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...FOR INTERGOVERNMENTAL USE ONLY...
TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
1130 PM EDT SAT AUG 24 1991
 
ATTN WSFOS NMC F/D

THE DEPRESSION HAS LOST A GREAT DEAL OF ITS ASSOCIATED DEEP
CONVECTION THIS EVENING.  IT IS NOT CERTAIN WHETHER THIS IS DUE TO
THE MARGINAL SEA SURFACE TEMPERATURES OR TO A DIURNAL
FLUCTUATION...OR BOTH.  REGARDLESS OF THIS...THE CURRENT INTENSITY
IS MAINTAINED AT 30 KNOTS IN ACCORDANCE WITH DVORAK RULES.  NO
CHANGE IN STRENGTH IS FORECAST ALTHOUGH SHIFOR DOES INDICATE SOME
SLIGHT INCREASE BY 72 HOURS.  HOWEVER IT REMAINS TO BE SEEN WHETHER
THE SYSTEM WILL HOLD TOGETHER THAT LONG.

INITIAL MOTION IS NOW ESTIMATED TO BE 290/10.  THE OFFICIAL TRACK
FORECAST IS VERY CLOSE TO THE MEDIUM DEPTH BAM AND IS ABOUT IN THE
MIDDLE OF ALL OF THE GUIDANCE.  THE DEEP LAYER MEAN FLOW FORECAST BY
THE NMC AVIATION RUN SHOWS AN INVERTED TROUGH JUST AHEAD OF THE
DEPRESSION WHICH WOULD TEND TO PULL THE SYSTEM MORE TOWARDS THE
NORTH.  HOWEVER...SINCE THIS IS A WEAK CYCLONE...IT IS FELT THAT ITS
STEERING SHOULD BE INFLUENCED MORE BY THE LOWER TO MIDDLE
TROPOSPHERIC FLOW.  THIS FAVORS A MORE WEST NORTHWEST TRACK.

PASCH

 
PRELIMINARY PROG POSITIONS AND MAX WINDS
 
INITIAL     25/0400Z 15.7N  25.8W    30 KTS.
12HR VT     25/1200Z 16.2N  27.1W    30 KTS.
24HR VT     26/0000Z 16.9N  29.2W    30 KTS.
36HR VT     26/1200Z 17.7N  31.4W    30 KTS.
48HR VT     27/0000Z 18.8N  33.3W    30 KTS.
72HR VT     28/0000Z 21.0N  37.0W    30 KTS.