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Tropical Depression GABRIELLE (Text)

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TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072013
1100 PM AST WED SEP 11 2013
 
DEEP CONVECTION ASSOCIATED WITH GABRIELLE HAS DISSIPATED 
AGAIN THIS EVENING...LEAVING THE CYCLONE AS A SWIRL OF LOW-LEVEL
CLOUDS...EXCEPT FOR ONE SMALL THUNDERSTORM THAT HAS RECENTLY
DEVELOPED WELL EAST OF THE CENTER.  SUBJECTIVE AND OBJECTIVE DVORAK
INTENSITY ESTIMATES HAVE DECREASED BELOW TROPICAL STORM STRENGTH...
AND BASED ON THESE DATA THE SYSTEM HAS BEEN DOWNGRADED TO A 30-KT
TROPICAL DEPRESSION. LITTLE CHANGE IN STRENGTH IS EXPECTED DURING
THE NEXT 24 HOURS AS THE CYCLONE REMAINS WITHIN AN AREA OF MODERATE
WESTERLY WIND SHEAR AND DRY MID-LEVEL AIR.  SOME INTENSIFICATION IS
POSSIBLE AS GABRIELLE INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH
IN 36 TO 48 HOURS.  THE TROUGH IS EXPECTED TO PROVIDE SOME
BAROCLINIC FORCING AND SHOULD ALSO CAUSE THE CYCLONE TO BECOME
EXTRATROPICAL IN ABOUT 2 DAYS.  THE SYSTEM IS LIKELY TO BE ABSORBED
BY A FRONT OVER NOVA SCOTIA SHORTLY THEREAFTER...HOWEVER A 72-HOUR
POINT WAS PROVIDED ONCE AGAIN FOR FORECAST CONTINUITY.  WITH THE
LACK OF DEEP CONVECTION THIS EVENING...AN ALTERNATIVE SCENARIO IS
THAT GABRIELLE COULD DEGENERATE INTO A REMNANT LOW ON THURSDAY OR
BECOME AN OPEN TROUGH AS IT BEGINS TO ACCELERATE NORTH-
NORTHEASTWARD IN A DAY OR SO.
 
GABRIELLE CONTINUES MOVING SLOWLY WEST-NORTHWESTWARD.  THE CYCLONE
SHOULD TURN NORTHWARD ON THURSDAY AS IT IS STEERED AROUND THE
WESTERN PORTION OF A LOW- TO MID-LEVEL RIDGE OVER THE WEST-CENTRAL
ATLANTIC.  AFTER 24 HOURS...GABRIELLE IS FORECAST TO ACCELERATE
NORTH-NORTHEASTWARD AHEAD OF THE TROUGH MOVING INTO THE
NORTHEASTERN UNITED STATES.  THE TRACK GUIDANCE AGREES ON THIS
SCENARIO AND THE UPDATED NHC TRACK IS ESSENTIALLY AN UPDATE OF THE
PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0300Z 33.0N  67.0W   30 KT  35 MPH
 12H  12/1200Z 33.7N  67.6W   30 KT  35 MPH
 24H  13/0000Z 35.7N  67.6W   30 KT  35 MPH
 36H  13/1200Z 39.4N  66.1W   35 KT  40 MPH
 48H  14/0000Z 44.4N  62.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  15/0000Z 54.5N  50.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  16/0000Z...ABSORBED BY FRONT
 
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FORECASTER BROWN
 
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