Official Discussion issued by the National Hurricane Center

Helene (AL082018) DATA RELEASED: 9/14/2018 5:00:00 AM UTC

Copy of official data

Tropical Storm Helene Discussion Number  28
NWS National Hurricane Center Miami FL       AL082018
500 AM AST Fri Sep 14 2018

Helene is looking increasingly like an extratropical cyclone, with
a rain shield extending from its northwest quadrant and a line of
clouds to the southeast, probably associated with a convergence
zone, that looks like a developing a front. However, earlier ASCAT
data suggested that the cyclone still had a compact wind field with
maximum winds of around 55 kt on the west side, and the most recent
available AMSU data still showed a distinct warm core.

The extratropical transition (ET) process will likely be completed
within the next 48 h, around the time that Helene will likely pass
near or over the Azores. While this process occurs, little weakening
is forecast by the various dynamical models, but gradual weakening
should occur once ET is completed. By the end of the forecast
period, nearly all of the global models depict the cyclone being
absorbed into a larger mid-latitude low pressure system over the far
northeast Atlantic.

Helene continues to accelerate northward, and the initial motion is
010/20 kt. Almost no change has been made to the track forecast.
Helene is still forecast to move quickly northward to
north-northeastward between a mid-level ridge to its east and a
sharp mid-latitude trough to its west.  A northeastward turn should
occur over the weekend as Helene reaches the northern extent of the
ridge and becomes embedded within the mid-latitude westerlies. The
official track forecast remains near the various consensus aids.

The government of Portugal has issued an orange wind warning for
the Azores, equivalent to a tropical storm warning.  Tropical Storm
conditions with gusty winds and heavy rains are likely over the
weekend as Helene passes the islands, regardless of whether the
cyclone is a tropical storm or post-tropical.

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  Local forecasts and
warnings for Ireland can be found on the website of Met Eireann at


INIT  14/0900Z 30.6N  36.0W   55 KT  65 MPH
12H  14/1800Z 33.4N  35.3W   55 KT  65 MPH
24H  15/0600Z 36.7N  33.8W   55 KT  65 MPH
36H  15/1800Z 39.3N  30.8W   55 KT  65 MPH
48H  16/0600Z 41.3N  26.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
72H  17/0600Z 45.5N  17.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
96H  18/0600Z 51.5N   8.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  19/0600Z...DISSIPATED

Forecaster Zelinsky