000 WTNT41 KNHC 020836 TCDAT1 HURRICANE OPHELIA DISCUSSION NUMBER 39 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 500 AM AST SUN OCT 02 2011 JUST PRIOR TO 06Z...UW-CIMSS ADT ESTIMATES WERE AVERAGING BETWEEN T62/119 KT AND T6.3/121 KT. SINCE THAT TIME...HOWEVER... THE ADT ESTIMATES HAVE BEEN STEADILY DECREASING BELOW T6.0/115 KT. AS A RESULT...THE INTENSITY HAS BEEN LOWERED TO 110 KT ON THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 010/25 KT. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK REASONING. THE NHC MODEL GUIDANCE REMAINS TIGHTLY PACKED THROUGH 36 HOURS. OPHELIA IS EXPECTED TO MOVE NORTH-NORTHEASTWARD DURING THE NEXT 12 HOURS OR SO AND THEN TURN NORTHEASTWARD...BRINGING THE CENTER OF THE HURRICANE OVER OR NEAR THE AVALON PENINSULA OF NEWFOUNDLAND IN ABOUT 30 HOURS. AFTER THAT...THE MODELS DIVERGE ON WHETHER THE EXTRATROPICAL LOW PRESSURE SYSTEM WILL MOVE OVER OR NORTH OF THE BRITISH ISLES. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK THROUGH 36 HOURS...AND IS A LITTLE NORTH OF THE PREVIOUS FORECAST AFTER THAT BASED ON GUIDANCE FROM THE NOAA OCEAN PREDICTION CENTER...AND THE ECMWF AND GFS MODELS. OPHELIA IS MOVING OVER SUB-27C SSTS NOW AND THE CLOUD PATTERN HAS BECOME ELONGATED NORTHWEST-TO-SOUTHEAST...SUGGESTING THAT SOUTHERLY TO SOUTHWESTERLY WIND SHEAR IS BEGINNING TO AFFECT THE CYCLONE. MUCH COOLER WATER LIES NORTH OF 40N LATITUDE AND THE VERTICAL SHEAR IS FORECAST TO INCREASE TO ABOVE 35 KT IN ABOUT 24 HOURS. THE COMBINATION OF STRONG SHEAR AND COLD WATER SHOULD INDUCE STEADY TO RAPID WEAKENING DURING THE NEXT 24 HOURS...WITH TRANSITION TO A POST-TROPICAL EXTRATROPICAL CYCLONE BY 36 HOURS...IF NOT SOONER. THE NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY... AND IS A BLEND OF THE SHIPS/LGEM INTENSITY MODELS AND GUIDANCE FROM THE NOAA OCEAN PREDICTION CENTER. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 36.2N 61.8W 110 KT 125 MPH 12H 02/1800Z 39.9N 60.2W 95 KT 110 MPH 24H 03/0600Z 44.4N 56.4W 75 KT 85 MPH 36H 03/1800Z 47.9N 48.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 04/0600Z 50.5N 39.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 05/0600Z 56.0N 17.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 06/0600Z...DISSIPATED $$ FORECASTER STEWART