Hurricane BERTHA

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HURRICANE BERTHA DISCUSSION NUMBER  30...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 10 2008

...CORRECTED TYPO IN LAST SENTENCE...
 
SATELLITE IMAGERY INDICATES THAT THE EYE OF BERTHA HAS BECOME
SOMEWHAT RAGGED THIS MORNING...AND THE CONVECTIVE TOPS IN THE
EYEWALL HAVE WARMED.  THIS HAS RESULTED IN THE SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB DECREASING TO 77 KT.  THE INITIAL
INTENSITY IS REDUCED TO 80 KT...AND THIS COULD BE A LITTLE
GENEROUS.  ALTHOUGH BERTHA HAS WEAKENED...THE OUTER BANDING HAS
INCREASED DURING THE NIGHT AND NOW SURROUNDS THE EYE AND CENTRAL
DENSE OVERCAST.  THE CIRRUS OUTFLOW IS FAIR TO GOOD IN ALL
DIRECTIONS EXCEPT THE SOUTHEAST...WHERE IT IS POOR TO NON-EXISTENT.
 
THE INITIAL MOTION REMAINS 315/8.  BERTHA IS ON THE SOUTH SIDE OF A
MID-LEVEL ANTICYCLONE SEEN IN WATER VAPOR IMAGERY NEAR 37N59W.  THE
ANTICYCLONE WILL WEAKEN AS A MID/UPPER-LEVEL SHORTWAVE TROUGH OVER
THE NORTHEASTERN UNITED STATES MOVES INTO THE ATLANTIC DURING THE
NEXT 24-36 HOURS.  THIS PATTERN EVOLUTION SHOULD CAUSE BERTHA TO
TURN NORTHWARD.  THE SHORTWAVE TROUGH IS FORECAST TO PASS NORTH OF
BERTHA...AND FROM 36-72 HR THE LARGE-SCALE MODELS FORECAST A
MID-LEVEL RIDGE TO BUILD NORTH OF THE HURRICANE IN THE WAKE OF THE
TROUGH.  THE TRACK MODELS RESPOND TO THIS BY FORECASTING ERRATIC
MOTION AS BERTHA APPROACHES BERMUDA.  THE NEW FORECAST TRACK WILL
CALL FOR A SLOW NORTHWARD MOTION DURING THIS TIME AS A COMPROMISE
BETWEEN THE VARIOUS TWISTS AND TURNS OF THE TRACK GUIDANCE. 
HOWEVER...THERE IS A POSSIBILITY THAT BERTHA COULD JOG LEFT OF THE
FORECAST TRACK CLOSER TO BERMUDA AS SHOWN BY THE GFS...UKMET...AND
CANADIAN MODELS.  AFTER 72 HR...A SECOND MID/UPPER-LEVEL TROUGH
MOVING INTO THE WESTERN ATLANTIC SHOULD WEAKEN THE RIDGE...WHICH
SHOULD CAUSE BERTHA TO MOVE SOMEWHAT FASTER TOWARD THE NORTH.

THE INTENSITY FORECAST IS A CONUNDRUM.  THE LARGE-SCALE MODELS
FORECAST A LARGE UPPER-LEVEL ANTICYCLONE TO DEVELOP OVER BERTHA
DURING THE NEXT 24-48 HR WHILE THE SYSTEM IS STILL OVER WARM WATER.
THIS ENVIRONMENT SHOULD BE FAVORABLE FOR STRENGTHENING...YET NONE
OF THE INTENSITY FORECAST GUIDANCE CALLS FOR SIGNIFICANT
STRENGTHENING DURING THIS TIME.  GIVEN THE ENVIRONMENT...THE
INTENSITY FORECAST WILL BUCK THE MODEL GUIDANCE AND CALL FOR SLIGHT
STRENGTHENING DURING THE FIRST 24-36 HR.  THEREAFTER...THE
LARGE-SCALE MODELS SUGGEST THE POSSIBILITY OF INCREASED VERTICAL
WIND SHEAR...ALTHOUGH THEY DIFFER ON THE DETAILS.  THIS...COMBINED
WITH COOLING SEA SURFACE TEMPERATURES...ARE EXPECTED TO CAUSE BERTHA
TO SLOWLY WEAKEN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 26.5N  60.2W    80 KT
 12HR VT     11/0000Z 27.5N  61.0W    80 KT
 24HR VT     11/1200Z 28.5N  61.6W    85 KT
 36HR VT     12/0000Z 29.5N  62.0W    85 KT
 48HR VT     12/1200Z 30.1N  62.0W    80 KT
 72HR VT     13/1200Z 31.5N  62.0W    75 KT
 96HR VT     14/1200Z 33.5N  61.5W    65 KT
120HR VT     15/1200Z 37.0N  61.0W    55 KT
 
$$
FORECASTER BEVEN
 
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