Tropical Depression FOUR

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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042006
500 AM EDT TUE AUG 22 2006
 
THE OVERALL CLOUD PATTERN HAS INCREASED SLIGHTLY IN ORGANIZATION
OVER THE PAST FEW HOURS AND NEW CONVECTION HAS BEEN DEVELOPING
CLOSE TO THE ESTIMATED CENTER.  HOWEVER...SATELLITE INTENSITY
ESTIMATES REMAIN 30 KT FROM TAFB AND SAB...AND 25 KT FROM AFWA.
THEREFORE...THE INITIAL INTENSITY WILL BE HELD AT 30 KT. 

THE INITIAL MOTION ESTIMATE IS 285/14...SLIGHTLY FASTER THAN 
BEFORE.  GLOBAL MODELS REMAIN IN GOOD AGREEMENT ON A WEST- 
NORTHWEST TO NORTHWESTWARD MOTION SOUTH OF A MID-TROPOSPHERIC
RIDGE THROUGH 48 HOURS.  THEREAFTER...THE UKMET MODEL DEPICTS A 
WEAKER CYCLONE...THAT IS STEERED MORE WESTWARD BY THE LOW- TO
MID-LEVEL FLOW.  THE GFS AND GFDL DEPICT A STRONGER SYSTEM THAT
CONTINUES NORTHWEST INTO A WEAKNESS IN THE RIDGE THAT DEVELOPS OVER
THE CENTRAL ATLANTIC. THE OFFICIAL TRACK FORECAST REMAINS A LITTLE 
LEFT OF THE DYNAMICAL MODELS EARLY IN THE FORECAST PERIOD...BUT 
IS NEAR THE MIDDLE OF THE MODEL GUIDANCE BEYOND 72 HOURS...AND IS 
CLOSEST TO THE GFDL AND CONU CONSENSUS.

THE DEPRESSION IS FORECAST TO REMAIN IN A FAVORABLE ATMOSPHERIC
ENVIRONMENT AND OVER WARM WATER FOR THE NEXT FEW DAYS...SO GRADUAL
STRENGTHENING IS ANTICIPATED.  THE OFFICIAL INTENSITY FORECAST
CLOSELY FOLLOWS THE SHIPS GUIDANCE AND IS UNCHANGED FROM THE
PREVIOUS ADVISORY.  IF CURRENT TRENDS CONTINUE...THE DEPRESSION
COULD BECOME A TROPICAL STORM LATER THIS MORNING.  IT SHOULD BE
NOTED THAT THE SHIPS MODEL HALTS STRENGTHENING AT DAYS 4 AND 5 DUE
TO INCREASING SOUTHERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL TROUGH
OVER THE CENTRAL ATLANTIC.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0900Z 12.8N  24.6W    30 KT
 12HR VT     22/1800Z 13.7N  26.6W    35 KT
 24HR VT     23/0600Z 15.1N  29.3W    40 KT
 36HR VT     23/1800Z 16.7N  32.0W    45 KT
 48HR VT     24/0600Z 18.3N  34.8W    50 KT
 72HR VT     25/0600Z 21.5N  40.5W    60 KT
 96HR VT     26/0600Z 24.5N  46.0W    65 KT
120HR VT     27/0600Z 27.5N  51.5W    65 KT
 
$$
FORECASTER BROWN
 
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