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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 202158

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2158 UTC Mon Nov 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 1800 UTC surface analysis and satellite imagery through
2100 UTC. 


The monsoon trough extends from 08N78W to 06N105W. Intertropical
convergence zone extends from 06N105W to 12N140W. Scattered
moderate convection is observed within 60 nm of the intertropical
convergence zone between 125W and 140W. 



An earlier scatterometer satellite pass indicaated strong gap 
winds still active into the Gulf of Tehuantepec, with a 60 nm 
wide plume extending as far as 450 nm offshore. Seas are 
estimated to be 13 ft in the area of strong winds. The strong
high pressure north of the area that has been supporting gale 
force winds in Tehuantepec is weakening, allowing winds to 
diminish through early Tue. Seas to 8 ft will linger well 
offshore with the assistance of long period southwest swell. 
These seas will subside through late Tue as the swell decays. The
window of relative diminished winds will be short, as another
front moving through the Gulf of Mexico will initiate a new 
round of strong winds into the Gulf of Tehuantepec late Wed, 
reaching gale force Wed night with seas building 12 to 17 ft.

A NW to SE orientated ridge just beyond 250 nm seaward will 
maintain moderate NW flow W of the Baja Peninsula through mid 
morning when the pressure gradient will relax, supporting light 
northerly winds through late wed when a trough will form SW from 
the central Baja Peninsula to near 22N116W and continue through 
early Fri before filling. Expect seas in the 3 to 5 ft range 
through Thu building to 5 to 7 ft N of 25N late in the week.  

Gulf of California: The earlier moderate NW flow has been 
diminishing this morning. This situation will continue, until 
reaching light breezes from later today until Tue morning. 
Moderate to locally fresh conditions will develop,again, on 
Tuesday morning, and continue until early Wed. Light to moderate 
NW flow is expected on Thu and Fri, becoming light and variable 
on Fri night.   


Gulf of Papagayo: Moderate to locally fresh NE drainage winds 
are forecast during the overnight hours tonight, then light 
drainage flow expected during the overnight hours through Thu 
night, with fresh to locally strong nocturnal drainage possible 
on Fri and Sat nights.

Light and variable winds, and 3 to 5 ft seas, are expected 
elsewhere to the N of the monsoon trough which has been 
meandering from 09N to 11N, while moderate to locally fresh 
southerly winds, and 4 to 7 ft seas, are forecast S of the 
monsoon trough this week.  


A NE to SW aligned ridge will meander from 32N125W to beyond 
20N140W for the next several days. Strong to occasionally near 
gale force southerly winds, that are currently across the waters 
N of 28N W of 138W, will spread E across the waters generally W 
of a line from 32N130W to 22N140W through late tonight before 
the pressure gradient relaxes. Associated seas are expected to 
build to 8 to 12 ft across the waters S of 30N, while 10 to 14 
ft seas are forecast from 30N to 32N. A series of cold fronts 
will approach, but stall just W of 140W through Tue night. Model 
guidance is suggesting a cold front will arrive at 32N140W on 
Wed, and stall from 32N136W to 23N140W on Thu, with seas 
building 12 to 17 ft W of the front through Thu. 

Moderate anticyclonic flow expected across the tropics N of the 
ITCZ and W of 120W through the middle of next week, with seas of 
4 to 7 ft. Long period NW swell will propagate E across the 
discussion waters W of 120W from mid to late week, and subside 
during the upcoming weekend.