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HURRICANE JIMENA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132015
800 AM PDT SAT AUG 29 2015

Convective cloud tops in the central dense overcast have warmed
since the last advisory, but the 10-15 n mi wide eye remains
distinct.  An 0913 UTC GCOM overpass clearly indicated that the
formation of a secondary outer eyewall was almost complete, which
could be a harbinger that Jimena will soon go through an eyewall
replacement.  Dvorak Current Intensity estimates at 1200 UTC were
6.0/115 kt from TAFB, 6.5/127 kt from SAB, and 6.8/135 kt from the
CIMSS ADT, and the initial intensity is held at 130 kt.

This advisory continues to show the possibility of Jimena reaching
category 5 intensity during the next 24 hours since the environment
remains conducive for strengthening.  However, if Jimena does go
through an eyewall replacement soon, then fluctuations in intensity
are likely to occur, and the hurricane could actually weaken a bit
in the short term.  The intensity forecast is somewhat challenging
after 24 hours.  Vertical shear is expected to remain low, and sea
surface temperatures remain above 26C through the forecast period,
but the hurricane models show a general decay to a category 1 or 2
cyclone by day 5.  On the other hand, the global models,
particularly the GFS and ECMWF, seem to take more advantage of the
favorable environment and retain central pressures that would
support a category 3 or 4 hurricane through day 5.  Therefore, the
NHC intensity forecast shows a much slower decay than indicated by
the hurricane models, keeping Jimena as a major hurricane through
day 4.

Jimena's eye has been wobbling around, but the longer-term motion
estimate is 275/7 kt.  The ridge to the north of the hurricane
appears to be weakening, and Jimena is expected to turn
west-northwestward later today.  This trajectory should continue
through day 5, with a decrease in forward speed by days 4 and 5
when the steering currents become much weaker.  The track guidance
is still in good agreement on the future track, and the updated NHC
forecast is similar to, but slightly faster than, the previous
forecast after 24 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 12.5N 125.6W  130 KT 150 MPH
 12H  30/0000Z 13.0N 127.0W  135 KT 155 MPH
 24H  30/1200Z 13.9N 129.1W  140 KT 160 MPH
 36H  31/0000Z 14.7N 131.5W  135 KT 155 MPH
 48H  31/1200Z 15.4N 133.9W  130 KT 150 MPH
 72H  01/1200Z 16.5N 137.9W  115 KT 130 MPH
 96H  02/1200Z 17.1N 140.5W  100 KT 115 MPH
120H  03/1200Z 17.6N 142.1W   90 KT 105 MPH

$$
Forecaster Berg

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