Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  52
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 PM EDT TUE JUL 15 2008
 
BERTHA'S SATELLITE PRESENTATION HAS CONTINUED TO SLOWLY DEGRADE THIS
EVENING AS THE CLOUD TOPS HAVE WARMED OVER THE SOUTHERN PORTION OF
THE STORM.  THE LATEST SUBJECTIVE DVORAK INTENSITY ESTIMATES FROM
TAFB AND SAB ARE 45 AND 55 KT...RESPECTIVELY.  A QUIKSCAT OVERPASS
FROM 2222 UTC SUGGEST THAT THE MAXIMUM WINDS WERE 50-55 KT...SO THE
INITIAL INTENSITY HAS BEEN LOWERED A LITTLE.  BERTHA STILL HAS A
LITTLE TIME TO RESTRENGTHEN...SINCE THE SHEAR IS EXPECTED TO REMAIN
LOW WHILE THE STORM MOVES SOUTHEASTWARD OVER SLIGHTLY WARMER WATERS
DURING THE NEXT DAY OR SO.  HOWEVER...THE NEW INTENSITY FORECAST
KEEPS BERTHA JUST SHY OF HURRICANE STRENGTH. AFTER 48 HOURS...
COOLER WATER AND INCREASING SOUTHWESTERLY SHEAR SHOULD BEGIN
BERTHA'S GRADUAL DEMISE AS A TROPICAL CYCLONE.  
 
BERTHA APPEARS TO BE PUTTING ON THE BRAKES ONCE AGAIN.  THERE ARE
INDICATIONS THAT THE ANTICIPATED EASTWARD TURN HAS COMMENCED AND
THE INITIAL MOTION ESTIMATE IS 055/5.  THE MODELS ARE IN GOOD
AGREEMENT SHOWING BERTHA TURNING SOUTHEASTWARD DURING THE NEXT
12-18 HOURS...FOLLOWED BY AN EASTWARD MOTION THEREAFTER...AROUND
THE LARGE DEEP-LAYER LOW TO THE EAST.  AS THE DEEP-LAYER LOW LIFTS
NORTHWARD IN ABOUT 72 HOURS...BERTHA SHOULD FINALLY FEEL THE
WESTERLIES AND STARTING HEADING NORTHEASTWARD.  THERE IS A LARGE
AMOUNT OF SPREAD ON BERTHA'S FORWARD SPEED AT DAYS 4 AND 5...WITH
THE UKMET AND GFS SHOWING LESS ACCELERATION...WHILE THE GFDL...
GFDN...AND NOGAPS RACE BERTHA NORTHEASTWARD.  FOR NOW...THE NEW
TRACK FORECAST IS BETWEEN THESE TWO SOLUTIONS...AND IS CLOSE THE
MODEL CONSENSUS AND THE 12Z ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0300Z 36.8N  61.6W    55 KT
 12HR VT     16/1200Z 36.9N  61.1W    55 KT
 24HR VT     17/0000Z 36.0N  60.2W    60 KT
 36HR VT     17/1200Z 34.7N  59.1W    60 KT
 48HR VT     18/0000Z 34.0N  57.5W    60 KT
 72HR VT     19/0000Z 36.5N  52.7W    50 KT
 96HR VT     20/0000Z 40.0N  48.0W    45 KT
120HR VT     21/0000Z 44.5N  42.5W    45 KT...EXTRATROPICAL
 
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FORECASTER BROWN
 
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