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
Based on 1200 UTC surface analysis and satellite imagery through
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 www.hurricanes.gov for
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
www.nhc.noaa.gov/text/MIAHSFEP@.shtml 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.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
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.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
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.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and
WITHIN 750 NM OF ECUADOR...
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.
REMAINDER OF THE AREA...
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.