Tropical Weather Discussion
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AXPZ20 KNHC 212157

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2157 UTC Sat Oct 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
2100 UTC.


Gulf of Tehuantepec Gale Warning...Fresh to strong northerly flow
will develop by Sunday evening as the pressure gradient N of the
area tightens combined with nighttime drainage flow. The
pressure gradient will continue to tighten thereafter and winds
will increase to gale force by early Monday as a cold front moves
through the western Gulf of Mexico. Cool and dry air behind the
front will reinforce already present local drainage effects
allowing the gale to persist through much of the week. Winds may
even approach minimal storm force by early Wednesday. Seas will
build to up to 18 ft by mid-week.


A tropical wave that was previously analyzed across Central
America has become diffuse and difficult to track.

A tropical wave is N of 07N along 97W moving W at around 5 to 10
kt. Associated convection is minimal.


The monsoon trough axis extends from 09N78W to 10N89W to 08N98W
to 10N112W to 09N120W. The intertropical convergence zone axis
extends from 09N120W to 10N130W to 09N140W. Scattered moderate
and isolated strong convection is within 75 nm either side of the
axis between 95W and 106W, within 120 nm S of a line from 11N110W
to 10N116W to 08N121W, and from 08N to 10N W of 128W.

Also, numerous moderate and scattered strong convection is N of
05N E of 80W, including the Gulf of Panama enhanced somewhat by
the southern portion of a tropical wave which extends into the SW
Caribbean Sea.



Please see the special features section above for information on
a developing gale event in the Gulf of Tehuantepec.

Fresh to locally strong NW winds are ongoing off the coast of
Baja California N of Cabo San Lazaro between strong high
pressure W of the area and troughing over the SW United States
and N central Mexico. These winds will diminish this evening as
the troughing weakens. Seas will are peaking near 16 ft off the
northernmost coast of Baja California Norte in northerly swell,
and are expected to subside through early next week as winds
diminish and the swell decays. The swell will propagate SE, with
seas 8 ft or greater covering all of the offshore forecast zones
W of Baja California through the remainder of the weekend before
subsiding to less than 8 ft by the middle of next week.

High pressure building over the Great Basin region of the
western United States will cause NW winds to strengthen over the
Gulf of California through Tuesday, diminishing thereafter as the
gradient weakens. Winds will be the strongest on Sunday night
through Monday when seas peak around 8 ft.


Gentle to moderate winds will prevail over the forecast area the
next several days, except increasing to moderate to fresh S of
the monsoon trough by Monday afternoon. NW swell originating
from the Gulf of Tehuantepec will propagate into the offshore
waters of Guatemala and El Salvador by the middle of next week.


A set of large NW swell with seas near 16 ft will continue to
propagate SE while gradually subsiding into early next week. Seas
will subside to less than 12 ft Sunday afternoon. Seas
associated to this swell are expected to further subside, to
less than 8 ft, by mid week.

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