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| #199680 (Received by flhurricane at: 10:37 AM 07.Jul.2008) TCDAT2 HURRICANE BERTHA DISCUSSION NUMBER 18 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008 1100 AM EDT MON JUL 07 2008 BERTHA'S SATELLITE PRESENTATION HAS BECOME MORE IMPRESSIVE DURING THE LAST 6 HOURS WITH A DISTINCT EYE NOW APPARENT. THE INITIAL INTENSITY IS INCREASED TO 80 KT IN LINE WITH THE CONSENSUS OF THE VARIOUS SATELLITE ESTIMATES. IN THE SHORT-TERM...THERE ARE NO APPARENT ENVIRONMENTAL FACTORS WHICH WOULD INHIBIT FURTHER INTENSIFICATION TODAY AND THE OFFICIAL FORECAST NOW CALLS FOR BERTHA TO BECOME A CATEGORY TWO HURRICANE. HOWEVER...THE INTENSITY FORECAST BECOMES MORE UNCERTAIN BEYOND 36 HOURS AS THE GLOBAL MODELS DISAGREE ON THE DETAILS OF THE DEVELOPMENT OF AN UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC. THE GFS FORECAST THE MOST UNFAVORABLE ENVIRONMENT WITH BERTHA ESSENTIALLY RUNNING INTO THE TROUGH. NOT SURPRISINGLY...THE SHIPS AND LGEM STATISTICAL MODELS...WHICH INCLUDE ATMOSPHERIC INFORMATION FROM THE GFS...SHOW CONSIDERABLE WEAKENING. MEANWHILE...THE UKMET...GFDL...AND HWRF MODELS SHOWS A MUCH MORE FAVORABLE ENVIRONMENT AND DELAY WEAKENING UNTIL THE VERY END OF THE FORECAST PERIOD. THE OFFICIAL INTENSITY FORECAST LEANS MORE TOWARDS THE HIGHER SHEAR SCENARIO INDICATED BY THE GFS BUT DOES NOT WEAKEN BERTHA AS FAST AS THE SHIPS AND LGEM MODELS. THERE HAS BEEN LITTLE CHANGE IN THE HURRICANE'S HEADING DURING THE LAST 6 HOURS WITH THE INITIAL MOTION ESTIMATE ESSENTIALLY UNCHANGED... 285/13. HOWEVER...BERTHA IS BEGINNING TO ENCOUNTER A WEAKNESS IN THE SUBTROPICAL RIDGE WHICH SHOULD RESULT IN A GRADUAL TURN TOWARDS THE NORTH AND A REDUCTION IN FORWARD SPEED. THE MODELS GENERALLY AGREE ON THIS EVOLUTION...BUT THERE REMAINS SOME SPREAD AMONGST THE MODELS ON WHAT LONGITUDE BERTHA WILL TURN NORTH. WHILE THE DEGREE OF THE TURN HAS IMPORTANT IMPLICATIONS REGARDING POTENTIAL IMPACTS TO BERMUDA...IT IS MUCH TO EARLY TO DETERMINE IF BERTHA WILL ACTUALLY THREATEN THAT ISLAND. HOWEVER...INTERESTS IN BERMUDA SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. THE NEW OFFICIAL FORECAST IS NUDGED SLIGHTLY EASTWARD TOWARD THE TRACK MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 07/1500Z 19.6N 51.3W 80 KT 12HR VT 08/0000Z 20.3N 53.3W 90 KT 24HR VT 08/1200Z 21.2N 55.5W 90 KT 36HR VT 09/0000Z 22.1N 57.5W 85 KT 48HR VT 09/1200Z 23.2N 59.2W 80 KT 72HR VT 10/1200Z 25.5N 62.0W 75 KT 96HR VT 11/1200Z 28.5N 63.5W 70 KT 120HR VT 12/1200Z 31.0N 63.5W 70 KT $$ FORECASTER RHOME |
