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HURRICANE DENNIS DISCUSSION NUMBER  28
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT MON AUG 30 1999
 
AS EXPECTED...THE MOTION OF DENNIS IS STARTING TO SLOW DOWN A
BIT...FROM 18 TO 15 KNOTS OVER THE PAST FEW HOURS.  THE EARLIER
ACCELERATION SEEMS TO HAVE BEEN RELATED TO A MID-UPPER LEVEL
VORTICITY MAXIMUM DIGGING SOUTH TO THE WEST OF THE CYCLONE.  TRACK
GUIDANCE IS SPLIT AGAIN...EVEN MORE SO THAN EARLIER...WITH THE GFDL
INSISTING ON A HARD LEFT TURN AND LANDFALL IN NORTHERN NORTH
CAROLINA WITHIN 36 HOURS.  THIS IS THE REASON THAT MOST OF THE
WARNINGS WILL REMAIN UP WITH THIS PACKAGE.  THE REST OF THE GUIDANCE
TAKES THE SYSTEM WELL OFFSHORE BEFORE SLOWING IT DOWN.  GIVEN THE
MOTION THIS AFTERNOON...THE OFFICIAL FORECAST IS SHIFTED RIGHT OF
THE PREVIOUS ADVISORY BY ABOUT 60 MILES...AND IS A COMPROMISE
BETWEEN THE HIGHLY DIVERGENT BAMD/LBAR AND GFDL.  THE AVN BEYOND 48
HOURS SHOWS DENNIS EMBEDDED WITHIN A DOUGHNUT-SHAPED RIDGE...AS THE
LONG-WAVE PATTERN UNDERGOES A MAJOR SHIFT.  IF THIS VERIFIES...
DENNIS WILL MOVE LITTLE...AND THIS IS STILL THE OPTION FAVORED BY
THE OFFICIAL FORECAST.
 
THE CENTRAL PRESSURE HAS BEEN IN THE UPPER 960S ALL DAY.  AIR FORCE
RESERVE UNIT RECONNAISSANCE AIRCRAFT FOUND 98 KNOTS IN THE SOUTHEAST
QUADRANT AT FLIGHT LEVEL.  DROPSONDE DATA OVER THE PAST FEW DAYS
SHOW THAT DENNIS HAS NOT BEEN PARTICULARLY EFFECTIVE AT BRINGING
HIGH WINDS DOWN TO THE SURFACE...AND THE INTENSITY ESTIMATE IS
LOWERED TO 80 KT.  NO SIGNIFICANT CHANGE IN STRENGTH IS ANTICIPATED
IN THE SHORT RUN...BUT SHIPS GUIDANCE WEAKENS DENNIS TO 48 KT IN 72
HOURS.  THE OFFICIAL INTENSITY FORECAST KEEPS DENNIS A HURRICANE
THROUGHOUT THE FORECAST PERIOD.
 
FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     30/2100Z 34.7N  74.2W    80 KTS
12HR VT     31/0600Z 35.3N  72.6W    80 KTS
24HR VT     31/1800Z 35.6N  72.3W    80 KTS
36HR VT     01/0600Z 36.0N  72.0W    75 KTS
48HR VT     01/1800Z 36.0N  72.0W    70 KTS
72HR VT     02/1800Z 36.0N  72.0W    65 KTS
 
 
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