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| #200963 (Received by flhurricane at: 11:09 AM 14.Jul.2008) TCDAT2 TROPICAL STORM BERTHA DISCUSSION NUMBER 46 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 1100 AM EDT MON JUL 14 2008 THE INITIAL MOTION IS 350/6. BERTHA IS EXPECTED TO CONTINUE ON A NORTHWARD TRACK FOR THE NEXT DAY OR SO AS MID-LEVEL HIGH PRESSURE TO THE NORTHEAST OF THE CYCLONE WEAKENS AND SLIDES EASTWARD. WITH THE STRONGEST WINDS LOCATED 50-60 NMI FROM THE CENTER... HOWEVER...THE PRECISE TRACK OF THE CENTER IS RELATIVELY UNIMPORTANT FOR CONDITIONS ON BERMUDA...WHERE TROPICAL STORM FORCE WINDS COULD CONTINUE THROUGH TOMORROW MORNING. AFTER BERTHA PASSES BERMUDA...A COMPLICATED STEERING PATTERNS AWAITS...WITH A STRONG UPPER-LEVEL LOW CURRENTLY NEAR 40N/42W FORECAST TO DROP SOUTHWESTWARD. MODEL GUIDANCE IS NOT IN GOOD AGREEMENT ON THE INTERACTION BETWEEN BERTHA AND THE UPPER LOW. THE HWRF AND GFDL MAINTAIN A STRONG TROPICAL CYCLONE AND SWING BERTHA RAPIDLY AROUND THE SOUTH SIDE OF THE UPPER LOW...WHILE THE GFS LIFTS THE UPPER LOW NORTHEASTWARD AFTER ABOUT 72 HOURS...LEAVING BERTHA BEHIND. AS THE UPPER-LOW AND BERTHA APPROACH...NORTHWESTERLY WIND SHEAR SHOULD INCREASE MARKEDLY...AND I SUSPECT THE HWRF/GFDL SOLUTIONS ARE KEEPING BERTHA TOO STRONG AND MAY THEREFORE BE OVERDOING THE INTERACTION. THE OFFICIAL FORECAST IS CLOSE TO THE FSSE SUPERENSEMBLE AND THE PREVIOUS ADVISORY. THERE IS NOT MUCH DEEP CONVECTION ASSOCIATED WITH BERTHA RIGHT NOW...AND A QUIKSCAT PASS AT 1030Z SUGGESTS THAT THE WINDS MIGHT BE A LITTLE BELOW THE ADVISORY INTENSITY OF 55 KT. A RECONNAISSANCE AIRCRAFT WILL BE IN THE CYCLONE IN ANOTHER COUPLE OF HOURS. THE QUIKSCAT DATA REVEALED A 50-60 NMI RMW. GIVEN THIS STRUCTURE...NO SIGNIFICANT CHANGES IN INTENSITY ARE EXPECTED WHILE THE STORM IS IN THE VICINITY OF BERMUDA. THE WILL BE SOME OPPORTUNITY FOR STRENGTHENING OVER THE NEXT DAY OR SO BEFORE BERTHA ENCOUNTERS SOME COOLER WATERS AND NORTHWESTERLY SHEAR. THE OFFICIAL INTENSITY FORECAST IS IN BEST AGREEMENT WITH THE SHIPS AND LGEM GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 14/1500Z 32.0N 63.8W 55 KT 12HR VT 15/0000Z 33.2N 63.9W 55 KT 24HR VT 15/1200Z 34.8N 63.2W 60 KT 36HR VT 16/0000Z 35.9N 62.0W 55 KT 48HR VT 16/1200Z 36.0N 61.0W 55 KT 72HR VT 17/1200Z 34.5N 58.5W 50 KT 96HR VT 18/1200Z 35.0N 55.0W 50 KT 120HR VT 19/1200Z 38.0N 51.0W 50 KT $$ FORECASTER FRANKLIN |
