062 
 WTNT44 KNHC 290253
 TCDAT4
 
 TROPICAL DEPRESSION NINE DISCUSSION NUMBER   2
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016
 1100 PM EDT SUN AUG 28 2016
 
 Flight-level wind data from an earlier NOAA reconnaissance mission
 along with WSR-88D Doppler radar data from Key West indicate that
 the depression had been moving southwestward between 1800-0000 UTC.
 However, the most recent radar data and nearby surface observations
 suggest that the cyclone has now turned toward the west. The last
 reliable wind data from the NOAA WP-3 recon aircraft supported an
 intensity of 30 kt, and that intensity is being maintained for this
 advisory given that the radar and satellite signatures haven't
 improved. The central pressure of 1007 mb is based on a reliable
 observation from ship WMKN, located just north of the center.
 
 The initial motion estimate is 270/08 kt. Now that deep convection
 has waned, the system has turned westward and this motion is
 expected to continue for the next 24 hours or so. This short term
 motion is supported by NOAA recon dropsonde data on the return leg
 home, which indicated that 500 mb heights were 10-20 meters higher
 over the southeastern Gulf of Mexico than what the global models
 have been forecasting. After that time, the global and regional
 models are in surprisingly good agreement on the cyclone slowing
 down and turning toward the west-northwest and then northward in the
 36- to 48-hour periods as the depression moves around the western
 periphery of a narrow subtropical ridge that is expected to be
 located over the Bahamas and South Florida at that time. By 72 hours
 and beyond, the tropical cyclone is forecast to lift out and
 accelerate to the northeast as a shortwave trough over the western
 Great Lakes digs southeastward and captures the depression. The new
 NHC forecast track has been shifted to the right of the previous
 advisory track mainly due to the more southerly initial position,
 and lies a little to the left of the consensus model TVCN.
 
 Strong vertical shear that has been plaguing this system for the
 past week is expected to gradually subside to less than 10 kt in
 18-24 hours, which should allow for more organized deep convection
 to develop. However, the southerly low-level inflow will still be
 disrupted by the terrain of western Cuba until the cyclone moves
 west of 85W longitude, which will then provide a straight trajectory
 across the Yucatan Channel and into the low-level center. By 36
 hours and beyond, the depression will moving over SSTs greater
 than 30C and the light vertical wind shear is expected to back
 around from a northerly to a southwesterly direction, which usually
 favors more significant intensification. However, dry air in the
 mid-/upper-levels noted in the recent 0000 UTC soundings from Key
 West northward to the Gulf coast is expected be entrained into the
 northwestern semicircle of the cyclone's circulation by 48 hours
 and beyond, and this appears to be the main inhibiting factor to
 strengthening by the global models. Given these mixed signals, the
 NHC intensity forecast remains conservative and closely follows the
 intensity model IVCN. The confidence in the intensity forecast
 remains lower than usual for this system.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  29/0300Z 23.4N  82.7W   30 KT  35 MPH
  12H  29/1200Z 23.5N  84.0W   30 KT  35 MPH
  24H  30/0000Z 23.8N  85.4W   35 KT  40 MPH
  36H  30/1200Z 24.4N  86.8W   35 KT  40 MPH
  48H  31/0000Z 25.1N  87.1W   40 KT  45 MPH
  72H  01/0000Z 27.0N  86.3W   45 KT  50 MPH
  96H  02/0000Z 29.1N  82.9W   50 KT  60 MPH
 120H  03/0000Z 31.2N  78.3W   50 KT  60 MPH
 
 $$
 Forecaster Stewart