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Hurricane Olivia Discussion Number  16
NWS National Hurricane Center Miami FL       EP172018
200 PM PDT Tue Sep 04 2018

Olivia has continued to strengthen and now has a well-defined 15-20
n mi wide eye inside a central dense overcast.  A complex of outer
bands is also occurring in the southwestern semicircle.  The various
satellite intensity estimates have increased into the 100-110 kt
range, and thus the initial intensity is increased to 105 kt.  It
should be noted that the current intensification has occurred in an
apparent environment of 10-20 kt of easterly vertical wind shear,
as indicated by the SHIPS model and analyses from CIMSS.

As with the earlier forecast, how much additional intensification
will occur is uncertain.  The intensity guidance suggests that
continued shear and decreasing sea surface temperatures along the
forecast track will allow 12 h or less of additional strengthening,
and the guidance again forecasts only modest strengthening during
this time.  Given the persistence of the rapid intensification, the
intensity forecast will not stop intensification that abruptly, and
it now calls for a peak intensity of 110 kt in 12 h at the upper
edge of the intensity guidance.  It is still possible that Olivia
could get stronger than this.  After 12-24 h, the cooler sea surface
temperatures and entrainment of dry air should cause gradual
weakening even though the shear is forecast to decrease. This part
of the intensity forecast lies a little above the intensity
consensus.

The initial motion is 270/10, and the short-term motion may be a
little to the south of due west.  As noted previously, a
building subtropical ridge over the eastern Pacific is forecast
to induce a westward and west-northwestward motion with an
increasing forward speed during the next several days.  Near the
end of the forecast period, a more westward motion is possible.
The model guidance again supports this scenario with a tight
clustering, and the new NHC track forecast is similar to, but
slightly south of the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 16.9N 119.2W  105 KT 120 MPH
 12H  05/0600Z 17.0N 120.9W  110 KT 125 MPH
 24H  05/1800Z 17.4N 123.2W  105 KT 120 MPH
 36H  06/0600Z 18.1N 125.7W  100 KT 115 MPH
 48H  06/1800Z 19.0N 128.5W   90 KT 105 MPH
 72H  07/1800Z 21.0N 134.5W   75 KT  85 MPH
 96H  08/1800Z 22.5N 139.5W   60 KT  70 MPH
120H  09/1800Z 23.0N 144.0W   50 KT  60 MPH

$$
Forecaster Beven

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