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| #201019 (Received by flhurricane at: 4:55 PM 14.Jul.2008) TCDAT2 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 |
