE OVERCAST. THE OUTFLOW CONTINUES TO BE
FAIRLY GOOD IN ALL QUADRANTS BUT THE NORTHEAST. SATELLITE INTENSITY
ESTIMATES AND AN EARLIER ADEOS SCATTEROMETER SUPPORT INCREASING THE
WINDS TO 45 KNOTS. THE OCEAN IS PLENTY WARM AHEAD OF ISABEL AS
INDICATED BY BUOYS AND THE SHEAR IS FORECAST TO REMAIN LOW.
THEREFORE...ISABEL IS FORECAST TO BECOME A HURRICANE.
 
A 24 TO 36 HOUR SATELLITE LOOP INDICATES THAT ISABEL HAS BEEN MOVING
SOUTH OF DUE WEST...OR PERHAPS IT WAS A REFORMATION UNDER THE
MID-LEVEL CIRCULATION. THE TROPICAL CYCLONE IS FORECAST TO MOVE
ABOUT 10 TO 12 KNOTS TOWARD THE WEST STEERED BY A RATHER STRONG
SUBTROPICAL RIDGE TO THE NORTH.  HOWEVER...IN 3 TO 5 DAYS...THE
RIDGE IS EXPECTED TO ERODE AND ISABEL COULD BEGIN TO MOVE TO THE
WEST-NORTHWEST.  THE OFFICIAL FORECAST IS SIMILAR TO THE GLOBAL
MODEL CONSENSUS...GUNA...BUT A LITTLE BIT BIASED TOWARD THE GFS.
THE LATTER IS THE ONLY MODEL THAT BRINGS THE TROPICAL CYCLONE VERY
CLOSE TO THE LEEWARD ISLANDS BEYOND 5 DAYS.
 
FORECASTER AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 13.4N  35.4W    45 KT
 12HR VT     07/0600Z 13.4N  36.8W    50 KT
 24HR VT     07/1800Z 13.5N  38.5W    60 KT
 36HR VT     08/0600Z 14.5N  40.5W    65 KT
 48HR VT     08/1800Z 15.5N  43.0W    70 KT
 72HR VT     09/1800Z 17.0N  48.5W    75 KT
 96HR VT     10/1800Z 18.0N  53.5W    75 KT
120HR VT     11/1800Z 18.5N  58.0W    75 KT
 
 
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