Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 261511

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1511 UTC Wed Oct 26 2016

Tropical Weather Discussion for the eastern Pacific Ocean from
the Equator to 32N, east of 140W. The following information is
based on satellite imagery, weather observations, radar, and
meteorological analysis.

Based on 1200 UTC surface analysis and satellite imagery through
1500 UTC.


Hurricane Seymour centered near 16.9N 120.2W at 1500 UTC or about
682 nm west-southwest of the southern tip of the Baja California
peninsula, moving west-northwest at 13 kt. Estimated minimum
central pressure is 949 mb. Maximum sustained winds are 120 kt
with gusts to 150 kt. Numerous moderate and scattered strong
convection is within 75 nm in the northeast semicircle, and within 
45 nm in the southwest semicircle. Scattered moderate and
isolated strong convection is elsewhere within 180 nm in the
northeast semicircle, and within 75 nm in the southwest
semicircle. Seymour is forecast to turn to the northwest later
today, then to the north-northwest and eventually north, with a
decrease in forward speed Thursday through Friday. Seymour is
forecast to weaken through the day today, with rapid weakening
occurring by tonight or Thursday. See latest NHC forecast/advisory
under AWIPS/WMO headers MIATCMEP5/WTPZ25.

Gulf of Tehuantepec Gale Warning...a locally tight pressure
gradient will persist across southeast Mexico between high
pressure located over eastern Mexico, and lower pressure south of
12N through the next several days. As a result, northerly winds
will continue to pulse to minimal gale force during the next
several days, with the strongest winds likely during the
overnight into the early morning hours. Winds are forecast to peak
to up to 40 kt late tonight into early Thursday as the pressure
gradient tightens even more. Seas will build to up to 12 ft during
the gale force winds, except up to 14 ft late tonight into early


The monsoon trough axis extends from 09N83W to 10.5N91W to low
pressure near 09N107W to 14N112W, then resumes from low pressure
near 16N128W to low pressure near 13N133W to 11N140W. Scattered
moderate convection is within 60 nm south of Central America east
of 86W, from 06N to 08N between 96W and 99W, and also within 150
nm southeast of the monsoon trough axis between 126W and 133W.

Scattered moderate and isolated strong convection is also within
120 nm in the southeast quadrant of the low near 09N107W, with
scattered moderate convection from 07N to 11N between 108W and



See the special features section for details on the persistent
Gulf of Tehuantepec gap wind event. High pressure at 1020 mb is
centered west of Baja California Norte near 30N120W with a ridge
axis extending southeast of the high to near 14N108W. This high
will continue to support gentle to moderate anticyclonic flow
across the waters offshore of the Baja California peninsula,
diminishing to gentle throughout this weekend, as the pressure
gradient weakens due to an approaching and decaying cold front.
Combined seas of 4 to 7 ft, except up to 8 ft in the southwest
portion of zone PMZ015 related to Hurricane Seymour, will subside
to 4 to 6 ft throughout late this week into the weekend, then will
build to 6 to 9 ft by Sunday as a new set of northwest swell

In the Gulf of California, gentle to moderate northerly flow
will prevail through Thursday, with winds becoming light and
variable by early Friday as an elongated northwest to southeast
trough sets up across the gulf. Seas will be 2 ft or less across
the northern gulf through the weekend, and 2 to 4 ft across the
southern half.


Offshore of the Gulf of Papagayo, fresh northeast to east winds
will diminish during the remainder of the morning hours. Elsewhere
gentle to moderate south to southwest winds are found south of the
monsoon trough, while mainly gentle west to northwest winds prevail
to the north of the trough axis. Combined seas are 4 to 7 ft,
primarily in long period southwest swell. Seas will decay to 3 to
5 ft this weekend.


See the special features section for details on Hurricane
Seymour. A cold front extends across the northern waters from
30N132.5W to 24N140W. Fresh to strong south to southwest winds are
occurring within 60 nm of the front, north of 26N. These winds are
forecast to diminish to 20 kt or less tonight. Associated
northwest swells of 8 to 11 ft is sweeping across the northwest
part of the discussion area mainly behind the front. The front
will move east-southeastward through early Thursday, temporarily
stalling as 1009 mb low pressure develops along it near 29N129W.
The low will move northeast of the area by Thursday night pulling
the trailing cold front to the east. The front will continue to
weaken as it approaches Baja California Norte late this weekend.
The northwest swell will continue to propagate southeast, and
eventually mix with seas generated by Seymour, resulting in a
sizable area of confused seas.

Otherwise, weak northeast to southwest ridging ahead of the cold
front will gradually dissipate through Wednesday. Mainly moderate
to locally fresh trades will prevail outside of the influences of
the cold front and Seymour, with combined seas of 4 to 7 ft. A new
cold front will move into the northwest corner this weekend,
bringing with it a reinforcing set of northwest swell.


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Page last modified: Wednesday, 26-Oct-2016 15:11:55 UTC