ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM

HURRICANE GUILLERMO DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092015
200 PM PDT FRI JUL 31 2015

The satellite presentation has improved a little more during past
few hours. Although the eye is much better defined on microwave, it
is not completely clear on visible or infrared imagery. The average
of intensity estimates from TAFB, SAB and objective numbers from
UW-CIMSS suggests an initial intensity of 90 kt. The current
environment of low shear and a warm ocean is quite favorable for
Guillermo to intensify further in the short term, and the NHC
forecast brings the winds up to 100 kt within 12 hours.  Beyond two
days, the hurricane will begin to move into a less favorable shear
environment as Guillermo approaches prevailing upper-level
westerlies. By the end of the forecast period, when Guillermo is
expected to be nearing the Hawaiian Islands, most of the guidance
indicate that Guillermo should have weakened to a tropical storm,
and so does the NHC forecast.

The hurricane continues to move west-northwestward or 285 degrees at
16 kt. Guillermo will likely continue at this fast pace for
another 24 to 36 hours while embedded within a layer of deep
easterlies to the south of the subtropical ridge. After that time,
the hurricane is expected to slow down as it approaches the
southwestern edge of the subtropical ridge and encounters weaker
steering currents. The latest multi-model consensus GFEX has
shifted considerably northward primarily due to the fact that the
ECMWF changed its tune, and is now closer to the northernmost GFS.
On this basis, the NHC forecast is adjusted northward a little bit,
but not as much as the consensus, in case the ECMWF changes its tune
again tonight. The NHC forecast is on southern edge of the guidance
envelope, and perhaps will have to be adjusted farther northward
when new model runs become available.


FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 12.7N 134.8W   90 KT 105 MPH
 12H  01/0600Z 13.3N 137.2W  100 KT 115 MPH
 24H  01/1800Z 14.0N 140.1W  100 KT 115 MPH
 36H  02/0600Z 14.8N 142.3W   90 KT 105 MPH
 48H  02/1800Z 15.5N 144.3W   80 KT  90 MPH
 72H  03/1800Z 17.0N 147.0W   65 KT  75 MPH
 96H  04/1800Z 18.5N 150.0W   60 KT  70 MPH
120H  05/1800Z 19.5N 153.0W   50 KT  60 MPH

$$
Forecaster Avila

NNNN