000
AXPZ20 KNHC 291004
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Thu Dec 29 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 0600 UTC surface analysis and satellite imagery through
0915 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning...The pressure gradient between
a surface ridge over the Gulf of Mexico and lower pressures within
the Monsoon Trough over the eastern Pacific is supporting gale
force winds over the Gulf of Tehuantepec. This synoptic setup
will prevail through Saturday morning. However, a slight
increase in the gale winds will occur during Friday as high
pressure behind a cold front moving across the Gulf of Mexico
strengthens. The area of high pressure will then shift rapidly
into the southwestern Atlantic waters Saturday morning, which
will cause the winds over the Gulf of Mexico to veer. Therefore,
winds funneling into the Gulf of Tehuantepec will decrease below
gale force. Please see the latest National Hurricane Center High
Seas Forecast product under AWIPS/WMO headers MIAHSFEP2/FZPN03
KNHC for further details.

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

The Monsoon Trough extends from 06N77W to 07N85W to 05N96W. The
ITCZ extends from 05N96W and continues along 09N118W to 09N136W.
Scattered moderate convection was noted from 08N to 13N between
124W and 137W.

...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 high pressure along Mexico and an elongated surface
trough over the Gulf of California is supporting fresh to strong
northwest winds over the southern portion of the Gulf of
California. The gradient will weaken during the next 24 hours as
the center of high pressure shift north-northeast to Texas,
which will result in winds diminishing to 20 kt or less Friday
morning. 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...

Fresh to strong winds will pulse at night over the Gulf of
Papagayo through Saturday. Peak winds will occur 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 28N128W to 22N128W. The pressure
gradient between 1026 mb high pressure centered north of the
area near 39N128W and the trough is supporting moderate to fresh
northerly winds mainly northwest of the trough's axis. Northwest
swell is propagating across the northern waters with seas in the
8 to 9 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 07N and west of
113W. The trough will prevail across the northern portion of the
basin through Friday 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. 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.

$$
Ramos