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#111479 (Received by flhurricane at: 10:40 PM 17.Sep.2006) TCDAT2 HURRICANE GORDON DISCUSSION NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072006 1100 PM EDT SUN SEP 17 2006 AN EYE IS STILL EVIDENT ON INFRARED IMAGES AND DVORAK INTENSITY ESTIMATES CONTINUE TO RANGE FROM 65 TO 77 KT FROM THE VARIOUS AGENCIES. GORDON CONTINUES TO MOVE UNDER AN UPPER-TROPOSPHERIC RIDGE...AND ASSOCIATED MODEST VERTICAL SHEAR...WITH SSTS AROUND 26 DEG C. THIS REGIME SHOULD ALLOW THE TROPICAL CYCLONE TO MORE OR LESS MAINTAIN ITS STRENGTH FOR ANOTHER DAY OR SO. THEREAFTER SOME WEAKENING COULD OCCUR DUE TO COOLER SSTS AND INCREASED SHEAR ASSOCIATED WITH STRONGER UPPER-LEVEL WESTERLIES. HOWEVER AS GORDON BEGINS TO INTERACT WITH AN LARGE AND INTENSE EXTRATROPICAL CYCLONE OVER THE EASTERN NORTH ATLANTIC...THE COMBINATION OF GORDON AND THE LARGER CYCLONE SHOULD RESULT IN A POTENT EXTRATROPICAL STORM. THE OFFICIAL FORECAST ASSUMES THAT THE LARGER CYCLONE WILL DOMINATE...AND THEREFORE ABSORB...THE EXTRATROPICAL VERSION OF GORDON. THIS IS SIMILAR TO THE PREVIOUS NHC FORECAST ALTHOUGH A LITTLE STRONGER IN VIEW OF THE EXPECTED INTENSITY OF THE ABSORBING SYSTEM. THERE IS A POSSIBILITY...AS SUGGESTED BY THE NOGAPS MODEL...THAT GORDON WILL BE ABLE TO MAINTAIN ITS IDENTITY AS AN EXTRATROPICAL CYCLONE LONGER THAN EXPECTED HERE. THE FORECAST TRACK TAKES THE CYCLONE VERY NEAR THE AZORES AS AN EXTRATROPICAL STORM IN ABOUT 48 HOURS.. THE HEADING HAS TURNED MORE TO THE RIGHT AND IS NOW AROUND 040...AT 12 KT. DYNAMICAL GUIDANCE ARE IN GOOD AGREEMENT ON ACCELERATION AS GORDON GETS CAUGHT UP IN INCREASING ZONAL FLOW. THE OFFICIAL FORECAST IS A LITTLE TO THE SOUTH OF THE PREVIOUS ONE AND VERY CLOSE TO THE LATEST GFDL...U.K. MET...AND GFS CONSENSUS. THE WIND RADII HAVE BEEN ADJUSTED SLIGHTLY USING A RECENT QUIKSCAT PASS. FORECAST POSITIONS AND MAX WINDS INITIAL 18/0300Z 35.4N 51.5W 70 KT 12HR VT 18/1200Z 36.9N 49.1W 65 KT 24HR VT 19/0000Z 38.0N 44.0W 65 KT 36HR VT 19/1200Z 38.4N 37.5W 60 KT 48HR VT 20/0000Z 38.5N 29.5W 60 KT...EXTRATROPICAL 72HR VT 21/0000Z...DISSIPATED $$ FORECASTER PASCH |