Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT SUN JUL 06 2008
 
A SERIES OF MICROWAVE OVERPASSES THIS MORNING SHOW THAT BERTHA HAS
CHANGED LITTLE IN ORGANIZATION DURING THE PAST 24 HOURS. QUIKSCAT
DATA FROM 0852 UTC INDICATE THAT THE MAXIMUM WINDS REMAIN ABOUT 45
KT...WHICH AGREES WITH THE LATEST DVORAK INTENSITY ESTIMATES.
HOWEVER...RECENT VISIBLE SATELLITE IMAGES REVEAL AN INCREASE IN
CONVECTION WHICH MAY FORETELL AN INCREASE IN STRENGTH. SSTS UNDER
BERTHA HAVE INCREASED TO AROUND 26 CELSIUS AND ARE EXPECTED TO WARM
A COUPLE OF DEGREES DURING THE NEXT 2 DAYS. SHEAR IS FORECAST TO
REMAIN LOW...SO GRADUAL STRENGTHENING IS EXPECTED DURING THE NEXT
48 HOURS AND BERTHA COULD BECOME A HURRICANE DURING THAT TIME.
LATER IN THE FORECAST PERIOD...IT IS DIFFICULT TO DETERMINE EXACTLY
WHAT EFFECT AN UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC WILL
HAVE ON THE CYCLONE. IF IT REMAINS IN PLACE...THE TROUGH WOULD
PRODUCE AN INCREASE IN SOUTHWESTERLY SHEAR. SOME OF THE GLOBAL
MODELS SUGGEST A WEAKENING OF THE TROUGH HOWEVER...WHICH WOULD KEEP
BERTHA IN A MORE FAVORABLE ENVIRONMENT. DUE TO THESE UNCERTAINTIES
THE INTENSITY FORECAST BEYOND 3 DAYS KEEPS BERTHA AT THE SAME
STRENGTH.

BERTHA CONTINUES MOVING RAPIDLY WESTWARD OR 280/18 KT. A
WEST-NORTHWESTWARD TRACK WITH A REDUCTION IS FORWARD SPEED IS
EXPECTED DURING THE NEXT DAY OR TWO. THERE IS A LITTLE LESS SPREAD
IN THE MODELS THIS MORNING...WITH THE MAJORITY OF THE GUIDANCE
SHOWING A MORE NORTHWESTWARD TURN IN 2-3 DAYS AS THE RIDGE OVER THE
WESTERN ATLANTIC BEGIN TO WEAKEN. THE HWRF CONTINUES TO INSIST ON
THE TURN OCCURRING MUCH SOONER...WHILE THE UKMET REMAINS THE
WESTERNMOST MODEL BUT WITH A WEAKENED TROPICAL CYCLONE OR EVEN AN
OPEN WAVE. THE OFFICIAL TRACK HAS BEEN ADJUSTED EASTWARD...BUT IT
REMAINS LEFT OF MOST OF THE GUIDANCE AND ALSO LEFT OF THE MODEL
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 17.4N  45.1W    45 KT
 12HR VT     07/0000Z 18.0N  47.8W    50 KT
 24HR VT     07/1200Z 18.9N  50.9W    55 KT
 36HR VT     08/0000Z 19.7N  53.5W    60 KT
 48HR VT     08/1200Z 20.5N  56.0W    65 KT
 72HR VT     09/1200Z 22.5N  60.5W    70 KT
 96HR VT     10/1200Z 25.0N  64.0W    70 KT
120HR VT     11/1200Z 27.0N  66.5W    70 KT
 
$$
FORECASTER BROWN
 
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