000
AXPZ20 KNHC 170830
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Tue Oct 17 2023

Tropical Weather Discussion for the eastern Pacific Ocean from
03.4S to 30N, east of 120W including the Gulf of California, and
from the Equator to 30N, between 120W and 140W. The following
information is based on satellite imagery, weather observations,
radar, and meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0830 UTC.

...SPECIAL FEATURES...

Gale Warning South of Southwestern Mexico (EP90): Showers and 
thunderstorms associated with an area of low pressure located a 
few hundred miles offshore of the southwestern coast of Mexico 
are gradually becoming better organized. Environmental conditions
are conducive for further development of this system, and a 
tropical depression is very likely to form today. This system is
expected to move slowly west-northwestward and then turn 
northwestward or northward late in the week offshore of the coast
of southwestern Mexico. Numerous moderate and isolated strong 
convection is noted from 10N to 20N between 100W and 110W. 
Associated winds are currently 20-30 kt, with seas to 12 ft. This
system has a high chance of tropical cyclone development in the 
next 48 hours. A gale warning is in effect for this system 
beginning this afternoon. Please read the latest NHC Tropical 
Weather Outlook at www.hurricanes.gov and the latest NHC High 
Seas Forecast at www.hurricanes.gov/marine for more details. 

Gulf of Tehuantepec Gale Warning: The pressure gradient between
high pressure along the eastern slopes of Mexico and the eastern
north Pacific monsoon trough is supporting gale-force gap winds.
An overnight ASCAT pass confirmed winds in the 30-40 kt range, 
with seas likely reaching near 18 ft with these winds. The area 
of high pressure will start to shift eastward tonight. This will
loosen the pressure gradient which will help diminish winds 
below gale- force Wed morning when seas will also likely subside 
below 12 ft. The pressure gradient will remain tight enough to 
support pulsing fresh to strong winds through the remainder of 
the week. Please read the latest NHC High Seas Forecast at 
website www.hurricanes.gov/marine for more details. 

NW Swell in the NW waters: Large NW swell will push SE of 30N140W
tonight building seas to 12 ft or greater N of 25N and W of 135W
by early Wed afternoon. Seas will peak around 15 ft Wed afternoon
into the evening near 30N140W. This swell will continue to 
spread SE with seas 8 ft or greater covering the majority of the 
waters W of 100W by the end of the week, when peak seas should 
subside to just below 12 ft. Seas will continue to gradually 
decay through the upcoming weekend. Please read the latest NHC 
High Seas Forecast at website www.hurricanes.gov/marine for more 
details. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends from 11N86W to low pres near 13N104W
(EP90) to 09N120W to 09N140W. Scattered moderate convection is 
noted from 04N to 14N between 82W and 100W. Numerous moderate 
and isolated strong convection is noted from 10N to 20N between 
100W and 110W. Scattered moderate convection is noted from 04N to
11N between 110W and 128W. 
 
...OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see the SPECIAL FEATURES section above for more on the 
ongoing Gulf of Tehuantepec gale-force gap wind event and a Gale
Warning in effect for EP90 near 13N104W, that is being monitored
for tropical cyclone development.

Aside from the Gulf of Tehuantepec and EP90, a ridge extends 
across the Baja California offshore waters. Gentle to moderate 
winds prevail west of the Baja California peninsula as well as 
the Gulf of California. Light to gentle winds are noted off SW 
Mexico. Seas are in the 4-6 ft range over the open waters off 
Mexico, except 6-7 ft offshore Baja California, and 1-3 ft over 
the Gulf of California.

For the forecast, gale- force gap winds will prevail over the 
Gulf of Tehuantepec through Wed morning. Fresh to strong winds 
will continue to pulse over the Tehuantepec region through the 
remainder of the week. Rough to very rough seas can be expected 
over this area through Wed. Gentle to moderate winds west of the 
Baja California peninsula and over Gulf of California will 
continue through tonight before diminishing. Fresh to strong 
winds offshore Baja California may develop this weekend. Large NW
swell is forecast to spread offshore Baja California by the end 
of the week into the weekend.

Looking ahead, an area of low pressure is expected to form south
of the coasts of Guatemala and southern Mexico in a couple of 
days. Gradual development of the disturbance is expected, and a 
tropical depression is likely to form late this week or over the 
weekend while the system meanders over the far eastern portion of
the basin. This system has a low chance of tropical cyclone 
formation in 48 hours and a high chance in the next 7 days. 

...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, 
AND WITHIN 750 NM OF ECUADOR...

Light to gentle winds are noted N of the monsoon trough, with
gentle to locally moderate winds S of the monsoon trough. Seas 
are in the 6-8 ft range well offshore Guatemala, and in the 3-5 
ft range elsewhere across the discussion waters.

For the forecast, moderate to rough seas from swell generated by
the Gulf of Tehuantepec gale- force gap wind event will prevail 
well offshore of Guatemala until early Wed. Winds will pulse 
moderate to fresh, locally strong, near the Gulf of Papagayo at 
night through Thu night. Gentle to moderate winds will prevail 
south of the monsoon trough. Seas may build slightly in SW swell 
offshore Ecuador to the Galapagos Islands by the end of the week 
into the weekend.

Looking ahead, an area of low pressure is expected to form south
of the coasts of Guatemala and southern Mexico in a couple of 
days. Gradual development of the disturbance is expected, and a 
tropical depression is likely to form late this week or over the 
weekend while the system meanders over the far eastern portion of
the basin. This system has a low chance of tropical cyclone 
formation in 48 hours and a high chance in the next 7 days. 

...REMAINDER OF THE AREA...

Please see the SPECIAL FEATURES section above for more on a Gale
Warning in effect for an area of low pressure, EP90, near
13N104W that is being monitored for tropical cyclone 
development, and for details on a large NW swell event over the 
NW waters.

A 1022 mb high pressure center near 29N130W extends a ridge to 
near the Revillagigedo Islands. Light winds are in the vicinity 
of the high center. Gentle to moderate winds are elsewhere over 
the discussion waters. NW swell, associated with a stationary 
front from 30N135W to 28N140W, is propagating across the NW 
waters bringing seas of 8-9 ft over these waters, extending SE to
the waters just ahead of the front. Elsewhere, seas of 5-7 ft 
prevail.

For the forecast, the NW swell will subside today while the 
stationary front gradually dissipates over the northern waters. 
A large set of NW swell is expected to move into the NW waters
tonight, with seas peaking near 13-15 ft on Wed and Wed night. 
Seas greater than 8 ft associated to this swell will merge with 
seas generated by EP90 to cover much of the discussion waters W 
of 100W by the end of the week. Meanwhile, southerly swell of 8 
ft or greater will spread N of the Equator mid-week through the 
end of the week. Seas will gradually subside from west to east
over the waters W of 125W Fri night through the weekend.

$$
AL