000
AXPZ20 KNHC 222132
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2100 UTC Sat Dec 22 2018

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
2100 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: Winds have diminished below
gale force across the Tehuantepec region this afternoon. Gale 
conditions are expected again in this area late Sun through Mon 
night as an area of high pressure builds southward over southern 
Mexico. The forecast calls for winds of 30-40 kt and seas of 9-13
ft on Sun night. Please refer to the latest high seas forecast 
issued under AWIPS/WMO headers HSFEP2/FZNPN03 for more specific 
marine details. 

Gulf of Papagayo Gale Warning: High pressure building southward 
over the northwestern Caribbean Sea is inducing a tight pressure
gradient over northern Central America, which is resulting in 
minimal gale force winds over the Gulf of Papagayo. Peak seas of 
9 to 12 ft are expected in and downstream of the Gulf during this
gale event. These winds are forecast to diminish to below gale 
force briefly early this afternoon, then increase again to 
minimal gale force tonight. Fresh to strong winds are then 
expected across the Gulf of Papagayo Sun afternoon through at 
least the middle of next week.

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

A surface trough extends from the coast of Colombia near 06N77W
to 07N85W and to 04N94W. The ITCZ continues from 04N94W to 
06N110W, where it is interrupted by a surface trough along a 
position from 13N110W to 05N115W. The ITCZ resumes to the west 
of this trough at 06N118W and continues to 08N127W and to beyond
07N140W. Scattered moderate convection is within 150 nm north of
the ITCZ west of 130W, and near the northern end of the surface 
trough from 12N to 15N between 105W and 111W. The trough is to 
the east of a rather vigorous upper-level trough.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Please see the Special Features Section above for information on
the ongoing strong gale force gap wind over the Gulf of 
Tehuantepec.

Long period northwest swell continues to propagate across the 
offshore forecast waters with seas of 7 to 9 ft covering much of 
the area. Seas elsewhere away from the Gulf of Tehunatepec 
region will subside to less than 8 ft by this evening. The next 
round of large swell is forecast to reach the offshore waters of 
Baja California Norte by early on Mon, and the remainder of the 
Baja California Peninsula offshore waters by early on Tue. Wave 
model guidance indicates that seas will build to 12 to 16 ft N 
of Punta Eugenia on Tue. By that time, fresh to strong NW winds 
are also forecast to affect the offshore waters N of 26N. These 
winds will increase to strong to near gale-force by Tue evening 
before diminishing early Wed. 

Gulf of California: Winds are light and variable across the area
with the typical climatological trough meandering along the west
coast of mainland Mexico. Overall, little changes are expected
with these conditions through Mon night. Deepening low pressure 
will move across the southwestern United States on Tue as high
pressure intensifies west of Baja California. With this scenario 
to take place, expect for the pressure gradient to increase over
northern Baja California and the northern Gulf of California on
Tue leading to possible minimal west to northwest gale force 
winds across the northern Gulf of California, with seas to 8 ft.

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

Please the Special Features Section for more on the gale force 
gap wind event over the Gulf of Papagayo.

Strong north winds will continue over the Gulf of Panama through
Sun night, with seas building to 8 ft by early Sun.

Elsewhere, gentle to moderate winds will prevail, with seas in 
the 4 to 7 ft range.

REMAINDER OF THE AREA...

The pressure gradient between high pressure centered near 32N135W
and lower pressure present near the ITCZ is producing fresh to 
strong northeast trades from 08N to 20N W of 137W along with 
seas ranging from 8 to 11 ft based on altimeter data. This area 
of trades and associated seas will expand north and east through 
early next week. Seas of 8 ft or greater in NW swell extend 
across all the open east Pacific discussion waters W of 105N. The
seas will diminish below 8 ft across the area by tonight except 
under the stronger trades, and in an area of mixed swell south of
about 15N between 90W and 110W, as the lingering NW swell mixes 
with shorter period northeast swell from the Tehuantepec and 
Papagayo gap wind events. 

Yet a new set of NW swell will propagate through the northern 
and central waters beginning on Sun and through the middle part 
of the forecast area next week as high pressure strengthens to 
the north. Seas induced by this new set of swell are expected to
be in the range of about 9 to 11 ft.

$$
GR