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SUBTROPICAL STORM GUSTAV DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON SEP 09 2002

THE SYSTEM CONTINUES TO LOOK A LITTLE MORE LIKE A TROPICAL CYCLONE
ON THE SATELLITE IMAGES...WITH MORE DEEP CONVECTION FORMING NEAR THE
CENTER.  SATELLITE-BASED INTENSITY ESTIMATES RANGE FROM 35 TO 45
KT...SO THE WIND SPEED IS HELD AT 40 KT FOR THIS ADVISORY.  AIR
FORCE RECONNAISSANCE SHOULD PROVIDE A BETTER ASSESSMENT OF THE
INTENSITY AND STRUCTURE OF GUSTAV LATER TODAY.  ALTHOUGH THE UPPER
TROPOSPHERIC ENVIRONMENT IS STILL DOMINATED BY A LARGE CYCLONIC
CIRCULATION...CIRRUS MOTIONS INDICATE THAT UPPER-LEVEL OUTFLOW IS
BECOMING ESTABLISHED OVER THE WESTERN SEMICIRCLE OF THE CYCLONE.
THE SYSTEM SHOULD BE IN A REASONABLY WEAK VERTICAL SHEAR ENVIRONMENT
AND OVER WARM WATERS FOR THE NEXT 36 H OR SO.  THUS...ASSUMING THAT
GUSTAV TAKES ON MORE TROPICAL CHARACTERISTICS...SOME STRENGTHENING
IS LIKELY.  NEAR THE END OF THE PERIOD...THE CYCLONE SHOULD BECOME
AN EXTRATROPICAL STORM AS IT BECOMES INVOLVED WITH A DISTINCT 
FRONTAL ZONE.

THE CENTER IS NOT WELL-DEFINED ON INFRARED IMAGERY AND THERE 
CONTINUES TO BE A LOT OF SPREAD IN POSITION ESTIMATES.  BEST 
ESTIMATE OF INITIAL MOTION IS 305/10.  THERE IS LITTLE CHANGE TO THE 
TRACK FORECAST FROM THE PREVIOUS ADVISORY. CURRENTLY...THERE IS A 
MID-TROPOSPHERIC RIDGE TO THE NORTH OF GUSTAV WHICH IS INDUCING THE 
NORTHWESTWARD MOTION.  HOWEVER...GLOBAL MODELS INDICATE A MAJOR 
CHANGE IN THE LONGWAVE PATTERN AT 500 MB WITH A MAJOR TROUGH 
REPLACING THE RIDGE OVER THE NORTHEAST U.S. COAST BY 72 H.  THIS 
SHOULD CAUSE GUSTAV TO TURN NORTHWARD AND NORTHEASTWARD.  THE 
OFFICIAL FORECAST IS IN GOOD AGREEMENT WITH THE CONSENSUS OF THE 
DYNAMICAL TRACK GUIDANCE.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     09/0900Z 31.7N  73.4W    40 KTS
12HR VT     09/1800Z 32.6N  74.7W    45 KTS
24HR VT     10/0600Z 33.8N  75.8W    55 KTS
36HR VT     10/1800Z 35.1N  75.4W    60 KTS
48HR VT     11/0600Z 36.5N  73.0W    65 KTS
72HR VT     12/0600Z 41.5N  62.0W    55 KTS...EXTRATROPICAL
 
 
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