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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 151540

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1540 UTC Fri Dec 15 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.


Gulf of Tehuantepec Gale Warning: A cold front moving southward 
across the western Gulf of Mexico will reach the isthmus of 
Tehuantepec later today. Cool and dense air will funnel through 
the Chivela pass into the Gulf of Tehuantepec this evening with 
winds rapidly ramping up to near gale force and further to gale 
force later tonight. The front will weaken Saturday, which will 
diminish winds funneling across the Gulf of Tehuantepec. This 
will keep this gale force gap wind event brief as winds are 
expected to diminish below gale force by Sat afternoon. 


The monsoon trough extends from 09N84W TO 06N98W, where it
transitions to the intertropical convergence zone and continues
to beyond 10N140W. No significant convection is observed near the
monsoon trough or ITCZ, but scattered moderate convection is
noted from 15N to 18N between 110W and 115W.



Gulf of California: Strong high pressure north of the area over
the Great Basin and northern Rockies is supporting fresh to
occasionally strong NW winds over the far northern Gulf of 
California this morning. Fresh winds will gradually spread 
across the northern half of the Gulf through tonight with seas to
5 ft. A cold front will move into across the northern Gulf Sat, 
before stalling and dissipating over the central Gulf Sun. Winds
over the northern Gulf will shift SW early Sat ahead of the
front, 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 Sonoran Desert. While the fetch
across the northern Gulf will be to 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.

Elsewhere, fresh N to NE gap wind will spill across Baja
California Norte into the Bay of Sebastian Vizcaino this
afternoon then diminish. A cold front will move through the
waters off Baja California Norte through early Sat followed by
strong NW winds and seas building to 8 to 12 ft by late Sat. 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 

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


Fresh to strong winds across the Gulf of Papagayo are 
diminishing this morning, but will strengthen again Sat night. 
Fresh N winds will funnel across the Gulf of Panama through late 
this morning before diminishing through the weekend. 


Ridging extends from 1033 mb high pressure near 42N138W to the
Revillagigedo Islands. The pressure gradient between this area 
of high pressure and lower pressure in the vicinity of the ITCZ 
is supporting moderate to fresh winds north of the ITCZ to 20N 
and west of 120W. Fresh to strong tradewinds are noted on a
earlier scatterometer satellite pass north of trough near 140W. 
Seas associated with a fresh pulse of NW swell are peaking near
13 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.