Hurricane BILL

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HURRICANE BILL DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
500 PM AST SUN AUG 23 2009
 
BILL IS GRADUALLY WEAKENING WHILE LOSING SOME OF ITS TROPICAL
APPEARANCE. THE SATELLITE PRESENTATION HAS BEEN GRADUALLY
DETERIORATING...WITH THE CLOUD PATTERN BECOMING MORE ASYMMETRIC AND
THE DEEPEST CONVECTION CONFINED TO THE NORTHEAST SEMICIRCLE.
DVORAK T-NUMBERS OF 3.5 AND 4.0 FROM TAFB AND SAB...RESPECTIVELY
...AND THE ASSUMPTION OF A CONTINUED SLOW WEAKENING AS BILL
TRAVERSES COOLER WATERS...YIELD AN INITIAL INTENSITY ESTIMATE OF 65
KT FOR THIS ADVISORY. THE FORECAST CALLS FOR STEADY WEAKENING...
AND EXTRATROPICAL TRANSITION IS EXPECTED TO BE COMPLETE WITHIN 24
HOURS...IN AGREEMENT WITH THE GLOBAL MODEL GUIDANCE. BY 96 HOURS
BILL IS PREDICTED TO HAVE MERGED WITH A LARGER CYCLONIC CIRCULATION
NEAR THE BRITISH ISLES.
 
BILL HAS CONTINUED TO ACCELERATE...AND THE INITIAL MOTION ESTIMATE
IS NOW 050/030. SOME FURTHER ACCELERATION IS LIKELY DURING THE NEXT
24-36 HOURS AS THE CYCLONE BECOMES FULLY EMBEDDED WITHIN STRONG
WEST-SOUTHWESTERLY FLOW AHEAD OF A SHORTWAVE TROUGH LIFTING OUT OF
THE EASTERN UNITED STATES. BEYOND 36 HOURS...SOME SLOWING OF THE
FORWARD SPEED IS EXPECTED AS THE EXTRATROPICAL REMNANT OF BILL
INTERACTS WITH THE LARGE CYCLONIC CIRCULATION OVER THE NORTHEAST
ATLANTIC. THE OFFICIAL FORECAST REPRESENTS AN UPDATE OF THE
PREVIOUS ADVISORY...WITH NO SIGNIFICANT CHANGES.
 
LARGE AND DANGEROUS SWELLS ASSOCIATED WITH BILL WILL CONTINUE
IMPACTING THE CANADIAN MARITIMES DURING THE NEXT 12 TO 24 HOURS...
WHILE SWELLS ALONG THE EAST COAST OF THE UNITED STATES WILL CONTINUE
TO SUBSIDE TONIGHT.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/2100Z 45.1N  60.8W    65 KT
 12HR VT     24/0600Z 47.7N  54.5W    60 KT
 24HR VT     24/1800Z 50.0N  43.8W    50 KT...EXTRATROPICAL
 36HR VT     25/0600Z 51.5N  32.0W    40 KT...EXTRATROPICAL
 48HR VT     25/1800Z 52.5N  21.0W    35 KT...EXTRATROPICAL
 72HR VT     26/1800Z 57.0N   5.0W    30 KT...EXTRATROPICAL
 96HR VT     27/1800Z...DISSIPATED
 
$$
FORECASTER KIMBERLAIN/PASCH
 
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