000
WTNT43 KNHC 182047
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST TUE AUG 18 2009
 
BILL REMAINS A VERY IMPRESSIVE AND SYMMETRIC HURRICANE IN SATELLITE
IMAGERY.  THE AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING
BILL THIS AFTERNOON REPORTED PEAK 700 MB FLIGHT-LEVEL WINDS OF 114
KT IN THE NORTHEAST QUADRANT.  THE SFMR OBSERVED MAXIMUM WINDS
AROUND 85 KT IN EACH QUADRANT OF THE HURRICANE.  USING A BLEND OF
THESE DATA...THE INITIAL INTENSITY HAS BEEN INCREASED TO 95 KT.
THIS IS ALSO SUPPORTED BY SUBJECTIVE DVORAK INTENSITY ESTIMATES OF
90 AND 102 KT FROM SAB AND TAFB RESPECTIVELY.
 
THE INITIAL MOTION IS 290/14.  THE FORECAST SCENARIO REMAINS
UNCHANGED FROM THE PREVIOUS ADVISORY.  BILL IS EXPECTED TO
GRADUALLY TURN TO THE NORTHWEST DURING THE NEXT DAY OR TWO AS A
WEAKNESS DEVELOPS IN THE SUBTROPICAL RIDGE OVER THE WESTERN
ATLANTIC.  THEREAFTER...THE HURRICANE IS FORECAST TO TURN NORTHWARD
AHEAD OF A STRONG TROUGH MOVING INTO THE EASTERN UNITED STATES.
THE TRACK GUIDANCE ENVELOPE CHANGED VERY LITTLE THROUGH 48
HOURS...BUT HAS GENERALLY SHIFTED WESTWARD DURING THE REMAINDER OF
THE FORECAST PERIOD.  AS BEFORE THE ECMWF AND GFS ARE ON THE RIGHT
SIDE OF THE ENVELOPE WHILE THE UKMET IS ON THE LEFT.  THE OFFICIAL
FORECAST IS VIRTUALLY UNCHANGED THROUGH DAY 2...AND HAS NOT BEEN
ADJUSTED APPRECIABLY BEYOND THAT TIME AS WELL.  THE NEW FORECAST
LIES BETWEEN THE DYNAMICAL MODEL CONSENSUS AND THE USUALLY
WELL-PERFORMING ECMWF AND GFS MODELS.
 
VERTICAL WIND SHEAR IS EXPECTED TO REMAIN LOW AND SSTS GRADUALLY
INCREASE ALONG THE FORECAST TRACK DURING THE NEXT COUPLE OF DAYS.
THE INTENSITY FORECAST CALLS FOR ADDITIONAL STRENGTHENING DURING THE
NEXT COUPLE OF DAYS IN LINE WITH THE CONSENSUS OF THE INTENSITY
GUIDANCE.  BEYOND 72 HOURS...DECREASING SSTS AND INCREASING
SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF THE AFOREMENTIONED TROUGH
SHOULD INDUCE SLOW WEAKENING.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z 16.6N  52.2W    95 KT
 12HR VT     19/0600Z 17.5N  54.3W   105 KT
 24HR VT     19/1800Z 18.9N  56.9W   115 KT
 36HR VT     20/0600Z 20.7N  59.3W   115 KT
 48HR VT     20/1800Z 22.6N  61.8W   115 KT
 72HR VT     21/1800Z 27.3N  65.8W   110 KT
 96HR VT     22/1800Z 33.5N  68.0W   100 KT
120HR VT     23/1800Z 40.5N  65.5W    85 KT
 
$$
FORECASTER BROWN/CANGIALOSI