840 
 WTNT44 KNHC 282055
 TCDAT4
 
 TROPICAL DEPRESSION NINE DISCUSSION NUMBER   1
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016
 500 PM EDT SUN AUG 28 2016
 
 Data from a NOAA Hurricane Hunter aircraft indicate that the area of
 low pressure located in the Florida Straits now has a well-defined
 center.  Satellite imagery shows a significant increase in the
 convective organization today, and as a result the system is now
 classified as a tropical cyclone.  The initial intensity is set to
 30 kt based on the highest believable wind data from the aircraft,
 which reported a central pressure of 1009 mb.
 
 The depression will be moving through a marginal environment for
 intensification during the next day or so, with vertical shear of
 15 to 20 kt.  As a result only slow strengthening is expected in
 the short term.  Later on, the environment may improve a little as
 the shear is forecast to decrease somewhat and become
 southwesterly, which should allow for a little more strengthening.
 However, there are mixed signals in the model guidance, with the
 ECMWF now showing the cyclone dissipating in the Gulf, while the
 GFS delays development until 4-5 days.  Much of the tropical
 cyclone guidance is more aggressive.  Given this uncertainty, the
 NHC intensity forecast is quite conservative and shows the system
 peaking at 45 kt, below all the explicit intensity guidance in
 consideration of the negative signal from the ECMWF.  Needless to
 say, the confidence in the intensity forecast is even lower than
 usual for this system.
 
 The initial motion estimate is an uncertain 270/09 given the recent
 formation of the center.  The cyclone will be steered in the short
 range by a mid-level ridge centered over the southeastern United
 States.  This ridge will weaken in 2-3 days, which will cause the
 cyclone to slow down and turn northward during this time.  Late in
 the period a northeastward acceleration is expected ahead of an
 approaching mid-latitude trough.  There is reasonable agreement in
 the track of the cyclone in the global model guidance, although
 there is a fair bit of along-track spread late in the period.  The
 NHC forecast is close to a consensus of the GFS and ECMWF through
 day 4 and is a little faster than the GFS and GEFS ensemble mean at
 day 5.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  28/2100Z 23.7N  81.7W   30 KT  35 MPH
  12H  29/0600Z 23.9N  83.6W   30 KT  35 MPH
  24H  29/1800Z 24.3N  85.4W   35 KT  40 MPH
  36H  30/0600Z 24.6N  86.8W   35 KT  40 MPH
  48H  30/1800Z 25.1N  87.6W   40 KT  45 MPH
  72H  31/1800Z 26.8N  87.4W   45 KT  50 MPH
  96H  01/1800Z 29.0N  84.5W   45 KT  50 MPH
 120H  02/1800Z 31.0N  80.0W   45 KT  50 MPH
 
 $$
 Forecaster Brennan