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| #201276 (Received by flhurricane at: 5:23 AM 16.Jul.2008) TCDAT2 TROPICAL STORM BERTHA DISCUSSION NUMBER 53 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 500 AM EDT WED JUL 16 2008 BERTHA IS CAUGHT BETWEEN MIDDLE TO UPPER-LEVEL SOUTHWESTERLY FLOW AHEAD OF A TROUGH OVER THE EASTERN UNITED STATES AND NORTHERLY FLOW ON THE WEST SIDE OF AN UPPER-LOW OVER THE CENTRAL ATLANTIC. THIS HAS RESULTED IN BERTHA'S CLOUD PATTERN BECOMING INCREASINGLY STRETCHED IN A SOUTHEAST TO NORTHWEST ORIENTATION. HOWEVER...THE DVORAK INTENSITY ESTIMATES STILL SUPPORT 55 KT. BERTHA IS BEGINNING AN ANTICIPATED TURN TOWARD THE SOUTH AND THIS TRACK IS EXPECTED TO TAKE THE CYCLONE OVER PROGRESSIVELY WARMER WATERS DURING THE NEXT 2 DAYS. SINCE THE SHEAR IS EXPECTED TO REMAIN LOW DURING THIS PERIOD...SOME RESTRENGTHENING IS POSSIBLE PRIOR TO THE CYCLONE ENCOUNTERING COOLER WATER AND INCREASING VERTICAL SHEAR BEYOND 72 HOURS. THE NEW OFFICIAL INTENSITY FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND SHOWS BERTHA REMAINING JUST SHY OF HURRICANE STRENGTH. BERTHA IS NOW MOVING TOWARD THE EAST-SOUTHEAST WITH AN INITIAL MOTION ESTIMATE OF 100/05. A SOUTHEAST TURN IS EXPECTED LATER TODAY FOLLOWED BY A TURN EASTWARD AND NORTHEASTWARD IN 2-3 DAYS AS THE CYCLONE CYCLONICALLY ROTATES AROUND A LARGE UPPER-LOW TO ITS EAST. TRACK GUIDANCE IS IN GOOD AGREEMENT DURING THE FIRST 2 DAYS OF THE FORECAST BUT THEN DIVERGES AT DAYS 3-5. THE GUIDANCE ENVELOPE SPANS NEARLY 1400 MILES AT DAY 5 AND IS BOUNDED BY THE NOGAPS MODEL...WHICH RACES THE CYCLONE NORTHEASTWARD...AND THE GFS MODEL...WHICH SHOWS A MUCH SLOWER EAST-NORTHEASTWARD MOTION. THE HWRF...GFDL...AND UKMET MODELS LIE IN BETWEEN THESE OUTLIER SOLUTIONS AND ARE THE BASIS FOR THE SOUTHWARD SHIFT AND SLOWER FORWARD SPEED SHOWN IN THE NEW OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 16/0900Z 36.4N 61.0W 55 KT 12HR VT 16/1800Z 36.1N 60.6W 55 KT 24HR VT 17/0600Z 35.0N 60.0W 60 KT 36HR VT 17/1800Z 34.1N 58.6W 60 KT 48HR VT 18/0600Z 34.0N 56.5W 60 KT 72HR VT 19/0600Z 36.5N 52.0W 50 KT 96HR VT 20/0600Z 40.0N 47.0W 45 KT 120HR VT 21/0600Z 43.5N 41.0W 40 KT...EXTRATROPICAL $$ FORECASTER RHOME |
