Tropical Weather Discussion
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000
AXPZ20 KNHC 200949
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon Nov 20 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 0600 UTC surface analysis and satellite imagery through
0945 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Gale force 30 to 40 kt
northerly winds will continue through sunrise this morning, with
maximum seas of 17 ft downstream of the gulf waters near
14N95.5W just before sunrise. Winds will gradually diminish to
20 kt or less on Tue morning. The associated NE swell will
propagate SW mixing with long-period cross-equatorial swell,
resulting in an area of 8 ft and greater seas of across the
waters from roughly 09N to 13N between 94W and 103W on Mon
night, with a small area of 8 ft seas subsiding near 10N104W on
Tue morning. Strong N winds are expected to resume on Wed
afternoon, with gale conditions on Wed evening through Fri
morning with max seas of 15 ft near 13N96W on Thu.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends W-SW across the southern Gulf of
Panama from 08N78W to 06N90W to 08N104W where scatterometer
winds indicate a transition to an ITCZ, which continues W-NW to
11N114W to 10N131W to beyond 11N140W. Scattered moderate
isolated strong convection is noted within 240 nm of 11.5N121W,
and along the ITCZ within 75 nm either side of a line from
09N128W to 14N140W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

See Special Features paragraph for Gulf of Tehuantepec Gale
Warning.

A NW to SE orientated ridge just beyond 250 nm seaward will
maintain moderate NW flow W of the Baja Peninsula through mid
morning when the pressure gradient will relax, supporting light
northerly winds through late wed when a trough will form SW from
the central Baja Peninsula to near 22N116W and continue through
early Fri before filling. Expect seas in the 3 to 5 ft range
through Thu building to 5 to 7 ft N of 25N late in the week.

Gulf of California: Moderate NW flow will diminish to a light
breeze later this morning and continue through Tue morning when
moderate to locally fresh conditions will develop, and continue
through early Wed. Light to moderate NW flow expected on Thu and
Fri becoming light and variable on Fri night.

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

Gulf of Papagayo:  Moderate to locally fresh NE drainage winds
are forecast during the overnight hours tonight, then light
drainage flow expected during the overnight hours through Thu
night, with fresh to locally strong nocturnal drainage
possible on Fri and Sat nights.

Light and variable winds, and 3 to 5 ft seas, are expected
elsewhere to the N of the monsoon trough which has been
meandering between 09N and 11N, while moderate to locally fresh
southerly winds, and 4 to 7 ft seas, are forecast S of the
monsoon trough this week.

REMAINDER OF THE AREA...

A NE to SW aligned ridge will meander from 32N125W to beyond
20N140W for the next several days. Strong to occasionally near
gale force southerly winds currently across the waters N of 28N
W of 138W, will spread E across the waters generally W of a line
from 32N130W to 22N140W through late tonight before the pressure
gradient relaxes. Associated seas are expected to build to 8 to
12 ft across the waters S of 30N, while 10 to 14 ft seas are
forecast from 30N to 32N. A series of cold front will approach,
but stall just W of 140W through Tue night. Model guidance is
suggesting a cold front will arrive at 32N140W on Wed, and stall
from 32N136W to 23N140W on Thu, with seas building 12 to 17 ft W
of the front through Thu.

Moderate anticyclonic flow expected across the tropics N of the
ITCZ and W of 120W through the middle of next week, with seas of
4 to 7 ft. Long period NW swell will propagate E across the
discussion waters W of 120W from mid to late week, and subside
over the upcoming weekend.

$$
Nelson


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