Tropical Weather Discussion
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AXPZ20 KNHC 181517

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1517 UTC Mon Dec 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.


A trough axis extends from the coast of western Colombia near
04N77W to 06N93W. The intertropical convergence zone axis
extends from 06N93W to 09N110W to 10N130W to 10N140W. Scattered
moderate and isolated strong convection is from 08N to 10N
between 106W and 109W, and also from 11N to 15N between 114W and
118W. Scattered moderate convection is from 07N to 10N between
125W and 129W.



In the Gulf of California, a cold front extends from low pressure
near the Arizona and Mexico border at 31N111W across Mexico to
the central Gulf of California near 27N110W, then to across and
offshore of the Baja California Peninsula. The low pressure will
shift NE of the area today and drag the weakening front SE
across the S portion of the Gulf before dissipating. Early
observations showed fresh to strong NW-N flow in the far NW
corner of the Gulf which should diminish this afternoon as
conditions improve. Seas are 3-6 ft N of the front, and 1-3 ft S
of the front. Moderate northerly winds are then expected across
the Gulf through late Wed before the next front sweeps SSE into
the area. Northerly winds will increase to strong to near Gale
force behind this next front early Thu through Fri with seas
building to 8 ft. These strong winds are also forecast to seep
through Baja California passages into the open Pacific waters W
of the peninsula.

Active convection continues in a broad zone across the offshore
waters of SW Mexico from the Manzanillo to Cabo Corrientes areas
SW to near 16N110W. An upper level trough that supported the
front that has moved through the Gulf of California lingers
across the region, with upper level jet energy enhancing this
convection. Active weather will continue across this region
through Tue before shifting SW and well offshore.

In the Gulf of Tehuantepec, offshore northerly winds will pulse
to fresh to strong mainly during the overnight and early morning
hours with seas occasionally building to 8 ft.

Elsewhere across the offshore waters of Mexico, gentle to
moderate mainly NW winds prevail. NW swell of 7-10 ft W of the
Baja California Peninsula will continue to subside through
tonight, with 4-6 ft seas elsewhere. A fresh pulse of NW swell
will propagate into the waters off the coast of Baja California
Norte Thu behind the next cold front, with seas building to near
9 ft.


In the Gulf of Papagayo, winds will pulse to fresh to strong
mainly during the night and early morning hours with seas
occasionally building to 8 ft.

In the Gulf of Panama, moderate to fresh winds will diminish
later this morning, then will pulse again tonight into early

Elsewhere, mainly gentle NE-E winds will prevail N of 09N, and
moderate SW flow S of 09N.


Northerly swell of 7-10 ft N of 20N continues to subside and will
be less than 8 ft by early Wed.

Mainly moderate winds prevail elsewhere over the forecast waters
N of the ITCZ to 20N and W of 125W. High pressure across the NE
Pacific will dominate the regional waters for the next few days
with little change in wind speed magnitude.

Looking ahead, the pressure gradient will increase N of 20N and W
of 130W between the high and low pressure moving northward W of
140W. SE flow around the high will increase to fresh to strong
with seas building to 7-9 ft Thu night. The low may then briefly
cross to near 30N140W by late Fri night. The gradient may
continue to tighten and if so, gale conditions may be possible
in the NW corner with seas building to well over 12 ft.

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