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| #200387 (Received by flhurricane at: 4:55 AM 11.Jul.2008) TCDAT2 HURRICANE BERTHA DISCUSSION NUMBER 33 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 500 AM EDT FRI JUL 11 2008 THE LATEST SATELLITE MICROWAVE DATA AT 02Z INDICATED THAT BERTHA WAS CONTINUING ITS EYEWALL REPLACEMENT CYCLE...WITH A FRAGMENT OF THE OLD INNER EYEWALL REMAINING INSIDE THE 60 N MI WIDE OUTER EYEWALL. INFRARED IMAGERY SINCE THEN SUGGESTS LITTLE CHANGE IN THE STRUCTURE OF THE HURRICANE. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 77 KT...SO THE INITIAL INTENSITY REMAINS 75 KT. THE CIRRUS OUTFLOW IS NOW FAIR TO GOOD IN ALL DIRECTIONS. THE INITIAL MOTION IS NOW 315/6. TRACK GUIDANCE IS IN GOOD AGREEMENT THAT BERTHA WILL TURN NORTHWARD DURING THE NEXT 36 HR AS A MID-LEVEL RIDGE NORTH OF THE HURRICANE MOVES EASTWARD. SERIOUS GUIDANCE DIVERGENCE OCCURS BEYOND THAT TIME. THE GFS IS NOW CALLING FOR A SLOW EASTWARD MOTION FROM 48-120 HR...THE UKMET CALLING FOR A SLOW NORTHWARD MOTION...AND THE ECMWF AND CANADIAN MODELS TRAPPING BERTHA IN THE SUBTROPICAL RIDGE AND STALLING IT NEAR 31N61W. THE OTHER DYNAMICAL GUIDANCE FORECAST BERTHA TO MOVE SLOWLY NORTH-NORTHEASTWARD IN RESPONSE TO WEAK RIDGING TO THE EAST AND A SERIES OF MID/UPPER-LEVEL SHORTWAVE TROUGHS MOVING THROUGH THE EASTERN UNITED STATES. SINCE THE ECMWF AND GFS ARE NOT SHOWING MUCH RUN-TO-RUN CONSISTENCY...THE ONLY CHANGE TO THE FORECAST TRACK FROM THE PREVIOUS ADVISORY WILL BE TO CALL FOR A SLOWER NORTH- NORTHEASTWARD MOTION AFTER 48 HR. THE NEW TRACK LIES ON THE LEFT SIDE OF THE MODEL CONSENSUS IN BEST AGREEMENT WITH THE FLORIDA STATE SUPERENSEMBLE. BERTHA IS CURRENTLY UNDER A LARGE UPPER-LEVEL ANTICYCLONE...WITH THE LARGE-SCALE MODELS FORECASTING THIS TO CONTINUE FOR AT LEAST 36 HR. BASED ON A CONSENSUS OF THE INTENSITY GUIDANCE...THE INTENSITY FORECAST WILL KEEP BERTHA AT 75 KT DURING THIS TIME. HOWEVER... THERE IS STILL A CHANCE OF SOME STRENGTHENING AT THE END OF THE EYEWALL REPLACEMENT CYCLE. STARTING IN 48-72 HR...IT IS EXPECTED THAT BERTHA WILL SLOWLY MOVE OUT FROM UNDER THE ANTICYCLONE AND ENCOUNTER VERTICAL WIND SHEAR. THIS...COMBINED WITH DECREASING SEA SURFACE TEMPERATURES ALONG THE FORECAST TRACK...SHOULD CAUSE BERTHA TO WEAKEN. OCEAN ANALYSES FROM THE ATLANTIC OCEANOGRAPHIC AND MARINE LABORATORY SHOW THAT THE WARM WATER UNDER BERTHA IS RELATIVELY SHALLOW...AND THERE IS A CHANCE THAT THIS SLOW-MOVING SYSTEM COULD UPWELL COLDER WATER UNDERNEATH IT. THIS COULD PARTICULARLY BE A FACTOR IF BERTHA STALLS FOR 24 HR OR MORE. THE LATEST WIND SPEED PROBABILITIES INDICATE THAT...GIVEN UNCERTAINTIES IN THE FORECASTS OF BERTHA'S TRACK...INTENSITY...AND SIZE...THERE REMAINS ROUGHLY A 50% CHANCE THAT WINDS OF TROPICAL STORM FORCE WILL AFFECT BERMUDA DURING THE NEXT FIVE DAYS. A TROPICAL STORM WATCH MAY BE ISSUED FOR THE ISLAND LATER TODAY. FORECAST POSITIONS AND MAX WINDS INITIAL 11/0900Z 28.0N 61.7W 75 KT 12HR VT 11/1800Z 28.8N 62.3W 75 KT 24HR VT 12/0600Z 29.7N 62.6W 75 KT 36HR VT 12/1800Z 30.4N 62.5W 75 KT 48HR VT 13/0600Z 31.3N 62.0W 70 KT 72HR VT 14/0600Z 32.5N 61.0W 65 KT 96HR VT 15/0600Z 34.0N 60.5W 60 KT 120HR VT 16/0600Z 36.0N 59.0W 55 KT $$ FORECASTER BEVEN |
