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#377510 (Received by flhurricane at: 10:40 AM 20.Sep.2010) TCDAT1 HURRICANE IGOR DISCUSSION NUMBER 50 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 1100 AM AST MON SEP 20 2010 STRONG SOUTHERLY SHEAR HAS DISPLACED ALL OF THE DEEP CONVECTION TO THE NORTH OF THE EXPOSED LOW-LEVEL CENTER. THERE HAVE BEEN NO RECENT OBSERVATIONS NEAR THE CENTER OF IGOR...BUT SATELLITE INTENSITY ESTIMATES SUPPORT AN INTENSITY AT OR JUST BELOW 65 KT. THE INTENSITY WILL BE HELD AT 65 KT...AND IT IS POSSIBLE THAT IGOR COULD REGAIN A LITTLE BIT OF STRENGTH AS IT BEGINS TO GO THROUGH EXTRATROPICAL TRANSITION. THAT PROCESS IS EXPECTED TO BE COMPLETE BY 36 HOURS WHEN IGOR SHOULD BE COMPLETELY EMBEDDED WITHIN A FRONTAL ZONE. THE OFFICIAL FORECAST SHOWS SOME RE-STRENGTHENING DURING THE FIRST 24 HOURS AND GRADUAL WEAKENING FROM 36-96 HOURS. THE CYCLONE IS EXPECTED TO DISSIPATE BY 120 HOURS. THIS FORECAST IS MORE OR LESS A BLEND OF DYNAMICAL GUIDANCE AND GUIDANCE PROVIDED BY THE OCEAN PREDICTION CENTER. IGOR CONTINUES TO ACCELERATE TO THE NORTH-NORTHEAST WITH A MOTION OF 025/21. THERE IS LITTLE SPREAD IN THE TRACK GUIDANCE DURING THE NEXT 36 HOURS...AND THE OFFICIAL TRACK FORECAST ONLY HAD TO BE SHIFTED A SMALL DISTANCE TO THE WEST OF THE PREVIOUS FORECAST. AFTER 36 HOURS...THERE IS MORE SPREAD IN THE GUIDANCE...BUT THE BULK OF THE MODELS SHOW POST-TROPICAL IGOR TURNING NORTHWESTWARD TOWARD GREENLAND. THE NHC FORECAST BY 96 HOURS IS TO THE WEST OF THE MODEL CONSENSUS TO PUT MORE WEIGHT ON THE GLOBAL MODELS AND LESS ON THE GFDL. THE OCEAN PREDICTION CENTER ALSO PROVIDED THE CURRENT 12-FOOT SEAS RADII AND THE WIND RADII DURING THE EXTRATROPICAL PHASE...ALL OF WHICH HAVE BEEN EXPANDED IN THIS ADVISORY PACKAGE. IGOR WILL CONTINUE TO BE A LARGE CYCLONE AS IT MOVES PAST NEWFOUNDLAND TOWARD GREENLAND. FORECAST POSITIONS AND MAX WINDS INITIAL 20/1500Z 36.1N 63.3W 65 KT 12HR VT 21/0000Z 38.9N 60.6W 70 KT 24HR VT 21/1200Z 42.9N 55.0W 75 KT...POST-TROP/EXTRATROP 36HR VT 22/0000Z 46.8N 48.9W 70 KT...POST-TROP/EXTRATROP 48HR VT 22/1200Z 50.4N 44.0W 60 KT...POST-TROP/EXTRATROP 72HR VT 23/1200Z 56.5N 40.5W 55 KT...POST-TROP/EXTRATROP 96HR VT 24/1200Z 62.5N 47.0W 30 KT...POST-TROP/EXTRATROP 120HR VT 25/1200Z...DISSIPATED $$ FORECASTER BERG |