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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 271554

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1559 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.


Hurricane Seymour continues to rapidly weaken near 20.2N 122.7W or
about 760 nm west of the southern tip of the Baja California
peninsula at 27/1500 UTC, moving north-northwest at 10 kt.
Estimated minimum central pressure is 986 mb. Maximum sustained
winds are 70 kt with gusts to 85 kt. Numerous moderate and
isolated strong convection is within 240 nm in the northeast and
east quadrants of Seymour. Seymour is forecast to continue to
rapidly weaken, becoming a tropical storm by this evening, then to
a post-tropical cyclone by Friday afternoon, and dissipating by
Sunday morning. See latest NHC forecast/advisory under AWIPS/WMO
headers MIATCMEP5/WTPZ25.

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 several
days, pulsing to minimal gale force, with the strongest winds
occurring during the overnight and early morning hours. Seas will
build to 12 or 13 ft during the periods of gale force winds.


The monsoon trough axis extends from 08N78W to 10N85W to 07N96W to
low pressure near 09N107W to 10N110W, then resumes from low
pressure near 15.5N130W to 11N140W. Scattered moderate and
isolated strong convection is from 12N to 14N between 127W and
129W. Scattered moderate convection is within 90 nm in the
northwest quadrant of the low pressure near 09N107W, and also
within 75 nm in the northeast quadrant of the low pressure near



See the special features section for details on a persistent Gulf
of Tehuantepec gap wind event. High pressure centered southwest of
Tijuana, Mexico 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 8 ft in NW swell will subside to 4 to 6 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

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. Low pressure is forecast to develop in the far
northern Gulf of California by early Sunday. Winds on the
southeast side of the low are forecast to increase to fresh to
strong Sunday, pulsing through early next week. Seas will be 2 ft
or less across the northern gulf through the weekend, building to
4 to 7 ft as the winds increase, and 2 to 4 ft across the
southern half throughout.


Gentle to moderate west to southwest winds are found south of
the monsoon trough, while gentle west to northwest winds prevail
north of the trough. Latest altimeter data shows seas ranging
between 4 to 6 ft, primarily in long period southwest swell. Seas
will decay to 3 to 5 ft by this weekend.


Please refer to the Special Features section for details on
Hurricane Seymour. A 1010 mb surface low is located near 28N133W,
with a cold front extending south-southwest from the low to
22N135W to 19N140W. Moderate to fresh northwest winds prevail N
of the front of 20N with northwest swell producing seas to 10 ft.
Gentle to moderate southwest winds prevail ahead of the front.
The front will temporarily stall today, then move again while
weakening as the low moves north of the area Friday. 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

Otherwise, the weak ridge 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 by this
weekend, bringing a reinforcing pulse of northwest swell.