314 
 WTNT42 KNHC 181454
 TCDAT2
 
 TROPICAL STORM KARL DISCUSSION NUMBER  17
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
 1100 AM AST SUN SEP 18 2016
 
 The overall appearance of Karl has changed little in satellite
 imagery since the previous advisory.  However, recent water vapor
 imagery suggest that the strong southwesterly shear that has been
 plaguing the cyclone for the past few days is beginning to relax.
 The initial wind speed is held at 35 kt based on a TAFB satellite
 estimate of T2.5/35 kt.  Ship BATFR18, which has been skirting the
 eastern portion of Karl's circulation the past 12 hours, has
 reported winds as high as 32 kt.  That data has been helpful in
 determining the extent of the 34-kt wind radius in the northeastern
 quadrant.
 
 Karl has trended westward and the initial motion estimate is now
 270/11 kt.  A deep-layer subtropical ridge over the central Atlantic
 to the north of Karl is expected to keep the cyclone moving in a
 general westward direction for the next 48 hours or so, followed by
 west-northwestward motion during the remainder of the forecast
 period.  The new NHC track forecast is similar to the previous
 advisory, and lies close to the various consensus model solutions.
 
 Although Karl's convective pattern is currently somewhat disheveled
 due to the hostile shear and dry mid-level conditions that the
 cyclone has been encountering the past several days, the surface
 wind field has remained remarkably robust, including a tight
 inner-core.  The GFS and ECMWF models are forecasting the vertical
 wind shear to decrease to less than 5 kt from 24-120 hours, which
 favors a strengthening trend, especially since Karl will be moving
 29-30C SSTs during that time.  However, only a marginally moist
 mid-level environment is expected, a condition that could slow down
 the intensification process.  The official intensity forecast
 follows the trend of the previous advisory, showing gradual
 strengthening throughout the forecast period, and remains on the
 conservative side close to the intensity consensus model IVCN.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  18/1500Z 18.0N  43.4W   35 KT  40 MPH
  12H  19/0000Z 18.2N  45.5W   35 KT  40 MPH
  24H  19/1200Z 18.6N  48.2W   40 KT  45 MPH
  36H  20/0000Z 19.3N  50.9W   45 KT  50 MPH
  48H  20/1200Z 20.2N  53.3W   50 KT  60 MPH
  72H  21/1200Z 22.3N  58.4W   55 KT  65 MPH
  96H  22/1200Z 24.7N  63.2W   65 KT  75 MPH
 120H  23/1200Z 27.3N  66.7W   75 KT  85 MPH
 
 $$
 Forecaster Stewart