Tropical Weather Discussion
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000
AXPZ20 KNHC 160938
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Dec 16 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
0830 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: A cold front has stalled across
the western Gulf of Mexico this morning and is extends across
the central Bay of Campeche and through the Chivelas Pass.
Recent ASCAT data prior to 0400 UTC showed northerly winds to
around 30 kt across the Gulf of Tehuantepec northward of 15.5N.
Winds are assumed to have increased to gale force over the Gulf
of Tehuantepec since this time. The cold front will weaken
during the day Saturday, and begin to drift northward by
afternoon. This will diminish winds funneling across the Gulf of
Tehuantepec with gales expected to end by late morning, or
around 1500 UTC, then continue to gradually diminish during the
afternoon.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

A weak trough extends from the Gulf of Panama westward to 90W.
The ITCZ extends from 06.5N91W to beyond 10N140W. Scattered
moderate to strong convection is noted within 120 nm N of the
ITCZ between 96W and 99W, and from 110W to 113W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of California: A cold front is moving SSE into Southern
California and the offshore Pacific waters tonight and will move
into the northern Gulf of California today, before stalling and
dissipating over the central Gulf on Sun. Winds over the
northern Gulf will shift SW early today ahead of the front, and
increase to strong by afternoon as associated low pressure
deepens over the lower Colorado River basin. The main issue by
Sat night will be the possibility of strong W to NW winds over
the northern Gulf as the low pressure shifts eastward into the
Sonora Desert. While the fetch across the northern Gulf will be
too limited to develop large seas, mariners should be aware of
the possibility of sudden strong winds through low lying areas
of Baja California Norte through early Sun. Winds diminish
through early next week after the low pressure dissipates. By
weeks end, another cold front sweeping across the region will
force strong to near gale force winds spreading the length of
the Gulf, with large seas developing.

This same cold front will move through the waters off Baja
California Norte through this morning followed by strong NW
winds and seas building to 8 to 12 ft late today. Seas of 8 to
10 ft will cover most of the waters beyond 60 nm of the Baja
coast through early next week in NW swell. Elsewhere gentle to
moderate winds and 3 to 5 ft will persist along the coast of
Mexico outside of the Gulf of Tehuantepec through mid week.

To the SE, and upper level trough extends from Sinaloa SW to the
tropics near 11N120W. A broad low level convergence zone extends
from near 10N120W to the coast of Mexico between Cabo Corrientes
and Manzanillo, where scattered moderate to strong convection is
active tonight under strong upper level SW winds occurring to
the SE of the upper trough. Weather across this zone is expected
to remain active today and shift slightly northward along the
coast tonight and Sunday ahead of the front moving across Baja
California.

Please see Special Features section for more information on the
latest Gulf of Tehuantepec gale warning.

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

Fresh winds forecast to develop across the Gulf of Papagayo
today are expected to strengthen to 20-25 kt tonight. Fresh N
winds will funnel into the Gulf of Panama through late this
morning.

REMAINDER OF THE AREA...

Fresh to strong tradewinds prevail from 11N to 21N west of 128W.
Moderate to fresh winds prevails elsewhere over the forecast
waters north of the ITCZ to 20N and west of 120W. Seas
associated with a fresh pulse of NW swell are reaching 13-14 ft
in the area of strong trades W of 135W. Seas will slowly subside
as the swell propagates southeast the next few days. A cold
front will move into the far northern waters Saturday. This will
usher in another set of northerly swell into the area.

$$

Stripling



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