Hurricane BERTHA

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HURRICANE BERTHA DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 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.   

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 23.1N  55.8W    70 KT
 12HR VT     09/1200Z 24.0N  57.0W    70 KT
 24HR VT     10/0000Z 25.5N  58.5W    70 KT
 36HR VT     10/1200Z 27.0N  60.0W    70 KT
 48HR VT     11/0000Z 28.0N  60.5W    70 KT
 72HR VT     12/0000Z 30.0N  61.0W    70 KT
 96HR VT     13/0000Z 31.5N  61.0W    65 KT
120HR VT     14/0000Z 33.5N  60.0W    60 KT
 
$$
FORECASTER AVILA
 
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