724 
 WTPZ43 KNHC 280255
 TCDEP3
 
 TROPICAL STORM JIMENA DISCUSSION NUMBER   6
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132015
 800 PM PDT THU AUG 27 2015
 
 Jimena has continued to rapidly intensify. Several convective bands
 are tightly coiled and wrapping into the center where a small
 central dense overcast feature has developed during the past couple
 of hours. Upper-level outflow is nearly symmetrical and continues
 to expand. The initial intensity of 60 kt is based on a blend of
 consensus Dvorak satellite intensity estimates of T3.5/55 kt from
 TAFB and SAB, and a UW-CIMSS ADT value of T3.9/63 kt.
 
 The initial motion estimate is 270/12 kt. There is no significant
 change to the previous track forecast or reasoning. The NHC model
 guidance is tightly packed about the previous forecast track, and
 Jimena is expected to move westward along the southern periphery of
 a strong subtropical ridge for the next 36-48 hours. After that
 time, a turn toward the west-northwest accompanied by a decrease in
 forward speed is expected as a mid-latitude trough digs southward
 along 130-135W longitude, weakening the ridge and the steering
 currents. The new forecast track is essentially just an extension of
 the previous advisory track.
 
 Jimena has been rapidly intensifying for the past 24 hours, so the
 question now is how long will Jimena continue this develop trend.
 The surrounding atmospheric and oceanic environments are quite
 conducive for additional strengthening.  Recent SSMI and SSMI/S
 microwave satellite images indicate that a nearly closed eye of
 15-20 nmi diameter has formed in the low- and mid-levels, which
 favors continued rapid strengthening. Those same images also
 indicated that dry mid-level air had wrapped into the northern
 semicircle and had penetrated the inner-core convective region,
 which could hinder development. However, this hindering factor
 should be short lived given the very robust circulation noted in
 conventional satellite imagery, which should quickly mix out any
 dry. air intrusions. Therefore, since the vertical wind shear is
 forecast to remain less than 10 kt, rapid intensification is
 forecast to continue for another 36 hours or so. After that time,
 the expected intense circulation of Jimena should begin to create
 cold upwelling since the cyclone will be moving over significantly
 lower upper ocean heat content values, which should cap the
 intensification process and induce slow weakening by days 4 and 5.
 The official intensity forecast is similar to the previous advisory,
 and lies between the forecasts of the SHIPS and LGEM models, which
 have performed quite well thus far with Jimena.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  28/0300Z 12.3N 119.9W   60 KT  70 MPH
  12H  28/1200Z 12.3N 121.7W   75 KT  85 MPH
  24H  29/0000Z 12.4N 123.7W   90 KT 105 MPH
  36H  29/1200Z 12.6N 125.6W  105 KT 120 MPH
  48H  30/0000Z 13.2N 127.3W  110 KT 125 MPH
  72H  31/0000Z 14.8N 131.7W  125 KT 145 MPH
  96H  01/0000Z 16.5N 136.0W  120 KT 140 MPH
 120H  02/0000Z 17.5N 139.0W  110 KT 125 MPH
 
 $$
 Forecaster Stewart