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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SAT SEP 15 2001

GABRIELLE HAS MOVED OFF THE FLORIDA COAST DURING THE MORNING.  THE
STORM CURRENTLY MORE RESEMBLES A SUBTROPICAL CYCLONE...WITH THE
STRONGEST WINDS AND CONVECTION WELL REMOVED FROM THE CENTER AND
AN UPPER LEVEL CYCLONE OVER THE SURFACE CENTER.  DESPITE THE LACK
OF CENTRAL CONVECTION...THE CENTRAL PRESSURE REMAINS 998 MB WITH
AIRCRAFT MEASURED WINDS OF 59 KT IN THE SOUTHEAST QUADRANT AND 58
KT IN THE NORTHWEST QUADRANT.  THE MAXIMUM INTENSITY IS SET TO 40 KT
BASED ON THE AIRCRAFT WINDS AND AN OBSERVATION OF 42 KT FROM THE
ST. AUGUSTINE C-MAN STATION.
 
THE INITIAL MOTION IS 070/6...AND RADAR AND AIRCRAFT FIXES SINCE
12Z SUGGEST IT MAY BE MOVING EVEN FASTER.  WATER VAPOR IMAGERY
SHOWS THAT GABRIELLE IS BECOMING EMBEDDED IN THE WESTERLIES...
WITH A DEEP-LAYER RIDGE TO THE SOUTHEAST OF THE SYSTEM AND A
BROAD MID/UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES.  THIS
PATTERN SUPPORTS A GENERAL EAST TO NORTHEAST TRACK...AND NHC
HURRICANE GUIDANCE IS CLUSTERED AROUND AN EAST-NORTHEASTWARD
MOTION.  THE TRACK FORECAST IS DOWN THE MIDDLE OF THE GUIDANCE AND
IS JUST A LITTLE FURTHER SOUTH OF THE PREVIOUS PACKAGE.  SOME
ADJUSTMENT OF THE TRACK MAY BE NECESSARY IN THE NEXT PACKAGE IF
GABRIELLE IS ACTUALLY MOVING FASTER THAN 6-8 KT.
 
THERE ARE SEVERAL POSSIBILITIES REGARDING THE INTENSITY OF
GABRIELLE.  THE FIRST IS THAT THE MID/UPPER LEVEL DRY AIR OVER THE
LOW LEVEL CENTER WILL INHIBIT CONVECTION AND PREVENT RE-DEVELOPMENT.
THE SECOND IS THAT CONVECTION WILL RETURN AND SOME STRENGTHENING
WILL OCCUR.  THE INTENSITY FORECAST IS A COMBINATION OF THESE TWO
POSSIBILITIES...CALLING FOR NO CHANGE IN STRENGTH FOR THE FIRST
12 HR FOLLOWED BY SLOW STRENGTHENING.  A THIRD POSSIBILITY IS THAT
THE CENTER MIGHT TRY TO REFORM CLOSER TO ONGOING CONVECTION TO THE
NORTHEAST...WHERE GABRIELLE IS INTERACTING WITH A FRONTAL ZONE.
IF THIS OCCURS...GABRIELLE MIGHT RE-INTENSIFY AS A HYBRID SYSTEM.
ONE FINAL POSSIBILITY IS THAT GABRIELLE MIGHT MERGE WITH THE
FRONTAL ZONE AND BECOME EXTRATROPICAL.  
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     15/1500Z 28.8N  79.8W    40 KTS
12HR VT     16/0000Z 29.2N  78.9W    40 KTS
24HR VT     16/1200Z 30.2N  76.7W    45 KTS
36HR VT     17/0000Z 31.9N  73.7W    50 KTS
48HR VT     17/1200Z 33.7N  70.5W    50 KTS
72HR VT     18/1200Z 37.0N  64.0W    50 KTS
 
 
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