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ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM Hurricane Ophelia Discussion Number 24 NWS National Hurricane Center Miami FL AL172017 1100 PM AST Sat Oct 14 2017 Ophelia remains an impressive hurricane in infrared satellite imagery. The hurricane continues to exhibit a large well-defined eye within a ring of cold cloud tops. However, the overall cloud pattern has started to elongate and there has been a slight erosion of the area of cloud tops over the west and southwest portions of the circulation as dry air and a frontal boundary encroaches on the hurricane. Satellite intensity estimates from all agencies continue to support an intensity of 100 kt. The aforementioned changes in the cloud pattern and an expansion of the wind field as noted by an earlier ASCAT overpass suggest that extratropical transition has begun. The wind field is expect to significantly expand over the next 12 to 24 hours, which is likely to lead to a gradual decrease in the maximum winds. Ophelia is forecast to complete extratropical transition within 24 hours, but it is expected to remain a powerful post-tropical cyclone with hurricane-force winds as it approaches 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. Ophelia is moving northeastward, or 055/24 kt ahead of a mid-latitude trough moving over the northeastern Atlantic. The hurricane should continue to accelerate northeastward tonight, then turn north-northeastward with an additional increase in forward speed by late Sunday and Sunday night. After the system occludes in a couple of days, it should begin to slow down. The track guidance is in good agreement, and the updated NHC track forecast is very close to the previous advisory. Although the center of Ophelia is not forecast to reach Ireland or the UK until Monday, wind 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. Tropical-storm-force winds are possible throughout the Azores tonight behind a cold front that has moved through the islands in the wake of Ophelia. Interests in the Azores should refer to products issued by the Azores Weather Forecast and Watch Center. 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 15/0300Z 37.3N 21.5W 100 KT 115 MPH 12H 15/1200Z 40.1N 17.7W 90 KT 105 MPH 24H 16/0000Z 45.7N 13.8W 80 KT 90 MPH...POST-TROP/EXTRATROP 36H 16/1200Z 51.4N 10.6W 70 KT 80 MPH...POST-TROP/EXTRATROP 48H 17/0000Z 56.0N 7.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 18/0000Z 60.0N 2.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 19/0000Z...DISSIPATED $$ Forecaster Brown NNNN