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Tropical Depression GABRIELLE (Text)

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TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072013
1100 AM AST THU SEP 05 2013

A COMBINATION OF SATELLITE...SAN JUAN DOPPLER RADAR...RAWINSONDE...
AND AIRCRAFT DATA INDICATES THAT GABRIELLE HAS BECOME VERY
DISORGANIZED.  THE LOW-LEVEL CENTER...WHICH IS POORLY DEFINED...IS
LOCATED SOUTH OF THE MONA PASSAGE ABOUT 130 N MI FROM THE MID-LEVEL
CENTER THAT IS LOCATED BETWEEN PUERTO RICO AND THE VIRGIN ISLANDS. 
THIS STRUCTURE MAY BE DUE TO SOME WESTERLY VERTICAL WIND SHEAR...
ALTHOUGH THE SHEAR APPEARS TO BE TOO LIGHT TO HAVE SUCH A DRASTIC
EFFECT ON THE CYCLONE.  NONE OF THE DATA CURRENTLY SUGGEST TROPICAL
STORM FORCE WINDS ARE OCCURRING...SO GABRIELLE IS DOWNGRADED TO A
30-KT TROPICAL DEPRESSION.
 
CONVECTION CONTINUES NEAR THE MID-LEVEL CENTER...SO THERE IS STILL A
CHANCE OF THE LOW-LEVEL CENTER REFORMING IN THAT AREA.  IF THAT
DOES NOT OCCUR...GABRIELLE IS EXPECTED TO WEAKEN AS IT INTERACTS
WITH THE TERRAIN OF THE DOMINICAN REPUBLIC AND ENCOUNTERS
INCREASING WESTERLY SHEAR.  THE REVISED INTENSITY FORECAST NOW
CALLS FOR THE CYCLONE TO DEGENERATE TO A REMNANT LOW PRESSURE AREA
IN 24 HOURS AND TO DISSIPATE COMPLETELY THEREAFTER.  

THE INITIAL MOTION IS AN UNCERTAIN 305/8.  LOW-LEVEL RIDGING NORTH
AND NORTHEAST OF GABRIELLE SHOULD ALLOW THIS GENERAL MOTION TO
CONTINUE UNTIL THE CYCLONE DISSIPATES.  IF THE SYSTEM SURVIVES
LONGER THAN CURRENTLY FORECAST...THE DYNAMICAL MODELS SUGGEST IT
WILL TURN NORTHWARD IN RESPONSE TO A DEVELOPING DEEP-LAYER TROUGH
OVER THE WESTERN ATLANTIC.

A HEAVY RAIN THREAT CONTINUES OVER PUERTO RICO AND THE VIRGIN
ISLANDS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 17.5N  68.1W   30 KT  35 MPH
 12H  06/0000Z 18.3N  68.8W   25 KT  30 MPH
 24H  06/1200Z 19.6N  69.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 36H  07/0000Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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