945 
 WTNT42 KNHC 150832
 TCDAT2
 
 TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER   4
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
 500 AM AST THU SEP 15 2016
 
 AMSR2 microwave data from a few hours ago indicated that the
 depression's center was about a degree west of the deep convection
 due to 20 kt of westerly shear.  Since the cyclone's structure has
 not improved, and subjective Dvorak estimates have not changed from
 six hours ago, the initial intensity remains 30 kt.  The westerly
 shear is expected to increase during the next 24 hours, and with a
 relatively drier air mass surrounding the cyclone, any strengthening
 during the next couple of days now appears less likely.  After 48
 hours, the shear is forecast to relax to some degree, but the global
 models disagree on exactly how much.  Nonetheless, if the depression
 can survive the next couple of days, the environment should improve
 enough to allow for some strengthening by the end of the forecast
 period.  The new NHC intensity forecast now holds the cyclone as a
 30-kt depression for the next 3 days, followed by slight
 strengthening on days 4 and 5.  This forecast is in best agreement
 with the statistical-dynamical SHIPS and LGEM models.
 
 The microwave data indicate that the depression has been moving a
 little faster toward the west at 275/14 kt.  The Bermuda-Azores
 high is expected to steer the depression generally westward across
 the tropical Atlantic during the entire 5-day forecast period.  A
 south-of-due-west motion is even possible on days 2 and 3,
 especially if the cyclone remains weak.  With the exception of the
 GFDL, which shows more strengthening and is an outlier way to the
 north of the other models, the guidance envelope is relatively
 tight.  To account for the apparent north bias of the GFDL, the
 updated NHC track forecast is a bit south of the TVCN multi-model
 consensus.  The new forecast is also a little faster than and south
 of the previous forecast, especially on days 4 and 5.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  15/0900Z 17.6N  29.3W   30 KT  35 MPH
  12H  15/1800Z 17.8N  31.2W   30 KT  35 MPH
  24H  16/0600Z 18.0N  33.7W   30 KT  35 MPH
  36H  16/1800Z 17.9N  36.4W   30 KT  35 MPH
  48H  17/0600Z 17.6N  39.0W   30 KT  35 MPH
  72H  18/0600Z 16.7N  43.8W   30 KT  35 MPH
  96H  19/0600Z 16.5N  49.0W   35 KT  40 MPH
 120H  20/0600Z 17.0N  53.5W   40 KT  45 MPH
 
 $$
 Forecaster Berg