Skip Navigation Links
NOAA NOAA United States Department of Commerce

Hurricane ROSA


Hurricane Rosa Discussion Number  19
NWS National Hurricane Center Miami FL       EP202018
200 PM PDT Sat Sep 29 2018

The strengthening trend seen earlier has at least slowed, as Rosa
has shown little change in organization since the last advisory.
The hurricane continues to have a well-defined 30-40 n mi wide eye
inside a central dense overcast with cloud tops as cold as -75C.
The various satellite intensity estimates have changed little, so
the initial intensity remains 90 kt.  The hurricane has good to
excellent cirrus outflow in the northeastern semicircle, and the
outflow has recently improved in the southwestern semicircle.

Rosa is now crossing the 26C isotherm, so additional significant
strengthening appears unlikely.  After 12 h, the combination of
decreasing sea surface temperatures and increasing shear should
cause steady to rapid weakening, and the intensity forecast
continues to call for the cyclone to weaken below hurricane strength
before the center reaches the Baja California peninsula in just
over 48 h.  After landfall, the surface circulation is forecast to
dissipate near the 72-h point in agreement with all of the dynamical
models.  However, the mid-level circulation and the associated
rainfall will continue moving across the southwestern United States
after the surface circulation dissipates.

The initial motion is 350/10.  During the forecast period, the
hurricane will recurve into the westerlies between a deep-layer
ridge over northern Mexico and a large mid- to upper-level trough
over California and the adjacent Pacific.  This should result in a
continued northward motion through tonight, followed by a turn
toward the north-northeast on Sunday.  The new forecast track is
a little to the left of the previous track for the first 12 h, but
otherwise is changed little from the previous track.  On the
forecast track, the center of Rosa or its remnants will move near or
over the central and northern portions the Baja California peninsula
on Monday and Monday night, and then move into the southwestern
United States on Tuesday.

Key Messages:

1. The main hazard expected from Rosa or its remnants is very heavy
rainfall in Baja California, northwestern Mexico, and the Desert
Southwest. These rains are expected to produce life-threatening
flash flooding and debris flows in the deserts, and landslides in
mountainous terrain.  For more information about potential rainfall
in that area, please see products from the Weather Prediction Center
and your local NWS forecast office.

2. Rosa could also bring tropical storm conditions to portions of
the central and northern Baja California peninsula starting on
Monday.  Interests in those locations should monitor the progress of


INIT  29/2100Z 21.4N 118.7W   90 KT 105 MPH
 12H  30/0600Z 22.9N 118.9W   85 KT 100 MPH
 24H  30/1800Z 24.8N 118.3W   70 KT  80 MPH
 36H  01/0600Z 26.7N 117.1W   55 KT  65 MPH
 48H  01/1800Z 28.8N 116.0W   40 KT  45 MPH
 72H  02/1800Z 34.5N 113.0W   20 KT  25 MPH...POST-TROP/INLAND
 96H  03/1800Z...DISSIPATED

Forecaster Beven