Tropical Weather Discussion
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AXPZ20 KNHC 180355

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Thu Jan 18 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 0000 UTC surface analysis and satellite imagery through
0245 UTC.


Gulf of Tehuantepec Gale Warning: Strong high pressure continues
to build southward across eastern Mexico and the western Gulf of
Mexico behind yet another cold front, and is supporting a tight
pressure gradient across southern Mexico. Gale force winds of 40
to 45 kt prevail across and downwind of Tehuantepec and are
expected to through the early morning hours of Thu. Winds are
then expected to gradually diminish below gale force by Friday
afternoon. The resultant plume of northerly swell will continue
to propagate well southward of the Gulf of Tehuantepec waters,
mixing with long period NW swell to produce seas in excess of 8
ft to near 650 nm due S of Tehuantepec and over 800 nm SW of the
there. Maximum seas tonight will remain around 19 ft near the
strongest winds, and gradually subside by the end of the week as
the winds diminish.


A surface trough axis extends from 07N77W TO 09N86W TO 05N93W.
The ITCZ extends from 05N93W TO 07N130W to beyond 09.5N140W.
Scattered moderate isolated strong convection is occurring from
03N to 10N between 77W and 91W. Scattered moderate isolated
strong convection is within 75 nm S and 120 nm N of the axis
between 95W and 110W. Scattered to locally numerous moderate to
strong convection is occurring within 90 nm S and 360 nm N of
ITCZ between 110W and 137W.



Please see the special features section for information about
the ongoing gale warning in the offshore waters of the Gulf of

In the Gulf of California, light to moderate NW flow is expected
across across the entire gulf waters through Friday afternoon.
Winds will become southerly Friday evening ahead of an
approaching cold front, increasing to fresh to strong in the
northern gulf Friday night, then shifting to NW to N behind the
front. The front will gradually become ill defined as it moves
southward across the gulf during the day Saturday with mainly
moderate to fresh northerly flow in its wake for the end of the
weekend, except increasing to fresh to strong in the central and
southern Gulf Sunday afternoon and night as the pressure
gradient tightens across that area.

Elsewhere across the offshore waters of Mexico, large NW swell
continues to propagate SE across the waters, with seas of 8-11
ft prevailing, except 5-8 ft between 98W and 105W. The large
swell is generating high and powerful surf along the coasts and
outer reefs of the Baja California peninsula and mainland Mexico
which will continue this evening, with coastal flooding possible.
Another pulse of NW swell will reach the offshore waters off
Baja California Norte Thursday night. Seas will peak near 13-15
ft by Friday, while seas of 12 ft or greater will spread across
the offshore waters off the entire length of the Baja Peninsula
through the upcoming weekend.


Fresh NE gap winds winds will pulse to strong each night and
early morning across the Gulf of Papagayo through Saturday
morning, diminishing thereafter. Winds will also pulse to fresh
to strong offshore of other Central America gulfs and gap wind
areas tonight into early Thursday. Elsewhere, mainly light to
gentle offshore winds will prevail N of 09N, with light to
gentle southerly flow S of 09N. NW swell originating from the
gale wind event in the Gulf of Tehuantepec along with longer
period NW swell will arrive across the area waters Thursday and
Friday, building seas offshore to 5-7 ft.


Large, long period NW swell continues to propagate SE across the
forecast waters, with seas of 8 to 12 ft across the waters W of
95W-100W. A weakening cold front has moved into the far NW
portion of the area from 30N137W TO 28N140W, and will continue
SE through early Thursday, and be reinforced by building high
pressure Thursday evening. Winds W of the reinforced front will
increase to fresh to strong Thursday evening, with fresh to
strong trades gradually spreading across the waters N of 10N W
of 110W during the upcoming weekend as the front dissipates
across the N central waters.

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