Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SAT JUL 05 2008
 
BERTHA HAS CHANGED LITTLE IN ORGANIZATION SINCE THIS MORNING. THE
CYCLONE CONTINUES TO MAINTAIN AN AREA OF CONVECTION NEAR AND TO THE
NORTH OF THE CENTER.  DVORAK INTENSITY ESTIMATES ARE A UNANIMOUS 45
KT...WHICH REMAINS THE INITIAL INTENSITY.  ENVIRONMENTAL CONDITIONS
ARE FORECAST TO BECOME MORE CONDUCIVE FOR STRENGTHENING ALONG THE
PROJECTED PATH.  BERTHA IS CURRENTLY OVER SSTS OF ABOUT 25 DEGREES
CELSIUS...BUT THE SSTS WILL BE INCREASING BY ABOUT ONE DEGREE PER
DAY DURING THE NEXT 3 DAYS.  SHEAR IS EXPECTED TO REMAIN LOW AT
LEAST DURING THE NEXT 72 HOURS...BUT PROJECTED TO INCREASE A LITTLE
THEREAFTER.  THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS ADVISORY WHICH SHOWED BERTHA BECOMING A HURRICANE IN ABOUT
3 DAYS...FOLLOWED BY LITTLE CHANGE IN STRENGTH AT DAYS 4 AND 5.  THE
INTENSITY FORECAST IS SIMILAR TO THE CONSENSUS OF THE HWRF...
GFDL...LGEM AND SHIPS MODELS.

BERTHA CONTINUES RACING WESTWARD WITH AN INITIAL MOTION OF 275/18. 
A GENERAL WEST TO WEST-NORTHWESTWARD MOTION SHOULD CONTINUE FOR THE
NEXT COUPLE OF DAYS.  THEREAFTER...THERE IS A VERY LARGE SPREAD IN
THE MODEL GUIDANCE.  THE MODELS WHICH MAINTAIN A DEEPER AND STRONGER
BERTHA TURN THE CYCLONE MORE NORTHWESTWARD IN RESPONSE TO A
WEAKNESS IN THE RIDGE CURRENTLY OVER THE CENTRAL ATLANTIC. 
MEANWHILE...THE MODELS THAT DEPICT A WEAKER AND SHALLOWER CYCLONE
CONTINUE TO TRACK IT WESTWARD SOUTH OF THE LOW-LEVEL RIDGE OVER THE
ATLANTIC.  THE NHC FORECAST TRACK ASSUMES THAT BERTHA WILL REMAIN
DEEP ENOUGH TO DECELERATE DUE TO THE WEAKER RIDGE.  THE NEW
FORECAST TRACK IS JUST A LITTLE SOUTH OF THE PREVIOUS ADVISORY
THROUGH 72 HOURS...BUT SIMILAR THEREAFTER...AND IN BEST AGREEMENT
WITH THE ECMWF...NOGAPS...AND THE GUNA MODEL CONSENSUS. 

IT IS TOO EARLY TO DETERMINE IF BERTHA WILL EVER POSE A THREAT
TO ANY LAND AREAS.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 16.7N  39.3W    45 KT
 12HR VT     06/0600Z 17.1N  42.1W    45 KT
 24HR VT     06/1800Z 17.8N  45.9W    50 KT
 36HR VT     07/0600Z 18.5N  49.5W    55 KT
 48HR VT     07/1800Z 19.3N  52.8W    60 KT
 72HR VT     08/1800Z 20.8N  58.1W    65 KT
 96HR VT     09/1800Z 22.5N  63.0W    65 KT
120HR VT     10/1800Z 25.0N  67.0W    65 KT
 
$$
FORECASTER BROWN
 
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