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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 251455

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1521 UTC Tue Oct 25 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
1430 UTC.


Hurricane Seymour centered near 15.6N 115.0W at 25/1500 UTC or
526 nm southwest of the southern tip of the Baja California
peninsula moving west at 12 kt. Estimated minimum central
pressure is 961 mb. Maximum sustained wind speed is 110 kt with
gusts to 135 kt. Numerous moderate and scattered strong convection
is within 75 nm of the center. Scattered moderate and isolated
strong convection is elsewhere within 120 nm of the center, and
within 90 nm southeast of a line from 15N113W to 12N122W. Seymour
is forecast to maintain a west to west-northwest motion through
tonight, then turn toward the northwest on Wednesday. Although the
forecast track keeps Seymour just outside of the Mexican offshore
waters zones, fresh to strong winds are expected in the southwest
portion of zone PMZ015 through the afternoon, while seas of 8 to
14 ft will impact the entire zone, gradually subsiding through
early Wednesday. 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
the offshore waters zone PMZ027. As a result, northerly winds
will continue to pulse to minimal gale force offshore of the Gulf
of Tehuantepec during the next few days, with the strongest winds
expected during the overnight and early morning hours. Seas will
build to up to 10 to 12 ft during the strongest winds.


The monsoon trough axis extends from 10N85W to 08N95W to 10N108W.
The intertropical convergence zone axis extends from 10N133W to
10N140W. Scattered moderate and isolated strong convection is from
07N to 07N east of 83W, and also from 04N to 08N between 92W and



See the special features section for details on the persistent
Gulf of Tehuantepec gap wind event. High pressure of 1020 mb is
centered near 28.5N121W, producing light to gentle anticyclonic
winds across the waters west of the Baja California peninsula.
Combined seas of 4 to 6 ft prevail north of 23N in northwest
swell. The high pressure center will shift slightly northeast
during the next 24 to 48 hours, resulting in a slight increase to
gentle to moderate northwest winds across the offshore waters,
which will then persist into the upcoming weekend.

Inside the Gulf of California, mainly gentle to moderate northerly
flow will prevail through Thursday, with winds becoming light and
southerly in the northern gulf by Thursday night through Saturday.
Winds will become light and variable in the southern Gulf by
early Friday as elongated northwest to southeast low pressure
troughing oscillates its position in the vicinity of the gulf
waters. Seas will be 2 ft or less across the northerly gulf, and 2
to 4 ft across the southern gulf through Thursday, then subsiding
to 2 ft or less thereafter.


Offshore of the Gulf of Papagayo, moderate to fresh northeast to
east winds will pulse late tonight into early Wednesday.
Elsewhere, gentle to moderate south to southwest winds are noted
to the south of the monsoon trough, while mainly gentle west to
northwest winds prevail to the north of the monsoon trough.
Combined seas are in the 4 to 6 ft range, primarily in long period
southeast swell which is dominating the offshore waters. These
marine conditions will persist over the next few days.


See the special features section for details on Hurricane Seymour.
A pre-frontal trough extends from 30N137W to 27N140W, while a
parent cold front is entering the area at 30N140W. Fresh to strong
southwest to west winds precede the front near the pre-frontal
trough, while northwest swells of 8 to 9 ft have already breached
the northwest corner. The front will propagate to the east-
southeast across the discussion waters to the north of 30N through
the end of the weak. Elongated low pressure is forecast to form
along the front by Wednesday night, translating northeast of the
discussion waters by Thursday morning, impacting California Friday
through the weekend. Associated winds are forecast to diminish to
20 kt or less by late Wednesday night into early Thursday, while
the set of northwest swell continues to shift to the southeast,
eventually mixing with seas generated by Seymour which will result
in very confused seas.

Otherwise, weak northeast to southwest ridging ahead of the pre-
frontal trough and cold front will gradually dissipate through
Wednesday. Mainly moderate to locally fresh trades will prevail,
along with combined seas of 5 to 7 ft.