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Hurricane Rosa Discussion Number   6
NWS National Hurricane Center Miami FL       EP202018
900 AM MDT Wed Sep 26 2018

Rosa is undergoing rapid intensification.  Rosa's inner core has
quickly consolidated, indicated by a 1134 UTC SSMI/S image that
showed a solid mid-level ring with a strong well-developed banding
feature in the south semicircle.  The lower frequency image from
the pass indicated a small break in the north portion, probably due
to the drier air and northeasterly shear that had been inhibiting
the cyclone's cloud pattern last night.  Based on the conventional
and microwave imagery presentation, the initial intensity is raised
to 65 kt.

Rosa should continue on this fast strengthening trend during the
next 12 hours or so.  Afterward, further intensification, at a
slower pace, is expected during the next couple of days.  Through
the remaining portion of the forecast, gradual weakening is expected
as a result of decreasing sea surface temperatures, increasing
southwesterly vertical shear, and an invading stable, more drier,
marine layer air mass.

The initial motion is estimated to be west-northwestward, or 290/9
kt, within the easterly mid-tropospheric flow produced by a
ridge to the north of the hurricane.  Around mid-period, the
large-scale models show a weakness developing the in the
aforementioned ridge in response to a mid-latitude trough
approaching the southwest U.S. and Baja California peninsula.  As a
result of this synoptic pattern change, Rose should move
northwestward Saturday and then north-northwestward Sunday.  The
large along and cross-track spread recognized in the guidance 24
hours ago has decreased significantly, increasing the forecast
confidence some beyond 48 hours.  The NHC forecast is fairly close
to the previous one, and is based primarily on the multi-model
consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 16.1N 111.4W   65 KT  75 MPH
 12H  27/0000Z 16.4N 112.7W   90 KT 105 MPH
 24H  27/1200Z 16.6N 114.6W  100 KT 115 MPH
 36H  28/0000Z 16.8N 116.2W  105 KT 120 MPH
 48H  28/1200Z 17.3N 117.5W  110 KT 125 MPH
 72H  29/1200Z 19.2N 119.5W  105 KT 120 MPH
 96H  30/1200Z 22.0N 120.2W   85 KT 100 MPH
120H  01/1200Z 24.9N 119.0W   60 KT  70 MPH

$$
Forecaster Roberts

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