000
AXPZ20 KNHC 220325
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Wed Dec 21 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
0300 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec: A gale warning remains in effect for the Gulf
of Tehuantepec. A NW flow persists across the SW Gulf of Mexico
with cooler and drier air continuing to be funneled through the
Chivela Pass southward. The latest scatterometer pass indicated
minimal gale force winds across the Gulf of Tehuantepec while a
recent altimeter pass showed seas up to 13 ft across the same
area. Minimal gale force winds are expected to persist across this
gulf through early Friday morning as continuous cold air advection
over the western Gulf is likely to reinforce this gap wind event.
Gale conditions should likely diminish Friday afternoon as winds
veer to the southeast over the western Gulf of Mexico. Then, northerly
winds of 20-30 kt are expected Friday night into Saturday morning
with the assistance of the nocturnal drainage flow. Winds will
further diminish to 20-25 kt Saturday night into Sun morning.

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

The monsoon trough extends from 06N77W to 07N85W to 06N97W. The
ITCZ axis continues from 06N97W to 10N117W, then resumes W of a
trough at 11N122W to beyond 07N140W. The trough extends from
13N117W to 08N119W. Scattered moderate convection is within 30 nm
of ITCZ axis W of 137W. No significant convection elsewhere.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of California: The pressure gradient across the area is
continuing to weaken and now light to moderate NW winds are noted
across much of the gulf. Moderate to locally strong NW winds are
still seen near the entrance of the gulf and southward to about
22N. A cold front approaching from the west will bring an increase
in winds across the north waters on Saturday. Southerly winds in
the 20-30 kt range are expected ahead of the front in the northern
Gulf of California. The cold front will be moving across northern
Baja California and the Gulf of California, including also forecast
zones PMZ009, PMZ011, and PMZ013 Saturday and Saturday night. NW
winds of 20-25 kt and building seas of 9 to 13 ft in NW swell are
expected in the wake of the front. The highest of these seas are
forecast to be confined to zone PMZ009, and the northwest section
of zone PMZ011 late on Saturday.

A 1012 mb surface low at 28N119W is associated with a strong
upper-level cutoff low. A trough extend from the low center to
23N116W to 17N118W. A diffluent pattern aloft to the east of the
low is helping to induce a swath of scattered moderate isolated
strong convection within about 150 NM E of the trough, mainly from
20N to 27N. Similar convection is also observed near the southern
end of the trough axis from 13n to 16n between 118W and 121W. The
low will lift to the north while dissipating on Thursday. Moisture
associated with this system will continue to spread northward
across parts of the Baja California Peninsula and the Gulf of
California, including also NW Mexico tonight and Thursday,
increasing the likelihood of showers and isolated thunderstorms.
  
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Gulf of Papagayo: Fresh to strong northeast winds are expected
to pulse in and downstream of the Gulf of Papagayo to near 90W
during the overnight and early morning hours through Friday night,
with the assistance of the nocturnal drainage flow. Locally, these
winds will produce seas up to 8 ft. The fresh northeast swells
will continue to merge with a Gulf of Tehuantepec gap wind event
to provide a large area of 8 to 11 ft seas downstream of the gap
regions on Thursday.

Elsewhere across the region, winds will remain 20 kt or less,
with seas below 8 ft through Sunday night. Moderate Northerly winds 
are expected across the Gulf of Panama during the overnight and
early morning hours.

REMAINDER OF THE AREA...

The combination of a 1027 mb high centered just north of the area
near 32N141W and lower pressures in the vicinity of the ITCZ will
continue to support a belt of fresh to strong trades from roughly
08N to 15N west of 130W. Seas of 8 to 11 ft in mixed wind waves
and northwest swell are noted per a couple of altimeter passes
within the area of the trade winds. The high center is forecast to
weaken through Saturday as it moves to the southwest. As a result,
the aerial coverage of fresh to strong winds will decrease.

Long period NW swell continues to impact much of the waters W of
115W with seas of 8 to 11 ft. Seas will slightly subside through
Friday, but will increase again across the N waters on Saturday
as a cold front reach the forecast area by Friday night. Fresh to
strong northerly winds and a new set of large northwest swell,
with building seas up to about 14 ft along 30N, will follow the
front. High pressure behind the front will shift southeastward to
near 30N134W by Saturday night. As this high pressure builds in,
the aerial extent of the trades will increase again.
  
$$
GR