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HURRICANE GUILLERMO DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092015
200 AM PDT FRI JUL 31 2015

Guillermo's cloud pattern has continued to become better organized,
with well-defined convective banding and a fairly symmetric
upper-level outflow pattern.  A recent GMI microwave image showed a
nearly closed low-level eyewall.  The current intensity is set to 70
kt, based on a blend of subjective and objective Dvorak estimates.
This makes Guillermo the fifth hurricane of the 2015 eastern North
Pacific season.  Given that the hurricane should be moving over warm
waters, and in a moist mid-level environment with moderate shear,
further strengthening is likely.  The official intensity forecast
is near or above the latest model consensus.  Since the SHIPS-RI
index still indicates a significant probability of rapid
intensification over the next 24 hours, the NHC forecast could be
conservative.  There is considerable uncertainty in the intensity
forecast beyond 48-72 hours, since Guillermo could encounter
stronger shear,  depending mainly on how far north the cyclone moves
late in the forecast period.

Based on geostationary and microwave center fixes, the initial
motion is west-northwestward or 300/14 kt.  A mid-tropospheric
ridge to the north of the tropical cyclone should maintain the
west-northwestward motion for the next several days.  In 48-72
hours, Guillermo should encounter a weakness in the ridge which
will likely cause some slowing of forward speed.  However most of
the guidance does not show much of a turn to the right in response
to this weakness.  The official track forecast is close to a
consensus of the latest GFS and ECMWF solutions, with the former
model to the north of the latter near the end of the period.  This
is similar to the previous NHC track.

FORECAST POSITIONS AND MAX WINDS

INIT  31/0900Z 11.5N 130.6W   70 KT  80 MPH
 12H  31/1800Z 12.1N 132.8W   80 KT  90 MPH
 24H  01/0600Z 12.7N 135.7W   90 KT 105 MPH
 36H  01/1800Z 13.3N 138.4W   95 KT 110 MPH
 48H  02/0600Z 14.1N 140.6W   95 KT 110 MPH
 72H  03/0600Z 15.5N 144.0W   80 KT  90 MPH
 96H  04/0600Z 16.5N 146.5W   70 KT  80 MPH
120H  05/0600Z 17.5N 150.0W   55 KT  65 MPH

$$
Forecaster Pasch

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