Tropical Storm BERTHA

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TROPICAL STORM BERTHA DISCUSSION NUMBER  47
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT MON JUL 14 2008
 
THE AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT INVESTIGATING
BERTHA FOUND SFMR SURFACE WINDS OF 60 KT IN THE SOUTHWEST
QUADRANT...WINDS THAT WERE WERE CONFIRMED BY A CO-LOCATED
DROPSONDE.  OVER THE PAST FEW HOURS...THERE HAS BEEN A RESURGENCE
IN DEEP CONVECTION...PERHAPS AS A RESULT OF BERTHA FINALLY MOVING
AWAY FROM WHERE IT HAD BEEN PARKED.   THIS STRENTHENING REQUIRED
THE ISSUANCE OF A HURRICANE WATCH FOR BERMUDA...AS THIS PORTION OF
THE CYCLONE HAS YET TO CLEAR THE ISLAND.  UPPER-LEVEL CIRRUS ARE
EXPANDING IN ALL QUADRANTS...AND IT IS NOW EXPECTED THAT BERTHA
WILL BECOME A HURRICANE BEFORE COOLER WATERS AND INCREASING
NORTHWESTERLY SHEAR AFFECT THE STORM IN 36-48 HOURS.  

THE INITIAL MOTION IS 350/6...WHICH REPRESENTS THE MOTION OF THE
OVERALL CYCLONE RATHER THAN THAT OF THE SMALL SWIRL THAT IS VISIBLE
ROTATING WITHIN THE CONVECTIVE RING.  THE SHORT TERM TRACK
PHILOSOPHY IS UNCHANGED...WITH BERTHA EXPECTED TO GRADUALLY TURN
NORTHEASTWARD OVER THE NEXT DAY OR TWO AROUND THE PERIPHERY OF A
MID-LEVEL ANTICYCLONE. AFTER THAT...BERTHA'S PATH WILL BE
DETERMINED BY ITS INTERACTION WITH A STRONG UPPER-LEVEL LOW
CURRENTLY NEAR 39N/43W BUT FORECAST TO DROP SOUTHWESTWARD TOWARD
THE TROPICAL CYCLONE. THE 12Z MODEL GUIDANCE AS A WHOLE IS SLOWER
THAN IT HAD BEEN...WITH THE BULK OF THE GUIDANCE INDICATING THAT
THE UPPER LOW WILL SHOVE BERTHA SOUTHEASTWARD...AWAY FROM THE
WESTERLIES. THE OFFICIAL FORECAST SHOWS LESS ACCELERATION ON DAYS
4-5 THAN THE PREVIOUS ADVISORY...BUT EVEN SO IS FASTER THAN JUST
ABOUT EVERYTHING EXCEPT THE HWRF AND GFDL. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 33.0N  64.1W    60 KT
 12HR VT     15/0600Z 34.2N  63.7W    65 KT
 24HR VT     15/1800Z 35.3N  62.8W    65 KT
 36HR VT     16/0600Z 35.7N  61.8W    65 KT
 48HR VT     16/1800Z 35.2N  60.7W    60 KT
 72HR VT     17/1800Z 34.0N  57.5W    55 KT
 96HR VT     18/1800Z 35.5N  54.5W    50 KT
120HR VT     19/1800Z 38.0N  51.0W    50 KT
 
$$
FORECASTER FRANKLIN
 
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