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Hurricane BILL (Text)

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HURRICANE BILL DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST SAT AUG 22 2009
 
AFTER DIMINISHING FOR A TIME...INFRARED SATELLITE IMAGERY SHOWS A
RECENT INCREASE OF COLD CLOUD TOPS NEAR AND TO THE NORTH OF THE
CENTER OF BILL. WHILE THE EYE IS NOT READILY APPARENT IN
GEOSTATIONARY IMAGERY...MICROWAVE IMAGERY STILL SHOWS AT LEAST A
PARTIAL EYEWALL NORTH OF THE CENTER. THE INITIAL INTENSITY IS HELD
AT 75 KT FOR THIS ADVISORY BASED ON FINAL CI-NUMBERS OF 4.5 FROM
TAFB AND SAB AT 0000 UTC. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL BE INVESTIGATING BILL LATER TONIGHT AND SUNDAY
MORNING...AND WILL PROVIDE ADDITIONAL INFORMATION ON THE
LOCATION...STRUCTURE AND INTENSITY OF BILL.
 
OVER THE PAST FEW HOURS...BILL APPEARS TO HAVE BEEN MOVING JUST EAST
OF DUE NORTH...AND THE INITIAL MOTION ESTIMATE IS 015/22. THE TRACK
MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON THE RECURVATURE OF
BILL IN THE NEXT COUPLE OF DAYS. THE OFFICIAL TRACK FORECAST IS
BASICALLY AN UPDATE OF THE PREVIOUS PACKAGE...AND LIES NEAR THE
MIDDLE OF THE TIGHTLY CLUSTERED TRACK GUIDANCE THROUGH 48 HOURS...
SHOWING A TURN TOWARD THE NORTHEAST AND EAST-NORTHEAST WITH AN
INCREASE IN FORWARD SPEED. BEYOND THAT TIME...THE TRACK FORECAST
LIES SOUTH OF THE MODEL CONSENSUS AND IS IN BEST AGREEMENT WITH THE
GFS ENSEMBLE MEAN AS THE POST-TROPICAL BILL APPROACHES THE BRITISH
ISLES LATE IN THE FORECAST PERIOD.
 
BILL WILL SOON BE MOVING ACROSS THE NORTH WALL OF THE GULF STREAM
AND INTO A MORE BAROCLINIC ENVIRONMENT. MOST OF THE GLOBAL MODEL
GUIDANCE SHOWS THAT BILL WILL BE EXTRATROPICAL BY 48 HOURS...AND
THE CYCLONE SHOULD BE WELL INTO THE TRANSITION PROCESS BY EARLY
MONDAY AS IT MOVES AWAY FROM NEWFOUNDLAND. THE OFFICIAL INTENSITY
FORECAST SHOWS SLOW WEAKENING THROUGH 24 HOURS DUE TO COOLER SEA
SURFACE TEMPERATURES AND INCREASING VERTICAL WIND SHEAR. BEYOND
THAT TIME...A MORE SIGNIFICANT DECREASE IN INTENSITY IS FORECAST...
ALONG WITH A LARGE EXPANSION OF THE 34-KT WIND RADII...AS BILL
COMPLETES EXTRATROPICAL TRANSITION. 
 
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 ON SUNDAY...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      23/0300Z 39.1N  67.8W    75 KT
 12HR VT     23/1200Z 42.3N  65.7W    70 KT
 24HR VT     24/0000Z 46.3N  59.2W    60 KT
 36HR VT     24/1200Z 49.3N  49.0W    45 KT
 48HR VT     25/0000Z 51.0N  37.0W    40 KT...EXTRATROPICAL
 72HR VT     26/0000Z 53.0N  16.5W    30 KT...EXTRATROPICAL
 96HR VT     27/0000Z 60.0N   6.0W    30 KT...EXTRATROPICAL
120HR VT     28/0000Z 64.0N   4.0W    25 KT...EXTRATROPICAL
 
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FORECASTER BRENNAN
 
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