000
AXPZ20 KNHC 290921
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
600 UTC Fri Dec 29 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
0900 UTC.

..SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: The pressure gradient between
High pressure over eastern Mexico and a surface trough over the
eastern North Pacific is supporting gale force winds over the
Gulf of Tehuantepec. The area of high pressure will weaken and
shift eastward Friday night into Saturday. This will loosen the
pressure gradient and diminish winds below gale force Saturday.
Winds will veer Saturday which will further diminish winds
funneling into the Gulf of Tehuantepec. By Sunday, winds will
diminish to 20 kt or less, bringing an end to this latest Gulf of
Tehuantepec gap wind event. Refer to the latest high seas 
forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more 
details.

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

A surface trough extends from 06.5N77W to 07N87W to 05N99W, 
where it transitions to the ITCZ and continues to 11N127W. It 
resumes from 10N132W to beyond 09N140W. Scattered moderate 
isolated strong convection is noted north of 07N east of 80W. 
Scattered moderate isolated strong convection is notes from 08N 
to 12N between 113W and 118W. Scattered moderate isolated strong 
convection is noted from 13N to 16N between 120W and 124W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of Tehuantepec: Please refer to the special features 
section above for details on an ongoing Gulf of Tehuantepec Gale 
event. Looking ahead, A cold front will push into the Gulf of
Mexico on Sunday. The front will reach the Bay of Campeche
Monday, and will bring the next gale force gap wind event into
the Gulf of Tehuantepec. 

Elsewhere, tranquil marine conditions are expected with light to
gentle winds prevailing over the forecast waters. Seas in the 
range of 3-5 ft will prevail over the offshore waters, while seas
in the 1-3 ft range will prevail in the Gulf of California.

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

Nocturnal winds will pulse to fresh to strong over the Gulf of 
Papagayo through Monday night. Light to gentle winds will prevail
elsewhere N of 09N with gentle to moderate winds prevailing S of
09N.

REMAINDER OF THE AREA...

Subsiding NW swell continues to produce seas to 8 ft from 15N to
20N between 122W and 129W. Seas will continue to subside, 
falling below 8 ft over this area by tonight. A cold front will 
move into the far NW portion of the forecast area tonight. 
Southerly winds ahead of the front will strengthen tonight with 
seas building to near 9 ft. The front will rapidly weaken and 
associated winds and seas will fall below advisory criteria by 
Sat night. Otherwise gentle to moderate winds with seas in the 
4-7 ft range will prevail through Sunday. Looking ahead, 
deepening low pressure will approach the NW portion of the 
forecast area Sunday. The pressure gradient between this 
deepening low and high pressure west of the area will bring 
strong to near gale force winds north of 25N and west of 130W,
with the possibility for winds to reach minimal gale force over 
this area Monday. 

$$
AL