Tropical Weather Discussion
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AXPZ20 KNHC 261010

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 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 0600 UTC surface analysis and satellite imagery through
0900 UTC.


Major Hurricane Seymour centered near 16.4N 119.0W AT 0900 UTC,
or about 640 nm, or 1195 km southwest of the southern tip of the
Baja California peninsula, moving west-northwest at 12 kt.
Estimated minimum central pressure is 943 mb. Maximum sustained
winds are 130 kt with gusts to 160 kt. Satellite imagery
overnight continues to show an impressive hurricane, with a 15
nm wide eye most of the night, and numerous strong convection
within 45 nm across the NW and 60 nm across the SE semicircles.
Scattered to numerous moderate to strong convection was
elsewhere within 120 nm across the NE and 60 nm across the SW
semicircles. Seymour remains a category 4 hurricane on the
Saffir-Simpson scale, and is the strongest of the 2016 Eastern
Pacific season. Seymour has reached its peak intensity
overnight, and is nearing cooler SSTs to the west and northwest.
A gradual turn toward the northwest is expected today and then
more NNW on Thursday and will lead to a very rapid weakening
trend for Seymour. Seymour is forecast to become a post tropical
remnant low by 72 hours. See latest NHC forecast/advisory under

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 Thursday. As a result, strong to near gale force
northerly winds will continue to blow across and downstream 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 around 12 ft during the period of
strongest winds.


The monsoon trough extends from 10N74W to 10N85W to 09N89W to
08.5N105W to 12N112W. The ITCZ extends from 12N123W TO
09.5N140W. Scattered moderate to strong convection is noted
within 210 nm N and 240 nm S of the trough E of 90W. Scattered
moderate isolated Strong convection is noted southwest of
Seymour and within 120 nm S of the ITCZ between 123W and 133W.



See the special features section for details on the persistent
strong Gulf of Tehuantepec gap wind event. 1018 mb high pressure
centered off the coast of southern California near 31N121W is
producing light to moderate anticyclonic winds across the waters
west of the Baja California peninsula. Combined seas of 5 to 6
ft prevail north of 23N in northwest swell. The high will shift
slightly northeast during the next 24 hours, resulting in gentle
to moderate northwest winds across the offshore waters, which
will then persist into the weekend.

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 3 ft or less across
the northern gulf through the weekend, and 3 to 5 ft across the
south half.


Offshore of the Gulf of Papagayo, fresh northeast to east winds
will continue this morning before diminishing modestly this
afternoon. 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 6 ft primarily in long period southwest
swell which dominates the offshore waters. These marine
conditions will persist over the next few days.


See the special features section for details on Hurricane
Seymour. A cold front extends across the NW waters from 30N133W
to 25N140W. Fresh to strong south to southwest winds precede the
front north of 27N. Northwest swell raising seas to 11 ft is
sweeping into the northwest part of the discussion area behind
the front. The front will move east southeastward through early
Thursday, then stall as low pressure develops along the boundary
near 30N129W, before dissipating from 30N124W to 22N130W
Thursday and Friday. The low pressure is forecast to move
northeast of the area Thursday. Winds ahead of the front are
expected to diminish below 20 kt early Thursday. 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 pre-
frontal trough and cold front will gradually dissipate through
Wednesday. Mainly moderate to locally fresh trades will prevail
south of 23N and west of 130W with combined seas of 5 to 7 ft
building to 6 to 9 ft on Thursday.

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