AXPZ20 KNHC 242204

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2204 UTC Sat Sep 24 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
2100 UTC.


A large low pressure area, analyzed as a 1006 mb low pressure
near 13N119W is showing slightly more organized shower and
thunderstorms activity. Satellite images indicate that the low's
circulation, although still broad, is gradually becoming better
defined, and a band of moderate to isolated strong convection is
seen within about 60 nm of a line from 12N123W to 16N119W.
Currently, the pressure gradient is supporting strong southwest winds
within 120 nm in the southeast semicircle of low center with seas
of 8 to 9 ft. Convergence of these winds is supporting another
area of scattered moderate to isolated strong convection from 11N
to 17N between 110W and 118W. 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 http://hurricanes.gov.


A tropical wave is analyzed north of 10N along 95W. The axis
crosses the Gulf of Tehuantepec. This is enhancing convection off
the coasts of southern Mexico and Guatemala mainly at night. Expect
the wave to gradually lose identity over the next couple of days.


The monsoon trough extends from 11N86W to 12N95W to 10N105W,
resuming at the 1006 mb low pressure area near 13N119W and
continuing to 1009 mb low pressure near 12N135W 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 127W and 137W.



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 through this evening. 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 12N135W. 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.