Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT SUN JUL 06 2008
 
THE SATELLITE PRESENTATION HAS GRADUALLY IMPROVED DURING THE PAST
SEVERAL HOURS. THE CONVECTION IS SYMMETRIC ABOUT THE CENTER WHILE
THE OUTFLOW HAS BEEN EXPANDING WESTWARD...TYPICAL OF AN
INTENSIFYING CYCLONE. FURTHERMORE...CONSECUTIVE MICROWAVE DATA SHOW
A WELL DEFINED RING OF DEEP CONVECTION...OR EYE-LIKE FEATURE...
WHICH IS GRADUALLY BECOMING ALIGNED VERTICALLY.  THIS COULD
EVENTUALLY BE THE PRECURSOR OF AN EYE FORMATION.  DVORAK T-NUMBERS
HAVE INCREASED AND NOW SUPPORT AN INITIAL INTENSITY OF 55 KNOTS. 
THE OCEAN IS PLENTY WARM AHEAD OF BERTHA SO THE SHEAR WILL BE THE
MAIN PRIMARY LARGE SCALE FACTOR CONTROLLING THE FUTURE INTENSITY.
WE ARE NOT CONSIDERING EYEWALL CYCLES AT THIS TIME...IN CASE AN EYE
FORMS.  BECAUSE THE SHEAR IS EXPECTED TO BE WEAK FOR THE NEXT DAY
OR TWO... STRENGTHENING IS INDICATED AND BERTHA COULD BECOME A
HURRICANE ON MONDAY. THEREAFTER...THE SHEAR IS EXPECTED TO
FLUCTUATE SO NO IMPORTANT CHANGES IN INTENSITY ARE FORECAST. 

THE CENTER IS A LITTLE FARTHER NORTH AS IT APPEARS TO BE REALIGNING
WITH THE MID-LEVEL VORTEX. THIS IS NOT A CHANGE IN TRACK SINCE 
BERTHA IS STILL MOVING TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT
17 KNOTS.  A WEAKNESS OF THE SUBTROPICAL RIDGE ALONG 50 TO 55
DEGREES WEST WILL PROBABLY CAUSE BERTHA TO BEGIN TO SLOW DOWN SOON. 
THE SUBTROPICAL RIDGE IS EXPECTED TO REBUILD SOME IN A DAY OR TWO
CAUSING BERTHA TO CONTINUE ON A WEST-NORTHWEST TO NORTHWEST TRACK.
BY THE END OF THE FORECAST PERIOD...THE STEERING CURRENTS ARE
FORECAST TO WEAKEN AGAIN AND BERTHA SHOULD SLOW DOWN CONSIDERABLY
AS INDICATED BY SOME GLOBAL MODELS. THE OFFICIAL FORECAST IS
CONSISTENT WITH MOST OF THE TRACK GUIDANCE WHICH IS IN MUCH BETTER
AGREEMENT TONIGHT. NO NEED TO DISCUSS EVERY MODEL. 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 18.6N  48.9W    55 KT
 12HR VT     07/1200Z 19.3N  51.5W    60 KT
 24HR VT     08/0000Z 20.0N  54.5W    70 KT
 36HR VT     08/1200Z 21.0N  57.0W    70 KT
 48HR VT     09/0000Z 22.0N  59.5W    70 KT
 72HR VT     10/0000Z 24.0N  62.0W    70 KT
 96HR VT     11/0000Z 27.0N  64.5W    70 KT
120HR VT     12/0000Z 30.0N  65.5W    70 KT
 
$$
FORECASTER AVILA
 
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