459 
 WTPZ43 KNHC 271442
 TCDEP3
 
 TROPICAL STORM JIMENA DISCUSSION NUMBER   4
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132015
 800 AM PDT THU AUG 27 2015
 
 Jimena is steadily becoming better organized with deep convection
 persisting near the center and more pronounced banding developing
 around the circulation.  The initial intensity is 40 kt based on
 Dvorak estimates of T2.5/35 kt from TAFB and T3.0/45 kt from SAB.
 Embedded in an environment of low shear, high moisture, and very
 warm ocean water, Jimena should have no problems continuing to
 intensify.  In fact, rapid intensification (RI) is a distinct
 possibility during the next 24 hours.  A low-level inner core ring
 was noted in the 37-GHz channel of a 0946 UTC GPM microwave pass,
 and the SHIPS RI index is showing a 1 in 3 chance of a 30-kt
 intensity change during the next 24 hours.  Therefore, the NHC
 intensity forecast shows Jimena becoming a hurricane on Friday.
 After 24 hours, the overall environment should remain favorable for
 strengthening, and Jimena is forecast to be a major hurricane from
 day 3 through day 5.  The updated NHC intensity forecast is a
 little higher than the IVCN intensity consensus and shows a bit
 more strengthening than the previous forecast through 96 hours.
 
 The storm has been moving quickly west-northwestward with a 12-hour
 motion of 285/15 kt.  A strong deep-layer ridge extends from
 northwestern Mexico to just east of the Hawaiian Islands, and this
 feature should steer Jimena generally westward during the next 48
 hours.  A weakness is expected to develop in the ridge by 72 hours,
 which should turn the cyclone west-northwestward through day 5.  The
 track guidance has shifted slightly southward during the first 48
 hours, and the updated NHC track forecast follows suit but still
 lies a little north of the model consensus.  The updated forecast is
 largely unchanged from the previous one after 48 hours.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  27/1500Z 12.4N 117.7W   40 KT  45 MPH
  12H  28/0000Z 12.7N 119.7W   50 KT  60 MPH
  24H  28/1200Z 13.0N 122.1W   65 KT  75 MPH
  36H  29/0000Z 13.1N 124.2W   80 KT  90 MPH
  48H  29/1200Z 13.1N 126.1W   90 KT 105 MPH
  72H  30/1200Z 13.9N 129.6W  105 KT 120 MPH
  96H  31/1200Z 15.5N 134.0W  115 KT 130 MPH
 120H  01/1200Z 17.0N 137.5W  115 KT 130 MPH
 
 $$
 Forecaster Berg