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Hurricane Rosa Discussion Number 15
NWS National Hurricane Center Miami FL EP202018
200 PM PDT Fri Sep 28 2018
Rosa's appearance has rapidly deteriorated since this morning.
There is still evidence of an ongoing eyewall replacement cycle,
and an apparent moat region has occasionally been apparent in
conventional satellite data during the past several hours. The slow
motion of the hurricane since last night could also be causing
upwelling that would lead to further weakening. Satellite
intensity estimates from all agencies have dropped substantially
accordingly, and the initial intensity has been lowered to 105 kt,
based on a blend of Final-T and CI numbers from TAFB and SAB.
Rosa is still moving northwestward, with an initial motion of
325/5 kt. The model spread has increased a little, with the GFS and
its associated regional models showing a slightly right (southeast)
track, compared to earlier cycles, while the ECMWF has shifted an
equal amount to the left (northwest). The consensus models have not
changed much as a result of these offsetting model trends, so almost
no change was made to the NHC track forecast. Rosa is still expected
to turn northward, and then north-northeastward ahead of a mid- to
upper-level trough approaching from the northwest. The cyclone
should then accelerate a little as it approaches the northern coast
of the Baja California peninsula early next week.
At this point, the structure of Rosa has degraded to the point that
substantial restrengthening appears unlikely. Since the hurricane
still has about 24-36 hours before it reaches much cooler SSTs,
only gradual weakening is forecast, though most of the intensity
guidance shows more rapid weakening than currently indicated.
After that time, a more rapid rate of weakening could occur due to
cooler SSTs and an increase in wind shear associated with an
upper-level trough approaching from the west.
By early next week, Rosa is forecast to move inland over northern
Baja California, and its surface circulation will likely dissipate
shortly thereafter. However, moisture associated with Rosa 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.
1. Rosa could bring tropical storm conditions to portions of the
central and northern Baja California peninsula in a few days.
Interests in those locations should monitor the progress of Rosa.
2. Heavy rainfall associated with Rosa or its remnants is expected
to affect parts of the southwest United States by early next week,
which could cause flooding in this region. For more information
about potential rainfall and flooding, please see products from the
Weather Prediction Center and your local NWS forecast office.
FORECAST POSITIONS AND MAX WINDS
INIT 28/2100Z 17.7N 117.8W 105 KT 120 MPH
12H 29/0600Z 18.6N 118.3W 95 KT 110 MPH
24H 29/1800Z 20.3N 118.8W 85 KT 100 MPH
36H 30/0600Z 22.1N 118.9W 75 KT 85 MPH
48H 30/1800Z 24.0N 118.4W 65 KT 75 MPH
72H 01/1800Z 27.7N 116.8W 45 KT 50 MPH
96H 02/1800Z 32.3N 114.5W 30 KT 35 MPH...INLAND