623 
 WTPZ44 KNHC 312036
 TCDEP4
 
 TROPICAL STORM ISELLE DISCUSSION NUMBER   1
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092014
 200 PM PDT THU JUL 31 2014
 
 Deep convection has been wrapping up quickly during the past few
 hours near the low pressure system located near 122W, and TAFB and
 SAB have both provided Dvorak estimates of T2.0/30 kt.  In
 addition, a partial 1800 UTC ASCAT-B pass indicated that the low is
 already producing winds to tropical storm force in the eastern
 semicircle.  Therefore, advisories are being initiated on Tropical
 Storm Iselle, and the maximum winds are conservatively set at 35 kt.
 
 With sea surface temperatures ahead of Iselle running between
 27-28C and vertical shear not expected to be a significant limiting
 factor, the storm is forecast to strengthen for at least the next 3
 days.  The strengthening rate could be quick for the next day or so,
 with the SHIPS rapid intensification index showing a 44 percent
 chance of a 25-kt increase in winds by this time tomorrow.  The
 SHIPS guidance is the most aggressive of the intensity models and
 brings Iselle to hurricane status within the next 24-36 hours.  The
 NHC official intensity forecast is not as high as the SHIPS model,
 but since the environment looks favorable for strengthening, it does
 lie a little above the intensity consensus ICON.
 
 Iselle is located to the south of a mid-level ridge which extends
 from northwestern Mexico southwestward to near 20N140W, and the
 cyclone's estimated initial motion is 295/9 kt.  In general, ridging
 is expected to maintain a relatively steady west-northwestward
 motion for the next several days.  Some slight decrease in forward
 speed is possible by day 4 when a weakness develops within the ridge
 near 135W and ridging strengthens near the Hawaiian Islands.  The
 track guidance is tightly clustered for this forecast, and the NHC
 track forecast lies very close to the multi-model consensus TVCE.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  31/2100Z 12.7N 122.3W   35 KT  40 MPH
  12H  01/0600Z 13.4N 123.5W   45 KT  50 MPH
  24H  01/1800Z 14.2N 125.0W   55 KT  65 MPH
  36H  02/0600Z 14.8N 126.7W   60 KT  70 MPH
  48H  02/1800Z 15.1N 128.3W   65 KT  75 MPH
  72H  03/1800Z 16.0N 132.0W   70 KT  80 MPH
  96H  04/1800Z 16.0N 135.0W   65 KT  75 MPH
 120H  05/1800Z 16.0N 138.0W   60 KT  70 MPH
 
 $$
 Forecaster Berg