000 WTNT43 KNHC 232036 TCDAT3 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