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Tropical Depression TWELVE


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TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122011
500 PM AST MON AUG 29 2011
 
THE DEPRESSION HAS NOT BECOME BETTER ORGANIZED DURING THE DAY. 
BANDING FEATURES HAVE NOT BECOME MORE DEFINED AND THE LOW-LEVEL
CENTER REMAINS NEAR THE NORTHEASTERN EDGE OF THE MAIN AREA OF DEEP
CONVECTION.  THE CURRENT INTENSITY IS HELD AT 30 KT IN AGREEMENT
WITH DVORAK ESTIMATES FROM BOTH TAFB AND SAB.  THE SHIPS GUIDANCE
INDICATES THAT THE STRONG EAST-NORTHEASTERLY VERTICAL WIND SHEAR
CURRENTLY AFFECTING THE SYSTEM WILL LESSEN WITHIN A DAY OR
SO...WHICH SHOULD ALLOW STRENGTHENING TO COMMENCE SOON.  THE
OFFICIAL WIND SPEED FORECAST IS NOT FAR FROM THE
STATISTICAL-DYNAMICAL INTENSITY GUIDANCE.

INITIAL MOTION IS JUST NORTH OF DUE WEST OR ABOUT 280/12. THERE HAS
BEEN LITTLE CHANGE TO THE TRACK FORECAST OR FORECAST REASONING FROM
THIS MORNING. A MID-LEVEL SUBTROPICAL RIDGE IS CURRENTLY NORTH OF
THE DEPRESSION. OVER THE NEXT COUPLE OF DAYS...THE TROPICAL CYCLONE
IS EXPECTED TO TURN TOWARD THE WEST-NORTHWEST IN RESPONSE TO A
WEAKNESS IN THE RIDGE NEAR 50W LONGITUDE. GLOBAL MODELS PREDICT
THAT THE WEAKNESS WILL GRADUALLY SHIFT WESTWARD OVER TIME. AS A
RESULT...A CONTINUED WEST-NORTHWESTWARD TRACK IS FORECAST THROUGH
THE REMAINDER OF THE PERIOD. THE OFFICIAL FORECAST TRACK IS BETWEEN
THE LATEST ECMWF AND GFS SOLUTION...BUT LEANS MORE TOWARD THE ECMWF
TRACK AS THE GFS SEEMS TO BE TOO SLOW IN THE LATTER PART OF THE
FORECAST PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 10.2N  28.4W   30 KT  35 MPH
 12H  30/0600Z 10.9N  30.1W   35 KT  40 MPH
 24H  30/1800Z 11.9N  32.5W   45 KT  50 MPH
 36H  31/0600Z 13.0N  35.5W   50 KT  60 MPH
 48H  31/1800Z 14.0N  38.6W   55 KT  65 MPH
 72H  01/1800Z 15.5N  45.0W   70 KT  80 MPH
 96H  02/1800Z 17.0N  50.0W   80 KT  90 MPH
120H  03/1800Z 19.0N  55.0W   90 KT 105 MPH
 
$$
FORECASTER PASCH
 
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