000
WTNT43 KNHC 230851
TCDAT3
HURRICANE BILL DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 AM AST SUN AUG 23 2009
 
INFRARED SATELLITE IMAGERY SHOWS COLD CONVECTIVE CLOUD TOPS CONTINUE
TO SURROUND THE CLOUD-FILLED EYE OF BILL.  RECENT AIRCRAFT FIXES
HAVE BEEN TO THE WEST AND SOUTHWEST OF THE EYE-FEATURE SEEN IN
SATELLITE IMAGERY...SUGGESTING SOME VERTICAL TILT TO THE HURRICANE. 
THE AIRCRAFT RECENTLY REPORTED A PEAK 700 MB FLIGHT-LEVEL WIND OF
93 KT AND A SFMR SURFACE WIND OF 67 KT TO THE SOUTHEAST OF THE
CENTER.  A DROPSONDE MEASURED A MEAN WIND OF 98 KT IN THE LOWEST
150 METERS OF THE SOUNDING.  THESE DATA SUPPORT MAINTAINING THE 
INITIAL INTENSITY AT 75 KT.
 
THE HURRICANE IS MOVING NORTH-NORTHEAST OR 025/23.  BILL IS
FORECAST TO TURN NORTHEASTWARD AND RECURVE AHEAD OF A STRONG
MID-LATITUDE TROUGH THAT IS MOVING ACROSS THE EASTERN UNITED
STATES.  THE NEW FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS
ADVISORY AND REMAINS NEAR THE MIDDLE OF THE TIGHTLY CLUSTERED
GUIDANCE THROUGH 36 HOURS.  THEREAFTER...THE TRACK HAS BEEN
ADJUSTED A LITTLE SOUTHWARD IN LINE WITH THE GFS AND UKMET
SOLUTIONS.
 
BILL WILL BE MOVING ACROSS THE NORTH WALL OF THE GULF STREAM AND
OVER MUCH COOLER WATERS VERY SOON.  THE INTENSITY FORECAST CALLS
FOR STEADY WEAKENING DURING THE NEXT 24 TO 36 HOURS.  BILL
SHOULD BEGIN ITS EXTRATROPICAL TRANSITION LATER TODAY AND BECOME
FULLY EXTRATROPICAL IN ABOUT 36 HOURS.  AFTER TRANSITION IS
COMPLETE...THE GLOBAL MODELS CONTINUE TO SHOW GRADUAL WEAKENING OF
THE CYCLONE...AS DOES THE OFFICIAL FORECAST.

THE 34-KT WIND RADII HAS BEEN EXPANDED OVER THE EASTERN SEMICIRCLE
BASED ON DATA FROM THE AIRCRAFT AND AN EARLIER QUIKSCAT PASS.
 
LARGE SWELLS GENERATED BY BILL ARE STILL AFFECTING THE EAST COAST OF
THE UNITED STATES. THESE SWELLS WILL CONTINUE TO SPREAD NORTHWARD
INTO THE CANADIAN MARITIMES TODAY...CAUSING EXTREMELY DANGEROUS
SURF AND LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS
ISSUED BY YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR
MORE DETAILS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 41.2N  66.5W    75 KT
 12HR VT     23/1800Z 44.1N  63.0W    65 KT
 24HR VT     24/0600Z 47.5N  55.1W    55 KT
 36HR VT     24/1800Z 49.8N  43.8W    45 KT...EXTRATROPICAL
 48HR VT     25/0600Z 50.5N  31.0W    40 KT...EXTRATROPICAL
 72HR VT     26/0600Z 54.0N  10.0W    30 KT...EXTRATROPICAL
 96HR VT     27/0600Z 61.0N   2.0W    25 KT...EXTRATROPICAL
120HR VT     28/0600Z...ABSORBED
 
$$
FORECASTER BROWN