Tropical Storm GABRIELLE

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TROPICAL STORM GABRIELLE DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072007
1100 PM EDT SAT SEP 08 2007
 
THE LOW-LEVEL CENTER OF GABRIELLE HAS DISAPPEARED UNDER A CIRRUS
OVERCAST CAUSED BY A STRONG CONVECTIVE BURST...WHICH INCLUDED A
SUPERCELL THUNDERSTORM WITH A WELL-DEFINED MESOCYCLONE ON THE
MOREHEAD CITY WSR-88D.  THE BURST HAS ENDED FOR NOW...BUT HAS LEFT
A MID-LEVEL CIRCULATION EVIDENT IN THE DOPPLER RADAR DATA.  WHILE
THE RADAR WINDS DO NOT YET SHOW AN OBVIOUS INCREASE IN INTENSITY...
A RECENT QUIKSCAT OVERPASS SHOWED A FEW 40-45 KT WIND VECTORS THAT
WERE POSSIBLY RAIN CONTAMINATED.  THE INITIAL INTENSITY REMAINS 35
KT...AND IT IS POSSIBLE THIS IS A LITTLE CONSERVATIVE.

THE SURFACE CENTER IS DIFFICULT TO LOCATE IN BOTH SATELLITE AND
RADAR IMAGERY...BUT IS ESTIMATED TO BE A LITTLE TO THE EAST OR
SOUTHEAST OF THE MID-LEVEL CENTER.  THIS MAKES THE INITIAL MOTION A
SOMEWHAT UNCERTAIN 325/10.  THERE IS LITTLE CHANGE TO THE TRACK
FORECAST PHILOSOPHY OTHER THAN THE SLIGHTLY MORE WESTERLY POSITION. 
GABRIELLE SHOULD TURN NORTHWARD AROUND THE WESTERN SIDE OF A
DEEP-LAYER RIDGE OVER THE WESTERN ATLANTIC DURING THE NEXT 12-24
HR.  BEYOND THAT TIME...IT SHOULD ACCELERATE NORTHEASTWARD INTO THE
WESTERLIES.

THE CENTER OF GABRIELLE IS PASSING OVER THE GULF STREAM...AND THE
VERTICAL WIND SHEAR THAT WAS AFFECTING THE SYSTEM EARLIER IS
DIMINISHING.  BASED ON THIS...THE INTENSITY FORECAST CALLS FOR SOME
STRENGTHENING BEFORE THE CENTER REACHES THE NORTH CAROLINA COAST. 
GABRIELLE IS FORECAST TO MAINTAIN INTENSITY DURING EXTRATROPICAL
TRANSITION...AND IT SHOULD BE ABSORBED BY A LARGER EXTRATROPICAL
LOW BETWEEN 72-96 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 33.1N  75.7W    35 KT
 12HR VT     09/1200Z 34.3N  75.9W    40 KT
 24HR VT     10/0000Z 35.8N  75.6W    45 KT...INLAND
 36HR VT     10/1200Z 37.1N  74.0W    45 KT...OVER WATER
 48HR VT     11/0000Z 39.0N  71.0W    45 KT
 72HR VT     12/0000Z 43.0N  62.5W    45 KT...EXTRATROPICAL
 96HR VT     13/0000Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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