HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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TROPICAL STORM DENNIS DISCUSSION NUMBER   9
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT WED AUG 25 1999
 
THE LATEST AIR FORCE RESERVE HURRICANE HUNTER CENTER FIX SUGGESTS
THAT DENNIS HAS BEGUN TO DRIFT WEST-NORTHWESTWARD...AS ANTICIPATED
IN THE LAST ADVISORY PACKAGE. THE INITIAL MOTION ESTIMATE IS NOW
300/3 KTS. THE SYNOPTIC REASONING BEHIND THE TRACK FORECAST IS
UNCHANGED AS THE MID-TROPOSPHERIC TROUGH OVER THE EASTERN U.S.
SHOULD GRADUALLY STEER DENNIS ON A GENERAL NORTHWEST HEADING BEFORE
PULLING THE CYCLONE NORTHWARD AFTER 48 HRS. THE 00Z TRACK MODEL
SUITE GENERALLY SUPPORTS THIS SCENARIO.  BAMD CONTINUES TO BE THE
LEFT-MOST OF THE MODEL GUIDANCE WHILE NOGAPS MOVES DENNIS ON A
GENERAL SLOW NORTHWARD TRACK THROUGH 72 HRS. THE OFFICIAL FORECAST
IS ON THE LEFT SIDE OF MOST OF THE GUIDANCE AND IS IN GOOD AGREEMENT
WITH LBAR AND THE 18Z GFDL RUN.  THIS TRACK IS SLIGHTLY RIGHT OF 
THE PREVIOUS ADVISORY MAINLY DUE TO THE INITIAL MOTION/POSITION
ESTIMATE.  ANOTHER SYNOPTIC FLOW MISSION IS BEING FLOWN THIS EVENING
BY THE NOAA G-IV AND P-3 AIRCRAFT TO COLLECT UPPER LEVEL DATA AROUND
DENNIS. THIS DATA WILL BE INCORPORATED INTO THE 00Z NCEP GLOBAL
MODEL SUITE.
 
RECONNAISSANCE AIRCRAFT RECENTLY REPORTED A MINIMUM CENTRAL PRESSURE
OF 998 MB...A 10 MB DROP OVER THE LAST 24 HRS...AND WINDS OF 67 KTS
AT 1500 FEET. THIS SUPPORTS MAINTAINING THE INITIAL INTENSITY AT
55 KTS. THE LATEST RECON FIX AS WELL AS SATELLITE ANIMATION SHOWS
THAT THE CIRCULATION CENTER IS ON THE WESTERN SIDE OF THE DEEP
CONVECTION. THIS SUGGESTS THAT THE SYSTEM IS EXPERIENCING SOME
NORTHWESTERLY WIND SHEAR...AND ANALYSES FROM CIMSS/UNIVERSITY OF
WISCONSIN SUPPORTING THIS. THE SHIPS INTENSITY MODEL ALSO
ACKNOWLEDGES THE SHEAR. HOWEVER...WITH WELL-ESTABLISHED OUTFLOW
AND FAVORABLE UPPER-LEVEL CONDITIONS FORECAST TO EVOLVE...GRADUAL
STRENGTHENING IS FORECAST IN LINE WITH THE PREVIOUS PACKAGE...AND
IN GOOD AGREEMENT WITH SHIPS.
 
THE 21Z REPORT FROM BUOY 41651 SHOWED 42 KT WINDS.  THIS DATA ALONG
WITH THE LATEST HRD WIND ANALYSIS WERE USED TO ADJUST THE WIND RADII
 
THE OFFICIAL FORECAST TRACK STILL BRINGS DENNIS FAR ENOUGH WEST
TO POSE A THREAT TO THE SOUTHEAST U.S...ESPECIALLY THE CAROLINAS...
LATE IN THE FORECAST PERIOD. ALL INTERESTS ALONG THE SOUTHEAST
COAST SHOULD CONTINUE TO CLOSELY MONITOR THE PROGRESS OF THIS
SYSTEM.
 
GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     26/0300Z 23.7N  72.7W    55 KTS
12HR VT     26/1200Z 24.1N  73.3W    65 KTS
24HR VT     27/0000Z 24.8N  74.3W    70 KTS
36HR VT     27/1200Z 25.8N  75.5W    75 KTS
48HR VT     28/0000Z 27.0N  77.0W    80 KTS
72HR VT     29/0000Z 30.5N  78.0W    90 KTS
 
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