000
WTNT43 KNHC 210248
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST THU AUG 20 2009
 
THE SATELLITE PRESENTATION OF BILL HAS CHANGED LITTLE THIS EVENING.
THE LARGE EYE REMAINS VERY WELL-DEFINED...HOWEVER THE CLOUD TOPS
SURROUNDING THE EYE HAVE WARMED SLIGHTLY DURING THE PAST COUPLE OF
HOURS. THE NOAA RECONNAISSANCE AIRCRAFT THAT HAS BEEN SAMPLING THE
CORE OF THE HURRICANE THIS EVENING REPORTED A PEAK BELIEVABLE
FLIGHT-LEVEL WIND OF 127 KT.  ALTHOUGH HIGHER WIND SPEEDS WERE
REPORTED...THE METEOROLOGISTS ON THE AIRCRAFT DID NOT CONSIDER
THOSE HIGHER WINDS TO BE VALID.  DVORAK DATA T-NUMBERS HAVE
DECREASED SLIGHTLY.  BASED ON ALL OF THE DATA...THE INITIAL
INTENSITY IS HELD AT 110 KT.  ENVIRONMENTAL FACTORS ARE EXPECTED TO
REMAIN CONDUCIVE FOR SOME RESTRENGTHENING DURING THE NEXT 24 HOURS
OR SO.  AFTERWARDS...SOME COOLING OF THE SSTS WILL LIKELY INDUCE A
SLOW WEAKENING TREND.  VERTICAL WIND SHEAR IS PREDICTED BY THE
SHIPS MODEL TO REMAIN LIGHT UNTIL THE HURRICANE NEARS THE CANADIAN
MARITIMES IN ABOUT 72 HOURS.  HOWEVER...SSTS ALONG THE FORECAST
TRACK WILL BEGIN TO COOL MORE RAPIDLY AROUND THAT TIME...AND SHEAR
IS FORECAST TO INCREASE SIGNIFICANTLY VERY SOON THEREAFTER.  THE
OFFICIAL WIND SPEED FORECAST IS GENERALLY BETWEEN THE SHIPS AND
LGEM GUIDANCE  
 
BILL CONTINUES TO MOVE NORTHWESTWARD OR 310/16 KT. THERE IS NOT MUCH
NEW TO SAY ABOUT THE TRACK FORECAST.  BILL IS EXPECTED TO TURN
NORTHWARD AHEAD OF A STRONG MID-LATITUDE TROUGH THAT WILL MOVE INTO
THE EASTERN U.S. DURING THE NEXT COUPLE OF DAYS...AND RECURVE AHEAD
OF THAT TROUGH THEREAFTER.  THE NEW TRACK FORECAST IS VIRTUALLY
UNCHANGED FROM THE PREVIOUS ADVISORY AND IS ONCE AGAIN IN EXCELLENT
AGREEMENT WITH THE TIGHTLY CLUSTERED MODEL GUIDANCE.
 
LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING...OR WILL
AFFECT...A LARGE PORTION OF THE WESTERN NORTH ATLANTIC COASTAL AREA
DURING THE NEXT FEW DAYS.  THESE SWELLS WILL LIKELY CAUSE EXTREMELY
DANGEROUS SURF AND LIFE-THREATENING RIP CURRENTS.  PLEASE CONSULT
STATEMENTS ISSUED BY YOUR LOCAL WEATHER OFFICE FOR MORE DETAILS.
 
DATA FROM A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION CONDUCTED BY
NOAA AND U.S. AIR FORCE RESERVE AIRCRAFT THIS EVENING SHOULD BE
ASSIMILATED INTO THE INITIALIZATION OF THE 0000 UTC MODEL RUNS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/0300Z 24.9N  64.3W   110 KT
 12HR VT     21/1200Z 26.9N  66.1W   115 KT
 24HR VT     22/0000Z 29.6N  67.9W   115 KT
 36HR VT     22/1200Z 32.7N  68.9W   110 KT
 48HR VT     23/0000Z 36.4N  68.6W   100 KT
 72HR VT     24/0000Z 44.3N  62.0W    80 KT
 96HR VT     25/0000Z 50.5N  43.0W    55 KT...EXTRATROPICAL
120HR VT     26/0000Z 55.0N  20.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER BROWN/PASCH