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HURRICANE GUSTAV DISCUSSION NUMBER  14
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT WED SEP 11 2002

A COMBINATION OF ACCELERATION AND THE START OF EXTRATROPICAL
TRANSITION HAS GIVEN GUSTAV A ELONGATED AND MESSY STRUCTURE.
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER INDICATES THAT
THE 850 MB WIND CENTER IS NORTHWEST OF THE SURFACE PRESSURE
CENTER...AS A DROPSONDE AT THE 850 MB CENTER SHOWED A 974 MB
SURFACE PRESSURE AND A DROP AT 850 MB WIND MAXIMUM FOUND A 964 MB
SURFACE PRESSURE.  THE LOWER VALUE IS ASSUMED TO BE THE CENTRAL
PRESSURE FOR THIS ADVISORY.  THE MAXIMUM FLIGHT-LEVEL WINDS WERE
104 KT...WHICH WOULD SUGGESTS MAXIMUM SURFACE WINDS OF 80-85 KT. 
HOWEVER...THE MAXIMUM SURFACE WINDS OBSERVED BY THE STEPPED
FREQUENCY MICROWAVE RADIOMETER ON THE NOAA RESEARCH AIRCRAFT WERE
71 KT.  BASED ON THESE DATA...MAXIMUM WINDS ARE INCREASED TO A
POSSIBLY CONSERVATIVE 80 KT FOR THIS ADVISORY.
 
THE INITIAL MOTION IS NOW 055/33.  A STRONG DEEP-LAYER TROUGH AND
SURFACE LOW NORTHWEST OF GUSTAV SHOULD CAUSE A RAPID NORTHEASTWARD
MOTION FOR THE NEXT 24-36 HR AS THE CYCLONE BECOMES EXTRATROPICAL... 
FOLLOWED BY DECELERATION AND A NORTHWESTWARD TURN.  THIS IS THE 
SCENARIO OF THE LARGE-SCALE MODELS AND THE FORECAST TRACK CLOSELY
FOLLOWS IT.

THE CENTER OF GUSTAV IS NOW NORTH OF THE GULF STREAM...AND
INFRARED IMAGERY INDICATES THAT THE CONVECTIVE TOPS NEAR THE
CENTER ARE STARTING TO WARM.  THIS SUGGESTS THAT GUSTAV IS NEAR
PEAK AS A TROPICAL CYCLONE AND WILL SOON START TO LOSE TROPICAL 
CHARACTERISTICS.  HOWEVER...THE STRONG BAROCLINIC DYNAMICS OF THE
TROUGH SHOULD MAINTAIN GUSTAV...OR WHATEVER RESULTS FROM A MERGER
OF GUSTAV WITH THE NON-TROPICAL LOW...AS A STRONG SYSTEM FOR THE
NEXT 48 HR.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     11/2100Z 41.2N  65.7W    80 KTS
12HR VT     12/0600Z 44.7N  61.9W    70 KTS
24HR VT     12/1800Z 49.2N  56.7W    60 KTS...EXTRATROPICAL
36HR VT     13/0600Z 53.0N  53.0W    55 KTS...EXTRATROPICAL
48HR VT     13/1800Z 57.0N  51.0W    55 KTS...EXTRATROPICAL
72HR VT     14/1800Z 61.0N  55.0W    40 KTS...EXTRATROPICAL
 
 
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