Blogging About Hurricane Bill #3

000
WTNT33 KNHC 192030
TCPAT3
BULLETIN
HURRICANE BILL ADVISORY NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
500 PM AST WED AUG 19 2009

...BILL REMAINS AN EXTREMELY DANGEROUS CATEGORY 4 HURRICANE...NOW
MOVING NORTHWESTWARD...

INTERESTS IN THE NORTHERN LEEWARD ISLANDS AND BERMUDA SHOULD MONITOR
THE PROGRESS OF BILL.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 500 PM AST...2100 UTC...THE CENTER OF HURRICANE BILL WAS LOCATED
NEAR LATITUDE 19.8 NORTH...LONGITUDE 57.6 WEST OR ABOUT 335 MILES...
535 KM...NORTHEAST OF THE LEEWARD ISLANDS AND ABOUT 970 MILES...1565
KM...SOUTH-SOUTHEAST OF BERMUDA.

BILL IS MOVING TOWARD THE NORTHWEST NEAR 20 MPH...32 KM/HR...AND
THIS GENERAL MOTION IS EXPECTED FOR THE NEXT DAY OR SO WITH A TURN
TOWARD THE NORTH-NORTHWEST FORECAST BY LATE FRIDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 135 MPH...215 KM/HR...WITH HIGHER
GUSTS. BILL IS A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON
SCALE. SOME ADDITIONAL STRENGTHENING IS POSSIBLE DURING THE NEXT
COUPLE OF DAYS.

BILL IS A LARGE TROPICAL CYCLONE. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 85 MILES...140 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 230 MILES...370 KM.

THE LATEST MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT WAS 947 MB...27.96 INCHES.

LARGE SWELLS ASSOCIATED WITH BILL WILL BE IMPACTING THE ISLANDS OF
THE NORTHEAST CARIBBEAN SEA DURING THE NEXT DAY OR TWO. LARGE
SWELLS ASSOCIATED WITH BILL SHOULD ALSO BEGIN TO AFFECT BERMUDA AND
PORTIONS OF THE EASTERN COAST OF THE UNITED STATES FRIDAY AND
SATURDAY.

...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...19.8N 57.6W
MAXIMUM SUSTAINED WINDS...135 MPH
PRESENT MOVEMENT...NORTHWEST OR 305 DEGREES AT 20 MPH
MINIMUM CENTRAL PRESSURE...947 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.

$$
FORECASTER BLAKE

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000
WTNT43 KNHC 192031
TCDAT3
HURRICANE BILL DISCUSSION NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
500 PM AST WED AUG 19 2009

VISIBLE SATELLITE IMAGES SHOW THAT BILL IS AN IMPRESSIVE HURRICANE
WITH MESOCYCLONES NOTED IN THE EYE...CURVED BANDING FEATURES IN ALL
QUADRANTS AND A WELL-ESTABLISHED OUTFLOW PATTERN. AN FORCE RESERVE
HURRICANE HUNTER RECENTLY MEASURED 135 KT AT 700 MB...ALONG WITH
SFMR WINDS OF 103 KT AND A MINIMUM PRESSURE OF 947 MB. IN
ADDITION...THERE WAS AN SFMR MEASUREMENT OF 106 KT FROM THE NOAA
MISSION THIS MORNING. SATELLITE CLASSIFICATION ARE 127 KT FROM
TAFB/SAB AND THE INITIAL INTENSITY IS KEPT AT 115 KT AS A
COMPROMISE OF ALL THESE DATA.

VERY WARM WATERS ARE ALONG THE PATH OF THE HURRICANE FOR THE NEXT
FEW DAYS. THE BIGGEST QUESTION IS WHETHER THE UPPER ENVIRONMENT
WILL REMAIN FAVORABLE FOR STRENGTHENING. A PAIR OF UPPER-LEVEL
TROUGHS HAVE THE POTENTIAL TO INDUCE SOME SHEAR ON BILL...ONE ALONG
60W AND OTHER AT ABOUT 70W. WHILE THE MODELS DISAGREE ON WHETHER
THE FIRST TROUGH WILL AFFECT THE HURRICANE MUCH...MOST MODELS SHOW
SOUTHWESTERLY SHEAR INCREASING IN A COUPLE DAYS AS A RESULT OF THE
SECOND FEATURE. IN ADDITION...AN EYEWALL REPLACEMENT CYCLE COULD
OCCUR AT ANY TIME WITH A SECONDARY WIND MAXIMUM NOTED AT ABOUT 75 N
MI FROM THE CENTER IN AIRCRAFT DATA. REGARDLESS...ALL OF THE
RELIABLE MODELS KEEP THE HURRICANE QUITE STRONG FOR THE NEXT
SEVERAL DAYS...AND THE OFFICIAL INTENSITY FORECAST REFLECTS THAT
LIKELIHOOD.

THE ESTIMATED MOTION IS A LITTLE MORE TO THE RIGHT AND FASTER...NOW
305/17. STRONG SUBTROPICAL RIDGING SHOULD KEEP BILL ON THIS
GENERAL TRACK FOR THE NEXT COUPLE OF DAYS WITH A GRADUAL BEND TOWARD
THE NORTH-NORTHWEST BY THE WEEKEND AS THE HURRICANE MOVES INTO A
BREAK IN THE RIDGE. SOME OF THE MODELS...SUCH AS THE GFS...NOW
SHOW A SLIGHTLY STRONGER RIDGE OVER THE WESTERN ATLANTIC AND A
SLOWER MID-LATITUDE TROUGH MOVING ACROSS THE EASTERN UNITED STATES.
IF THIS SOLUTION IS CORRECT...BILL WOULD BE ABLE TO MOVE A LITTLE
FARTHER TO THE WEST BEFORE TURNING TO THE NORTH AND NORTHEAST.
THERE HAS BEEN A SMALL WESTWARD SHIFT IN MOST OF THE AFTERNOON
MODEL GUIDANCE...AND THE OFFICIAL FORECAST IS SHIFTED IN THAT
DIRECTION. THIS IS A GOOD TIME TO POINT OUT THAT THERE IS A LOT OF
UNCERTAINTY IN THE LONG-RANGE TROPICAL CYCLONE FORECAST AND ONE
SHOULD NOT FOCUS ON THE EXACT TRACK AT THOSE TIME PERIODS.

BECAUSE BILL IS A LARGE AND STRONG HURRICANE...SWELLS TRIGGERED BY
THE HURRICANE SHOULD AFFECT THE NORTHERN LEEWARD ISLANDS...THE
BAHAMAS...BERMUDA AND MOST OF THE EASTERN UNITED STATES 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.

FORECAST POSITIONS AND MAX WINDS

INITIAL 19/2100Z 19.8N 57.6W 115 KT
12HR VT 20/0600Z 21.1N 59.7W 120 KT
24HR VT 20/1800Z 23.0N 62.4W 125 KT
36HR VT 21/0600Z 25.2N 64.6W 120 KT
48HR VT 21/1800Z 27.9N 66.6W 120 KT
72HR VT 22/1800Z 34.0N 69.0W 110 KT
96HR VT 23/1800Z 42.0N 65.5W 95 KT
120HR VT 24/1800Z 51.5N 50.5W 55 KT...EXTRATROPICAL

$$
FORECASTER BLAKE