000
AXPZ20 KNHC 190926
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
910 UTC Wed Dec 19 2018

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
0926 UTC.

...SPECIAL FEATURES...
Gulf of Tehuantepec Gale Warning: A powerful cold front will sweep
across the Gulf of Mexico today through Thu. The tight pressure gradient
and cool, dry airmass behind the front will support gap winds into
the Gulf of Tehuantepec reaching gale force by late Thu. The plume
of strong gap winds will reach at least 500 nm to the south and 
southeast of the Gulf of Tehuantepec by late Fri, with seas building
as high as 18 ft with the area of strong winds. The gales will persist
through Fri night, then diminish into Sat as the high pressure north
of the area weakens and shifts east, although fresh to strong 
gap winds will persist across the Gulf of Tehuantepec into early 
next week.

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

The ITCZ extends from 05N98W to 06N140W. Scattered moderate 
convection is noted within 60 nm north of the ITCZ west of 135W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Large NW swell is impacting the forecast waters, with the 
leading edge of 12 ft seas or greater noted in the waters off 
Baja California Peninsula to the Revillagigedo Islands. This 
swell will produce hazardous seas for mariners, and create large 
and powerful surf along the Pacific reefs and beaches. This high 
surf may also produce coastal flooding and beach erosion in many
exposed locations from southern California to western Mexico. 
This swell will decay to 8 to 11 ft by this evening, just ahead 
of another round of NW swell to 12 ft reaching Guadalupe Island 
and the northern coast of Baja California early on Thu. This 
swell will decay below 12 ft by Thu evening, leaving 8 to 10 ft 
NW swell in place for the Mexican open waters west of 110W 
through Sat.

Across the Gulf of California, recent ship observations over the
southern Gulf of California are showing fresh strong NW winds. 
This is due to high pressure building over the Great Basin well
north of the region, and this will support fresh to strong winds
across the northern and central Gulf through Thu morning, with 
seas build to 5-8 ft.

In addition, ship observations on the Pacific side of the Baja 
California Peninsula indicates some of this momentum appears to 
be crossing the southern portion of Baja California Sur, from La 
Paz to Todos Santos. This gap wind will persist through much of 
today, bringing localized strong winds and higher seas between 
Cabo San Lucas and 

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

A strong cold front will move across the SW Caribbean on Fri 
morning. Strong northerly winds behind the front will funnel 
through the Gulf of Papagayo increasing to near gale force by 
late Fri night. A strong pressure gradient between the ridge 
building behind the front and lower pressure in the SW Caribbean 
will support the continuation of the gap wind event through Sun 
night. Seas are expected to peak to 12 ft by Sat morning. Winds 
and seas will gradually diminish from Sun night to Mon night. 

Northerly fresh winds are expected in the Gulf of Panama Sat 
night through early on Mon with seas to 7 ft.

Elsewhere, gentle to moderate winds will persist, with seas 
in the 4 to 7 ft range.

REMAINDER OF THE AREA... 

1027 mb high pressure centered north of the area near 34N126W
will will maintain a weak pressure pattern and moderate wind flow over
the waters north of 20N over the next several days, and moderate
to fresh trade winds farther south to the ITCZ. The front will 
weaken as it moves eastward north of 20N through Fri. Meanwhile a
sharp upper trough will become cutoff west of the area and east
of Hawaii. This will support development of a quasi-stationary
trough along the ITCZ west of 135W by late Thu. The combination 
of the surface trough and high pressure building in the wake of
the cold front will support fresh to strong trade winds along the
ITCZ west of 135W by late Thu into early Fri.

Lingering NW swell of 11 to 14 ft over the entire basin will be 
reinforced by additional NW swell today, with the leading edge of
12 to 14 ft reaching from 30N125W to 18N140W by tonight. 
Elsewhere, older NW swell will subside below 12 ft through 
today. The combined NW swell groups will subside across the
region through late Thu, leaving 8 to 11 ft in most areas, except
for up to 12 ft near the area of fresh to strong trade winds 
along the ITCZ west of 135W by late Thu. 

By Fri, much of the older swell north of 20N will have decayed 
below 8 ft, leaving mixed NW swell and shorter period trade wind 
swell along the ITCZ south of 15N west of 110W, and another area 
south of 15N east of 110W where NW swell will be mixed with 
shorter period easterly swell associated with renewed gap wind 
gales from Tehuantepec and Central America. Looking ahead, a 
modest reinforcing NW swell of 8 to 9 ft will move into the
region Sat and Sun. 

$$
Christensen