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TROPICAL STORM GUSTAV DISCUSSION NUMBER   9
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT TUE SEP 10 2002

GUSTAV HAS FORMED A POORLY-DEFINED INNER WIND MAXIMUM THAT APPEARS
TO BE ROTATING AROUND THE INSIDE OF THE LARGER CENTER.  OVERALL...
THE CYCLONE IS SHOWING INCREASED ORGANIZATION IN BOTH SATELLITE
AND RADAR IMAGERY.  BASED ON THIS...SUBTROPICAL STORM GUSTAV HAS
BECOME A TROPICAL STORM.  THE MAXIMUM FLIGHT-LEVEL WINDS RECENTLY
REPORTED BY AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT ARE 62
KT WHILE THE LATEST CENTRAL PRESSURE WAS 987 MB.  BASED ON THAT
DATA...THE MAXIMUM WINDS REMAIN 50 KT.
 
SMOOTHING THROUGH THE GYRATIONS OF THE INNER CENTER...THE INITIAL
MOTION IS 005/8.  WATER VAPOR IMAGERY INDICATES A MID/UPPER LEVEL
TROUGH MOVING ACROSS THE WESTERN GREAT LAKES WITH RIDGING TO THE
EAST AND NORTHEAST OF GUSTAV.  LARGE-SCALE MODELS INDICATE THE
TROUGH WILL AMPLIFY AS IT MOVES EASTWARD...CAUSING THE RIDGE TO
WEAKEN AND SHIFT SOUTHWARD.  THIS WOULD ALLOW GUSTAV TO TURN
NORTHEASTWARD AND ACCELERATE.  ALL TRACK MODELS AGREE WITH THIS
SCENARIO...AND THIS IS A HIGH CONFIDENCE FORECAST.  THE ONLY
QUESTION IS HOW CLOSE THE CENTER WILL GET TO CAPE HATTERAS BEFORE
THE TURN OCCURS.  THE FORECAST TRACK CALLS FOR THE TURN TO BEGIN
IN 6-12 HR...FOLLOWED BY ACCELERATION AWAY FROM THE U. S. COAST. 
 
GUSTAV IS SHOWING GOOD OUTFLOW AND INCREASING CONVECTIVE BANDING.
SEA SURFACE TEMPERATURES AND SHEAR CONDITIONS APPEAR FAVORABLE
FOR STRENGTHENING FOR 24 HR...AND BAROCLINIC SUPPORT FROM THE
UPPER-LEVEL TROUGH MAY HELP AS WELL.  THUS...THE INTENSITY FORECAST
CALLS FOR STRENGTHENING INTO A HURRICANE.  AFTER THAT...GUSTAV
WILL START TO LOSE TROPICAL CHARACTERISTICS AS THE CYCLONE BECOMES
INCREASINGLY INVOLVED WITH THE TROUGH.  LARGE-SCALE MODELS ALL
INDICATE THE COMBINATION OF GUSTAV AND A NON-TROPICAL LOW SPAWNED
BY THE TROUGH WILL RESULT IN A POWERFUL EXTRATROPICAL STORM OVER
THE NORTHWESTERN ATLANTIC...AND THE INTENSITY FORECAST REFLECTS
THIS.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     10/1500Z 34.4N  75.3W    50 KTS
12HR VT     11/0000Z 35.4N  74.4W    60 KTS
24HR VT     11/1200Z 37.4N  70.8W    65 KTS
36HR VT     12/0000Z 41.0N  64.4W    65 KTS
48HR VT     12/1200Z 46.2N  55.9W    60 KTS...EXTRATROPICAL
72HR VT     13/1200Z 54.0N  46.0W    55 KTS...EXTRATROPICAL
 
 
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