000
AXPZ20 KNHC 121602
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Wed Apr 12 2017

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
1545 UTC.

...SPECIAL FEATURES...

...Gulf of Tehuantepec Gale Warning...

The pressure gradient between high pressure ridging surging down
eastern Mexico and lower pressures present to the south of the 
Tehuantepec region has tightened enough during the past few hours
to allow for minimal gale force north to northeast to develop 
across the Isthmus of Tehuantepec and funnel out across the Gulf 
in a narrow swath area within 15 nm either side of a line from 
16N95W to 15N95.5W. Seas associated with these wind conditions 
are in the 8 to 10 ft range. Strong to near gale force north to 
northeast winds are within 45 nm either side of a line from 
16N95W to 14N96W with seas up to 9 ft. The culprit tight gradient
is forecast to slacken slightly by early this afternoon to allow
for the gale force to diminish to just below gale force, however
seas of 8 to 10 ft will remain. North to northeast minimal gale 
force winds then develop late tonight within 30 nm either side of
a line from 16N95W to 14.5N95.5W, with seas building higher to 
around 12 ft. The winds then diminish to just below gale force 
Thursday morning as the gradient relaxes again, with fresh to 
strong northerly flow pulsing thereafter through the remainder of
the week and the upcoming weekend, mainly at night with 
nocturnal drainage flow.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
 
The intertropical convergence zone axis extends from 05N104W to 
02N116W to 04N126W to 04N133W where it is disrupted by an 
embedded surface trough. It then resumes at 04N137W to beyond
the area at 03N140W. A southern ITCZ axis extends from 03.4S110W
to 03.4S115W to 03.4S124W. Scattered moderate/isolated strong 
convection is within 240 nm north of the axis between 117W and 
127W. Scattered moderate to strong convection is within 60 nm 
north of the southern ITCZ axis between 110W and 115W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

See the special features section for details on the presently
in effect Gulf of Tehuantepec gale warning.

A 1021 mb high center is analyzed at 26N128W, with a ridge axis 
extending from northwest to southeast across the offshore waters.
Moderate to fresh anticyclonic winds prevail along the Pacific 
coast of Baja with long period northwest swell contributing to 
combined seas of 6 to 9 ft. The pressure gradient between the 
ridge and troughing along Baja California will tighten by 
this evening increasing winds along Baja California Norte
to mostly the strong category. These winds are expected to
persist through Friday with combined seas of about 7 to 9 ft.
These conditions are also expected to expand westward to near
117W during this forecast time.

In the Gulf of California, light to gentle variable flow will 
then prevail through the week and into the upcoming weekend with 
seas mainly 2 ft or less, except 3 to 4 ft near the entrance to 
the Gulf.

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

In the Gulf of Papagayo, fresh to locally strong nocturnal 
drainage winds are expected to pulse through the week and the 
upcoming weekend. These winds may possible max out to near 30 kt 
tonight, with seas expected to build to around 8 ft downstream 
of the gulf waters during and shortly after the pulsing 
conditions.

In the Gulf of Panama, moderate to fresh nocturnal northerly 
flow is expected during the overnight hours through the remainder
of the week and the upcoming weekend. Seas are expected to build
to a range of 5 to 7 ft downstream of the gulf waters.
  
Elsewhere, light to gentle winds and combined seas of 3 to 6 ft 
will prevail during the next several days.

A mid/upper level trough is noted on water vapor imagery along a 
position from 12N91W to 05N90W to the equator at 90W. Scattered 
moderate convection is within 120 nm east of the trough from 
01N to 03N. Isolated showers and thunderstorms are elsewhere 
within 180 nm east of the trough.

REMAINDER OF THE AREA...

A cold front is analyzed over the northwest portion of the 
area from near 32N127W ton 27N133W to 26N140W. The front will 
begin to weaken shortly as its upper level support is shunted to 
the north as broad upper level high pressure builds over the 
northwest and north-central portions of the discussion area. A 
second and stronger cold front is quickly approaching the 
northwest corner of the area. The first cold front will move to a
position from near 32N121W to 26N129W, and become a dissipating 
stationary front to 25N140W by early on Thursday at which time 
the second cold front is forecast along a position from near 
32N126W to 28N131W to 27N140W. A set of new northwest swell will 
propagate southeastward to a line from 32N129W to 27N134W to 
26N140W, with seas of 8 to 11 ft. The two fronts are forecast by 
the NWP models to eventually merge by late Thursday night with 
the merged front forecast from near 32N115W to 26N125W to 
24N140W, however seas up to 10 ft in northwest swell are forecast
to be north of 19N west of a line from 32N121W to 26N127W to 
19N132W at that time. Wave model guidance indicates that these 
seas will slowly subside Friday.

Elsewhere, a ridge extends from a 1021 mb high centered near 
26N130W southeastward to near 13N105W. The pressure gradient 
between the ridge and lower pressure in the tropical belt region
has resulted in fresh to strong northeast to east winds from 
09N to 14N west of 126W, with seas of 9 to 11 ft. Elsewhere from
06N to 20N west of 130W, and also from 05N to 14N between 116W
and 130W winds are generally in the fresh range. Seas of 8 to 9
ft in mixed northeast trade wind produced swell mixing with 
long-period northwest swell are found within this area. The 
fresh to strong northeast to east winds will weaken to fresh 
winds by early this evening as the aforementioned second cold 
front helps break down the ridging in place some. These  
conditions will vary little through Friday.
  
$$
Aguirre