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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
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