Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 180339

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 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 0000 UTC surface analysis and satellite imagery through 
0230 UTC.


A meandering trough extends from 06N76W TO 03N100W. The ITCZ 
extends from 03N100W TO 07N122W TO beyond 06.5N140W. Scattered 
moderate isolated strong convection is located within 270 nm N 
of the ITCZ between 112W and 130W. Scattered to locally numerous 
strong convection is occurring from 11.5N to 18N between 110W 
and 121W.



Satellite imagery shows a dissipating frontal trough across the 
Pacific offshore waters west of Baja California extending from 
23N113W to 27N120W and has become nearly stationary. A 
supporting upper level trough extends from a deep layered cut 
off low across SW New Mexico border SW to beyond 19N130W. An 
upper level jetstream is moving through the base of this trough 
and into central Mexico, and transporting an upper level cloud 
and moisture plume. Strong low level convergence is occurring in 
a broad zone about 200 nm wide from offshore of Cabo Corrientes 
near 20N107W to near 13N122W. Scattered to numerous convection 
described above is occurring within this zone and being enhanced 
by the jetstream energy aloft, with lighter elevated convection 
likely moving NE and inland across western Mexico between 
Manzanillo and Mazatlan and continuing NE across the Sierra 
Madres. Gentle to moderate mainly northwest winds prevail off 
the coast of Baja California and in the Gulf of California. 
Light to gentle northerly winds prevail south and east of 
Acapulco. Seas across the area are running 5-6 ft west of Baja 
California, 1-3 ft in the Gulf of California, and 3-5 ft 

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 front will be accompanied by fresh to strong winds and 
large northwest swell. This swell is expected to build seas to 
12-19 ft over the waters off Baja California Norte Saturday, and 
8-13 ft seas off Baja California Sur. This will produce 
hazardous marine conditions to mariners navigating the nearshore 
and coastal waters, and very dangerous surf conditions along the 
coasts and beaches.


Moderate northwest winds this afternoon will pulse to 25 kt late 
tonight through Wednesday morning, and then again briefly late 
Wednesday night across the Gulf of Papagayo and downwind to 
about 89W. 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.


1024 mb high pressure centered near 28N134W extends a ridge 
southeast to the Revillagigedo Islands. The gradient between 
this high and lower pressure associated with the Itch is 
supporting an area of fresh to strong northeast trade winds from 
10N TO 15N W OF 130W, with 9-11 ft seas. Fresh trades are found 
elsewhere from 11N TO 14N BETWEEN 119W AND 130W, with seas 8-10 
ft in mixed northwest swell and northeast wind waves. The zone 
of strongest trade winds will decrease in coverage and shift 
westward during the next couple of days. Fresh trades will 
remain from 07N to 20N west of 122W, with 8-10 ft seas in mixed 
northeast waves and northwest swell.

As mentioned above, a very active jet stream branch is rounding 
the base of the deep layered trough across northwest Mexico. The 
upper trough will move eastward during the next couple of days 
as high pressure aloft builds eastward behind the previously 
mentioned cold fronts, with associated moisture and weather 
shifting eastward with it.

Looking ahead, northwest swell with seas to 8-12 ft associated 
with a cold front moving eastward across the waters north of 25N 
Wednesday and Thursday will be followed by a second front 
expected to sweep southeastward into 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 to 15-20 ft in the 
far northern waters east of 130W late Friday into Saturday. 


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Page last modified: Wednesday, 18-Jan-2017 03:40:05 UTC