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Tropical Storm Helene Forecast Discussion Number 33
2018-09-15 16:35:06| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Sep 15 2018 582 WTNT43 KNHC 151435 TCDAT3 Tropical Storm Helene Discussion Number 33 NWS National Hurricane Center Miami FL AL082018 1100 AM AST Sat Sep 15 2018 The cloud pattern of Helene is starting to show signs of decay, with the central convection decreasing since the previous advisory and the low-level center becoming partly exposed in a region between convective bands. The initial intensity is held at 60 kt for this advisory in best agreement with the CIMSS satellite consensus, but it is possible this is generous. The 34-kt wind radii in the southeastern quadrant were revised based on a partial ASCAT pass. Helene is moving toward colder water and into an area of strong shear associated with the mid-latitude westerlies. This should cause the system to weaken and, as it merges with a frontal system, become an extratropical cyclone in about 36 h. The global models forecast Helene to be absorbed into a large non-tropical low over the far north Atlantic after it passes Ireland and the United Kingdom, and thus the system is forecast to dissipate completely between 72-96 h. Helene has turned northeastward with the initial motion now 035/18. A faster motion toward the northeast should occur during the remainder of the cyclone's life as it becomes more embedded in the westerlies. On the forecast track, Helene should pass near or over the western Azores later today or tonight, and head toward Ireland and the United Kingdom late this weekend and early next week. There are no significant changes to either the track guidance or the official forecast track since the last advisory. Tropical storm conditions should spread over portions of the Azores during the next several hours and continue through tonight. Helene is also expected to be a storm-force post-tropical cyclone when it approaches Ireland and the United Kingdom in two to three 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 15/1500Z 38.8N 34.0W 60 KT 70 MPH 12H 16/0000Z 40.8N 31.4W 60 KT 70 MPH 24H 16/1200Z 43.0N 27.2W 55 KT 65 MPH 36H 17/0000Z 45.5N 21.6W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 17/1200Z 49.0N 15.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 18/1200Z 59.0N 1.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 19/1200Z...DISSIPATED $$ Forecaster Beven
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