Tropical Storm DEAN

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TROPICAL STORM DEAN DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042007
1100 PM EDT WED AUG 15 2007
 
DEAN HAS CONTINUED TO GRADUALLY BECOME BETTER ORGANIZED THIS
EVENING...WITH A 2311 UTC TRMM PASS SUGGESTING THAT A SMALL BANDING
EYE FEATURE MAY BE FORMING. THE 00Z DVORAK SATELLITE INTENSITY
ESTIMATES WERE 55 KT...HOWEVER...THE SATELLITE APPEARANCE HAS
IMPROVED SINCE THEN AND THE ADVISORY INTENSITY HAS BEEN INCREASED
TO 60 KT. 

THE INITIAL MOTION ESTIMATE IS 280/20. DEAN IS FORECAST TO CONTINUE
MOVING WEST TO WEST-NORTHWESTWARD SOUTH OF A DEEP-LAYER RIDGE
LOCATED OVER THE CENTRAL ATLANTIC. THE TRACK GUIDANCE IS TIGHTLY
CLUSTERED ON THIS MOTION DURING THE NEXT 72 HOURS. AT DAYS 4 AND
5...THE TRACK GUIDANCE HAS A BIT MORE SPREAD...BUT STILL IS IN GOOD
AGREEMENT ON A CONTINUED WEST-NORTHWEST MOTION INTO THE
NORTHWESTERN CARIBBEAN SEA. THE GLOBAL MODELS SHOW VERY LITTLE
INTERACTION BETWEEN DEAN AND A MIDDLE-LEVEL TROUGH CURRENTLY OVER
THE BAHAMAS...AS THEY CONTINUE TO MOVE THE TROUGH WESTWARD AHEAD OF
DEAN. THE NOGAPS IS A LITTLE SLOWER TO MOVE THE TROUGH WEST AND ITS
TRACK IS THEREFORE A LITTLE FARTHER NORTH THAN THE REST OF THE
GUIDANCE. THE NEW OFFICIAL TRACK FORECAST IS NEAR THE MIDDLE OF THE
GUIDANCE ENVELOPE AND CLOSE TO THE GUNA MODEL CONSENSUS.
 
THERE ARE SEEMINGLY FEW FACTORS THAT WOULD INHIBIT STRENGTHENING
DURING THE FORECAST PERIOD.  AS MENTIONED IN THE PREVIOUS
DISCUSSION...THE MODELS UNANIMOUSLY DEVELOP A LARGE UPPER-LEVEL
ANTICYCLONE OVER DEAN AS IT MOVES INTO THE CARIBBEAN SEA.
MYSTERIOUSLY...THE GFDL AND HWRF MODELS HAVE BACKED OFF ON THEIR
RESPECTIVE INTENSITY FORECASTS.  HOWEVER...THE SHIPS AND LGEM
MODELS CONTINUE TO INDICATE STEADY STRENGTHENING AND THE OFFICIAL
INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY.

AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL BE 
INVESTIGATING DEAN TOMORROW AFTERNOON...AND THE NOAA GULFSTREAM-IV
WILL CONDUCT A SYNOPTIC SURVEILLANCE MISSION FOR THE 17/00Z
ANALYSIS CYCLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 13.1N  50.2W    60 KT
 12HR VT     16/1200Z 13.6N  53.2W    65 KT
 24HR VT     17/0000Z 14.2N  57.2W    70 KT
 36HR VT     17/1200Z 14.8N  61.1W    75 KT
 48HR VT     18/0000Z 15.3N  64.7W    85 KT
 72HR VT     19/0000Z 16.3N  71.5W    95 KT
 96HR VT     20/0000Z 17.8N  78.5W   105 KT
120HR VT     21/0000Z 19.5N  85.5W   115 KT
 
$$
FORECASTER BROWN
 
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