Tropical Weather Discussion
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000
AXPZ20 KNHC 180935
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 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 0600 UTC surface analysis and satellite imagery through
0845 UTC.

...SPECIAL FEATURES...

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 continue 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 through this morning. Maximum seas tonight
will remain around 20 ft near the strongest winds, and gradually
subside by the end of the week as the winds diminish.

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

A surface trough axis extends from 07N77W TO 09N86W TO 04N98W.
Overnight scatterometer winds suggest a transition to ITCZ from
04N98W continuing on to 06.5N109W to beyond 07N140W. Scattered
moderate isolated strong convection is occurring from 04N to 10N
between 77W and 86W. Scattered moderate isolated strong
convection is within 60 nm of the axis between 90W and 107W.
Scattered to locally numerous moderate to strong convection is
occurring within 90 nm S and 150 nm N of ITCZ between 108W and
121W, and from 06N to 14N between 121W and 136W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

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

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 through the gulf during the day Saturday with mainly
moderate to fresh northerly flow in its wake for the end of the
weekend. The ill defined remnants of the front are expected to
push S to the entrance of the gulf by Sun afternoon, when the
pressure gradient will begin to tight across the area leading to
fresh to strong winds developing across the full length of the
gulf Sun evening and night.

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. This large
swell continues to generate high and powerful surf along the
coasts and outer reefs of the Baja California peninsula and
mainland Mexico, which will continue through Thu, 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.

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

Fresh NE gap winds prevailing across the regional waters between
Papagayo and Tehuantepec will pulse to strong each night and
early morning across the Gulf of Papagayo and other typical gap
wind areas through Saturday morning, diminishing thereafter.
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.

REMAINDER OF THE AREA...

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
100W. A weakening cold front has moved into the far NW portion
of the area from 30N136W TO 28N140W, and will continue SE
through early Thursday, and be reinforced by building high
pressure Thursday evening. Winds NW of the reinforced front will
increase to fresh to strong Thursday evening, and shift E and SE
with the front as it moves through Baja California Fri and Sat.
Strong high pressure behind the front will induce 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.

$$
Stripling


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