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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT SUN SEP 22 2002

ALTHOUGH THE CONVECTIVE CLOUD PATTERN APPEARS WELL ORGANIZED...WITH
GOOD BANDING FEATURES OVER THE EASTERN PORTION OF THE
SYSTEM...VISIBLE IMAGES CONTINUE TO SUGGEST THAT THE LOW-LEVEL
CENTER IS DISPLACED TO THE WEST OF THE DENSE OVERCAST.  THIS WAS
ALSO CONFIRMED BY A TRMM OVERPASS AT 1728Z.  THE CYCLONE HAS A VERY
SUBSTANTIAL OVERALL CIRCULATION...AND THE UPPER-LEVEL OUTFLOW
PATTERN IS EXPANDING WESTWARD.  THERE IS A WEAK UPPER-LEVEL TROUGH
OR SHEAR AXIS IN THE VICINITY OF THE LESSER ANTILLES.  THE NCEP
GLOBAL MODEL 200 MB FORECAST SHOWS THIS SYSTEM WEAKENING INTO AN
INVERTED TROUGH AND SHIFTING WESTWARD OVER THE CARIBBEAN.  THIS
WOULD FAVOR EVENTUAL STRENGTHENING OF THE TROPICAL CYCLONE.  HOWEVER
GIVEN THE CURRENT LACK OF VERTICAL COUPLING..NO CHANGE IN STRENGTH
IS FORECAST FOR THE NEXT DAY OR SO.  THE WESTWARD DISPLACEMENT OF
THE LOW-LEVEL CENTER COULD BE DUE TO STRONG LOWER-TROPOSPHERIC FLOW
WHICH CAN ALSO IMPART NET WESTERLY SHEAR.  ASSUMING THE CYCLONE
MOVES INTO AN ENVIRONMENT OF SLIGHTLY WEAKER LOW-LEVEL
EASTERLIES...INTENSIFICATION COULD OCCUR.  DUE TO UNCERTAINTIES IN 
THE INTENSITY FORECAST...A TROPICAL STORM WATCH HAS BEEN ISSUED FOR 
A PORTION OF THE LESSER ANTILLES.

THE TRACK FORECAST IS SHIFTED SLIGHTLY WESTWARD FROM THE PREVIOUS 
ADVISORY DUE TO THE MORE WESTWARD CURRENT MOTION...275/20.  THIS IS 
WELL SUPPORTED BY THE NUMERICAL GUIDANCE. A DEEP-LAYER MEAN RIDGE IS 
FORECAST TO PERSIST TO THE NORTH OF THE TROPICAL CYCLONE...WHICH 
SHOULD MAINTAIN A WEST TO WEST-NORTHWESTWARD TRACK OVER THE NEXT FEW 
DAYS.

FORECASTER AVILA/PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/2100Z 12.1N  54.0W    30 KTS
12HR VT     23/0600Z 12.5N  57.0W    30 KTS
24HR VT     23/1800Z 13.5N  60.0W    30 KTS
36HR VT     24/0600Z 14.5N  63.0W    45 KTS
48HR VT     24/1800Z 15.5N  66.0W    55 KTS
72HR VT     25/1800Z 17.0N  69.5W    65 KTS
 
 
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