380 
 WTNT43 KNHC 080850
 TCDAT3
 
 Tropical Storm Helene Discussion Number   4
 NWS National Hurricane Center Miami FL       AL082018
 500 AM AST Sat Sep 08 2018
 
 Helene's structure appears to be quickly improving this morning.
 The initial intensity has been increased to 40 kt based on a blend
 of the latest subjective Dvorak intensity estimates and the
 UW-CIMSS SATCON.  Several microwave passes overnight indicate that
 the cyclone has become more vertically aligned, likely due to a
 reformation of the center beneath the strongest convection.  In
 fact, a 0733 UTC SSMIS image shows the early development of a low-
 to mid-level eye, which is often a precursor to intensification.
 
 Nearly all of the intensity guidance seems to have picked up on the
 improved structure of Helene, and the models show far more
 intensification than before, especially through 48 h.  Consequently,
 a significant change has been made to the intensity forecast, which
 now calls for Helene to become a hurricane on Sunday while it is
 near the Cabo Verde islands.  Once the cyclone passes the islands,
 the environment is expected to remain favorable for intensification
 for at least 72 h.  By the end of the forecast period, all of the
 guidance shows some weakening due primarily to increased shear
 associated with an approaching mid- to upper-level trough over the
 central Atlantic.  Given the recent microwave imagery signature, low
 shear, and warm SSTs, its possible that the current forecast is
 still too conservative, especially for the first 36 h of the
 forecast, and further adjustments could be required if it becomes
 clear that Helene is intensifying at a faster rate than expected.
 
 Smoothing through the possible reformation of the center, Helene
 appears to be moving west with an initial motion around 275/10 kt.
 Little change was required to the track forecast, which has been
 nudged only slightly south for the first 48 h of the forecast, in
 line with the latest track model consensus.  A westward motion
 should continue for the next couple of days, as Helene is steered
 by a mid-level ridge to the north.  By day 5, the aforementioned
 trough over the central Atlantic should force Helene to turn toward
 the northwest.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  08/0900Z 13.7N  19.6W   40 KT  45 MPH
  12H  08/1800Z 13.9N  21.2W   50 KT  60 MPH
  24H  09/0600Z 14.1N  23.5W   60 KT  70 MPH
  36H  09/1800Z 14.7N  26.3W   70 KT  80 MPH
  48H  10/0600Z 15.4N  29.3W   75 KT  85 MPH
  72H  11/0600Z 17.2N  35.1W   80 KT  90 MPH
  96H  12/0600Z 19.0N  39.5W   70 KT  80 MPH
 120H  13/0600Z 22.0N  42.5W   65 KT  75 MPH
 
 $$
 Forecaster Zelinsky