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Hurricane ROSA


Hurricane Rosa Discussion Number  14...Corrected
NWS National Hurricane Center Miami FL       EP202018
800 AM PDT Fri Sep 28 2018

Corrected typo in second paragraph.

Cloud tops surrounding the distinct eye of Rosa have warmed
considerably over the past few hours.  A recent SSMI overpass
showed a distinct double eyewall structure, and this is likely the
reason for the degradation of Rosa's appearance.  Dvorak intensity
estimates from TAFB and SAB have decreased as a result, and the
initial intensity has been therefore decreased to 120 kt.  Given
the continued warming of cloud tops since 1200 UTC, it is possible
that Rosa has weakened a little more than this.

Since an eyewall replacement cycle is ongoing, Rosa is no longer
expected to intensify.  In the short term, some additional
weakening is likely, typical of major hurricanes undergoing eyewall
replacements.  If this process completes within the next 24 hours,
there will be some opportunity for the hurricane to re-intensify
while the shear is low and the hurricane remains over warm SSTs.
However, steady weakening is anticipated beginning Saturday night
since the cyclone is forecast to cross over much cooler SSTs. By 96
h, a weaker Rosa will likely approach the northern west coast of
the Baja California peninsula and the resulting interaction with
land will likely cause the cyclone to dissipate.  It is worth
noting that a farther northwest track would likely result in Rosa
weakening faster than currently indicated, while a farther
southeast track could allow Rosa to maintain a slightly stronger
circulation as it crosses the northern Gulf of California.

Rosa has begun its long-anticipated turn toward the northwest, and
the initial motion estimate is 315/6 kt.  The track models remain
in good agreement that Rosa will gradually turn toward the north,
and then north-northeast over the next few days ahead of an
approaching mid- to upper-level trough to the northwest.  No
significant changes were made to the official track forecast, but
it has been adjusted slightly to the left (or northwest) at most
times, in line with the latest consensus guidance.

Even though the NHC forecast calls for the surface circulation of
Rosa to dissipate after making landfall along the northern Baja
California coast, its associated moisture is expected to spread
northeastward through parts of the southwest United States.  For
more information about potential rainfall in that area, please see
products from the Weather Prediction Center and your local NWS
forecast office.


INIT  28/1500Z 17.2N 117.5W  120 KT 140 MPH
 12H  29/0000Z 17.8N 118.1W  110 KT 125 MPH
 24H  29/1200Z 19.2N 118.6W  105 KT 120 MPH
 36H  30/0000Z 21.0N 118.9W   95 KT 110 MPH
 48H  30/1200Z 23.0N 118.8W   80 KT  90 MPH
 72H  01/1200Z 26.7N 117.4W   55 KT  65 MPH
 96H  02/1200Z 31.6N 115.0W   35 KT  40 MPH...INLAND
120H  03/1200Z...DISSIPATED

Forecaster Zelinsky