163 
 WTNT43 KNHC 140852
 TCDAT3
 
 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 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  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