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Tropical Storm Helene Forecast Discussion Number 31
2018-09-15 04:36:30| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Sep 14 2018 033 WTNT43 KNHC 150236 TCDAT3 Tropical Storm Helene Discussion Number 31 NWS National Hurricane Center Miami FL AL082018 1100 PM AST Fri Sep 14 2018 Data from a timely ASCAT pass indicate that Helene still carries winds of 60 kt, primarily in the eastern semicircle. The cloud pattern continues to show a low-level center just south of the main convection, marking the strong shear which is affecting the system. Guidance indicates that Helene will not change much in intensity in the next 12 hours, and only a slight decrease in the winds is anticipated after that time. The wind field is forecast to expand mainly in the southeast quadrant, which is the area of the cyclone that most likely will affect the Azores. After passing to the north of, or near, the Azores in about 24 hours, Helene will be moving over cold waters and become post-tropical. The cyclone should be absorbed by a larger extratropical low, as the cyclone quickly approaches Ireland and the United Kingdom. Satellite fixes indicate that Helene is moving toward the north-northeast or 030 degrees at about 16 kt. Helene is embedded within the fast southwesterly flow ahead of a sharp mid-level trough and this pattern should steer the cyclone toward the northeast with a gradual increase in forward speed. Track guidance is very consistent with this solution, and the NHC forecast continues in the middle of the tight guidance envelope. Helene is expected to be a post-tropical cyclone when it approaches Ireland and the United Kingdom in a few days. Interests in those locations should consult products from their local meteorological service for information about potential impacts from Helene. Local forecasts and warnings for the UK can be found on the website of the UK Met Office at https://www.metoffice.gov.uk/. Local forecasts and warnings for Ireland can be found on the website of Met Eireann at https://www.met.ie/. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 35.8N 35.8W 60 KT 70 MPH 12H 15/1200Z 38.0N 34.5W 60 KT 70 MPH 24H 16/0000Z 40.3N 31.2W 55 KT 65 MPH 36H 16/1200Z 42.5N 26.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 17/0000Z 45.0N 21.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 18/0000Z 51.5N 9.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 19/0000Z...DISSIPATED $$ Forecaster Avila
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