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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 250200

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
200 UTC Sun Sep 25 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.


A large low pressure area, analyzed as a 1006 mb low pressure
near 14N120W continues to slowly become more organized. Although
still broad, the low center is gradually becoming better defined,
and a band of moderate to isolated strong convection within
about 150 nm northwest of a line from 12N123W to 17N116W.
Fresh to strong southwest winds persist within 120 nm in the
southeast semicircle of low center with seas of 8 to 10 ft.
Convergence of these winds is supporting another area of scattered
moderate convection from 12N to 17N between 110W and 115W.
Environmental conditions are conducive for a tropical depression
to form during the next day or two. This disturbance is expected
to move slowly northward during the next few days. A gale warning
is already in effect in association with this feature beginning on
Sunday morning. Please refer to the latest Graphical Tropical
Weather Outlook for more information at


A tropical wave north of 09N along 96W will enhance convection
off the coast of southern Mexico and Guatemala mainly at night.
Expect the wave to gradually lose identity over the next couple of


The monsoon trough extends from 08N84W to 12N94W to 09N102W,
resuming at the 1006 mb low pressure area near 14N120W and
continuing to 1009 mb low pressure near 12N136W to beyond
11N140W. Scattered moderate convection within 120 nm north and 90
nm south of the axis between 90W and 97W. Scattered moderate
within 120 nm either side of the monsoon trough axis between 130W
and 138W.



Gentle to moderate breezes continue across the region north of
20N between the subtropical ridge to the west and weak troughing
over the Gulf of California. Northerly swell to 8 ft persist off
Baja California Norte beyond 200 nm, but will be decaying to below
8 ft tonight. Building high pressure over the Great Basin to the
north of the region will allow a brief surge of fresh to strong
northerly winds into the northern Gulf of California early Sunday,
diminishing slightly Sunday night, then veering more east to
southeast and increasing again on Monday on the tail end of a weak
frontal boundary drifting into northern Mexico.

A cold front is forecast to move across the Gulf of Mexico
waters. High pressure behind the front will likely induce the
first Gulf of Tehuantepec gap wind event of the season by late
Tuesday into Wednesday morning. At this time, marine guidance
suggests northerly winds of 20-25 kt and building seas to 8 ft.
Winds will further increase to 25-30 kt Wednesday night into
Thursday morning with seas up to 9-10 ft.


Mainly light and variable winds are noted north of the monsoon
trough while gentle to locally moderate south to southwest flow
is expected south of monsoon trough through early next week.
Combined seas of 4 to 7 ft will continue today primarily in long-
period southwest swell, then subside to 4 to 5 ft late on Sunday and
continuing into early next week.


A 1009 mb low pressure area is analyzed along the monsoon trough
near 12N136W. Expect the low to likely reach 140W on Monday, then
will remain near 140W through mid-week. The pressure gradient
between this low and the subtropical ridge to the north is
resulting in an area of fresh to strong northeast winds within 120
nm to the north of the low pressure center. Seas of 8 to 9 ft in
this area is merging with a greater area of 8 ft seas due to
northeast swell, reaching as far north as 22N. This area will
diminish in areal extent, covering an area from 13N to 20n between
135W and 140W by late Sunday. Seas of 8 to 9 ft will persist from
10N to 15N west of 138W through early next week on the eastern
side of the low pressure.