448 
 WTPZ41 KNHC 311438
 TCDEP1
 
 TROPICAL STORM VANCE DISCUSSION NUMBER   6
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212014
 800 AM PDT FRI OCT 31 2014
 
 There hasn't been a lot of significant change with the structure of
 Vance during the past several hours.  While the central convection
 has weakened some, the convection associated with a banding feature
 on the east side has increased.  Dvorak estimates are similar to 6
 hours ago, so the initial wind speed will remain 40 kt.  Vance
 continues to struggle with southwesterly shear and dry air.  Most
 of the models, however, suggest that the shear should abate over the
 weekend, with increasing moisture and upper-level divergence
 expected as well.  The latest model guidance generally shows a
 higher peak intensity, and the NHC forecast is now a bit higher at
 48-72 hours.  After that time, a significant increase in
 southwesterly shear is forecast, which will likely cause weakening
 while the cyclone approaches Mexico.
 
 The center has not been easy to track with this cyclone, but the
 latest microwave and visible satellite data suggest it has been
 creeping toward the south-southwest.  A ridge over the eastern
 Pacific is expected to move eastward over the next few days,
 steering the cyclone more steadily west-southwestward by late today,
 westward tomorrow, and to the northwest by late this weekend. Vance
 is then forecast to turn northward and then northeastward ahead of a
 trough moving over Baja California.  While the models are in good
 agreement on the overall track, there remains some spread in the
 timing of the turn toward Mexico.  The guidance is generally faster
 than the last cycle, so the updated NHC forecast follows that trend.
 Overall the forecast is also little east of the previous one, mostly
 because of the initial motion and position.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  31/1500Z 10.1N 100.8W   40 KT  45 MPH
  12H  01/0000Z  9.7N 101.7W   45 KT  50 MPH
  24H  01/1200Z  9.6N 103.2W   50 KT  60 MPH
  36H  02/0000Z 10.2N 105.2W   55 KT  65 MPH
  48H  02/1200Z 11.4N 107.0W   65 KT  75 MPH
  72H  03/1200Z 15.0N 109.3W   75 KT  85 MPH
  96H  04/1200Z 19.3N 107.9W   55 KT  65 MPH
 120H  05/1200Z 23.5N 105.0W   30 KT  35 MPH...INLAND
 
 $$
 Forecaster Blake