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WTNT41 KNHC 010855
TCDAT1

HURRICANE OPHELIA DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
500 AM AST SAT OCT 01 2011

SINCE THE PREVIOUS ADVISORY...THE EYE HAS BECOME MORE DISTINCT IN
INFRARED IMAGERY AND THE EYE TEMPERATURE HAS WARMED TO ABOUT 11
DEGREES CELSIUS. THE EYE OF OPHELIA PASSED DIRECTLY OVER NOAA BUOY
41049 AROUND 08Z...AND THE BUOY REPORTED A 1-MINUTE SUSTAINED WIND
OF 84 KT WITH A GUST OF 101 KT AT A HEIGHT OF 5 METERS...AND A
PRESSURE OF 951.9 MB. BASED ON THE BUOY PRESSURE AND SATELLITE
INTENSITY ESTIMATES OF T5.5/102 KT FROM BOTH TAFB AND SAB...THE
ADVISORY INTENSITY WILL REMAIN AT 105 KT. WIND RADII WERE ADJUSTED
SLIGHTLY BASED ON WINDS OBTAINED FROM A 01/0106Z ASCAT OVERPASS.

THE INITIAL MOTION IS A STEADY 360/15 KT.  OPHELIA IS FORECAST TO
CONTINUE MOVING NORTHWARD FOR THE NEXT 12 HOURS OR SO...AND THEN
GRADUALLY TURN TOWARD THE NORTHEAST AND ACCELERATE AS THE HURRICANE
COMES UNDER THE INFLUENCE OF INCREASING SOUTHWESTERLY STEERING FLOW
AHEAD OF A DEEP-LAYER TROUGH CURRENTLY MOVING EASTWARD OFF THE U.S.
EAST COAST. BY 48 HOURS...THE CYCLONE IS EXPECTED TO TURN SHARPLY
EASTWARD AS IT ENTERS A BAND OF FAST-MOVING WESTERLIES NORTH OF 45N
LATITUDE. BY THAT TIME...OPHELIA IS FORECAST TO BE OVER WATERS
COLDER THAN 20C AND ALSO BEGIN TO MERGE WITH A STRONG FRONTAL
SYSTEM...WHICH SHOULD INDUCE A QUICK TRANSITION INTO A POWERFUL
POST-TROPICAL WINTER-TYPE CYCLONE. THE OFFICIAL FORECAST TRACK IS
SIMILAR TO THE PREVIOUS ADVISORY...AND LIES DOWN THE MIDDLE OF THE
TIGHTLY PACKED NHC MODEL GUIDANCE SUITE.

THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS INTENSITY FORECAST.
OPHELIA COULD STRENGTHEN SLIGHTLY TODAY AS THE MAJOR HURRICANE
REMAINS OVER SSTS NEAR 28C AND IN A VERTICAL SHEAR CONDITIONS OF
LESS THAN 5 KT. BY 24 HOURS...HOWEVER...INCREASING SOUTHWESTERLY
WIND SHEAR AND COOLER WATERS SHOULD INDUCE GRADUAL WEAKENING UNTIL
THE 36-HOUR TIME PERIOD. AFTER THAT...OPHELIA WILL MOVE OVER MUCH
COLDER WATER AND ENCOUNTER STRONG VERTICAL SHEAR OF MORE THAN 30
KT...WHICH SHOULD CAUSE MORE RAPID WEAKENING AND ALSO TRANSITION
INTO AN EXTRATROPICAL CYCLONE. THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY AND IS CLOSE TO THE INTENSITY
CONSENSUS MODEL...ICON.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 27.7N  63.1W  105 KT 120 MPH
 12H  01/1800Z 30.4N  62.8W  100 KT 115 MPH
 24H  02/0600Z 34.8N  61.9W   95 KT 110 MPH
 36H  02/1800Z 40.1N  60.3W   90 KT 105 MPH
 48H  03/0600Z 44.8N  55.9W   60 KT  70 MPH
 72H  04/0600Z 51.0N  36.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  05/0600Z...ABSORBED

$$
FORECASTER STEWART


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