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ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM Hurricane Ophelia Discussion Number 25 NWS National Hurricane Center Miami FL AL172017 500 AM AST Sun Oct 15 2017 Although the satellite appearance of Ophelia has been slowly degrading this morning, the cyclone remains an impressive hurricane due to it being over the relatively cool waters of the northeastern Atlantic. A testament to Ophelia's strength is a late arriving buoy report 25 nmi southeast of the center of the eye from around 0200Z, which indicated that the pressure in the southeastern portion of the large eye or eyewall was 970.9 mb. However, Dvorak intensity estimates have been steadily decreasing since that buoy report, so the intensity has been lowered to 90 kt for this advisory. Ophelia continues to accelerate and the hurricane is now moving 050/30 kt. Water vapor imagery indicates that a deepening trough just to west of Ophelia is moving quickly eastward, and that the cyclone is now well embedded within the deep-layer southwesterly flow on the east side of the trough. As a result, Ophelia is expected to turn toward the north-northeast by tonight and be accompanied by a slight increase in forward speed. The NHC model guidance remains in excellent agreement on Ophelia reaching the southern coast of Ireland in 24-30 hours, and then move across the remainder of the country Monday night, and then move across Northern Ireland and northern Great Britain on Tuesday. Ophelia is forecast to become a post-tropical cyclone by 24 hours when extratropical transition should be completed, although the transition to an extratropical cyclone could occur as early as 12 hours. Regardless of the exact timing, post-tropical cyclone Ophelia is forecast to remain a powerful storm with hurricane-force winds when it reaches Ireland on Monday. The system is forecast to occlude and interact with land, which should cause a faster rate of weakening in 48 to 72 hours, with dissipation expected shortly thereafter. Although the center of Ophelia is not forecast to reach Ireland or the UK until Monday, strong winds and rains will arrive well in advance of the cyclone center. Residents in those locations should consult products from their local meteorological service for more information on local impacts. KEY MESSAGES: 1. Ophelia is expected to be a powerful extratropical cyclone with hurricane force winds Monday while it moves near Ireland and the United Kingdom. Direct impacts from wind and heavy rain in portions of these areas are likely, along with dangerous marine conditions. For more details on the magnitude, timing, and location of impacts from post-tropical Ophelia, residents in Ireland should refer to products issued by Met Eireann, and residents in the United Kingdom should refer to products issued by the Met Office. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 39.0N 18.3W 90 KT 105 MPH 12H 15/1800Z 43.0N 15.1W 85 KT 100 MPH 24H 16/0600Z 49.0N 11.5W 80 KT 90 MPH...POST-TROP/EXTRATROP 36H 16/1800Z 54.0N 8.6W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 17/0600Z 57.7N 4.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 18/0600Z 60.8N .1W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 19/0600Z...DISSIPATED $$ Forecaster Stewart NNNN