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Tropical Storm GABRIELLE (Text)

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TROPICAL STORM GABRIELLE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072013
500 AM AST THU SEP 05 2013
 
ALTHOUGH THE AREA OF DEEP CONVECTION HAS EXPANDED SIGNIFICANTLY
DURING THE PAST SEVERAL HOURS AND THE OUTFLOW IS EXCELLENT...
SURROUNDING SURFACE OBSERVATIONS DO NOT SUGGEST THAT THERE HAS 
BEEN ANY IMPROVEMENT OF THE CIRCULATION. IN ADDITION...MICROWAVE OR
DOPPLER RADAR DATA DO NOT SHOW ANY DEVELOPMENT OF AN INNER
CORE...ALTHOUGH RADAR IMAGES SHOW A WELL-DEFINED MID-LEVEL CENTER
TO THE EAST OF THE SURFACE LOCATION. I WOULD NOT BE SURPRISED IF
THERE IS A REFORMATION OF THE SURFACE CENTER. A RECONNAISSANCE
PLANE LATER THIS MORNING WILL HELP US TO DETERMINE IF THIS IS THE
CASE. SUBJECTIVE ESTIMATES FROM TAFB AND SAB AS WELL AS OBJECTIVE
ESTIMATES FROM THE UNIVERSITY OF WISCONSIN...CIMSS...ARE 2.5 ON THE
DVORAK SCALE. ON THIS BASIS...THE INITIAL INTENSITY IS KEPT AT 35
KNOTS...AND THESE WINDS ARE PROBABLY CONFINED TO A VERY SMALL AREA
NEAR THE CENTER. THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. MOST
OF THE GLOBAL MODELS KEEP A WEAK CYCLONE FOR A FEW DAYS WITH THE
EXCEPTION OF THE ECMWF WHICH DISSIPATES GABRIELLE JUST NORTH OF
HISPANIOLA IN A COUPLE OF DAYS. GIVEN THE STRONG WESTERLY SHEAR
WHICH IS FORECAST TO BECOME ESTABLISHED ALONG THE FORECAST PATH OF
GABRIELLE...THE DISSIPATION OPTION OF THE ECMWF IS NOT OUT OF THE
QUESTION. AT THIS TIME...THE NHC FORECAST FOLLOWS THE MODEL
CONSENSUS SHOWING SOME SLIGHT STRENGTHENING GIVING CREDIT TO THE
OTHER MODELS.   

ALTHOUGH THE SURFACE CENTER IS DIFFICULT TO FIND ON IR IMAGES...IT
APPEARS TO BE ON THE WESTERN EDGE OF THE DEEP CONVECTION. THE BEST
ESTIMATE OF THE INITIAL MOTION IS TOWARD THE NORTHWEST OR 320
DEGREES AT 7 KNOTS.  GABRIELLE IS EMBEDDED WITHIN A WEAK STEERING
FLOW SOUTH OF A NARROW RIDGE OF HIGH PRESSURE OVER THE WESTERN
ATLANTIC. IN A DAY OR TWO...A MID-LEVEL TROUGH IS FORECAST TO MOVE
FROM THE UNITED STATES EASTWARD ACROSS THE ATLANTIC...CAUSING
GABRIELLE TO RECURVE AND MOVE TOWARD THE OPEN ATLANTIC. THE
OFFICIAL FORECAST IS VERY CLOSE TO THE MULTI-MODEL CONSENSUS AND IS
NOT TOO DIFFERENT FROM THE PREVIOUS ONE. 
  
REGARDLESS OF THE EXACT TRACK OF THE CENTER OF GABRIELLE DURING THE
NEXT 24 HOURS...THE MAIN THREAT WILL BE HEAVY RAINFALL OVER PORTIONS
OF PUERTO RICO AND THE EASTERN PORTION OF THE DOMINICAN REPUBLIC.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0900Z 17.5N  66.9W   35 KT  40 MPH
 12H  05/1800Z 18.5N  67.7W   35 KT  40 MPH
 24H  06/0600Z 19.7N  68.5W   40 KT  45 MPH
 36H  06/1800Z 20.9N  69.1W   45 KT  50 MPH
 48H  07/0600Z 21.8N  69.5W   50 KT  60 MPH
 72H  08/0600Z 24.0N  69.0W   50 KT  60 MPH
 96H  09/0600Z 27.0N  66.0W   50 KT  60 MPH
120H  10/0600Z 31.5N  62.5W   50 KT  60 MPH
 
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FORECASTER AVILA
 
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