Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  51
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT TUE JUL 15 2008
 
THE SATELLITE PRESENTATION OF BERTHA HAS DEGRADED A BIT OVER THE
PAST FEW HOURS AS THE EYE HAS BECOME LESS DISTINCT.  HOWEVER...
THERE HAS BEEN NO CHANGE IN THE SATELLITE CLASSIFICATIONS...AND THE
CURRENT INTENSITY WILL BE KEPT AT 60 KT FOR THIS ADVISORY...WHICH
MIGHT BE A LITTLE GENEROUS.  IT APPEARS THAT THE STORM HAS ABOUT A
DAY LEFT TO POSSIBLY INTENSIFY BEFORE WIND SHEAR INCREASES...
ALTHOUGH SO FAR BERTHA SHOWS NO SIGNS OF BECOMING A HURRICANE. THE
INTENSITY FORECAST WILL REMAIN SIMILAR TO PREVIOUS... AND NOT TOO
FAR FROM THE FSU SUPERENSEMBLE.  THE GFS AND ECMWF ARE FORECASTING
THE SYSTEM TO INTERACT WITH AN UPPER-LEVEL TROUGH STARTING IN ABOUT
96 HR...WHICH SHOULD CAUSE AN EXTRATROPICAL TRANSITION OF BERTHA
AROUND DAY 5.
 
BERTHA HAS SHOWN NO INDICATION OF THE FORECAST RIGHT TURN AND
CONTINUES ON A TRACK OF ABOUT 030/8.  HOWEVER THIS CHANGE IN
DIRECTION SHOULD OCCUR SOON AS MIDDLE-LEVEL RIDGING IS BECOMING
WEAKER ON WATER VAPOR IMAGES.  AS THE RIDGE COLLAPSES...BERTHA
SHOULD BE STEERED MORE TO THE EAST...THEN SOUTHEAST AND NORTHEAST
IN AN ARCING SEMICIRCLE FASHION AROUND A LARGE DEEP-LAYERED LOW TO
THE EAST. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT IN TRACK
AND THE OFFICIAL FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS
ONE.  

BERTHA IS NOW THE LONGEST-LIVED JULY TROPICAL STORM IN ATLANTIC
HISTORY...WITH 12.5 DAYS AS A TROPICAL STORM OR GREATER.  THIS
ECLIPSES THE PREVIOUS RECORD OF 12.25 DAYS OCCURRING IN 1916 FROM
STORM #2.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 36.4N  62.3W    60 KT
 12HR VT     16/0600Z 36.8N  61.5W    60 KT
 24HR VT     16/1800Z 36.3N  60.5W    65 KT
 36HR VT     17/0600Z 35.1N  59.5W    60 KT
 48HR VT     17/1800Z 34.2N  57.5W    55 KT
 72HR VT     18/1800Z 35.7N  53.5W    50 KT
 96HR VT     19/1800Z 39.5N  49.0W    45 KT
120HR VT     20/1800Z 43.5N  44.0W    45 KT...EXTRATROPICAL
 
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FORECASTER BLAKE
 
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