143 
 WTNT41 KNHC 171436
 TCDAT1
 
 TROPICAL DEPRESSION SIX DISCUSSION NUMBER   3
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
 1100 AM AST WED AUG 17 2016
 
 The depression's overall cloud pattern and low-level wind field have
 continued to improve, although cloud tops have warmed considerably
 near the center since the previous advisory. An 1139Z ASCAT-B
 overpass showed a well-defined low-level circulation center with a
 tight radius of maximum winds of only 10-15 nmi. Although there were
 a few vectors near tropical storm force, and satellite estimates at
 1200Z were T2.5/35 kt from TAFB and SAB, the intensity is being
 maintained at 30 kt for this advisory due to the sharp decrease in
 deep convection near the center during the past few hours.
 
 The modest northeasterly vertical wind shear across the cyclone is
 forecast to weaken and veer to the southeast during the next 12
 hours, and remain less than 10 kt for the next 36-48 hours, which
 typically favors strengthening. Sea-surface temperatures just below
 27C are marginal for intensification and the small cyclone will be
 moving through dry mid-level air with humidity values dropping below
 50 percent by 48 hours and beyond, conditions that are generally not
 conducive for significant strengthening. But given the tight
 inner-core wind field noted in recent ASCAT data, the cyclone is
 expected to be able to mix out any dry air intrusions and slowly
 strengthen for about the next 48 hours. By 72 hours and beyond,
 however, increasing southwesterly to westerly wind shear is expected
 to induce gradual weakening. The official intensity forecast is
 similar to the previous advisory and closely follows the intensity
 consensus model IVCN.
 
 The initial motion estimate is 300 /13 kt, based primarily on
 microwave and scatterometer fixes. The NHC model guidance is in
 good agreement on the cyclone moving west-northwestward to
 northwestward toward a weakness in the Bermuda-Azores ridge for the
 next 48 hours or so. After that, however, there is significant
 divergence in the models with the GFDL, GFS, and GFS-ensemble mean
 models taking a stronger and more vertically deep cyclone more
 toward the northwest, whereas the HWRF, UKMET, NAVGEM, and ECMWF
 models show a weaker and shallower cyclone turning more westward
 and moving along the southern periphery of the low-level ridge. As
 a result, the forecast track depends heavily on the strength and
 vertical structure of the cyclone. The new NHC forecast track is a
 little to the south or left of the previous advisory, but not nearly
 as far south as the ECMWF model due to expectations that the cyclone
 will not weaken nearly as much as that model is indicating.
 
 The forecast wind radii were decreased somewhat based on the smaller
 wind field depicted in recent ASCAT data.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  17/1500Z 14.0N  36.4W   30 KT  35 MPH
  12H  18/0000Z 14.9N  37.7W   35 KT  40 MPH
  24H  18/1200Z 16.0N  39.3W   40 KT  45 MPH
  36H  19/0000Z 17.0N  40.7W   45 KT  50 MPH
  48H  19/1200Z 17.9N  42.3W   50 KT  60 MPH
  72H  20/1200Z 19.6N  45.9W   45 KT  50 MPH
  96H  21/1200Z 21.8N  49.8W   40 KT  45 MPH
 120H  22/1200Z 23.9N  53.4W   35 KT  40 MPH
 
 $$
 Forecaster Stewart