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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 202136

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1929 UTC Thu Oct 20 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 1800 UTC surface analysis and satellite imagery through
2030 UTC.

Showers and thunderstorms have increased near a small area of low
pressure located near 13N114W. Numerous moderate and isolated
strong convection is noted from 11N to 15N between 111W and 115W.
The most recent scatterometer pass showed winds of 20-25 kt in
association with this system and a well defined cyclonic
circulation at the surface. The low has a medium chance of
developing into a tropical cyclone as it drifts slowly N over the
next several 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 20-25 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 12N103W to 1006 mb low pres near
13N114W to 10N125W to 14N137W to 13N140W. Scattered moderate
isolated strong convection is noted from 10N to 17N between 101W
and 111W. Similar convection is present from 10N to 13N between
115W and 123W.



A ridge extends SE from 32N134W to near the Revillagigedo Islands
at 19N113W. Near the ridge axis...gentle to moderate NW to N
winds are noted per scatterometer data. The combination of these
winds and long period NW swell support seas of 7 to 9 ft W of Baja
California Norte, and 5 to 7 ft seas W of Baja California Sur.
The ridge will weaken through 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 N of 30N
are 20-25 kt with seas of 4-6 ft. NW winds of 15-20 kt with seas
of 4-5 ft are across the central waters, mainly N of 26N. 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 winds 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.


Light to gentle winds are noted in satellite-derived wind data
across the waters between Ecuador and the Galapagos Islands with
seas of 5-7 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
90W and 105W. Seas in this area are in the 8-9 ft range in SW
swell. These marine conditions are forecast to persist during the
next few days. An area of disorganized cloudiness and showers has
persisted near the coast of Central America. Environmental
conditions are forecast to become more favorable for some
development of this disturbance over the weekend and early next
week while the system moves toward the WNW at about 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 20N W of 133W with seas of 8-9 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 26N between 121W and 129W. Seas will
gradually subside to less than 8 ft in about 12 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 W of a line from 30N125W to 25N134W by Saturday evening.