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TROPICAL STORM DENNIS DISCUSSION NUMBER   6
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT WED AUG 25 1999
 
THE POORLY-DEFINED CENTER OF DENNIS REMAINS DIFFICULT TO LOCATE ON
INFRARED IMAGERY...BUT APPEARS TO STILL BE EXPOSED WEST OF THE MAIN
CONVECTION. SATELLITE CENTER LOCATIONS FROM TAFB AND SAB ARE OVER 60
MILES APART...WHICH ADDS TO THE LOW LOCATION CONFIDENCE. THE INITIAL
MOTION FOR THIS PACKAGE IS SET TO 285/7 AND THE MAXIMUM WINDS REMAIN
40 KT.

THE 00Z AVIATION MODEL WAS WEAKER WITH THE EASTERN U.S. TROUGH...
WITH THE RESULT THAT AVN-BASED GUIDANCE TAKES THE STORM FURTHER WEST
THAN 6 HOURS AGO. THE OFFICIAL TRACK FORECAST REFLECTS THIS AND
ADJUSTS THE TRACK TO THE LEFT AND SOMEWHAT SLOWER THAN THE PREVIOUS
PACKAGE. IT IS NOTEWORTHY THE AVN IS THE WEAKEST MODEL WITH THE
TROUGH...AS THE NOGAPS...UKMET...AND ECMWF MODELS USE A STRONGER
TROUGH TO TURN DENNIS MORE QUICKLY NORTHWARD.

DESPITE THE ANTICYCLONE OVER DENNIS...THE CONVECTION IS DISPLACED
EAST AND SOUTHEAST OF THE CENTER AS IF THE SYSTEM IS SHEARED. IT MAY
BE THAT AN UPPER LEVEL ANTICYCLONE OVER THE FLORIDA STRAITS IS
PRODUCING A NORTHWESTERLY FLOW THAT IS UNDERCUTTING DENNIS'
ANTICYCLONE. THE INTENSITY FORECAST IS REDUCED BY 5 KT FROM THE
PREVIOUS PACKAGE TO REFLECT THE SLOWER THAN EXPECTED DEVELOPMENT TO
THIS TIME.
 
THE NEW FORECAST TRACK REQUIRES CHANGES IN THE WATCHES AND WARNINGS
IN THE BAHAMAS. ADDITIONALLY...RESIDENTS ALONG THE ENTIRE
SOUTHEASTERN UNITED STATES COAST SHOULD CLOSELY MONITOR THE PROGRESS
OF THIS SYSTEM.
 
BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     25/0900Z 23.1N  72.8W    40 KTS
12HR VT     25/1800Z 23.5N  74.0W    45 KTS
24HR VT     26/0600Z 24.5N  75.4W    55 KTS
36HR VT     26/1800Z 25.5N  76.5W    65 KTS
48HR VT     27/0600Z 27.0N  77.5W    75 KTS
72HR VT     28/0600Z 30.0N  78.5W    85 KTS
 
 
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