000
AXPZ20 KNHC 091520
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1520 UTC Sun Oct 9 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.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning...High pressure building
southward over eastern Mexico and the Gulf of Mexico behind a cold
front will tighten the pressure gradient across the Isthmus of
Tehuantepec over the next several days. This will allow the strong
northerly gap winds currently spilling across the Gulf of
Tehuantepec to combine with nocturnal drainage effects to result
in strong winds over the next few days, reaching gale force in the
late evening and overnight hours. Gap winds may briefly diminish
to 20 to 25 kt during the afternoon hours before surging again at
night into the early morning hours. Gale force winds are not
expected after Monday night as the airmass to the north modifies
and shifts east, however, strong to near gale force gap winds
will continue to pulse into the Gulf of Tehuantepec through the
end of the week.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...  

The monsoon trough axis extends from 08N78W to low pressure near
13N111W to 11N119W to 10N130W to 11N140W. Scattered moderate
convection is from 02N to 06N east of 80W, within 90 nm either
side of the monsoon trough axis between 88W and 98W, within 120 nm
south of the axis between 100W and 109W, within 90 nm either side
of the axis between 110W and 121W, and also from 07N to 11N west
of 133W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A weak sub-tropical ridge axis extends from northwest to
southeast across the Pacific waters to just northwest of the
Revillagigedo Islands. Light to gentle northerly breezes will
persist across the region north of 20N, including the Gulf of
California, through the next several days on the western periphery
of the weak ridge. Meanwhile, light to moderate east to southeast
winds are expected across the waters between the Gulf of
Tehuantepec and Cabo Corrientes through the week. 

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Moderate southwest winds persist from 05N to the monsoon trough
which is meandering north to south along roughly 10N to 11N, with
light to gentle southwest breezes farther south toward the
Galapagos Islands. Scattered showers and thunderstorms remain
active off the coast from Nicaragua to Guatemala where light
northeast winds persist. This is largely nocturnal drainage
related convection being enhanced by an upper low migrating
westward across the region. Associated surface low pressure is
expected to form along the monsoon trough off the coast of
El Salvador or Guatemala in the next few days. This will increase
winds especially in the waters beyond 150 nm off El Salvador and
Guatemala Monday, aided in part by a plume of strong gap winds
originating from the Gulf of Tehuantepec. The low pressure will
continue west of the area through mid week. Elsewhere combined
seas of 3 to 6 ft, primarily in long-period southwest swell, are
expected across the offshore waters later in the period from the
early to middle part of next week.

REMAINDER OF THE AREA... 

High pressure of 1017 mb centered north of the area near 39N130W
will shift southeastward through the next couple of days, ahead of
a cold front moving into the forecast area in the next 12 hours.
Areas of moderate to fresh trade winds persist north of the
monsoon trough to near 20N, with seas of 5 to 7 ft. Global models
are in good agreement showing a series of broad, weak, and
transient low pressure areas forming along the monsoon trough.
Although the model depictions differ somewhat in precise
locations, there is some general agreement showing 1008 mb low
pressure currently developing near 11N119W will deepen over the
next couple of days and move slowly northwest, reaching near
17N127W by mid week. In addition, models are also showing the low
pressure area that will form off Central America today gradually
developing and crossing west of 120W by late Wednesday. At a
minimum, strong winds and seas of 8 to 12 ft are likely with
these two low pressure areas.
      
$$
LEWITSKY