000
WTNT42 KNHC 171442
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER  58
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
1100 AM EDT THU JUL 17 2008
 
A QUIKSCAT PASS AT 0912 UTC SUGGESTED THAT THE MAXIMUM WINDS OF
BERTHA WERE ABOUT 50 KT AT THAT TIME. SINCE THEN...NEW
THUNDERSTORMS HAVE DEVELOPED IN THE EASTERN SEMICIRCLE OF THE
STORM. ALTHOUGH SATELLITE CLASSIFICATIONS ARE DECREASING...I'M
HESITANT TO LOWER THE WINDS TOO MUCH BASED ON THE QUIKSCAT DATA AND
THE RESILENCY OF THE SYSTEM. 50 KT WILL BE USED AS THE INITIAL
INTENSITY. LITTLE CHANGE IN STRENGTH IS FORECAST FOR THE NEXT DAY
OR SO IN AGREEMENT WITH MOST GUIDANCE. HOWEVER...IT IS TEMPTING TO
LOWER THE WINDS A LITTLE MORE BEFORE EXTRATROPICAL TRANSITION
OCCURS. THE OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS
FORECAST AND IS BELOW MOST OF THE INTENSITY GUIDANCE. BERTHA MAY
BECOME A LARGE POWERFUL EXTRATROPICAL LOW IN THE HIGH LATITUDES OF
THE NORTH ATLANTIC BY DAY 5.
 
THE STORM APPEARS TO HAVE TURNED TOWARD THE EAST-SOUTHEAST AT ABOUT
8 KT.  THE CYCLONE SHOULD BEGIN ITS MOTION TOWARD THE NORTHEAST BY
TOMORROW AS IT IS STEERED AROUND A MIDDLE- TO UPPER-LEVEL LOW TO
THE NORTH.  MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK AND
LITTLE CHANGE IS MADE TO THE OFFICIAL FORECAST.  THEREAFTER THE
BIGGEST QUESTION IS WHETHER A NEW MIDDLE-LATITUDE TROUGH WILL
CAPTURE BERTHA...LIKE THE UKMET/ECMWF SHOWS...OR THE STORM WILL
REMAIN A MORE SEPARATE ENTITY LIKE THE GFS/GFDL/HWRF SOLUTIONS. 
THE OFFICAL FORECAST LEANS ON THE WESTERN SIDE OF THE
GUIDANCE...SHOWING A LITTLE MORE TROUGH INTERACTION. 

BERTHA COULD BECOME ONE OF THE TOP 10 LONGEST-LIVED STORMS IN
HISTORY IF IT SURVIVES UNTIL THE WEEKEND.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/1500Z 34.2N  58.4W    50 KT
 12HR VT     18/0000Z 34.1N  56.9W    45 KT
 24HR VT     18/1200Z 35.2N  54.5W    45 KT
 36HR VT     19/0000Z 37.3N  51.8W    45 KT
 48HR VT     19/1200Z 39.3N  49.1W    45 KT
 72HR VT     20/1200Z 43.5N  43.0W    45 KT...BECOMING EXTRATROPICAL
 96HR VT     21/1200Z 51.0N  34.0W    50 KT...EXTRATROPICAL
120HR VT     22/1200Z 57.5N  22.0W    50 KT...EXTRATROPICAL
 
$$
FORECASTER BLAKE