000
AXPZ20 KNHC 200838
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0750 UTC Wed Dec 20 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
0800 UTC.

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

The ITCZ extends from 08N140W to 07N104W. There is no 
significant convection. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of California: Northerly winds will increase abruptly to 
fresh or strong breeze behind the next cold front expected to 
move through most of the basin early Thursday through Friday.
Winds should drop back to fresh breeze by Saturday. Seas will 
build quickly to 8 ft by late Thursday. These strong winds are 
also forecast to seep through Baja California mountain passages 
and into the open Pacific waters west of the peninsula on Friday,
but only to gentle or moderate breeze conditions.

Gulf of Tehuantepec: Northerly winds will pulse fresh to strong 
early this morning and Wednesday night before diminishing. 
Looking ahead - gale force winds will be possible over the gulf 
Sunday night as a strong cold front moves across the Gulf of 
Mexico, and winds funnel through the Chivela pass into the Gulf 
of Tehuantepec beginning late Saturday night. Gale conditions may
persist through Tuesday morning. The peak magnitude of the event
is likely to be early Monday with the GFS suggesting strong gale,
while the ECMWF and UKMET indicating near gale to minimal gale
conditions. Peak seas may reach 20 ft or greater on Monday.

Elsewhere across the offshore waters of Mexico, fresh breeze or
weaker winds and seas less than 8 ft prevail.  A fresh pulse of 
NW swell will propagate into the waters off the coast of Baja 
California Norte Thursday behind the next cold front, with seas 
building briefly 8-9 ft across the far northern waters, then 
fading to less than 8 ft by Friday.

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

A 0330 UTC ASCAT scatterometer pass indicates 25 kt NE winds in
the Gulf of Papagayo. These should persist as strong breeze
during late night and early morning hours through Thursday before
diminishing on Friday. However, these winds are not extensive
enough or lasting long enough to produce 8 ft seas.  Elsewhere 
winds in the area are fresh breeze or weaker and seas less than 8
ft.

REMAINDER OF THE AREA...

The remainder of the forecast waters current has winds fresh 
breeze or weaker and seas less than 8 ft.

On Friday and Saturday, a low latitude extratropical cyclone 
will be developing along a frontal boundary to the west of 140W.
The tightening pressure gradient should cause the SE tradewinds
to pick up to strong breeze to possibly gale conditions on those
days. The low should push northward on Sunday, taking with it 
the high winds. Combined seas from the SE wind waves and NW swell
spreading southeastward may reach around 15 ft on Saturday near 
30N140W. The main global models are all in reasonable agreement 
on this scenario.

$$
Landsea