Hurricane Bertha Advisory 24 With Forecast Discussion

BULLETIN
HURRICANE BERTHA ADVISORY NUMBER 24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
11:00 PM ATLANTIC STANDARD TIME TUE JUL 08 2008
BERTHA CONTINUES TOWARD THE NORTHWEST OVER THE ATLANTIC...
AT 11:00 PM ATLANTIC STANDARD TIME, 3:00Z, THE CENTER OF HURRICANE BERTHA
WAS LOCATED NEAR LATITUDE 23.1 NORTH, LONGITUDE 55.8 WEST, OR ABOUT 580
MILES, 935 KM NORTHEAST OF THE NORTHERN LEEWARD ISLANDS AND ABOUT 840 MILES,
1350 KM SOUTHEAST OF BERMUDA. BERTHA IS MOVING TOWARD THE NORTHWEST NEAR 12
MPH, 19 KM HR. THIS MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 TO 36
HOURS.
MAXIMUM SUSTAINED WINDS ARE NEAR 80 MPH, 130 KM HR, WITH HIGHER GUSTS. NO
SIGNIFICANT CHANGE IN STRENGTH IS FORECAST DURING THE NEXT DAY OR TWO.
HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES, 45 KM FROM THE CENTER,
AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES, 220 KM. LARGE
SWELLS AND HIGH SURF COULD BEGIN TO AFFECT PORTIONS OF BERMUDA LATE
TOMORROW.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 985 MB, 29.09 INCHES.
REPEATING THE 11:00 PM ATLANTIC STANDARD TIME POSITION, 23.1 N, 55.8 W.
MOVEMENT TOWARD, NORTHWEST NEAR 12 MPH. MAXIMUM SUSTAINED WINDS, 80 MPH.
MINIMUM CENTRAL PRESSURE, 985 MB.
THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT 5:00 AM
ATLANTIC STANDARD TIME.
HURRICANE BERTHA DISCUSSION NUMBER 24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
11:00 PM EDT TUE JUL 08 2008
THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE CLOUD PATTERN ASSOCIATED
WITH BERTHA. THERE IS A LITTLE BIT OF SOUTHEASTERLY SHEAR AND MOST
OF THE DEEP CONVECTION IS IN A WELL-DEFINED CYCLONICALLY CURVED
CONVECTIVE BAND TO THE WEST OF THE CENTER. BASED ON DVORAK T-NUMBERS, THE
BEST ESTIMATE OF THE INTENSITY IS 70 KNOTS. I AM
NOT QUITE SURE IF BERTHA HAS GIVEN UP AND WILL CONTINUE TO WEAKEN.
THE HURRICANE IS HEADING FOR WARMER WATERS AND LOWER SHEAR SO
REINTENSIFICATION IS NOT OUT OF THE QUESTION. BECAUSE OF THE MIXED
SIGNALS AMONG GUIDANCE, WITH THE SHIPS MODEL WEAKENING THE
HURRICANE AND BOTH GFDL AND HWRF SUGGESTING SLIGHT
STRENGTHENING, THE OFFICIAL FORECAST HAS OPTED TO KEEP BERTHA AS A
70 KT HURRICANE FOR THE NEXT 3 DAYS. THEREAFTER, THE SHEAR IS
FORECAST TO INCREASE AND GRADUAL WEAKENING IS INDICATED.
BERTHA HAS CONTINUED TO MOVE TOWARD THE NORTHWEST OR 310 DEGREES AT
10 KNOTS. A GRADUAL TURN TO THE NORTH IS EXPECTED BEYOND 48 HOURS
AS THE MID-LEVEL RIDGE CURRENTLY NORTH OF THE CYCLONE WEAKENS AND A
SHORT WAVE APPROACHES THE U.S. EAST COAST FROM THE WEST. HOWEVER, THIS
GENERAL NORTHWARD MOTION BETWEEN 48 AND 120 HOURS IS
EXPECTED TO BE PAINFULLY SLOW SINCE STEERING CURRENTS ARE FORECAST
TO BE VERY WEAK. THERE WAS A SLIGHT CHANGE IN THE 00Z GUIDANCE.
UNANIMOUSLY, THEY ALL SHIFTED A DEGREE OR TWO WESTWARD, INCLUDING
THE HWRF WHICH WAS FARTHER EAST AND HAS NOW JOINED THE REST OF THE
MODEL SUITE. THE OFFICIAL TRACK FORECAST WAS SHIFTED A LITTLE BIT
TO THE WEST AND IS NOW ON THE RIGHT SIDE OF THE GUIDANCE
ENVELOPE. IN FACT, JUST EAST OF THE GFDL AND THE HWRF. I DO NOT
WANT TO CHANGE THE TRACK TOO MUCH SINCE I WOULD NOT BE SURPRISED IF
THE GUIDANCE SHIFTS BACK TO THE EAST IN THE NEXT RUN.
This information is provided as a public service from the
National Hurricane Center
http://www.nhc.noaa.gov

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