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Tropical Storm GABRIELLE (Text)

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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072013
500 PM AST WED SEP 11 2013
 
GABRIELLE CONTINUES TO MAINTAIN A SMALL AREA OF DEEP CONVECTION TO
THE NORTHEAST OF THE CENTER IN AN ENVIRONMENT OF MODERATE
SOUTHWESTERLY SHEAR. THE INITIAL INTENSITY IS LOWERED TO 35 KT
BASED ON THE LATEST DVORAK DATA-T NUMBER FROM TAFB. LITTLE CHANGE
IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS OR SO AS MODERATE
SHEAR CONTINUES...BUT SOME INTENSIFICATION IS SHOWN FROM 36 TO 48
HOURS AS AN UPPER-LEVEL TROUGH MAY PROVIDE SOME BAROCLINIC SUPPORT
FOR INTENSIFICATION. GABRIELLE SHOULD BECOME EXTRATROPICAL BY 72
HOURS...AND MAY BE DISSIPATED ENTIRELY BY THEN...HOWEVER A 72-HOUR
POINT WAS PROVIDED IN THIS FORECAST FOR CONTINUITY.
ALTERNATIVELY...IF DEEP CONVECTION DISSIPATES ENTIRELY...GABRIELLE
COULD BECOME A POST-TROPICAL CYCLONE AT ANY TIME DURING THE
FORECAST PERIOD.
 
GABRIELLE HAS MOVED SLOWLY WEST-NORTHWESTWARD THIS AFTERNOON...AND
THE INITIAL MOTION ESTIMATE IS 295/04. THIS MOTION IS PROBABLY DUE
TO THE SHALLOW CYCLONE NOT FEELING THE INFLUENCE OF THE UPPER-LEVEL
LOW OFF THE SOUTHEAST U.S. COAST AND THE DOMINANT STEERING FLOW
COMING FROM A WEAK LOW-LEVEL RIDGE TO THE NORTH AND EAST. THE MODEL
GUIDANCE CONTINUES TO INSIST ON A NORTHWARD TURN SOON...WITH A
MOTION TOWARD THE NORTHWEST EXPECTED TOMORROW FOLLOWED BY A
NORTH-NORTHEASTWARD ACCELERATION ON FRIDAY AHEAD OF AN
EASTWARD-MOVING UPPER-LEVEL TROUGH.  DUE TO THE WESTWARD MOTION
TODAY...AND A WESTWARD SHIFT IN THE GUIDANCE DURING THE FIRST
COUPLE OF DAYS...THE NHC FORECAST HAS BEEN ADJUSTED WESTWARD TOWARD
THE NEW MULTI-MODEL CONSENSUS AND LIES ABOUT A DEGREE WEST OF THE
PREVIOUS FORECAST BY 48 HOURS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/2100Z 32.8N  66.4W   35 KT  40 MPH
 12H  12/0600Z 33.2N  67.1W   35 KT  40 MPH
 24H  12/1800Z 34.4N  67.7W   35 KT  40 MPH
 36H  13/0600Z 37.1N  67.2W   40 KT  45 MPH
 48H  13/1800Z 41.5N  65.0W   45 KT  50 MPH
 72H  14/1800Z 51.5N  55.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  15/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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