Tropical Weather Discussion
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000
AXPZ20 KNHC 212140
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Tue Nov 21 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
2130 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: Gale force winds are expected
to develop rapidly late Wed afternoon, as a cold front moves
quickly southward across Mexico and the western Gulf of Mexico.
Light winds across the Tehuantepec region Wed morning and
afternoon with quickly increase to 20-25 kt by mid-afternoon and
then blast 30-40 kt by late afternoon into the evening hours, and
continue through Thu morning. Minimal gale force winds will persist
through Fri morning. Expect seas to build to 14 to 16 FT near
14.5N95.5W by late Thu. The resultant NE swell will propagate SW,
mixing with long-period cross equatorial swell, with seas 8 ft
or higher across the waters well downstream of the Gulf of
Tehuantepec, roughly within 120 nm of line from 12N97W to 07N100W
early Fri before beginning to subside.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The eastern Pacific monsoonal circulation has weakened in recent
days with the monsoon trough currently extending from the semi-
permanent low pressure near 10N75W across Panama on to 08N94W.
the ITCZ then begins from 08N94W TO 08N110W TO 10N130W to low
pres near 12.5N140W 1011 MB. Scattered moderate to strong
convection is noted generally from 10N to 15N and W of 135W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

See Special Features paragraph above for information on the
developing Gulf of Tehuantepec Gale Warning.

A weak NW to SE orientated ridge extends across the waters just
beyond 250 nm seaward of the Baja Peninsula and will maintain
light to moderate NW winds across the offshore waters N of 20N
through Wed morning. A weak trough is expected to form extending
SW from the central Baja Peninsula to near 23N116W, and continue
through early Fri before filling. This will occur as the ridge
shifts slightly NW and act to weaken weaken winds through the
week, with light to gentle winds prevailing.  Expect seas in the
3 to 4 ft range through Thu, building to 4 to 7 ft across the
waters N of 25N late in the week.

Gulf of California: Moderate to fresh NW winds are peaking at 20
KT or so this afternoon due to diurnal heating. These winds
should gradually subside overnight. Seas are expected to peak at
around 5-7 ft through central portions early tonight. The
pressure gradient will relax thu and Fri, with light and variable
winds expected through Sun.

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

Gulf of Papagayo: Light drainage flow expected during the
overnight hours through Thu, with fresh to locally strong
nocturnal drainage beginning on Thu night and continuing through
the upcoming weekend.

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 3 to 6 ft seas, are forecast S of the
monsoon trough through the upcoming weekend.

REMAINDER OF THE AREA... A NE to SW aligned ridge will meander
from 32N125W to 22N137W for the next several days. Strong
southerly winds, currently across the waters N of 28N W of 136W,
will diminish to 20 kt or less on Wed as the ridge weakens
allowing a cold front to approach the far NW portion the area
Wed and enter the forecast night Wed. The front will stall from
32N137W to 28140W on Thu. Long period NW swell, in the form of 12
to 15 ft seas at 13 to 15 seconds, will propagate E into the far
NW portion of the area late Wed and generally NW of a line from
29N115W to 17N140W by late Thu with seas subsiding to 8 to 12 FT.

$$
Cobb



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