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HURRICANE DENNIS DISCUSSION NUMBER  17
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT FRI AUG 27 1999
 
DENNIS HAS CONTINUED TO GRADUALLY BECOME BETTER ORGANIZED THIS
EVENING. RADAR IMAGES RELAYED FROM THE NOAA P-3 RECONNAISSANCE
AIRCRAFT NOW SHOW A FULLY FORMED EYE...35-40 MILES IN DIAMETER.
THE AIR FORCE HURRICANE HUNTER REPORTS THE MINIMUM CENTRAL PRESSURE
IS NOW 980 MB...A 12 MB DROP OVER THE LAST 24 HRS....ALTHOUGH THE
WINDS HAVE NOT YET RESPONDED. SATELLITE IMAGERY SHOWS THAT THE
CENTER IS NOW EMBEDDED WITHIN VERY COLD CLOUD TOPS...-75C...WITH
THE DEEP CONVECTION WRAPPING AROUND THE CENTER. ALL THESE SIGNALS
SUGGEST THAT THE INTENSIFICATION PROCESS IS BEGINNING. WE WILL
HOLD THE INITIAL INTENSITY AT 70 KTS FOR THIS ADVISORY UNTIL HIGHER
WINDS ARE CONFIRMED BY RECONNAISSANCE AIRCRAFT. THE INTENSITY
FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY WHICH BRINGS
DENNIS TO A CATEGORY THREE HURRICANE BY 48 HRS.
 
AIR FORCE RECONNAISSANCE FIXES THIS EVENING INDICATE THAT THE CENTER
HAS BEEN DRIFTING WEST-NORTHWESTWARD DURING THE LAST 3-6 HRS. THE
INITIAL MOTION ESTIMATE...300/06 KT...IS BASED ON A 12-24 HR MEAN.
DENNIS REMAINS IN A LIGHT STEERING ENVIRONMENT.  THE DATA FROM THE
NOAA G-IV SYNOPTIC FLOW MISSION AROUND THE HURRICANE SHOWS A 500MB
RIDGE ALONG 31N/32N FROM BERMUDA TO NEAR 78W. THIS FEATURE SHOULD
CONTINUE TO STEER DENNIS ON A SLOW WEST-NORTH TO NORTHWEST COURSE
FOR THE NEXT DAY OR SO. THEREAFTER...THINGS BECOME A BIT MORE
UNCERTAIN AS THE IMPACT OF A MID- TO UPPER-LEVEL LOW...SEEN IN
WATER VAPOR IMAGERY OVER CENTRAL MISSISSIPPI...CUTS OFF OVER THE
GULF COASTAL REGION.  THE EXACT LOCATION OF THIS LOW WILL HELP
DETERMINE...IN PART...THE STEERING OF DENNIS NEAR THE END OF THE
FORECAST PERIOD. THE 00Z TRACK GUIDANCE MODELS ARE VERY SIMILAR TO
THEIR 18Z COUNTERPARTS WITH BAMS AND BAMM THE WESTERN-MOST OF THE
TRACKS. MOST OF THE DYNAMICAL-BASED GUIDANCE TURNS DENNIS AWAY FROM
THE SOUTHEAST COAST BEYOND 48 HRS HOWEVER...WE WILL WAIT FOR THE 00Z
MODEL CYCLE...WHICH WILL INCLUDE THE G-IV DATA...BEFORE MAKING ANY
SIGNIFICANT CHANGES TO THE OFFICIAL FORECAST TRACK.  THE NHC TRACK
REPRESENTS AN UPDATE TO THE PREVIOUS PACKAGE.
 
THERE HAVE BEEN NO CHANGES TO THE WATCHES/WARNINGS HOWEVER...ALL
INTERESTS ALONG THE SOUTHEAST COASTS SHOULD CONTINUE TO CLOSELY
MONITOR THE PROGRESS OF THIS HURRICANE.
 
GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     28/0300Z 26.4N  76.6W    70 KTS
12HR VT     28/1200Z 26.9N  77.3W    80 KTS
24HR VT     29/0000Z 27.6N  78.2W    90 KTS
36HR VT     29/1200Z 28.8N  78.9W    95 KTS
48HR VT     30/0000Z 30.0N  79.5W   100 KTS
72HR VT     31/0000Z 32.5N  79.5W   100 KTS
 
 
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