000
AXPZ20 KNHC 182140
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Wed Jan 18 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 1800 UTC surface analysis and satellite imagery through 
2100 UTC.

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

The ITCZ axis extends from 04N85W to 05N107W to 02N109W to 
08N120W to 06N140W. A large area of moderate convection with 
embedded stronger cells is from 07N to 14N between 114W and 123W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Satellite water vapor imagery shows a large moisture plume of 
mid and upper level clouds advecting northeastward towards much 
of central Mexico. Jet stream energy will combine with the deep 
moisture to produce scattered showers and isolated thunderstorms 
offshore the Mexican coast from south of Manzanillo northward to 
southern Baja California and the coast of Mexico near Los Mochis.
The upper trough will continue to slide eastward through Friday 
while shearing out. A stronger trough will sweep southeastward 
and merge into the first trough on Thursday, with associated 
moisture and weather shifting eastward with it.

Scatterometer data shows gentle to moderate northwest to north 
winds west of Baja California and in the Gulf of California. 
Light to gentle northerly winds prevail south and east of 
Acapulco. Seas in the area are 5-6 ft west of Baja California, 1 
to 3 ft in the Gulf of California, and 3-5 ft elsewhere. 

Global models indicate a cold front will move into the waters 
off Baja California Norte Thursday, then become diffuse ahead of 
a much stronger cold front that will quickly move in across Baja 
California and the Gulf of California Friday and Saturday. The 
second cold front will be accompanied by fresh to strong winds 
and large northwest swell. This swell event is expected to build 
seas to 12-19 ft off Baja California Norte Saturday, and 8-13 ft 
seas off Baja California Sur. Wave model guidance indicates max 
seas may be around 21 ft in the waters north of 29N on Saturday. 
These marine conditions are likely to bring hazardous marine 
conditions to mariners navigating the nearshore and coastal 
waters, and very dangerous surf conditions along the coast. 
Southwest winds ahead of the second cold front are expected to 
increase to near gale force over much of the northern Gulf of 
California late Friday nigh, with seas building to 8-9 ft.
  
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Moderate northeast winds this afternoon will pulse to 25 kt late 
tonight across the Gulf of Papagayo and downwind to about 88W. 
Winds area then expected to diminish by Thursday night. Light to 
gentle variable winds are expected there Friday.

Light to gentle easterly winds will prevail elsewhere through 
Saturday. Seas will be generally 3-5 ft in the forecast waters.

REMAINDER OF THE AREA...

High pressure centered near 25N139W extends a ridge eastward to 
the Baja peninsula. The gradient between the high and lower 
pressure associated with the ITCZ is supporting an area of fresh 
to strong northeast trade winds from 08N TO 13N west of 130W in 
9-10 ft seas. Scatterometer data shows fresh trades elsewhere, 
roughly from 07N to 20N west of 115W. Seas with these trades are 
7-10 ft in mixed northwest swell and northeast wind waves. The 
high will be nudged southwest over the next two days in response 
to the aforementioned cold fronts forecast to pass across the 
waters north of 25N. This will allow the trades to decrease in 
coverage and shift westward through Friday.  

Looking ahead, northwest swell with seas to 8-16 ft associated 
with a cold front moving eastward across the waters north of 25N 
through Thursday will be followed by a second front expected to 
sweep southeastward across the northern waters Thursday night 
and Friday. Wave model guidance shows large northwest swell will
propagate southeastward into the waters north of 20N behind the 
second front, with seas building quite large to 15-21 ft in the 
far northern waters east of 130W late Friday into Saturday. 

$$
Mundell