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TROPICAL DEPRESSION SIX DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT FRI AUG 18 2000
 
A PERSISTENT CLUSTER OF CONVECTION HAS FORMED NEAR OR TO THE NORTH
OF THE HARD TO LOCATE CENTER OF TROPICAL DEPRESSION SIX.  THE EXACT
LOCATION OF THE CENTER IS RATHER IMPORTANT...BECAUSE IF THE CENTER
IS NEAR THE CONVECTION THE SYSTEM IS MOVING MORE TO THE NORTHWEST
AND IS NEAR TROPICAL STORM STRENGTH.  THIS ADVISORY WILL KEEP THE
CENTER CLOSER TO THE PREVIOUS FORECAST TRACK AND AT 30 KT INTENSITY.

THE BEST ESTIMATE OF THE INITIAL MOTION IS 295/8.  A LOW/MID LEVEL
RIDGE IS PRESENT NORTH OF THE DEPRESSION...WHILE WATER VAPOR IMAGERY
SHOWS AN UPPER LEVEL TROUGH ORIENTED NORTHEAST-SOUTHWEST TO THE
NORTHWEST OF THE CYCLONE.  THE RIDGE SHOULD KEEP THE DEPRESSION ON A
GENERALLY WEST-NORTHWEST TRACK...AND NHC TRACK FORECAST GUIDANCE
AGREES WITH THIS.  ONE NOTE ABOUT THE GUIDANCE IS THAT THE
GFDL...WHICH WAS THE NORTHERNMOST MODEL 6 HR AGO...IS NOW THE
SOUTHERNMOST MODEL.  WITH THE UNCERTAINTY IN THE LOCATION...THERE IS
ONLY A SMALL NUDGING NORTHWARD OF THE OFFICIAL FORECAST FROM THE
PREVIOUS ADVISORY.

THE CYCLONE IS MOVING INTO AN AREA OF SOUTHWESTERLY SHEAR...AND
LARGE-SCALE MODELS SUGGEST THIS SHOULD PERSIST FOR 24-48 HR BEFORE
DECREASING.  THIS SHEAR IS NOT STRONG...SO THE MOST LIKELY SCENARIO
IS THAT IT WILL SLOW THE INTENSIFICATION.  THE INTENSITY FORECAST
GOES WITH THIS SCENARIO...CALLING FOR ONLY SLOW STRENGTHENING FOR
THE FIRST 24 HR AND A SLIGHTLY FASTER STRENGTHENING AFTER THAT.  
 
AN AIR FORCE PLANE WILL CHECK THE DEPRESSION THIS AFTERNOON. 
DEPENDING ON THE EXACT POSITION...COURSE...AND INTENSITY...WATCHES
OR WARNINGS MAY BE NECESSARY FOR PORTIONS OF THE LESSER ANTILLES
LATER TODAY.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     18/0900Z 15.6N  54.4W    30 KTS
12HR VT     18/1800Z 16.2N  55.6W    35 KTS
24HR VT     19/0600Z 17.0N  57.4W    35 KTS
36HR VT     19/1800Z 17.8N  59.2W    45 KTS
48HR VT     20/0600Z 19.0N  61.5W    50 KTS
72HR VT     21/0600Z 21.0N  66.0W    60 KTS
 
 
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