Tropical Storm GUSTAV

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TROPICAL STORM GUSTAV DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
1100 PM EDT MON AUG 25 2008
 
THE CLOUD PATTERN HAS BECOME BETTER DEFINED OVER THE PAST FEW
HOURS...WITH A WELL-DEFINED EYE AND A THICKENING EYEWALL.  DVORAK
CLASSIFICATIONS AT 00Z WERE T3.5 FROM BOTH TAFB AND SAB BUT THE
STRUCTURE HAS IMPROVED SINCE THEN.  THE INITIAL INTENSITY IS
INCREASED TO 60 KT AND THE NEXT AIRCRAFT AT 06Z WILL MOST LIKELY
FIND A HURRICANE.  A MICROWAVE PASS AT 2243Z SHOWED A LOW-LEVEL
EYEWALL.  GIVEN THIS STRUCTURE...AND A SHIPS RI INDEX WELL ABOVE
CLIMATOLOGY...SIGNIFICANT STRENGTHENING IS LIKELY PRIOR TO THE
CENTER OF GUSTAV REACHING HAITI.  AFTER THAT...THE INTENSITY OF
GUSTAV WILL DEPEND LARGELY ON HOW MUCH THE CIRCULATION INTERACTS
WITH THE LAND MASSES OF HAITI AND CUBA.  GLOBAL MODELS FORECAST AN
UPPER LEVEL PATTERN THAT...WHILE NOT ANTICYCLONIC...IS AT LEAST
DIFLUENT AND OF LIGHT SHEAR.  THE LATEST FORECAST TRACK INDICATES
MORE TIME OVER WATER THAN THE PREVIOUS ADVISORY AND SO THE
INTENSITY FORECAST HAS BEEN INCREASED TO REFLECT THAT.  BOTH THE
GFDL AND THE HWRF SHOW GUSTAV AVOIDING NEARLY ALL OF CUBA AND HAVE
GUSTAV AS A MAJOR HURRICANE IN FIVE DAYS.
 
THE INITIAL MOTION IS 310/10.  A MID-TROPOSPHERIC ANTICYCLONE
CENTERED IN THE NORTHWESTERN BAHAMAS IS FORECAST TO REMAIN LARGELY
IN PLACE FOR THE NEXT THREE DAYS OR SO.  THIS PATTERN SHOULD RESULT
IN A SLOWING OF GUSTAV'S FORWARD SPEED AND A TURN TO THE LEFT. 
EXCEPT FOR THE NOGAPS...THE DYNAMICAL GUIDANCE MODELS KEEP GUSTAV
SOUTH OF CENTRAL CUBA.  THE OFFICIAL FORECAST IS ADJUSTED SOUTHWARD
OF THE PREVIOUS ADVISORY BUT MOST OF THE PRIMARY GUIDANCE IS EVEN
FARTHER SOUTH.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0300Z 16.6N  71.4W    60 KT
 12HR VT     26/1200Z 17.5N  72.6W    65 KT
 24HR VT     27/0000Z 18.5N  73.9W    80 KT...INLAND
 36HR VT     27/1200Z 19.3N  75.1W    75 KT
 48HR VT     28/0000Z 19.8N  76.2W    80 KT
 72HR VT     29/0000Z 20.5N  78.0W    75 KT
 96HR VT     30/0000Z 21.5N  80.5W    75 KT
120HR VT     31/0000Z 23.0N  83.5W    75 KT
 
$$
FORECASTER FRANKLIN
 
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