Tropical Weather Discussion
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AXPZ20 KNHC 271010

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


Hurricane Seymour has begun to weaken rapidly tonight, and is
centered near 19.5N 122.1W 980 mb at 0900 UTC moving NNW at 10
kt. Maximum sustained winds have diminished to 80 kt with gusts
to 100 kt. The center of Seymour is located satellite imagery on
the SW edge of the deep convection as SW upper level wind shear
is having a negative impact on the system. Scattered to numerous
strong convection is within 90 nm across the northeast
semicircle, while scattered moderate isolated strong convection
is elsewhere within 180 nm NE and 60 nm SW semicircles. Seymour
will turn northward today and continue to weaken rapidly as it
moves into an increasingly unfavorable environment and cool
SSTs. Seymour is expected to spin down and dissipate by 72
hours. through Friday. See latest NHC forecast/advisory under

Gulf of Tehuantepec Gale Warning...a high pressure ridge
extending nearly N to S across eastern Mexico continues to
produce a tight pressure gradient across southeast Mexico. As a
result, strong northerly winds will continue to blow across the
Gulf of Tehuantepec and spill downstream for the next
severaldays. Winds will pulse to minimal gale force at night,
with the strongest winds 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 TO 12N112W...then resumes from low pressure near 15N130W
TO 10N140W. Minimal convection associated with the trough.



See the special features section for details on a persistent
Gulf of Tehuantepec gap wind event. High pressure centered SW of
Tijuana near 30N120W 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. Seas of
5 to 7 ft in NW swell 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 pulse of northwest swell moves across the northern waters.

In the Gulf of California, gentle to moderate northerly flow
will prevail today, 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 west 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
30N1329W to 20N140W. Fresh southwest winds N of 27N ahead of the
front will diminish later this morning. Northwest swell
producing seas to 10 ft is sweeping across the northwest part of
the discussion area mainly behind the front. The front will move
slowly east-southeast today, then temporarily stall as a low
develops along it near 30N127W, then as the low moves north of
the area Friday, it will drag the dying cold front further
eastward. The associated NW swell will continue to propagate
southeastward, and eventually mix with seas generated by
Seymour, resulting in a sizable area of confused seas
between 118W and 126W through Friday night.

Otherwise, weak northeast to southwest ridging ahead of the cold
front will gradually collapse today. 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 pulse of
northwest swell.

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