Tropical Weather Discussion
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566
AXPZ20 KNHC 182140
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Wed Jan 18 2017

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 1800 UTC surface analysis and satellite imagery through
2100 UTC.

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

The ITCZ axis extends from 04N85W to 05N107W to 02N109W to
08N120W to 06N140W. A large area of moderate convection with
embedded stronger cells is from 07N to 14N between 114W and 123W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Satellite water vapor imagery shows a large moisture plume of
mid and upper level clouds advecting northeastward towards much
of central Mexico. Jet stream energy will combine with the deep
moisture to produce scattered showers and isolated thunderstorms
offshore the Mexican coast from south of Manzanillo northward to
southern Baja California and the coast of Mexico near Los Mochis.
The upper trough will continue to slide eastward through Friday
while shearing out. A stronger trough will sweep southeastward
and merge into the first trough on Thursday, with associated
moisture and weather shifting eastward with it.

Scatterometer data shows gentle to moderate northwest to north
winds west of Baja California and in the Gulf of California.
Light to gentle northerly winds prevail south and east of
Acapulco. Seas in the area are 5-6 ft west of Baja California, 1
to 3 ft in the Gulf of California, and 3-5 ft elsewhere.

Global models indicate a cold front will move into the waters
off Baja California Norte Thursday, then become diffuse ahead of
a much stronger cold front that will quickly move in across Baja
California and the Gulf of California Friday and Saturday. The
second cold front will be accompanied by fresh to strong winds
and large northwest swell. This swell event is expected to build
seas to 12-19 ft off Baja California Norte Saturday, and 8-13 ft
seas off Baja California Sur. Wave model guidance indicates max
seas may be around 21 ft in the waters north of 29N on Saturday.
These marine conditions are likely to bring hazardous marine
conditions to mariners navigating the nearshore and coastal
waters, and very dangerous surf conditions along the coast.
Southwest winds ahead of the second cold front are expected to
increase to near gale force over much of the northern Gulf of
California late Friday nigh, with seas building to 8-9 ft.

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

Moderate northeast winds this afternoon will pulse to 25 kt late
tonight across the Gulf of Papagayo and downwind to about 88W.
Winds area then expected to diminish by Thursday night. Light to
gentle variable winds are expected there Friday.

Light to gentle easterly winds will prevail elsewhere through
Saturday. Seas will be generally 3-5 ft in the forecast waters.

REMAINDER OF THE AREA...

High pressure centered near 25N139W extends a ridge eastward to
the Baja peninsula. The gradient between the high and lower
pressure associated with the ITCZ is supporting an area of fresh
to strong northeast trade winds from 08N TO 13N west of 130W in
9-10 ft seas. Scatterometer data shows fresh trades elsewhere,
roughly from 07N to 20N west of 115W. Seas with these trades are
7-10 ft in mixed northwest swell and northeast wind waves. The
high will be nudged southwest over the next two days in response
to the aforementioned cold fronts forecast to pass across the
waters north of 25N. This will allow the trades to decrease in
coverage and shift westward through Friday.

Looking ahead, northwest swell with seas to 8-16 ft associated
with a cold front moving eastward across the waters north of 25N
through Thursday will be followed by a second front expected to
sweep southeastward across the northern waters Thursday night
and Friday. Wave model guidance shows large northwest swell will
propagate southeastward into the waters north of 20N behind the
second front, with seas building quite large to 15-21 ft in the
far northern waters east of 130W late Friday into Saturday.

$$
Mundell



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