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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 311541

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Sat Oct 31 2020

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 1200 UTC surface analysis and satellite imagery through
1515 UTC. 


Gulf of Tehuantepec Gale Warning: High pressure and cooler, 
denser air behind a frontal boundary that moved across the 
southwest Gulf of Mexico and is currently stationary over the 
Yucatan Peninsula continues to spill through the isthmus of 
Tehuantepec. Earlier scatterometer data confirmed gale force 
winds peaking around 45 kt. Large fresh seas have built due to 
these winds, near 15 ft. Winds will diminish slightly to minimal
gale force through tonight with resultant peak seas also 
subsiding to 12 ft. A reinforcing cold front is expected to move 
into the southwest Gulf by early Sun allowing for gale force 
winds to increase back to near 45 kt Sun night through early next
week. Northerly swell will mix with longer period southerly 
swell to support seas in excess of 8 ft well downstream of the 
Gulf of Tehuantepec, with peak seas building back to near 20 ft 
early next week. Please refer to the latest High Seas Forecast 
issued by the National Hurricane Center at: for further 

Potential Heavy Rainfall event: Heavy rainfall is possible 
across portions of Central America late this weekend into early 
next week, particularly western Panama and Costa Rica to begin 
with, then spreading northwestward early next week. If heavy 
rainfall occurs, flash flooding and mudslides may be possible. 
Refer to statements provided by your national meteorological 
service for more details.


A tropical wave axis is along 91W from 02N-16N, moving W at 
around 10 kt. Associated convection is described below.


The monsoon trough extends from 08N81W to 1010 MB low near
12N111W to 10N140W. Scattered moderate convection is noted within
120 nm on either sides of the axis between 92W-138W.


Please refer to the Special Features section above for details 
on the Gulf of Tehuantepec Gale Warning.

High pressure west of Baja California is supporting gentle to
moderate northerly breezes across the Mexican offshore waters 
off Baja California and the Gulf of California. Seas of 2 to 4 
ft prevail in both the open waters and in the Gulf of 
California. Seas will build to 4 to 6 ft in the waters of Baja 
California by early next week. Elsewhere, little change is 
expected through the next several days.

Gentle winds persist south of Cabo Corrientes outside of the
Gulf of Tehuantepec plume, with seas of 4 to 6 ft in mostly 
southerly swell. Little change is expected.


Moderate south to southwest winds will prevail south of the 
monsoon trough through Sun, with isolated areas of fresh winds
ahead of a tropical wave. Seas are expected to increase offshore
of Guatemala and El Salvador through Sat night due to gale force
winds in the Gulf of Tehuantepec pushing northerly waves into 
the area. Larger seas are expected early next week across this
same area due to greater coverage and strength of the 
Tehuantepec gap winds NW of the area. Elsewhere seas are mainly 5
to 7 ft in mainly long period southerly swell. Seas will build 
slightly to the south and east of the Galapagos Islands late this
weekend into early next week due to reinforcing southerly swell.

Moderate offshore gap winds are expected across the Papagayo 
region through Sun before turning onshore Mon through Tue.


High pressure dominates the waters north of 20N. The gradient 
between the high pressure and lower pressures associated with 
the monsoon trough will continue to support moderate to locally 
fresh NE trade winds from the monsoon trough to 20N and west of 
115W, for the next several days. Seas are 5 to 7 ft across this 
region, in a mix of swell and easterly wind waves. Little change 
is expected through the weekend.

A complex low pressure system north of the Hawaiian Islands is 
forecast to move NE through the weekend. A weak trailing cold 
front may slip southeast of 30N140W by early next week with 
winds remaining 20 kt or less. Associated seas will build to 8-9 
ft behind this boundary Sun night through Mon night, impacting 
the waters north of 25N and west of 135W.

South of the monsoon trough, moderate to fresh S to SW winds 
prevail between 100W and 140W, where seas are 5 to 8 ft. Minor 
fluctuations in winds and seas are expected across this area 
through the weekend. 

Looking ahead, computer models suggest that a tropical wave 
moving offshore of SW Mexico Sun and Mon could spawn a low 
pressure center forming west of the offshore waters in the 
vicinity of 10N110W by Mon morning, and move WNW through mid 
week. There is broad disagreement among the main global models,
and confidence remains low on the exact locations and intensity 
of this low pressure at this time.