The Insiders' Guide to St. Barths: Bertha Tuesday

WTNT32 KNHC 081441
BULLETIN
HURRICANE BERTHA ADVISORY NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
1100 AM AST TUE JUL 08 2008

...BERTHA WEAKENS BUT STILL A CATEGORY TWO HURRICANE...

AT 1100 AM AST...1500Z...THE CENTER OF HURRICANE BERTHA WAS LOCATED
NEAR LATITUDE 22.1 NORTH...LONGITUDE 53.8 WEST OR ABOUT 660 MILES...
1065 KM...EAST-NORTHEAST OF THE NORTHERN LEEWARD ISLANDS AND ABOUT
975 MILES...1570 KM...SOUTHEAST OF BERMUDA.

BERTHA IS MOVING TOWARD THE NORTHWEST NEAR 10 MPH...17 KM/HR...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE WITH A REDUCTION IN
FORWARD SPEED DURING THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 105 MPH...165
KM/HR...WITH HIGHER GUSTS. ADDITIONAL WEAKENING IS FORECAST DURING
THE NEXT 24 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 115
MILES...185 KM.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 970 MB...28.64 INCHES.

REPEATING THE 1100 AM AST POSITION...22.1 N...53.8 W. MOVEMENT
TOWARD...NORTHWEST NEAR 10 MPH. MAXIMUM SUSTAINED WINDS...105 MPH.
MINIMUM CENTRAL PRESSURE...970 MB.

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

WTNT42 KNHC 081440
HURRICANE BERTHA DISCUSSION NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
1100 AM EDT TUE JUL 08 2008

CONVENTIONAL AND MICROWAVE IMAGERY SHOW A RAPID DEGRADATION OF
BERTHA'S STRUCTURE DURING THE LAST 6 HOURS. THE EYE HAS
DISAPPEARED AND CLOUD TOPS HAVE WARMED CONSIDERABLY. THERE IS ALSO
EVIDENCE IN MICROWAVE IMAGERY THAT THE WESTERN PORTION OF THE
EYEWALL HAS ERODED. A BLEND OF THE FINAL T AND CI NUMBERS FROM THE
DVORAK TECHNIQUE SUPPORTS AN INITIAL INTENSITY OF 90 KT AND LATEST
OBJECTIVE T NUMBERS SUGGEST AN EVEN LOWER INTENSITY. THE INITIAL
INTENSITY IS CONSERVATIVELY SET AT 90 KT. IT WOULD APPEAR THAT
BERTHA HAS FINALLY ENCOUNTERED THE HIGHER SHEAR ENVIRONMENT WE'VE
BEEN FORECASTING. ADDITIONALLY...THE CYCLONE IS MOVING OVER
SLIGHTLY COOLER WATERS AND THERE ARE SOME INDICATIONS IN SATELLITE
IMAGERY THAT IT COULD BE ENTRAINING DRY AIR. BOTTOM LINE...THE
ENVIRONMENT LOOKS RATHER HOSTILE AND BERTHA SHOULD CONTINUE TO
WEAKEN IN THE SHORT-TERM. TOWARDS THE END OF THE FORECAST
PERIOD...THE SHEAR COULD RELAX AND SSTS INCREASE SO THERE IS SOME
POTENTIAL FOR A LITTLE RE-INTENSIFICATION. HOWEVER...GIVEN THE
UNCERTAINTY IN INTENSITY FORECASTING...THE OFFICIAL FORECAST MERELY
SHOWS SLOW WEAKENING THROUGH THE FORECAST PERIOD AND IS IN GOOD
AGREEMENT WITH A CONSENSUS OF THE VARIOUS INTENSITY MODELS.

BERTHA HAS BEEN MOVING A LITTLE TO THE RIGHT OF THE PREVIOUS
ESTIMATE OR 315/9. BERTHA SHOULD CONTINUE TO GRADUALLY TURN
NORTHWARD OVER THE NEXT COUPLE OF DAYS AS A MID-LEVEL RIDGE OVER
THE WESTERN ATLANTIC WEAKENS AND IS REPLACED BY A WEAK TROUGH.
SINCE THE STEERING CURRENTS COULD BECOME RATHER WEAK AS A RESULT OF
THIS EVOLUTION...BERTHA COULD MOVE SLOWLY AND ERRATICALLY
TOWARDS THE END OF THE FORECAST. IT IS FOR THIS REASON THAT
INTERESTS IN BERMUDA SHOULD CONTINUE TO MONITOR THE PROGRESS OF
THIS SYSTEM. TRACK MODELS HAVE NOT CHANGED SIGNIFICANTLY SINCE THE
LAST FORECAST SO ONLY COSMETIC CHANGES TO THE OFFICIAL TRACK
FORECAST ARE NEEDED AT THIS TIME.

FORECAST POSITIONS AND MAX WINDS

INITIAL 08/1500Z 22.1N 53.8W 90 KT
12HR VT 09/0000Z 23.1N 54.9W 85 KT
24HR VT 09/1200Z 24.3N 56.4W 80 KT
36HR VT 10/0000Z 25.5N 57.8W 80 KT
48HR VT 10/1200Z 26.6N 58.7W 75 KT
72HR VT 11/1200Z 28.5N 59.5W 70 KT
96HR VT 12/1200Z 30.5N 59.5W 65 KT
120HR VT 13/1200Z 32.5N 58.5W 65

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