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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 210239

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
053 UTC Fri Oct 21 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
0230 UTC.

Showers and thunderstorms have increased near a small area of low
pressure located near 13N114W. Numerous moderate and isolated
strong convection is seen from 10N to 15N between 111W and 116W. The
low has a medium chance of developing into a tropical cyclone as
it drifts slowly N over the next couple of days.

A gale warning remains in effect for the Gulf of Tehuantepec.
This gap wind event is being initiated by a cold front moving S
through the western Gulf of Mexico tonight through Friday night. N
winds of 20 to 30 kt are already surging into the Gulf of
Tehuantepec. Winds will reach minimal gale force by Friday morning
with seas building to 8-12 ft by Friday afternoon. Model guidance
suggests this event will be long lived with winds pulsing to gale
force through the end of next week. Expect the strongest winds in
conjunction with nocturnal drainage flow during the overnight and
early morning hours, particularly between 0600-1200 UTC.


The monsoon trough extends from 12N104W to 1006 mb low pres near
13N114W to 11N125W to 13N137W to 13N140W. Scattered moderate
isolated strong convection is noted within 120 nm either side of a
line from 09N100W to 13N108W. Similar convection is present from
10N to 13N between 115W and 123W. Scattered moderate from 09N to
12N between 119W and 124W and also from 12N to 15N W of 137W.



A ridge extends SE from 32N134W to just W of the Revillagigedo
Islands at 19N116W. Near the ridge axis...moderate NW to N winds
are noted in satellite-derived wind data. The combination of
these winds and long period NW swell support seas of 6 to 8 ft W
of Baja California Norte, and 5 to 7 ft seas W of Baja California
Sur. The ridge will weaken tonight and Friday as a cold front
approaches the forecast region. The front is expected to stall and
weaken near 30N140W by late Friday. Then, the ridge now in place
will be reinforced by high pres in the wake of the front. A new
batch of swell of 8 to 9 ft generated N of the front is forecast
to arrive offshore Baja California Norte late Saturday into
Sunday. Seas will subside once again by Monday night.

Winds across the northern part of the Gulf of California have
subsided below 20 kt. Seas of 4-5 ft are prevalent across the Gulf.
By early Friday morning, expect mainly gentle to moderate winds
and seas generally less than 5 ft across the entire Gulf of
California or Sea of Cortez. Surface troughing developing over the
Baja peninsula will promote a light to gentle wind regime over
the Gulf of California S of 28N and gentle to moderate winds for
the waters N of 28N Saturday through Monday.

Farther S, a gap wind event is producing minimal gale force
winds across the Gulf of Tehuantepec. See Special Features
section for details.


Gentle to moderate winds are noted in satellite-derived wind data
across the waters between Ecuador and the Galapagos Islands with
seas of 4-6 ft in SW swell, except to the lee of the Galapagos
Islands. Farther N, mainly gentle to moderate SW winds prevail
with an area of moderate to fresh SW winds roughly from 05N-10N
between 95W and 110W. Seas in this area are in the 7-9 ft range
in NW swell. These marine conditions are forecast to persist
during the next few days. An area of disorganized cloudiness and
showers is located S of the Gulf of Tehuantepec. Environmental
conditions are forecast to become more favorable for some
development of this system over the weekend and early next week
while it moves toward the WNW around 10 kt.


The pres gradient between the ridge to the N and lower pres near
the monsoon through is generating an area of fresh to locally strong
trade winds from 14N to 17N W of 138W with seas to 8 ft in mixed
NE and NW swell. Winds and seas will continue to diminish across
the west-central waters during the next couple of days.

Currently, seas of 8-9 ft, primarily in NW swell, dominate the
forecast waters N of 27N between 124W and 128W. Seas will subside
to less than 8 ft in about 6 hours, but another batch of long
period NW swell will reach the NW waters by Friday evening. This
swell event will propagate SE to cover the waters N of a line from
30N123W to 26N128W to 24N136W to 27N140W by Saturday evening.