000
AXPZ20 KNHC 280347
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Thu Dec 28 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.

..SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: The tight pressure gradient 
associated with strong high pressure surging southward along the 
Sierra Madre Oriental mountains is in the process of inducing 
gale force northerly winds through the Chivela Pass and over
the Gulf of Tehuantepec. These winds will continue into 
Friday morning. Waveheights are expected to reach a range of 
10-14 ft early on Friday with these gale force winds. As the 
tight pressure gradient over southeastern Mexico weakens during 
Friday and through Saturday, this will allow for winds and seas. 
Beyond Thursday, a strong cold front will enter the Gulf of 
Mexico by Sunday night, and move across the western Gulf of 
Mexico on Monday. Strong high pressure will ridge southward in 
the wake of the front along the Sierra Madre Oriental mountains, 
with the associated tight pressure gradient expected to usher 
another round of winds to gale force across the Gulf of 
Tehuantepec. Presently, model guidance indicates that these winds
may reach strong gale force category. There may be a possibility
that even storm strength winds could occur. 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 axis extends from a 1009 mb low near 05N78W to 
06N90W to 06N100W to 07N109W, where latest scatterometer data 
indicates it transitions to the Intertropical Convergence Zone 
and continues to 09N118W to 09N127W and briefly ends as a result 
of a surface trough that extends from 10N129W to 15N128W. It then
resumes at 09N131W to beyond 08N140W. No significant convection 
is noted at the present time.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please refer to the special features section above for details 
of a Gulf of Tehuantepec Gale event.

A fairly tranquil synoptic pattern associated with a nearly 
stationary subtropical high to the W of California and a surface 
ridge extending SE from the high will persist for several days. 
This will maintain gentle to moderate NW to N winds off Mexico 
through the weekend. Seas will be in the general range of 4-6 ft 
over the offshore waters and 2-4 ft in the Gulf of California.

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

Moderate high pressure gradient in the western Caribbean will 
continue to support fresh to strong NE winds from 09N to 11N 
east of 90W, including the Gulf of Papagayo, through Sun night 
with seas to 7-9 ft primarily from NE wind waves. Mainly gentle 
winds are expected elsewhere through the end of the week, with 
offshore seas generally 4-5 ft.

REMAINDER OF THE AREA...

Long-period NW swell is producing 8-10 ft seas north of 15N and 
west of 125W. Seas will continue to gradually diminish today as 
the peak swell continues moving southeastward. Divergence aloft 
on the southeast side of an upper trough along 120W in
combination with jet stream energy with the jet stream branch 
that stretches from the base of the trough northeastward to just 
S of Baja California and towards central Mexico is supporting an 
area of scattered showers and thunderstorms from 10N to 18N 
between 109W and 119W. A surface trough and weak low pressure 
area is expected to form along the intertropical convergence zone
on Thursday between the area roughly between 120W and 123W in 
association to the upper trough. The trough and low pressure is 
expected to drift westward over the next 48 hours then dissipate.
Presently a surface trough along 129W from 10N to 15N will
dissipated Thursday. The gradient between the trough that forms
on Thursday and the high pressure over the northern waters will 
tighten enough to increase the trades slightly from 15N and 20N 
between 118W- 130W through Friday, with seas building to 8-9 ft 
due to a mix of NE wind waves and longer period NW swell. There 
are expected to be pockets of strong trades from about 18N- 21N 
between 123W- 127W.

$$
Aguirre