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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 122205

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2204 UTC Wed Dec 12 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.


The monsoon trough extends from 06N77W to 05.5N95W. A segment of 
the intertropical convergence zone continues from 05.5N95W to 
08N125W, and again from 08N135W to beyond 08N140W. No 
significant convection is observed.



Gulf of Tehuantepec...Winds continue to diminish this afternoon 
and evening as high pressure over the Gulf of Mexico weakens and 
shifts east. Light to gentle winds are expected tonight through 
Thu night. Seas of 8 to 9 ft within 250 nm of the coast of 
Oaxaca and Chiapas will subside below 8 ft through tonight as 
well. he reprieve will be short however, as a cold front 
forecast to move into the Gulf of Mexico on Thu is expected to 
initiate another strong gale force wind event late Fri through 

Farther north, strong high pressure building over the Great 
Basin will support a push of fresh to strong winds into the 
northern Gulf of by early Thu, eventually spreading across most 
of the Gulf through Fri with seas approaching 8 ft over the 
southern Gulf where the fetch would be longest. Winds and seas 
will subside through Sat as the high pressure shifts eastward 
into the Central Plains.

Over open waters off the Baja California coast, lingering long 
period NW swell along the length of the coast and in the 
Revillagigedo Islands will decay below 8 ft through tonight, 
just ahead of another group of NW swell reaching the northern 
section of Baja California Norte and Guadalupe Island by Thu 
night. This new swell will reclaim the territory vacated by the 
previous swell through early Sat with significant wave heights 
reaching 10 ft. 


Gulf of Papagayo...Overnight gap winds have been active for the 
past several nights, but will only reach 20 kt tonight and Fri 
night as high pressure north of the area shifts east. Fresh to 
strong gap winds with seas to 9 ft will resume during overnight 
and early morning hours Sat night as the next system builds 
north of the region.

Gulf of Panama...Northerly swell from early gap winds will 
persist into the evening then subside.

Elsewhere, gentle to moderate winds will persist on either side 
of the monsoon trough through the remainder of the week, with 
seas in the 4-6 ft range.


A large area of confused seas persists over much of the north 
Pacific east of 110W, consisting of primarily NE and E swell 
mixed from gap winds with a component of longer period NW swell. 
Combined sea heights in this area are still reaching up to 11 
ft, but will be subsiding below 8 ft through Thu night.

Farther west, a surface trough persists form 07N130W to 15N125W. 
The gradient between this trough and 1032 mb high pressure north 
of the region centered along the subtropical ridge near 32N140W 
is supporting generally fresh trade winds from the ITCZ to 20N, 
west of 115W. Scatterometer passes from 18 UTC indicated this, 
as well as fresh to strong NE winds within 180 nm west of the 
trough. Seas are 8 to 12 ft in this area, in a mix of local seas 
from the trade winds and longer period NW swell. The high 
pressure will weaken through Thu ahead of a cold front 
approaching from the west, allowing the trade winds to diminish.

The cold front will reach from 30N135W to 28N140W by early Fri, 
and be accompanied by a new round of NW swell of 12 to 15 ft. 
The front will dissipate as it moves east to the north of 20N, 
with the swell subsiding as well. Elsewhere NW swell in excess 
of 8 ft will more or less dominate the waters west of 110W 
through Sun. Looking ahead, a more substantial group of NW well 
will move into the area by early Sun.