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Bertha remains a tricky system to say the least.... a part of the 5am Discussion... BERTHA'S FORWARD MOTION HAS SLOWED A BIT AND IS NOW ABOUT 315/8. AN ANTICYCLONE TO THE NORTH OF THE HURRICANE WILL CONTINUE TO SLIDE EASTWARD OVER THE NEXT DAY OR TWO...SO THE TRACK OF THE HURRICANE IS LIKELY TO BEND TOWARD THE NORTH THROUGH 48 HOURS. BEYOND THAT TIME...THE TRACK FORECAST IS COMPLICATED BY THE FACT THAT THE DYNAMICAL MODELS...IN PARTICULAR THE GFS...SHOW A MID-LEVEL ANTICYCLONE DEVELOPING TO THE NORTH OF BERTHA IN AROUND 72 HOURS. THIS DEVELOPMENT WOULD AT LEAST RETARD THE NORTHWARD PROGRESS OF THE HURRICANE AND...IF THE ANTICYCLONE TURNS OUT TO BE STRONG ENOUGH...COULD EVEN FORCE A TURN TO THE LEFT AS INDICATED BY THE GFS. THE GFDL AND HWRF MODELS RESPOND TO THE INCREASED RIDGING MAINLY BY SLOWING THE TROPICAL CYCLONE AS IT CROSSES 30N LATITUDE. IT IS CERTAINLY POSSIBLE FOR BERTHA TO MOVE ERRATICALLY IN ABOUT 3 DAYS...BUT THE DETAILS OF THAT MOTION ARE OF COURSE UNKNOWN. |