000 WTNT43 KNHC 202036 TCDAT3 HURRICANE BILL DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009 500 PM AST THU AUG 20 2009 BOTH NOAA AND AIR FORCE RECONNAISSANCE PLANES HAVE BEEN SENDING VERY VALUABLE DATA FROM HURRICANE BILL. THE LATEST MINIMUM PRESSURE WAS DOWN TO 948 MB AND THE PEAK FLIGHT-LEVEL WIND WAS 135 KNOTS. THE SFMR REPORTED EARLIER A PEAK WIND OF 101 KNOTS. SINCE THEN...THE SATELLITE PRESENTATION HAS IMPROVED AND THE EYE IS NOW BETTER DEFINED. IN FACT...GOES SATELLITE SUPER-RAPID SCAN SHOWS THE STRUCTURE OF THE EYEWALL AND SEVERAL MESOVORTICES INSIDE THE EYE...TYPICAL OF STRONG HURRICANES. BASED ON THE AIRCRAFT DATA AND THE CURRENT SATELLITE PRESENTATION...THE INITIAL INTENSITY IS ADJUSTED UPWARD TO 110 KNOTS. THE LARGE SCALE ENVIRONMENT CONTINUES TO BE CONDUCIVE FOR REINTENSIFICATION SINCE BILL IS ABOUT TO ENCOUNTER THE WARMEST WATERS ALONG ITS PATH SO FAR. FURTHERMORE...GLOBAL MODELS SHOW BILL EMBEDDED IN A WELL DEFINED 200 MB ANTICYCLONE. GIVEN THE FAVORABLE ENVIRONMENT...THE OFFICIAL FORECAST CALLS FOR RESTRENGTHENING AND BILL IS EXPECTED TO REACH CATEGORY FOUR STATUS AGAIN WITHIN THE NEXT 12 TO 36 HOURS. THEREAFTER...THE HURRICANE SHOULD GRADUALLY BEGIN TO INTERACT WITH A MID-LATITUDE TROUGH AND BY 96 HOURS IT SHOULD BE EXTRATROPICAL. THERE IS PRACTICALLY NO CHANGE IN THE FORECAST TRACK. BILL IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 16 KNOTS EMBEDDED IN VERY STRONG AND WELL DEFINED STEERING CURRENTS AROUND THE SOUTHWESTERN PORTION OF THE AZORES-BERMUDA HIGH. HOWEVER...IN A DAY OR SO A LARGE MID-LATITUDE TROUGH IS EXPECTED TO SWEEP ACROSS THE EASTERN UNITED STATES AND THE FLOW BETWEEN THE TROUGH AND THE SUBTROPICAL HIGH SHOULD FORCE THE HURRICANE TO MOVE ON A NORTHERLY AND THEN NORTHEASTERLY TRACK. THE DYNAMICAL TRACK GUIDANCE IS EXTREMELY TIGHTLY CLUSTERED DURING THE FIRST 48 HOURS...INCREASING CONSIDERABLY THE CONFIDENCE IN THE OFFICIAL TRACK FORECAST FOR THAT PERIOD. ON THIS TRACK...THE CORE OF THE HURRICANE WILL MOVE OVER THE OPEN WATERS BETWEEN BERMUDA AND THE EAST COAST OF THE UNITED STATES SATURDAY MORNING AND BY SUNDAY...THE HURRICANE WILL BE APPROACHING THE WATERS SOUTH OF NOVA SCOTIA. LARGE SWELLS GENERATED BY THIS HURRICANE ARE AFFECTING THE NORTHERN LEEWARD ISLANDS...PUERTO RICO...HISPANIOLA AND SHOULD BEGIN AFFECTING THE BAHAMAS...BERMUDA...MOST OF THE EASTERN U.S. COAST...AND THE ATLANTIC MARITIMES OF CANADA 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. THE NOAA AND THE 53RD AIR FORCE RESERVE HURRICANE HUNTERS ARE CURRENTLY CONDUCTING A TWO-AIRCRAFT SYNOPTIC SURVEILLANCE MISSION AROUND HURRICANE BILL TO IMPROVE THE INITIAL ANALYSIS FOR THE NUMERICAL MODELS. THIS INFORMATION WILL BE INCLUDED FOR THE 0000 UTC MODEL RUN. FORECAST POSITIONS AND MAX WINDS INITIAL 20/2100Z 23.8N 63.2W 110 KT 12HR VT 21/0600Z 25.6N 65.2W 115 KT 24HR VT 21/1800Z 28.3N 67.1W 115 KT 36HR VT 22/0600Z 31.0N 68.5W 115 KT 48HR VT 22/1800Z 34.5N 69.0W 105 KT 72HR VT 23/1800Z 42.5N 64.5W 85 KT 96HR VT 24/1800Z 49.0N 49.5W 60 KT...EXTRATROPICAL 120HR VT 25/1800Z 53.5N 24.0W 50 KT...EXTRATROPICAL $$ FORECASTER AVILA/BLAKE