Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  48
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT MON JUL 14 2008
 
THE CENTER OF BERTHA IS STEADILY MOVING AWAY FROM BERMUDA.  THE
CYCLONE IS IN THE PROCESS OF MAKING A GRADUAL RIGHT TURN...SO THE
DIRECTION OF MOTION HAS BEEN FREQUENTLY CHANGING...BUT THE ESTIMATE
VALID AT ADVISORY TIME IS 015/8.  WATER VAPOR IMAGERY SHOWS THAT
THE CUTOFF LOW CURRENTLY ABOUT 1000 N MI EAST-NORTHEAST OF BERTHA
IS SLIDING SOUTHWESTWARD AND PUTTING THE SQUEEZE ON WHAT IS LEFT OF
THE NARROW MID-LEVEL RIDGE IN BETWEEN.  THAT RIDGE HAS BEEN
STEERING BERTHA NORTHWARD TODAY...SO AS IT ERODES...BERTHA IS
FORECAST BY ALL OF THE DYNAMICAL MODELS TO MAKE A SHARPER RIGHT
TURN IN ABOUT 24 HOURS...AND THEN HEAD SOUTHEASTWARD AS IT MORE
DIRECTLY INTERACTS WITH THE CUTOFF LOW.  ALL OF THE MODELS AGREE
THAT THE CUTOFF LOW WILL LIFT OUT IN ABOUT 72 HOURS...LEAVING
BERTHA TO BE STEERED GENERALLY NORTHEASTWARD BY THE MID-LATITUDE
WESTERLIES LATE IN THE FORECAST PERIOD.  THE NEW OFFICIAL FORECAST
TRACK CONTINUES TO DEPICT WHAT LOOKS LIKE A SINE WAVE...THIS TIME
WITH SLIGHTLY MORE AMPLITUDE...BUT WITH THE NET MOTION OVER FIVE
DAYS BEING EAST-NORTHEASTWARD.  THE FORWARD SPEED OF BERTHA BEYOND
72 HOURS IS RATHER UNCERTAIN...AS THE VARIOUS MODELS AGREE ON THE
PATH BUT NOT ON HOW FAST THE CYCLONE WILL GO.

THE DEEPEST CONVECTION HAS ROTATED AROUND THE CENTER FROM THE
SOUTHWESTERN QUADRANT...WHICH DIRECTLY AFFECTED BERMUDA EARLIER
TODAY...AND NOW IS FOCUSED SOUTHEAST AND EAST OF THE CENTER. 
OTHERWISE...THE OVERALL STRUCTURE OF THE CYCLONE IS ESSENTIALLY
UNCHANGED...AS ARE THE DVORAK ESTIMATES AT 55 KT.  USING CONTINUITY
FROM EARLIER AIRCRAFT OBSERVATIONS...THE ADVISORY INTENSITY REMAINS
60 KT.  THE INTENSITY FORECAST IS MOSTLY UNCHANGED...CALLING FOR
BERTHA TO BE AT HURRICANE STATUS DURING THE NEXT COUPLE OF DAYS. 
THIS FORECAST MIGHT NOT BE EXACTLY RIGHT...BUT THE INTENSITY
CONSENSUS SUGGESTS BERTHA WILL BE NEAR THE THRESHOLD BETWEEN
TROPICAL STORM AND HURRICANE INTENSITY FOR A FEW DAYS.  A WEAKENING
TREND IS INDICATED IN THE OFFICIAL FORECAST AT DAYS 4 AND 5 AS
BERTHA HEADS NORTHEASTWARD TOWARD NOTICEABLY COOLER WATERS...IN
BEST AGREEMENT WITH THE SHIPS AND LGEM STATISTICAL-DYNAMICAL
MODELS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0300Z 33.8N  63.7W    60 KT
 12HR VT     15/1200Z 34.9N  63.0W    65 KT
 24HR VT     16/0000Z 35.7N  61.9W    65 KT
 36HR VT     16/1200Z 35.4N  60.6W    65 KT
 48HR VT     17/0000Z 34.4N  59.2W    65 KT
 72HR VT     18/0000Z 33.5N  55.5W    60 KT
 96HR VT     19/0000Z 36.0N  52.0W    55 KT
120HR VT     20/0000Z 39.5N  49.0W    50 KT
 
$$
FORECASTER KNABB
 
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