Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  46
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT MON JUL 14 2008
 
THE INITIAL MOTION IS 350/6.  BERTHA IS EXPECTED TO CONTINUE ON A
NORTHWARD TRACK FOR THE NEXT DAY OR SO AS MID-LEVEL HIGH PRESSURE
TO THE NORTHEAST OF THE CYCLONE WEAKENS AND SLIDES EASTWARD.  WITH
THE STRONGEST WINDS LOCATED 50-60 NMI FROM THE CENTER...
HOWEVER...THE PRECISE TRACK OF THE CENTER IS RELATIVELY UNIMPORTANT
FOR CONDITIONS ON BERMUDA...WHERE TROPICAL STORM FORCE WINDS COULD
CONTINUE THROUGH TOMORROW MORNING. AFTER BERTHA PASSES BERMUDA...A
COMPLICATED STEERING PATTERNS AWAITS...WITH A STRONG UPPER-LEVEL
LOW CURRENTLY NEAR 40N/42W FORECAST TO DROP SOUTHWESTWARD.  MODEL
GUIDANCE IS NOT IN GOOD AGREEMENT ON THE INTERACTION BETWEEN BERTHA
AND THE UPPER LOW.  THE HWRF AND GFDL MAINTAIN A STRONG TROPICAL
CYCLONE AND SWING BERTHA RAPIDLY AROUND THE SOUTH SIDE OF THE UPPER
LOW...WHILE THE GFS LIFTS THE UPPER LOW NORTHEASTWARD AFTER ABOUT
72 HOURS...LEAVING BERTHA BEHIND.  AS THE UPPER-LOW AND BERTHA
APPROACH...NORTHWESTERLY WIND SHEAR SHOULD INCREASE MARKEDLY...AND
I SUSPECT THE HWRF/GFDL SOLUTIONS ARE KEEPING BERTHA TOO STRONG AND
MAY THEREFORE BE OVERDOING THE INTERACTION.  THE OFFICIAL FORECAST
IS CLOSE TO THE FSSE SUPERENSEMBLE AND THE PREVIOUS ADVISORY.

THERE IS NOT MUCH DEEP CONVECTION ASSOCIATED WITH BERTHA RIGHT
NOW...AND A QUIKSCAT PASS AT 1030Z SUGGESTS THAT THE WINDS MIGHT BE
A LITTLE BELOW THE ADVISORY INTENSITY OF 55 KT.  A RECONNAISSANCE
AIRCRAFT WILL BE IN THE CYCLONE IN ANOTHER COUPLE OF HOURS.  THE
QUIKSCAT DATA REVEALED A 50-60 NMI RMW.  GIVEN THIS STRUCTURE...NO
SIGNIFICANT CHANGES IN INTENSITY ARE EXPECTED WHILE THE STORM IS IN
THE VICINITY OF BERMUDA.  THE WILL BE SOME OPPORTUNITY FOR
STRENGTHENING OVER THE NEXT DAY OR SO BEFORE BERTHA ENCOUNTERS SOME
COOLER WATERS AND NORTHWESTERLY SHEAR.  THE OFFICIAL INTENSITY
FORECAST IS IN BEST AGREEMENT WITH THE SHIPS AND LGEM GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/1500Z 32.0N  63.8W    55 KT
 12HR VT     15/0000Z 33.2N  63.9W    55 KT
 24HR VT     15/1200Z 34.8N  63.2W    60 KT
 36HR VT     16/0000Z 35.9N  62.0W    55 KT
 48HR VT     16/1200Z 36.0N  61.0W    55 KT
 72HR VT     17/1200Z 34.5N  58.5W    50 KT
 96HR VT     18/1200Z 35.0N  55.0W    50 KT
120HR VT     19/1200Z 38.0N  51.0W    50 KT
 
$$
FORECASTER FRANKLIN
 
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