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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 191456
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1304 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.

...SPECIAL FEATURES...
Gulf of Tehuantepec Gale Warning: A cold front will sweep across
the Gulf of Mexico today through Thu. High pressure building in
the wake of the front will help generate a tight pressure 
gradient over the area and usher in the next gale force gap wind
event. Winds will rapidly increase to gale force gale force by 
late Thu. The plume of strong gap winds will reach at least 500 
nm to the south and southwest 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. Fresh to strong gap winds will then persist across 
the Gulf of Tehuantepec into early next week.

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

The ITCZ extends from 05N98W to 05N115W to 08N136W to 08N140W.
Scattered moderate isolated strong convection is noted from 02N
to 06N E of 80W. Scattered moderate convection is noted from 03N
to 06N between 85W and 92W. Scattered moderate convection is 
noted from 04N to 07N between 101W and 105W. Scattered moderate
isolated strong convection is noted within 60 nm of the ITCZ 
west of 132W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Please see above for more on the upcoming gale force gap wind
event over the Gulf of Tehuantepec.

Large NW swell continues to impact the forecast waters, with seas
in the 11 to 13 ft range over the waters off the Baja California
Peninsula to the Revillagigedo Islands. This swell will continue
to 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 next 
swell will decay below 12 ft by Thu evening, with seas in the 8 
to 10 ft range over the open waters off Mexico west of 110W 
through Sat.

High pressure building over the Great Basin will support fresh 
to strong winds across the central Gulf of California through 
Thu morning, with seas building to 5-8 ft.

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

Gulf of Papagayo: A 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 tight pressure gradient between high 
pressure 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 near 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... 

High pressure of 1027 mb is centered north of the area near 
33N127W. The pressure gradient between this area of high 
pressure and lower pressure in the vicinity of the ITCZ will 
support moderate to fresh trade winds north of the ITCZ to around
20N. A sharp upper trough will cutoff west of the area, and help
develop a quasi- stationary trough along the ITCZ west of 135W 
by late Thu. This will lead to a locally tighter pressure 
gradient over this area, with tradewinds strengthening N of the 
ITCZ to near 15N and west of 135W by late Thu into early Fri.

NW swell continues to prevail across the discussion area. Seas of
8 ft or greater are noted W of 103W. Another set of NW swell has
entered the NW waters, with seas of 12 to 16 ft noted NW of a 
line from 30N133W to 24N140W. Seas will start to subside over the
area today, falling below 8 ft N of 20N by Sat morning. 

$$
AL