425 
AXPZ20 KNHC 150401
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Dec 15 2023

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 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
0345 UTC.

...SPECIAL FEATURES...

Tehuantepec Gale Warning: The combination of strong high pressure 
that stretches from the eastern United States southwestward to
southeastern Mexico and relatively lower pressure south of Mexico 
is allowing for gale-force gap winds in the Gulf of Tehuantepec.
The fresh to strong winds extend downstream from the Gulf to 
near 12N97W. Peak seas are near 12 ft. The 8 ft seas extend 
west-southwestward to near 04N97W. The gale-force winds will end 
late tonight as the tight pressure gradient currently in place 
becomes disrupted as troughing becomes established in the SW Gulf 
of Mexico prior to the development of low pressure there on Fri 
night. Seas will subside below 12 ft early on Fri. Strong winds 
will continue into the weekend, with gale force winds returning 
by Sat afternoon. This next round of gale force winds will last 
through the weekend, and continue into early next week. Rough to 
very rough seas are expected. 

NW Eastern Pacific Gale Warning: Low pressure of 1003 mb is just
northwest of the area near 31N138W. A cold front extends from the 
low to just west of 140W. The low is forecast to deepen over the
next few days as it gradually lifts northward. As the front 
reaches the NW corner late tonight from near 30N138W to 26N140W,
near gale to gale winds are expected ahead and behind the front 
through Fri night. Another cold front will enter the forecast 
waters from the same extratropical low on Sat, bringing another 
round of gale-force winds. Expect these winds to occur north
of 26N and west of 128W. The gale force winds will end by Sat 
night with strong winds continuing across the northwest waters 
through Sun. Very large NW swell will be accompanying this system
with seas over 12 ft entering the waters by tonight and 
continuing through Mon. These seas will expand across the Pacific
waters through the weekend, extending as far south as 14N and 
west of about 130W. Peak seas will be well over 20 ft and 
expected to occur Fri through Sun, with the maximum seas expected 
in the far northwest corner of the area. Seas will begin to 
slowly subside starting Sun afternoon and into early next week.

Please read the latest High Seas Forecast and the Offshore 
Waters Forecast issued by the National Hurricane Center at 
https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and 
www.nhc.noaa.gov/marine/offshores.php for details on the special 
feature.

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

The monsoon trough axis extends from low pressure over northwest 
Colombia southwestward to 06N77W to 06N92W to 05N105W and to
05N112W, where latest scatterometer data indicates that it
transitions to the ITCZ to 06N122W to 09N127W to 10N135W and
to beyond 10N140W. Scattered moderate convection is 180 nm 
south of the trough between 87W-90W, also within 60 nm south 
of the trough between 77W-79W, within 60 nm of the trough between
92W-96W and within 30 nm of the trough between 106W-109W.

...OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please refer to the Special Features section for details on a 
Gale Warning for the Tehuantepec region.

The combination of high pressure over the U.S. Great Basin and 
relatively lower pressure over northwest Mexico and the Gulf of 
California area is allowing for mostly fresh northwest to 
north winds over the Gulf of California with seas to 6 ft. 
Meanwhile, weak pressure gradient dominates the Mexican offshore 
waters, outside of the Gulf of Tehuantepec. Moderate or weaker 
winds and slight to moderate seas continue across the rest of 
the offshore waters. Seas across the Baja California offshore
waters and over the southern Mexico offshore waters are in 
the 4-6 ft range due to long-period west to northwest swell.
No significant convection is noted at this time.

For the forecast, the high pressure over the eastern United 
States is helping to sustain gale-force gap winds in the Gulf of
Tehuantepec. The gale-force winds will end late tonight. Strong 
winds will persist through Sat. Meanwhile, ridging will build 
over the Great Basin in the western United States through Sat. 
This will sustain fresh to strong NW winds over the Gulf of 
California tonight through Sat with winds subsiding through Sun. 
Another round of gale-force winds across the Gulf of Tehuantepec 
is expected to begin on Sat and continue into early next week. 
Rough to possibly very rough seas can be expected with these 
winds. 

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

The combination off strong high pressure that stretches from the
eastern United States southwestward to southeastern Mexico and 
relatively lower pressure found south of Mexico is maintaining
persistent fresh to strong easterly trade winds across the Gulf 
of Papagayo region, including the coast of southern Nicaragua. 
These winds extend as far west as 07N92W as was depicted in an 
ASCAT data pass from Thu afternoon. Wave heights with these
winds are in the range of 5-7 ft. In addition, seas to 9 ft in 
a northwest swell generated by the Gulf of Tehuantepec gap wind 
event continue to impact the offshore waters of Guatemala and El 
Salvador through Fri. 

The aforementioned strong pressure gradient is also supporting 
moderate to fresh northerly winds in the Gulf of Panama. These 
winds reach south to near 06N. Seas over these waters are 4-6 
ft. South of 06N, mostly gentle south to southwest winds are 
occurring, with seas of 4-5 ft due to mixed swell. 

For the forecast, the strong northeast to east gap winds in the 
Gulf of Papagayo are expected through Fri, diminishing to 
moderate to fresh speeds this weekend. Winds will increase to 
strong speeds by Mon and continue till around the middle of 
the week. Expect rough seas in this area once again due to 
another Gulf of Tehuantepec gap wind event on Sun. Elsewhere, 
winds are moderate or weaker for the next several days. 

...REMAINDER OF THE AREA...

Please see the Special Features section for more information on
the gale warning for the far northwest waters of the area. 

Fresh to strong south to southwest winds over the northwest 
part of the area north of 25N and west of 136W precede a
strong frontal system that is just northwest to west of the 
discussion area. Seas with these winds are 10-12 ft. A recent
altimeter data pass indicated seas to 11 ft just to the east
of the fresh to strong winds.

A 1021 mb high center is analyzed just west of southern
California. The associated gradient controls the wind regime
over most of the tropical eastern Pacific. Moderate to fresh 
trade winds are noted from the ITCZ north to 21N. Seas over 
these waters are 6-8 ft. Meanwhile, moderate southerly winds are 
found south of 03N. Seas over these waters are 6-8 ft. Elsewhere,
light to gentle winds and moderate seas are prevalent.

For the forecast, trade winds will slowly diminish to be 
moderate or weaker by Fri and through the weekend as the 
extratropical low moves across the area. Large swell from the 
extratropical low will impact most of the waters, with the 8 ft 
seas extending as far south as the equator and as far east as 
100W. An upcoming gap wind gale event across the Gulf of 
Tehuantepec will bring rough waters to the high seas later on Sun
and into Mon, merging with the aforementioned swell. 

$$
Aguirre