001 
 WTNT43 KNHC 142035
 TCDAT3
 
 Tropical Storm Helene Discussion Number  30
 NWS National Hurricane Center Miami FL       AL082018
 500 PM AST Fri Sep 14 2018
 
 The 40-45 kt of southwesterly vertical shear has really taken its
 toll on Helene's cloud pattern.  A severe tilt toward the northeast
 is evident in conventional and microwave imagery.  Despite the
 sheared structure of the cyclone, the initial intensity is held at
 60 kt due to the earlier scatterometer pass showing that value in
 the northeast quadrant, and a 1603 UTC SATCON analysis that yields
 an intensity estimate of 58 kt.
 
 Little change in strength is forecast during the next 12 hours as
 Helene remains over 26 to 27C sea surface temperatures.  Beyond that
 brief period, the cyclone should weaken a bit as it completes
 extratropical transition while passing just to the northwest of the
 Azores Islands and traversing much cooler waters.  The European
 models and the Canadian still show Helene being absorbed by a larger
 baroclinic system in 4 days, as the cyclone quickly approaches
 Ireland and the United Kingdom.  The GFS, which earlier indicated a
 different solution resulting in Helene taking a more north-
 northeastward to northwest track around the periphery of a
 larger, complex non-tropical low, now shows Helene merging with a
 front, similar to the European and Canadian scenario.
 
 A series of recent microwave passes reveal that Helene's surface
 circulation has been tracking quite a bit to the left of the
 previous forecasts.  Consequently, an adjustment to the best track
 was made to conform more with the microwave overpasses.  The initial
 motion is estimated to be northward, or 010/16 kt.  It is also quite
 possible that there maybe some binary involvement between Helene and
 Tropical Storm Joyce that could be influencing a motion just to the
 left of track.  In any event, a north-northeast to northeast turn is
 expected over the weekend as the cyclone accelerates within the
 mid-latitude westerlies.  The NHC forecast is again adjusted to the
 left through 36 hours, due to the much welcomed microwave images,
 and is in best agreement with TVCN multi-model consensus.
 
 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  14/2100Z 34.1N  36.8W   60 KT  70 MPH
  12H  15/0600Z 36.4N  36.0W   60 KT  70 MPH
  24H  15/1800Z 38.9N  33.7W   55 KT  65 MPH
  36H  16/0600Z 41.0N  30.0W   50 KT  60 MPH
  48H  16/1800Z 43.3N  25.2W   50 KT  60 MPH...POST-TROP/EXTRATROP
  72H  17/1800Z 49.5N  12.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
  96H  18/1800Z...DISSIPATED
 
 $$
 Forecaster Roberts