Hurricane OPHELIA

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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
 
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