532 
 WTNT43 KNHC 081444
 TCDAT3
 
 Tropical Storm Helene Discussion Number   5
 NWS National Hurricane Center Miami FL       AL082018
 1100 AM AST Sat Sep 08 2018
 
 The structure of Helene continues to improve, with convective
 banding wrapping around almost completely around the center of the
 cyclone in visible satellite imagery.  Infrared imagery suggests
 this convection is not very strong at the moment, though, and this
 may be why recent scatterometer data indicates that the storm has
 not strengthened since the last advisory.  The initial intensity
 remains 40 kt based on the scatterometer winds.
 
 All indications are that Helene should strengthen through at least
 72 h in a light vertical shear environment over sea surface
 temperatures near 27C.  This part of the intensity forecast is
 similar to the previous forecast and lies near the intensity
 consensus.  However, there are a couple of alternate forecast
 scenarios.  The first is that Helene could rapidly intensify and
 become stronger than currently forecast.  The second is that a
 large plume of African dust and associated dry air that has spread
 over the northern Cabo Verde Islands starts entraining into the
 cyclone and inhibits intensification.  The former alternative seems
 more likely than the latter at this time, and if RI begins later
 intensity forecasts will need to be increased.  After 72 h, Helene
 is expected to encounter increasing southwesterly shear associated
 with a mid- to upper-level trough over the central Atlantic, which
 should cause the system to weaken.
 
 Helene's center appears to have again re-formed, this time a little
 to the south.  The somewhat uncertain initial motion is 265/11.
 Other than a slight nudge to the south due to the initial position,
 there is little change in the forecast track for Helene.  The
 cyclone should moved westward to west-northwestward for the next
 3-4 days on the south side of the subtropical ridge, then turn
 northwestward in response to the aforementioned trough.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  08/1500Z 13.4N  20.6W   40 KT  45 MPH
  12H  09/0000Z 13.6N  22.4W   50 KT  60 MPH
  24H  09/1200Z 13.9N  24.9W   60 KT  70 MPH
  36H  10/0000Z 14.6N  27.8W   70 KT  80 MPH
  48H  10/1200Z 15.3N  30.8W   80 KT  90 MPH
  72H  11/1200Z 17.0N  36.0W   80 KT  90 MPH
  96H  12/1200Z 19.0N  40.0W   70 KT  80 MPH
 120H  13/1200Z 22.5N  42.5W   60 KT  70 MPH
 
 $$
 Forecaster Beven