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Hurricane BILL


ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
HURRICANE BILL DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032009
1100 PM AST FRI AUG 21 2009
 
THE STRUCTURE OF BILL HAS CONTINUED TO EVOLVE THIS EVENING...WITH
MICROWAVE IMAGERY SHOWING THE REMNANT OF AN INNER EYEWALL AND THE
FORMATION OF AN OUTER EYEWALL. ALSO...THERE HAVE ALSO BEEN SIGNS OF
A LARGER EYE TRYING TO FORM IN GEOSTATIONARY INFRARED IMAGERY IN
THE PAST COUPLE OF HOURS. OVERALL...THE CLOUD PATTERN LOOKS LESS
IMPRESSIVE...AS COLD CLOUD TOPS HAVE DIMINISHED OVER THE WESTERN
SEMICIRCLE. ALL THAT BEING SAID...THE INITIAL INTENSITY IS HELD AT
90 KT BASED ON 0000 UTC DVORAK T-NUMBERS OF 5.0 FROM TAFB AND
SAB...BUT THIS COULD BE GENEROUS. AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT IS CURRENTLY IN ROUTE TO INVESTIGATE BILL AND WILL
PROVIDE MORE INFORMATION ON THE INTENSITY AND STRUCTURE OF THE
CYCLONE IN THE NEXT FEW HOURS.

IF BILL IS ABLE TO COMPLETE THE EYEWALL REPLACEMENT CYCLE...THERE IS
SOME OPPORTUNITY FOR RESTRENGTHENING IN THE NEXT 24 HOURS BEFORE
THE HURRICANE CROSSES THE NORTHERN WALL OF THE GULF STREAM...AND
SOME STRENGTHENING IS SHOWN IN THE OFFICIAL FORECAST. THERE
IS THE POSSIBILITY THAT BILL COULD INTENSIFY A LITTLE MORE THAN
SHOWN HERE...AS THE INTENSITY PROBABILITY TABLE SHOWS ABOUT A 30 TO
35 PERCENT CHANCE THAT BILL WILL BE A CATEGORY 3 HURRICANE IN 12 TO
24 HOURS. BEYOND 24 HOURS...STEADY WEAKENING IS FORECAST AS THE
CYCLONE ENCOUNTERS MUCH LOWER SEA SURFACE TEMPERATURES AND
INCREASING WIND SHEAR. EXTRATROPICAL TRANSITION IS EXPECTED TO
OCCUR IN TWO OR THREE DAYS...AND THE WIND RADII AND INTENSITY
FORECASTS ATTEMPT TO ACCOUNT FOR THESE STRUCTURAL CHANGES. 

THE INITIAL MOTION ESTIMATE IS 345/17. THE TRACK GUIDANCE REMAINS IN
VERY GOOD AGREEMENT...ACCELERATING BILL TOWARD THE NORTH AND
NORTHEAST AHEAD OF A LARGE MID-LATITUDE TROUGH MOVING INTO THE
NORTHEASTERN UNITED STATES. AS A RESULT...ONLY MINOR CHANGES HAVE
BEEN MADE TO THE PREVIOUS PACKAGE. 
 
LARGE SWELLS GENERATED BY BILL ARE BEGINNING TO ARRIVE ALONG THE
EAST COAST OF THE UNITED STATES. THESE SWELLS WILL SPREAD NORTHWARD
OVER THE WEEKEND...CAUSING EXTREMELY DANGEROUS SURF AND
LIFE-THREATENING RIP CURRENTS. PLEASE CONSULT STATEMENTS ISSUED BY
YOUR LOCAL WEATHER OFFICE AND METEOROLOGICAL SERVICES FOR MORE
DETAILS.
 
WHILE TROPICAL-STORM-FORCE WINDS ARE NOT CURRENTLY FORECAST TO REACH
NEW ENGLAND...A SHIFT IN THE FORECAST TRACK TO THE LEFT COULD
REQUIRE THE ISSUANCE OF A TROPICAL STORM WATCH OR WARNING ON
SATURDAY. THE WIND SPEED PROBABILITY PRODUCT INDICATES A 15 TO 20
PERCENT CHANCE OF TROPICAL-STORM-FORCE WINDS REACHING EXTREME
SOUTHEASTERN NEW ENGLAND. 

THE INITIAL WIND RADII WERE ADJUSTED BASED ON DATA FROM A 2322 UTC
QUIKSCAT PASS...DATA FROM NOAA BUOY 41048 AND OBSERVATIONS FROM
BERMUDA. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0300Z 31.0N  67.5W    90 KT
 12HR VT     22/1200Z 33.5N  68.1W    95 KT
 24HR VT     23/0000Z 37.3N  67.8W    95 KT
 36HR VT     23/1200Z 41.3N  65.4W    80 KT
 48HR VT     24/0000Z 45.1N  59.9W    70 KT
 72HR VT     25/0000Z 50.5N  40.0W    45 KT...EXTRATROPICAL
 96HR VT     26/0000Z 55.0N  19.0W    40 KT...EXTRATROPICAL
120HR VT     27/0000Z 60.5N   6.0W    35 KT...EXTRATROPICAL
 
$$
FORECASTER BRENNAN
 
NNNN


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Page last modified: Thursday, 31-Dec-2009 12:09:05 UTC