Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT TUE JUL 15 2008

BERTHA IS MAINTAINING ITS STRUCTURE ON SATELLITE IMAGES THIS MORNING
WITH A NEW BURST OF CONVECTION ON THE NORTHEAST SIDE OF THE STORM...
AND APPARENT EYEWALL MESOVORTICES ROTATING QUICKLY AROUND THE
CENTER. HIGH-RESOLUTION QUIKSCAT SHOWS WINDS OF 55-60 KT...SO THE
INITIAL INTENSITY WILL REMAIN 60 KT FOR THIS ADVISORY.  THE STORM
STILL HAS A CHANCE TO BECOME A HURRICANE AGAIN DURING THE NEXT DAY
OR SO BEFORE VERTICAL WIND SHEAR INCREASES AS INDICATED BY ALL
MODELS.  THE STATISTICAL MODELS SUGGEST NO INTENSIFICATION BUT THE
DYNAMICAL MODELS SUCH AS THE GFDL/HWRF EMPHATICALLY SUGGEST BERTHA
WILL BECOME...AND MAINTAIN HURRICANE STRENGTH THROUGHOUT THE
FORECAST PERIOD.  THE INTENSITY FORECAST WILL BE CLOSER TO THE
STATISTICAL GUIDANCE AT THIS TIME AS THE UPPER ENVIRONMENT DOES NOT
SEEM TO BE TOO FAVORABLE FOR A HURRICANE BEYOND A COUPLE OF DAYS.  

THE STORM IS CURRENTLY MOVING 030/10...A LITTLE FASTER THAN BEFORE. 
A NARROW RIDGE TO THE EAST OF BERTHA IS STEERING THE CYCLONE
NORTHEASTWARD FOR THE TIME BEING.  THIS RIDGE IS FORECAST TO BE
ERODED BY ALL THE GLOBAL MODELS WITHIN 24 HOURS AS A LARGE
DEEP-LAYERED TROUGH APPROACHES FROM THE EAST.  THE BIGGEST
DISCREPANCY IS WHEN THE EXPECTED RIGHT TURN OF THE CYCLONE
EMERGES.   THE ECMWF/UKMET SHOW THAT THE TURN WILL BE DELAYED FOR
AN EXTRA 12 HOURS...ALLOWING THE STORM TO GAIN MORE LATITUDE AS
COMPARED TO THE GFS/GFDL/HWRF.  THE OFFICIAL FORECAST WILL SPLIT
THE DIFFERENCE BETWEEN THESE TWO MODEL CAMPS...AND SHIFTS THE TRACK
NORTHWARD IN THE SHORT-TERM.  UNCERTAINTY ALSO REMAINS HIGH IN THE
LONG-RANGE FORECAST AS THE GFDL/HWRF ARE STILL SHOWING BERTHA
SHOOTING OUT TO SEA WHILE THE GFS/ECMWF/UKMET ARE MUCH SLOWER. 
BECAUSE THE STORM IS NOT EXPECTED TO HAVE SUCH A WELL-DEVELOPED
STRUCTURE LIKE THE FORMER MODELS ARE INDICATING...THE OFFICIAL
FORECAST WILL LEAN MORE HEAVILY ON THE LARGE-SCALE MODELS THAT DELAY
THE TROPICAL CYCLONE'S EVENTUAL DEMISE.  AROUND 120 HOURS A
COMBINATION OF COOLER WATERS AND AN UPPER-LEVEL TROUGH INTERACTION
MAY...HOPEFULLY...START TO SIGNAL THE DEMISE OF BERTHA AS A
TROPICAL CYCLONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 35.6N  62.7W    60 KT
 12HR VT     16/0000Z 36.4N  61.8W    65 KT
 24HR VT     16/1200Z 36.2N  60.7W    65 KT
 36HR VT     17/0000Z 35.1N  59.6W    65 KT
 48HR VT     17/1200Z 34.1N  58.2W    60 KT
 72HR VT     18/1200Z 34.5N  54.5W    55 KT
 96HR VT     19/1200Z 37.5N  50.0W    50 KT
120HR VT     20/1200Z 41.5N  46.0W    45 KT...BECOMING EXTRATROPICAL
 
$$
FORECASTER BLAKE
 
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