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Tropical Storm Rosa Discussion Number  28
NWS National Hurricane Center Miami FL       EP202018
800 PM PDT Mon Oct 01 2018

Rosa continues to lack deep convection near the center, which is
currently over sea surface temperatures of 21C.  However, strong
convection is occurring to the northeast of the center over the
northern Gulf of California and the adjacent land areas.  The
Mexican automated station at Isla Cedros reported 30 kt winds with
gusts near 40 kt a few hours ago, and passive microwave data
suggests the strongest winds in the cyclone are currently moving
onshore south of Punta Eugenia where no surface observations are
available.  The initial intensity is kept at 35 kt, and it is
possible that this is generous.  Rosa should weaken as it crosses
Baja California, but it is likely the warm water of the Gulf of
California will maintain the system as a tropical cyclone until
final landfall in northwestern Mexico.  After that landfall, Rosa
should quickly degenerate into a remnant low over the southwestern
United States on Tuesday.

The initial motion is 035/9. Rosa should move generally
northeastward between a deep-layer ridge over northern Mexico and a
mid- to upper-level trough over the northeastern Pacific until the
cyclone dissipates.  The dynamical models suggests the possibility
that the center of Rosa will reform over the Gulf of California in
the next 12 h, which may lead to some erratic changes in the forward
speed.


Key Messages:

1. The main hazard expected from Rosa or its remnants is very heavy
rainfall in Baja California, northwestern Sonora, and the U.S.
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. Tropical storm conditions are affecting portions of the central
and northern Baja California peninsula, especially over higher
elevations.  These conditions could spread into the northern
Gulf of California later tonight. Interests in those locations
should monitor the progress of Rosa.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 28.9N 115.3W   35 KT  40 MPH
 12H  02/1200Z 30.8N 114.5W   25 KT  30 MPH
 24H  03/0000Z 33.5N 113.5W   15 KT  15 MPH...POST-TROP/INLAND
 36H  03/1200Z...DISSIPATED

$$
Forecaster Beven

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