Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT THU JUL 03 2008
 
THE CLOUD TOPS ASSOCIATED WITH BERTHA HAVE WARMED THIS
AFTERNOON...HOWEVER...BANDING FEATURES REMAIN WELL-DEFINED IN
VISIBLE IMAGERY AND A RECENT SSMIS MICROWAVE OVERPASS.   A SHIP
LOCATED ABOUT 45 NM NORTHEAST OF THE CENTER AT 1700 UTC REPORTED
SUSTAINED WINDS OF 29 KT.  THE LATEST DVORAK ESTIMATES FROM TAFB
AND SAB ARE 35 KT...WHICH REMAINS THE INITIAL ADVISORY INTENSITY. 

THE FORECAST SCENARIO REMAINS UNCHANGED AS BERTHA IS EXPECTED TO
CONTINUE MOVING WEST-NORTHWESTWARD SOUTH OF A MID-LEVEL RIDGE OVER
THE EASTERN ATLANTIC DURING THE NEXT FEW DAYS.  THEREAFTER...A
WEAKNESS IN THE RIDGE BETWEEN ABOUT 50W-60W WILL PLAY A ROLE IN THE
FUTURE TRACK OF BERTHA.  THE UKMET...ECMWF...AND HWRF MODELS DEPICT
A WEAKER AND SHALLOWER BERTHA...KEEPING THE CYCLONE ON A GENERAL
WEST-NORTHWESTWARD TRACK.  THE GFS AND GFDL MAINTAIN A STRONGER
TROPICAL CYCLONE THAT TURNS NORTHWESTWARD INTO THE WEAKNESS. THE
OFFICIAL FORECAST ASSUMES THAT BERTHA WILL BE STRONG AND DEEP
ENOUGH TO BE STEERED BY THE MID-LEVEL FLOW...FOLLOWING CLOSELY THE
GFDL AND THE GFS. 

SHEAR IS EXPECTED TO REMAIN LIGHT...BUT BERTHA IS FORECAST TO TRACK
OVER SSTS OF 25 DEGREES C....WHICH IS THE MAIN LIMITING FACTOR FOR
THE NEXT COUPLE OF DAYS.  THEREAFTER...THE SSTS ALONG THE TRACK ARE
EXPECTED TO INCREASE BUT SHEAR IS FORECAST TO BE STRONGER LATER IN
THE PERIOD.  THE SHIPS... LGEM...AND GFDL MODELS PREDICT BERTHA TO
REACH HURRICANE STRENGTH IN 3-5 DAYS.  THE NEW INTENSITY FORECAST
IS UNCHANGED AND CONSERVATIVE DUE TO THE AFOREMENTIONED LIMITING
FACTORS. 
 
THE CENTER OF BERTHA SHOULD MOVE AWAY FROM THE SOUTHERN CAPE VERDE
ISLANDS TONIGHT...HOWEVER OUTER RAINBANDS WILL CONTINUE TO BRING
GUSTY WINDS AND LOCALLY HEAVY RAINFALL TO PORTIONS OF THE SOUTHERN
CAPE VERDE ISLANDS DURING THE NEXT 24 HOURS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/2100Z 13.6N  25.6W    35 KT
 12HR VT     04/0600Z 14.1N  27.6W    40 KT
 24HR VT     04/1800Z 15.0N  30.8W    45 KT
 36HR VT     05/0600Z 16.0N  34.2W    45 KT
 48HR VT     05/1800Z 16.9N  37.7W    50 KT
 72HR VT     06/1800Z 18.8N  44.5W    55 KT
 96HR VT     07/1800Z 21.5N  49.5W    55 KT
120HR VT     08/1800Z 25.0N  52.5W    55 KT
 
$$
FORECASTER BROWN
 
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