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TROPICAL DEPRESSION ONE DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT TUE JUL 28 1998

THE DEPRESSION HAS NOT BECOME ANY BETTER ORGANIZED...AND THE CLOUD
PATTERN REMAINS ELONGATED FROM SOUTHWEST TO NORTHEAST.  WATER VAPOR
IMAGERY SHOWS AN UPPER-LEVEL TROUGH EXTENDING FROM NEAR 30N 20W
SOUTHWESTWARD TO NEAR 20N 30W...WHICH MAY BE PARTLY RESPONSIBLE FOR
THE DISTORTION OF THE CLOUD PATTERN.  MOREOVER THE CYCLONE IS STILL 
INVOLVED WITH THE LOW-LEVEL MONSOONAL FLOW FEEDING TOWARDS WESTERN
AFRICA.  THE ABOVE TWO FACTORS MAY BE PREVENTING THE DEPRESSION FROM
STRENGTHENING AT THIS TIME.  HOWEVER...THE LATEST NCEP GLOBAL MODEL
RUN SHOWS THE UPPER TROUGH MIGRATING WEST-NORTHWESTWARD AND A MORE
ANTICYCLONIC FLOW BUILDING OVER THE AREA OF THE DEPRESSION.  ALSO AS
THE DEPRESSION MOVES FARTHER WEST IT SHOULD ESCAPE FROM THE MONSOON
TROUGH AND PERHAPS ENCOUNTER BETTER LOW-LEVEL INFLOW.  ONLY TIME
WILL TELL OF COURSE.  THE OFFICIAL INTENSITY FORECAST IS THE SAME AS
THE PREVIOUS ONE AND CALLS FOR SLOW STRENGTHENING...BUT ONE SHOULD
BEAR IN MIND THE FACT THAT WE HAVE EXCEEDINGLY LIMITED SKILL IN
INTENSITY PREDICTION.

IT IS NOT EASY TO FIX A CENTER FROM INFRARED IMAGERY...BUT THE BEST
ESTIMATE IS THAT THE FORWARD MOTION HAS SLOWED A LITTLE MORE.  THE
OFFICIAL TRACK FORECAST IS SIMILAR TO THAT FROM THE LAST ADVISORY
BUT SLIGHTLY SLOWER.  THIS IS CLOSEST TO THE SHALLOW-LAYER STEERING.

IF THE SYSTEM WERE TO STRENGTHEN SIGNIFICANTLY MORE THAN
FORECAST...IT WOULD LIKELY TURN MORE NORTHWESTWARD IN RESPONSE TO
THE HIGHER-LEVEL TROUGH TO ITS NORTH. 

PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     28/0900Z 12.6N  30.9W    25 KTS
12HR VT     28/1800Z 13.0N  33.5W    30 KTS
24HR VT     29/0600Z 13.7N  36.5W    35 KTS
36HR VT     29/1800Z 14.5N  39.0W    40 KTS
48HR VT     30/0600Z 15.5N  41.5W    45 KTS
72HR VT     31/0600Z 17.5N  46.5W    55 KTS
 
 
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