000
AXPZ20 KNHC 282121
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2009 UTC Wed Dec 28 2016

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
2215 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning...The pressure gradient between
high pressure over eastern Mexico and low pressure within the
monsoon trough over the eastern north Pacific is supporting gale
force winds over the Gulf of Tehuantepec. This synoptic setup will
prevail today and Thursday supporting the gale force winds.
Thursday night high pressure will strengthen north of the area
behind a cold front moving through the Gulf of Mexico. This will
bring a slight increase to the gale force winds over the Gulf of
Mexico by Thursday night into Friday morning. A progressive
pattern will see this area of high pressure shift rapidly into the
southwestern Atlantic waters Friday night into Saturday. Winds
over the Gulf of Mexico will veer and winds funneling into the
Gulf of Tehuantepec will decrease. This will bring an end to the
latest gale force gap wind event in the Gulf of Tehuantepec on
Saturday. Please see latest National Hurricane Center high seas
forecast MIAHSFEP2/FZPN03 KNHC for further details.

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

The Monsoon Trough extends from 05N78W to 09N84W to 05N102W. The
ITCZ extends from 05N102W to 13N120W. Surface trough from 16N122W
to 12N124W. ITCZ resumes from 12N126W to 08N140W. Scattered
moderate convection was noted within 100 nm on either side of the
ITCZ between 126W and 140W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see the special features for details on the Gulf of
Tehuantepec gale-force gap wind event. The pressure gradient
between a high pressure west of the Baja California and lower
pressures over western Mexico is supporting fresh to strong
northwest winds over the southern portion of the Gulf of
California. The gradient will weaken through the next 48 hours and
winds will diminish. Elsewhere, winds will remain 20 kt or less,
with seas below 8 ft through the end of the week.
  
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Winds will pulse over the Gulf of Papagayo the next several
nights, peaking to near 25 kt during the overnight hours as the
gap winds are enhanced by nocturnally induced drainage flow. Winds
will decrease to 20 kt during the late afternoon and early evening
hours. Elsewhere, winds will remain 20 kt or less, with seas below
8 ft through the end of the week.

REMAINDER OF THE AREA...

A surface trough extends from 25N128W to 22N124W. The pressure
gradient between 1030 mb high pressure centered north of the area
near 36N136W and the trough is supporting fresh to strong
northerly winds mainly northwest of the trough's axis. Northwest
swell is propagating across the northern waters with seas in the 8
to 12 ft range. Northwesterly swell is mixing with northeasterly
generated wind waves to produce seas greater than 8 ft over much
of the forecast waters north of 05N and west of 115W. The trough
will prevail across the northern portion of the basin the next two
days before dissipating. The area of high pressure will weaken
through the next 48 to 72 hours. This will help decrease winds
and seas over the forecast area. Winds are expected to diminish
below advisory criteria Thursday, while the areal extent of seas 8
ft or greater will continue to decrease through the weekend. A
frontal boundary will approach the far northwest waters by Friday
where it will stall. The front will usher in another set of long
period northwesterly swell into the area. Seas associated to this
swell will peak near 10 ft on Friday.

$$

NATIONAL HURRICANE CENTER