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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 270241

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Thu Oct 27 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 0000 UTC surface analysis and satellite imagery through
0200 UTC.


Hurricane Seymour centered near 18.7N 121.7W at 0300 UTC moving
northwest at 12 kt. Estimated minimum central pressure 969 mb.
Maximum sustained winds are 95 kt with gusts to 115 kt.
Scattered strong convection is within 75 nm northeast and 45 nm
southwest of the center. Scattered moderate isolated strong
convection is elsewhere within 180 nm in the northeast
semicircle, and 75 nm in the southwest semicircle. Seymour is
expected to turn northward Thursday, and begin to weaken rapidly
as it moves into an increasingly unfavorable environment through
Friday. See latest NHC forecast/advisory under AWIPS/WMO headers

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. Seas will build to 12 or 13 ft during the
periods of gale force winds.


The monsoon trough axis extends from 10N85W to low pressure near
09N106W 1010 mb to 12N112W, then resumes from low pressure near
15N130W 1010 mb to 10N140W. Minimal convection associated with
the convergence zone.



See the special features section for details on a persistent
Gulf of Tehuantepec gap wind event. High pressure centered west
of Tijuana near 32N121W continues to support gentle to moderate
anticyclonic flow across waters offshore of the Baja California
peninsula. Winds will slowly diminish this weekend, as a dying
cold front moves east and the pressure gradient weakens. 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 another cold front and a new set of
northwest swell moves eastward across the northern waters.

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
30N129W to 22N140W. Fresh southwest winds ahead of the front
will diminish tonight. Northwest swell to 10 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 develops along it
near 29N129W, then as the low moves north of the area Thursday
night it will drag the dying cold front further eastward.
Northwest swell will continue to propagate southeast, and
eventually mix with seas generated by Seymour, resulting in a
sizable area of confused seas through Friday night.

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.