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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   2
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST THU AUG 19 1999
 
TROPICAL DEPRESSION FOUR HAS CHANGED LITTLE OVER THE LAST 6 HRS
WITH DEEP CONVECTION...TOPS TO -80C...SOUTH AND WEST OF THE
SUSPECTED LOW-LEVEL CENTER.  THE SYSTEM IS STILL NOT VERY WELL
ORGANIZED AND DVORAK INTENSITY ESTIMATES REFLECT...25 KT FROM SAB
AND AFGW AND 35 KT FROM TAFB.  THE INITIAL INTENSITY WILL BE HELD 
AT 30 KT FOR THIS ADVISORY. THE DEPRESSION CONTINUES TO EXPERIENCE
EASTERLY VERTICAL WIND SHEAR ON THE ORDER OF 25-30 KT PER CLOUD
DRIFT WIND DATA.  THE STATISTICAL HURRICANE INTENSITY PREDICTION
SCHEME...SHIPS...CONTINUES TO INDICATE MODEST STRENGTHENING...50 KT
BY 72 HRS...LIMITED BY THE EASTERLY SHEAR CONDITIONS. SINCE THE
SYSTEM SEEMS TO BE HOLDING ITS OWN IN SPITE OF THE SHEAR...THE
INTENSITY TREND FROM THE PREVIOUS ADVISORY WILL BE MAINTAINED.

THE INITIAL MOTION ESTIMATE IS 280/13 KT WHICH REPRESENTS A SLIGHT
INCREASE IN FORWARD SPEED FROM THE LAST ADVISORY.  HOWEVER...THERE
IS STILL A FAIR AMOUNT OF UNCERTAINTY REGARDING THE CENTER LOCATION
AS DEMONSTRATED IN THE 45-60 NM SPREAD IN THE SATELLITE-BASED FIXES.
THE MID-TROPOSPHERIC RIDGE TO THE NORTH OF THE DEPRESSION WILL
PRODUCE A GENERAL WEST TO WEST-NORTHWEST MOTION OVER THE NEXT THREE
DAYS. THE 00Z AVN SUGGESTS THAT A WEAKNESS MAY DEVELOP TOWARDS THE
END OF THE FORECAST PERIOD AND THE OFFICIAL FORECAST SHOWS A BEND TO
THE NORTH AND A DECELERATION BEYOND 48 HOURS. THE OFFICIAL FORECAST 
TRACK IS SLIGHTLY TO THE RIGHT OF PREVIOUS PACKAGE PRIMARILY DUE TO
THE INITIAL POSITION. 
 
GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/0900Z 14.0N  21.3W    30 KTS
12HR VT     19/1800Z 14.4N  23.2W    40 KTS
24HR VT     20/0600Z 14.9N  25.6W    50 KTS
36HR VT     20/1800Z 15.3N  27.6W    60 KTS
48HR VT     21/0600Z 15.5N  29.0W    60 KTS
72HR VT     22/0600Z 16.0N  31.0W    60 KTS
  
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