Tropical Weather Discussion
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000
AXPZ20 KNHC 190945
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sun Nov 19 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: Strong northerly drainage
winds will begin just before sunrise this morning, quickly
increase to minimal gale force before noon, and gradually to
strengthen to at least 40 kt tonight, with seas building to a
max of 18 ft downstream of the gulf waters near 14N95.5W late
tonight. Winds will diminish below gale force on Mon morning,
and gradually diminish to 20 kt or less late Mon night. 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 morning with gale conditions on Wed evening
through Fri morning.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends W across the Gulf of Panama to the
Pacific coast of Panama at 09N78W to 09N105W where scatterometer
winds indicate a transition to an ITCZ, which continues W-NW to
beyond 12N140W. Scattered moderate isolated strong convection is
noted within 150 nm either side of a line from 11.5N116W to
09N125W to 12N133W.

...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 to locally fresh NW flow W of the Baja
Peninsula through mid morning when the pressure gradient will
relax, supporting moderate NW flow this afternoon through
sunrise on Mon. Light N winds winds then expected through Thu
with a trough forming to SW from the central Baja Peninsula on
Thu night and Fri, accompnaied by a light W to NW wind shift.
Expect seas in the 4 to 7 ft range today with these conditions
resuming again late in the week, with 3 to 5 ft seas during
early and mid part of the week.

Gulf of California: Strong N winds expected to continue across
the gulf waters N of 25N through early afternoon. The pressure
gradient will relax tonight with moderate NW flow forecast
across the entire gulf waters at sunrise on Mon, then becoming
light northerly flow by Mon evening.  Moderate to locally fresh
NW flow will resume across the entire gulf on Tue and Wed, then
diminishing some on Thu.

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 and on Mon
night, then light drainage flow expected during the overnight
hours through Thu night, with moderate to fresh nocturnal
drainage resuming on Fri night.

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 32N124W 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 tonight through Tue 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 15 ft W
of the front through Thu.

Moderate to locally fresh anticyclonic flow expected across the
tropics N of the ITCZ and W of 120W through the middle of next
week, with seas subsiding to 4 to 7 ft by this evening, with
little change through mid week. Long period NW swell will
propagate SE into the tropics w of 130W on Thu, and continue
E across the tropical waters W of 120W late in the week.

$$
Nelson



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