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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 281604

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon Sep 28 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
1500 UTC. 


A broad area of disturbed weather is located a few hundred miles 
south of the southwestern coast of Mexico. Shower and thunderstorm 
activity associated with a small low embedded within this area has 
decreased since yesterday. However, environmental conditions are 
expected to gradually become more conducive for development and a 
tropical depression will likely form within the next two or three 
days. The disturbance is forecast to move generally westward for the 
next several days and then turn west-northwestward by the weekend.
The latest Tropical Weather Outlook states that this system has a
high chance of tropical cyclone formation through 48 hours. Refer
to the latest Tropical Weather Outlook at for
more details.

Gulf of Tehuantepec gale warning: A strong gale force gap wind 
event is expected across the Gulf of Tehuantepec late Tue through
Fri night as cold front moves across the Gulf of Mexico. Marine 
guidance suggests N winds blasting across the Tehuantepec waters 
Tue afternoon and quickly increasing to 30 to 45 kt by Tue night 
with seas building up to 16 or 17 ft.
Please, read the latest NWS High Seas Forecast issued by the 
National Hurricane Center at website for more details.

Of note, the 20-year climatology of the Tehuantepec gap wind
events indicates that on average 16 gale-force events and 5 
storm force-events occur in the Gulf of Tehuantepec each cold 
season. Most gale-force events occurred during November and 
December, while most storm-force winds occurred in January. 
Based on latest model trends and the present evolving synoptic 
scale setup, it appears that the forecast gale to near strong 
force wind event may supersede the previously recorded earliest 
start date of October 3rd.


The axis of a tropical wave is near 101W N of 03N, moving 
westward at 5 to 10 kt. Associated convection is described below.


The monsoon trough extends from 10N85W to 1007 mb low pres
located near 13.5N104.5W to 11N125W to 10N140W. Scattered 
moderate isolated strong convection is noted from 07N to 12N 
between 92W and 101W, and from 10N to 16N between 105W and 109W.
Scattered moderate convection is observed from 03N to 07N E of
80W to the coast of Colombia, from 10n to 12n between 110W and 
118W, and from 08N to 10N W of 128W.


Please see above for more on the Gulf of Tehuantepec gale force
gap wind event.

Elsewhere, a weak ridge west of Baja California will maintain 
gentle to moderate NW to N winds across the region for the next 
few days. NW to N swell over the waters west of Baja California 
will subside through late today. Light to gentle southerly winds 
will prevail across the Gulf of California through this 
afternoon before shifting to the north. Elsewhere, light to 
gentle winds are generally expected across the waters from Las 
Tres Marias to Puerto Angel for the next several days.


Moderate southerly flow prevails S of the monsoon trough, with 
gentle winds north of the monsoon trough. Combined seas are 
currently 5 to 7 ft in a mix of wind waves and southerly swell. 
Long period SW swell is moving over the waters between Ecuador 
and the Galapagos Islands, with seas to 8 ft. This swell event 
will continue to propagate northward and reach the offshore 
waters of Central America today, where seas will build to 6 to 8 
ft. In addition, seas generated by the gap wind event in the 
Tehuantepec region will propagate across the offshore waters of 
Guatemala and El Salvador on Wed.


Please see Special Features section above for tropical cyclone

Cross equatorial SW swell, combined with a developing low 
pressure located near 13.5N104.5W is producing a large area of 8
to 10 ft from 05N to 12N between 100W and 120W. Sea heights of 8
to 9 ft are noted elsewhere across much of the waters S of 20N 
between 90W and 130W. These seas will gradually subside across 
the waters S of 20N and E of 120W by the middle of the week,
except near the possible tropical cyclone.