HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
10 AM EST THU AUG 19 1999
 
VISIBLE SATELLITE IMAGERY INDICATES THAT TROPICAL DEPRESSION FOUR IS
NEAR TROPICAL STORM STRENGTH WITH THE LOW LEVEL CENTER NEAR THE
EASTERN EDGE OF THE CONVECTIVE MASS. HOWEVER...EASTERLY SHEAR
CONTINUES OVER THE SYSTEM AND THE CONVECTIVE CLOUD TOPS HAVE WARMED
SOME DURING THE PAST FEW HOURS. IF THE CONVECTION PERSISTS...THE
CYCLONE WILL LIKELY BE UPGRADED TO A TROPICAL STORM THIS AFTERNOON.

THERE IS STILL A FAIR AMOUNT OF SCATTER IN THE SATELLITE-BASED
CENTER LOCATIONS...WHICH PRODUCE A BEST ESTIMATE OF THE MOTION OF
280/10. THERE IS LITTLE CHANGE TO EITHER THE FORECAST PHILOSOPHY OR
FORECAST TRACK FROM THE PREVIOUS PACKAGE. THE STRONG LOW LEVEL RIDGE
NORTH OF THE DEPRESSION SHOULD KEEP THE SYSTEM ON A WEST TO WEST-
NORTHWEST TRACK...WITH PERHAPS A SLIGHT BEND TO THE NORTH AFTER 48
HOURS DUE TO AN UPPER LEVEL TROUGH TO THE NORTHWEST.

TROPICAL DEPRESSION FOUR HAS MAINTAINED ITSELF AGAINST MODERATE TO
STRONG SHEAR. THE AVN...NOGAPS...AND ECMWF MODELS SUGGEST SOME
DECREASE IN THE SHEAR MAY OCCUR DURING THE FORECAST PERIOD...WHICH
WOULD ALLOW SOME STRENGTHENING. THE FORECAST TRACK TAKES THE CYCLONE
OVER 25C-26C WATER AFTER 36 HOURS...WHICH WOULD LIKELY SLOW OR HALT
INTENSIFICATION. THUS...THE INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS PACKAGE.
 
BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     19/1500Z 14.1N  22.1W    30 KTS
12HR VT     20/0000Z 14.4N  23.6W    40 KTS
24HR VT     20/1200Z 14.8N  25.8W    50 KTS
36HR VT     21/0000Z 15.1N  27.9W    60 KTS
48HR VT     21/1200Z 15.5N  30.0W    60 KTS
72HR VT     22/1200Z 16.5N  34.0W    60 KTS
 
 
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