Tropical Storm BONNIE

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TROPICAL STORM BONNIE DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT TUE AUG 10 2004
 
IN SATELLITE IMAGERY...BONNIE REMAINS A RATHER UNIMPRESSIVE TROPICAL
CYCLONE...WITH A SMALL CDO...CENTRAL DENSE OVERCAST...AND BANDING
THAT IS LIMITED BUT INCREASING.  THE CENTRAL CONVECTION HAS BEEN
RATHER PERSISTENT THOUGH...AND DATA FROM A RECONNAISSANCE AIRCRAFT
CURRENTLY INVESTIGATING BONNIE SHOWS THAT THE CYCLONE IS
MAINTAINING ITS ORGANIZATION AND STRENGTH. THE CREW REPORTED A 10
MILE WIDE EYE...ALMOST UNHEARD OF IN A SYSTEM OF THIS INTENSITY. 
THE PEAK FLIGHT-LEVEL WINDS WERE 49 KT...AND A DROPSONDE IN THE
SOUTHEAST QUADRANT REPORTED SURFACE WINDS OF 43 KT.  BASED ON THESE
DATA...THE INITIAL INTENSITY ESTIMATE IS HELD AT 45 KT FOR THIS
ADVISORY.
 
SMALL TROPICAL CYCLONES SUCH AS BONNIE ARE PRONE TO RAPID CHANGES IN
INTENSITY...EITHER UP OR DOWN. THERE ARE A COUPLE OF FACTORS THAT
WOULD ARGUE FOR SUBSTANTIAL STRENGTHENING OVER THE NEXT DAY OR TWO.
FIRST...ALTHOUGH BONNIE IS CURRENTLY EXPERIENCING SOME NORTHERLY
SHEAR...IT SHOULD BE MOVING UNDER LIGHT ANTICYCLONIC FLOW IN THE
CENTRAL GULF LATER TODAY. SECOND...THE FORECAST TRACK TAKES BONNIE
OVER OR VERY NEAR A POOL OF DEEP WARM WATER IN THE NORTH-CENTRAL
GULF. A MITIGATING FACTOR WOULD BE THE RELATIVELY DRY AIR IN THE
NORTHWESTERN GULF. THE LAST TWO RUNS OF BOTH THE GFDL AND SHIPS
MODELS MAKE BONNIE A HURRICANE PRIOR TO LANDFALL. THE GFS DOES NOT
SHOW INTENSIFICATION...BUT IN FACT BARELY ACKNOWLEDGES BONNIE'S
EXISTENCE DUE TO THE CYCLONE'S SMALL SIZE. THE OFFICIAL FORECAST IS
ADJUSTED UPWARD FROM THE PREVIOUS ADVISORY...AND CALLS FOR BONNIE
TO REACH HURRICANE STRENGTH WITHIN 48 HOURS. HOWEVER...IT IS STILL
BELOW THE SHIPS GUIDANCE...AND IS CONSIDERABLY BELOW THE GFDL
GUIDANCE.   
 
THE CURRENT MOTION ESTIMATE IS 295/7...SOMEWHAT TO THE LEFT OF THE
PREVIOUS TRACK.  MOST OF THE 3-DIMENSIONAL DYNAMICAL GUIDANCE TURNS
BONNIE SHARPLY NORTHWARD AND THEN NORTHEASTWARD AHEAD OF A
MID-LEVEL TROUGH ABOUT TO ENTER THE WESTERN GULF.  THE OFFICIAL
FORECAST IS ADJUSTED A LITTLE TO THE LEFT OF THE PREVIOUS TRACK FOR
THE FIRST 24 HOURS...IS FAIRLY SIMILAR THEREAFTER...AND IS IN BEST
AGREEMENT WITH THE GFDL GUIDANCE.  

THE NOAA G-IV JET WILL CONDUCT A MISSION IN THE ENVIRONMENT OF
BONNIE THIS EVENING TO IMPROVE THE INITIAL CONDITION FOR THE
NUMERICAL TRACK GUIDANCE MODELS. 
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 23.6N  90.1W    45 KT
 12HR VT     10/1800Z 24.2N  90.7W    50 KT
 24HR VT     11/0600Z 25.5N  90.7W    55 KT
 36HR VT     11/1800Z 26.6N  89.8W    60 KT
 48HR VT     12/0600Z 28.0N  88.0W    65 KT
 72HR VT     13/0600Z 33.5N  81.0W    25 KT...INLAND
 96HR VT     14/0600Z...ABSORBED INTO FRONTAL ZONE
 
 
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