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Hurricane Ophelia Forecast Discussion Number 23
2017-10-14 22:37:32| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sat Oct 14 2017 000 WTNT42 KNHC 142037 TCDAT2 Hurricane Ophelia Discussion Number 23 NWS National Hurricane Center Miami FL AL172017 500 PM AST Sat Oct 14 2017 Ophelia continues to have an impressive appearance in satellite imagery. The eye has remained clear all afternoon, surrounded by a very symmetric ring of cold cloud tops. Since the cloud pattern has not changed significantly over the past few hours, the intensity has been held at 100 kt. Microwave imagery and scatterometer retrievals indicate that beneath the cold canopy, Ophelia's structure is beginning to deteriorate, at least slightly. A GMI overpass around 1700 UTC indicated that the vortex is beginning to tilt toward the east with height, probably a result of increasing southwesterly shear associated with a large upper-level trough to the west. Furthermore, a pair of earlier ASCAT passes suggested that an approaching cold front is already infringing on the NW quadrant of the circulation, within about 80 n mi of Ophelia's eye. Given the close proximity of the cold front and upper-level trough, extratropical transition will likely begin within about 12 hours. A favorable baroclinic environment may allow the cyclone to deepen as the wind field increases in size, so only a slight decrease of the maximum wind is expected through 36 hours. After that time, the post-tropical cyclone will likely occlude and interact with land, causing a faster rate of weakening and resulting in the eventual dissipation of the surface circulation in about 96 hours. Ophelia continues to pick up forward speed and the initial motion estimate is now 055/24 kt. The hurricane remains embedded within the southwesterly flow ahead of the aforementioned mid-latitude trough, and this will keep Ophelia on a northeast or north-northeast heading through the next 72 hours. The track guidance remains in fairly good agreement, though it has shifted southward a little for the first 24 hours. The new NHC track forecast has been adjusted in that direction, and is close to the GFS/ECMWF consensus throughout the forecast period. 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. Individuals 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 after Ophelia passes to the south and east tonight as a cold front moves through the islands. 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 14/2100Z 35.9N 23.7W 100 KT 115 MPH 12H 15/0600Z 38.0N 20.0W 95 KT 110 MPH 24H 15/1800Z 42.8N 15.3W 85 KT 100 MPH 36H 16/0600Z 48.8N 12.3W 75 KT 85 MPH...POST-TROP/EXTRATROP 48H 16/1800Z 54.0N 9.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 17/1800Z 59.5N 3.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 18/1800Z...DISSIPATED $$ Forecaster Zelinsky
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