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Hurricane Rosa Discussion Number 22
NWS National Hurricane Center Miami FL EP202018
800 AM PDT Sun Sep 30 2018
Rosa continues to be affected by increasing southwesterly shear and
cooler waters. Most of the deep convection has been eroded over
the southern semicircle of the circulation. The current intensity
estimate is reduced to 65 kt in agreement with ADT estimates from
UW/CIMSS. An Air Force Reserve Unit Hurricane Hunter aircraft will
investigate Rosa later today to provide a better estimate of the
intensity of the system. Since the vertical shear is predicted to
continue to increase and SSTs should cool to below 23 deg C by
Monday, additional weakening is likely before Rosa reaches the
Baja California peninsula. The official intensity forecast is near
the high end of the numerical guidance.
The hurricane is moving just east of north, or around 010/11 kt.
The track forecast reasoning is unchanged from the previous
advisory package. Rosa is likely to be steered north-northeastward
in the flow ahead of a large mid-level trough approaching from the
west. This should take the center of the cyclone across Baja
California in the Tropical Storm Warning area by Monday night.
Rosa or it's remnant should move over the Desert Southwest on
Tuesday. The official track forecast is similar to the previous
one and roughly in the middle of the dynamical guidance.
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 expected over portions of the
central and northern Baja California peninsula on Monday, possibly
spreading to the northern Gulf of California Monday night.
Interests in those locations should monitor the progress of Rosa.
FORECAST POSITIONS AND MAX WINDS
INIT 30/1500Z 24.4N 118.6W 65 KT 75 MPH
12H 01/0000Z 25.9N 117.9W 60 KT 70 MPH
24H 01/1200Z 27.5N 116.7W 55 KT 65 MPH
36H 02/0000Z 29.3N 115.4W 45 KT 50 MPH
48H 02/1200Z 31.8N 114.0W 30 KT 35 MPH...INLAND
72H 03/1200Z 36.5N 111.5W 20 KT 25 MPH...POST-TROP/INLAND