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Hurricane DEAN


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HURRICANE DEAN DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042007
500 AM EDT SUN AUG 19 2007

THE LAST PENETRATION OF THE EYE OF THE HURRICANE BY THE AIR FORCE
HURRICANE HUNTERS WAS AT 0511 UTC.  THE AIRCRAFT REPORTED A MINIMUM
PRESSURE OF 921 MB BY DROPSONDE AND PEAK FLIGHT-LEVEL WINDS OF 130
KT OUTBOUND IN THE NORTHEAST QUADRANT.  SATELLITE IMAGERY SHOWS A
LESS DISTINCT EYE WITH SOME WARMING OF THE SURROUNDING CLOUD
TOPS...ALTHOUGH THE CLOUD PATTERN REMAINS VERY IMPRESSIVE WITH GOOD
SYMMETRY AND STRONG OUTFLOW OVER ALL QUADRANTS.  THE INITIAL
INTENSITY ESTIMATE IS KEPT AT 125 KT FOR THIS ADVISORY...WHICH MAY
BE A LITTLE ON THE HIGH SIDE.  IF INDEED DEAN HAS WEAKENED...THIS 
IS LIKELY THE RESULT OF INNER CORE PROCESSES...AND IS PROBABLY ONLY
A SHORT-TERM CHANGE.  THE LARGE-SCALE ATMOSPHERIC AND OCEANIC
ENVIRONMENT STILL APPEAR TO BE VERY FAVORABLE FOR STRENGTHENING...
SO....ASIDE FROM INNER-CORE-RELATED FLUCTUATIONS...DEAN HAS THE
POTENTIAL TO ATTAIN CATEGORY FIVE HURRICANE STATUS OVER THE
NORTHWESTERN CARIBBEAN SEA.  THIS IS SUPPORTED BY THE GFDL...
SHIPS...LGEM...AND FSSE GUIDANCE.  INTERACTION WITH THE YUCATAN
PENINSULA WILL CAUSE WEAKENING...AND THE AMOUNT OF RE-STRENGTHENING
OF DEAN OVER THE SOUTHWESTERN GULF OF MEXICO DEPENDS MAINLY ON HOW
LONG THE SYSTEM STAYS OVER WATER BEFORE MAKING ITS FINAL LANDFALL.

ASIDE FROM THE TROCHOIDAL WOBBLES THAT ARE COMMON WITH SUCH INTENSE
HURRICANES...THE MOTION HAS BEEN BETWEEN WEST AND WEST-NORTHWEST
OVER THE PAST 12-24 HOURS.  INITIAL MOTION ESTIMATE IS 285/16.  AS
THE MID- TO UPPER-LEVEL CYCLONE OVER THE EASTERN GULF OF MEXICO
CONTINUES TO SHIFT WESTWARD AHEAD OF DEAN...THE FUTURE TRACK OF THE
HURRICANE WILL BE CONTROLLED LARGELY BY A DEEP-LAYER HIGH PRESSURE
SYSTEM THAT IS FORECAST TO BUILD OVER THE SOUTHEASTERN UNITED
STATES.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON A CONTINUED
WEST-NORTHWESTWARD MOTION THROUGHOUT THE FORECAST PERIOD.  ANY
CHANGES FROM THE PREVIOUS OFFICIAL TRACK FORECAST DURING THE FIRST
48 HOURS OR SO SHOULD BE CONSIDERED COSMETIC.  WE HAVE SHIFTED THE
OFFICIAL FORECAST TRACK SLIGHTLY SOUTHWARD IN THE LATTER PART OF
THE PERIOD...BUT NOT AS FAR SOUTH AS SHOWN BY THE GFS...U.K. MET.
AND ECMWF MODELS.  

IT IS IMPERATIVE NOT TO FOCUS ON THE EXACT FORECAST TRACK. 
CONSIDERING THE MARGIN OF ERROR OF NHC PREDICTIONS...THE CORE OF
THIS LARGE HURRICANE COULD EASILY BE 30-50 N MI ON EITHER SIDE OF
THE FORECAST TRACK DURING THE NEXT 12 HOURS OR SO.

ANOTHER AIR FORCE RECONNAISSANCE PLANE IS SCHEDULED TO MAKE A
POSITION AND INTENSITY FIX ON DEAN AROUND 1200 UTC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0900Z 16.6N  73.4W   125 KT
 12HR VT     19/1800Z 17.1N  76.0W   130 KT
 24HR VT     20/0600Z 17.9N  79.5W   130 KT
 36HR VT     20/1800Z 18.7N  83.0W   135 KT
 48HR VT     21/0600Z 19.5N  86.6W   140 KT
 72HR VT     22/0600Z 21.0N  93.5W    85 KT
 96HR VT     23/0600Z 22.5N  99.0W    50 KT...INLAND
120HR VT     24/0600Z 23.5N 103.0W    25 KT...INLAND
 
$$
FORECASTER PASCH/BROWN
 
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