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KF5JRV > WX 01.10.18 12:45l 126 Lines 5483 Bytes #999 (0) @ NA
BID : 22281_KF5JRV
Read: GUEST
Subj: NWS NHC Eastern N Pacific WX - Oct 01
Path: IW8PGT<CX2SA<SV1CMG<PI8BDG<AB0AF<KF5JRV
Sent: 181001/1115Z 22281@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.16
428
WTPZ41 KNHC 010854
TCDEP1
Tropical Storm Sergio Discussion Number 8
NWS National Hurricane Center Miami FL EP212018
300 AM MDT Mon Oct 01 2018
Sergio's convective pattern in infrared satellite imagery has waxed
and waned since the previous advisory. A previously large, solid
curved band has become broken during the past couple of hours, but
the comma head or CDO of the cloud band has increased in size while
cloud tops have cooled to near -80C. Passive microwave imagery
indicates that within the comma head feature an 18-20-nmi-wide
closed eye has developed in the low-levels, while the mid- and
upper-level eye remains open and ragged. Subjective intensity
estimates remain T3.5/55 kt from TAFB and SAB. However, based on the
well-defined, low-level eye, the intensity has been nudged upward to
60 kt for this advisory.
The initial motion is now 270/12 kt, based primarily on microwave
satellite fix positions. Sergio is forecast to move generally
westward for the next 36 hours or so, under the influence of a
strong, deep-layer ridge located to the north of the cyclone. By 48
hours, a mid- to upper-level trough moving southeastward along and
offshore of the western U.S. is expected to gradually erode the
western part of the ridge, allowing Sergio turn west-northwestward
on day 2 and move northwestward on days 3-5. The new NHC track
forecast is similar to the previous advisory track, and lies near a
blend of the consensus models TCVA, TVCE, and HCCA.
Both the statistical and dynamical intensity models have been too
bullish on Sergio strengthening during the past 36 hours. Although
the environment is quite moist with near 80 percent mid-level
humidity values, a pronounced dry intrusion eroding the inner-core
convection remains. By the time the dry air mixes out, modest
northerly vertical wind shear is expected to hinder development in
the 24-48 hour period. By 72 hours and beyond, the shear is
forecast to decrease below 10 kt, but Sergio will be moving over
cooler waters at that time. Given the mixed environmental signals,
the official intensity is on the conservative side and remains well
below the stronger HCCA and FSSE models, and closer to the simple
consensus model IVCN.
FORECAST POSITIONS AND MAX WINDS
INIT 01/0900Z 11.5N 108.6W 60 KT 70 MPH
12H 01/1800Z 11.4N 110.3W 70 KT 80 MPH
24H 02/0600Z 11.5N 112.5W 85 KT 100 MPH
36H 02/1800Z 12.0N 114.5W 95 KT 110 MPH
48H 03/0600Z 12.8N 116.1W 100 KT 115 MPH
72H 04/0600Z 14.9N 118.8W 100 KT 115 MPH
96H 05/0600Z 16.8N 121.2W 95 KT 110 MPH
120H 06/0600Z 17.9N 123.2W 90 KT 105 MPH
$$
Forecaster Stewart
431
WTPZ45 KNHC 010839
TCDEP5
Tropical Storm Rosa Discussion Number 25
NWS National Hurricane Center Miami FL EP202018
200 AM PDT Mon Oct 01 2018
Convection has been steadily decreasing due to the combination
of southwesterly shear of about 30 kt and cool SSTs of less than
24 deg C. As a result, only a small patch of thunderstorms
remains in the northeastern quadrant of Rosa's circulation. ASCAT
passes around 0414Z and 0516Z only indicated wind speeds of 41-42 kt
in the eastern semicircle. Assuming that some undersampling is
occurring, the intensity has only been decreased to 45 kt for this
advisory. Additional weakening is expected due to a further increase
in the vertical wind shear and decreasing ocean temperatures beneath
the cyclone. The official intensity forecast calls for Rosa to be
near 35 kt at the time of landfall later today, but it is possible
that more weakening could occur than currently indicated.
Regardless, strong tropical-storm-force wind gusts will be
widespread across the higher elevations of the northern Baja
California peninsula. Rosa is expected to become remnant low before
the cyclone reaches Arizona due to the rugged terrain of Baja and
northwestern Mexico, and the continued strong wind shear.
Rosa is moving northeastward now, or 035/10 kt. A northeastward to
north-northeastward motion is expected until and after landfall,
with some acceleration beginning later tonight. The latest NHC
model guidance remains tightly clustered, and the official forecast
track lies close to the previous track and an average of the TVCE,
HCCA, and FSSE multi-model consensus aids.
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 expected over portions of the
central and northern Baja California peninsula later today,
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 01/0900Z 26.7N 117.0W 45 KT 50 MPH
12H 01/1800Z 28.0N 116.1W 35 KT 40 MPH
24H 02/0600Z 30.1N 114.8W 30 KT 35 MPH...INLAND NRN BAJA CALIF
36H 02/1800Z 32.9N 113.5W 20 KT 25 MPH...POST-TROP/INLAND
48H 03/0600Z 35.9N 112.2W 15 KT 15 MPH...POST-TROP/INLAND
72H 04/0600Z...DISSIPATED INLAND
$$
Forecaster Stewart
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
email: KF5JRV@ICLOUD.COM
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