000
AXPZ20 KNHC 090900
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
900 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 0600 UTC surface analysis and satellite imagery through
0900 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 across the region
remain 20-25 kt this evening. Gale force winds are not expected
after Monday morning as the airmass to the north modifies and
shifts east. However, strong gap winds will continue to pulse into
the Gulf of Tehuantepec through mid week.

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

The monsoon trough axis extends from low pres near 10N85W to
14105W to low pres near 13N110W to low pressure near 12N119W to
10N130W to beyond 11N140W. Scattered moderate to isolated strong
convection is occurring within 150 nm north and 120 south of the
axis between 85W and 100W. Scattered moderate convection is
occurring within 150 nm south of the axis between 100W and 110W.
Scattered moderate to isolated strong convection is occurring
within 60 nm north and 120 nm south of the axis between 110W and
130W and west of 135W.

...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 mid 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 about 10N to 11N, with light to
gentle southwest breezes farther south toward the Galapagos
Islands. Scattered showers and thunderstorms are 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 Nicaragua by late today. 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. 20 to 25 kt
winds within 90 nm of the center of this low will allow seas to
build to 9 ft by late Monday. 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 1018 mb centered north of the area near 38N130W
will shift southeastward through the next couple of days, ahead of
a cold front moving into the forecast area in the next 12 to 24
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 1009 mb low
pressure currently developing near 11N118W will deepen over the
next couple of days and move 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. Strong winds and seas
of 10 to 12 ft are likely with these two low pressure areas. In
addition, there are high chances of tropical cyclone development
with both of these low pressure areas by mid week.
      
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CHRISTENSEN