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Hurricane Rosa Discussion Number   8
NWS National Hurricane Center Miami FL       EP202018
900 PM MDT Wed Sep 26 2018

During the past several hours, the convective pattern of Rosa has
become more symmetric, and perhaps an eye is trying to emerge in the
last few satellite images.  Overall, Rosa appears somewhat stronger
than the past advisory, so the initial wind speed is slightly raised
to 75 kt- near the TAFB Dvorak estimate and the CIMSS ADT.

The hurricane has been steadily strengthening over the past day,
and, with conducive atmospheric and oceanic conditions in the
forecast for the next couple of days, this trend should continue.
A more rapid intensification period is possible if the inner core
becomes better defined.  Curiously, the intensity guidance has come
in lower than the last cycle, despite no obvious inhibiting factors
from all of the global models. I'd rather keep the high forecast of
my predecessor until the reasons for this lower peak intensity
become clear.  In addition, the corrected-consensus guidance is
higher than the rest of the aids, supporting the stronger forecast.
By day 3 weakening should commence as Rosa moves over cooler waters,
and rapid weakening is possible by the end of the forecast while the
cyclone encounters high shear over quite cool waters.

Rosa has turned westward, now moving at about 10 kt.  A mid-level
high over the southwestern United States should steer the hurricane
on this general course for the next day or so.   After that time,
the high shifts eastward due to a series of troughs approaching the
west coast of the United States, causing Rosa to gradually turn
toward the northwest by Friday, north on Saturday and to the
northeast by Monday.  There are still some pretty large speed
differences in the models at long range, with the GFS-based guidance
a lot faster than the ECMWF or UKMET models and their ensembles.
There are no obvious reasons to favor either solution at this time,
so the track forecast will stay close to the dynamical model
consensus and the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 16.9N 113.1W   75 KT  85 MPH
 12H  27/1200Z 17.0N 114.6W   90 KT 105 MPH
 24H  28/0000Z 17.1N 116.2W  100 KT 115 MPH
 36H  28/1200Z 17.6N 117.4W  105 KT 120 MPH
 48H  29/0000Z 18.4N 118.2W  110 KT 125 MPH
 72H  30/0000Z 21.2N 119.2W   90 KT 105 MPH
 96H  01/0000Z 24.6N 118.6W   70 KT  80 MPH
120H  02/0000Z 28.0N 116.0W   45 KT  50 MPH

$$
Forecaster Blake

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