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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 262122

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.


Hurricane Seymour centered near 17.5N 121.2W at 2100 UTC moving
west-northwest at 11 kt. Estimated minimum central pressure is
958 mb. Maximum sustained winds are 110 kt with gusts to 135 kt.
Numerous moderate scattered strong convection is within 60 nm of
the center. Scattered moderate isolated strong convection is
elsewhere within 150 nm in the northeast semicircle, and within
75 nm in the southwest semicircle. Seymour is forecast to turn
northwest tonight, then north on Thursday, with a decrease in
forward speed. It is expected to weaken rapidly as it moves into
an unfavorable environment Thursday and Friday. 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 weekend. As a result, northerly winds will
continue to pulse to minimal gale force 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 12 ft during the gale
force winds, except up to 14 ft late tonight and early Thursday.


The monsoon trough axis extends from 09N84W to low pressure near
08N107W 1010 mb to 12N114W, then resumes from low pressure near
15N120W 1011 mb to 11N140W. Scattered moderate convection within
150 nm southeast of the trough axis between 127W and 135W.



See the special features section for details on the persistent
Gulf of Tehuantepec gap wind event. 1019 mb high pressure is
centered west of Tijuana near 32N121W. This high will continue
to support gentle to moderate anticyclonic flow across waters
offshore of the Baja California peninsula, diminishing to gentle
throughout this weekend, as the pressure gradient weakens due to
the approach of a dying cold front. 5 to 7 ft seas will subside
to 4 to 5 ft by the weekend, then build to 6 to 9 ft by Sunday
as a new set of northwest swell arrives.

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.


Gentle to moderate south to southwest winds are found south of
the monsoon trough, while mainly gentle west to northwest winds
prevail 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
30N131W to 23N140W. Fresh southwest winds within 60 nm east of
the front, north of 26N will diminish tonight. Northwest swell
to 11 ft is sweeping across the northwest part of the discussion
area mainly behind the front. The front will move slowly east-
southeast through early Thursday, temporarily stall as a low
pressure area develops along it near 29N129W, then the low will
move northeast of the area Thursday night pulling the trailing
but dying cold front eastward. 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 tonight. Moderate to fresh trades
will prevail outside of the influences of the front and Seymour,
with combined seas of 4 to 6 ft. A new cold front will reach the
area near 30N140W this weekend, bringing a reinforcing set of
northwest swell.