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| #201075 (Received by flhurricane at: 11:11 PM 14.Jul.2008) TCDAT2 TROPICAL STORM BERTHA DISCUSSION NUMBER 48 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 1100 PM EDT MON JUL 14 2008 THE CENTER OF BERTHA IS STEADILY MOVING AWAY FROM BERMUDA. THE CYCLONE IS IN THE PROCESS OF MAKING A GRADUAL RIGHT TURN...SO THE DIRECTION OF MOTION HAS BEEN FREQUENTLY CHANGING...BUT THE ESTIMATE VALID AT ADVISORY TIME IS 015/8. WATER VAPOR IMAGERY SHOWS THAT THE CUTOFF LOW CURRENTLY ABOUT 1000 N MI EAST-NORTHEAST OF BERTHA IS SLIDING SOUTHWESTWARD AND PUTTING THE SQUEEZE ON WHAT IS LEFT OF THE NARROW MID-LEVEL RIDGE IN BETWEEN. THAT RIDGE HAS BEEN STEERING BERTHA NORTHWARD TODAY...SO AS IT ERODES...BERTHA IS FORECAST BY ALL OF THE DYNAMICAL MODELS TO MAKE A SHARPER RIGHT TURN IN ABOUT 24 HOURS...AND THEN HEAD SOUTHEASTWARD AS IT MORE DIRECTLY INTERACTS WITH THE CUTOFF LOW. ALL OF THE MODELS AGREE THAT THE CUTOFF LOW WILL LIFT OUT IN ABOUT 72 HOURS...LEAVING BERTHA TO BE STEERED GENERALLY NORTHEASTWARD BY THE MID-LATITUDE WESTERLIES LATE IN THE FORECAST PERIOD. THE NEW OFFICIAL FORECAST TRACK CONTINUES TO DEPICT WHAT LOOKS LIKE A SINE WAVE...THIS TIME WITH SLIGHTLY MORE AMPLITUDE...BUT WITH THE NET MOTION OVER FIVE DAYS BEING EAST-NORTHEASTWARD. THE FORWARD SPEED OF BERTHA BEYOND 72 HOURS IS RATHER UNCERTAIN...AS THE VARIOUS MODELS AGREE ON THE PATH BUT NOT ON HOW FAST THE CYCLONE WILL GO. THE DEEPEST CONVECTION HAS ROTATED AROUND THE CENTER FROM THE SOUTHWESTERN QUADRANT...WHICH DIRECTLY AFFECTED BERMUDA EARLIER TODAY...AND NOW IS FOCUSED SOUTHEAST AND EAST OF THE CENTER. OTHERWISE...THE OVERALL STRUCTURE OF THE CYCLONE IS ESSENTIALLY UNCHANGED...AS ARE THE DVORAK ESTIMATES AT 55 KT. USING CONTINUITY FROM EARLIER AIRCRAFT OBSERVATIONS...THE ADVISORY INTENSITY REMAINS 60 KT. THE INTENSITY FORECAST IS MOSTLY UNCHANGED...CALLING FOR BERTHA TO BE AT HURRICANE STATUS DURING THE NEXT COUPLE OF DAYS. THIS FORECAST MIGHT NOT BE EXACTLY RIGHT...BUT THE INTENSITY CONSENSUS SUGGESTS BERTHA WILL BE NEAR THE THRESHOLD BETWEEN TROPICAL STORM AND HURRICANE INTENSITY FOR A FEW DAYS. A WEAKENING TREND IS INDICATED IN THE OFFICIAL FORECAST AT DAYS 4 AND 5 AS BERTHA HEADS NORTHEASTWARD TOWARD NOTICEABLY COOLER WATERS...IN BEST AGREEMENT WITH THE SHIPS AND LGEM STATISTICAL-DYNAMICAL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 15/0300Z 33.8N 63.7W 60 KT 12HR VT 15/1200Z 34.9N 63.0W 65 KT 24HR VT 16/0000Z 35.7N 61.9W 65 KT 36HR VT 16/1200Z 35.4N 60.6W 65 KT 48HR VT 17/0000Z 34.4N 59.2W 65 KT 72HR VT 18/0000Z 33.5N 55.5W 60 KT 96HR VT 19/0000Z 36.0N 52.0W 55 KT 120HR VT 20/0000Z 39.5N 49.0W 50 KT $$ FORECASTER KNABB |
