871
AXPZ20 KNHC 192040
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Thu Sep 19 2024

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 1800 UTC surface analysis and satellite imagery through
2030 UTC.

...TROPICAL WAVES...

A western Caribbean tropical wave has its axis along 86W. It
extends southward across central Honduras, western Nicaragua
to just west of northern Costa Rica and reaches to the eastern
Pacific near 05N. It is moving westward at about 10 kt. Scattered
moderate to isolated strong convection is within 180 nm east of
the wave from 06N to 09N and within 120 nm west of the wave from
08N to 10N.

A tropical wave has its axis along 101W from 04N to 19N. It is
moving westward at 10 to 15 kt. Scattered moderate to isolated
strong convection is within 180 nm west of the wave from 10N to
14N, and within 120 nm east of the wave from 10N to 14N.

A tropical wave has its axis along 119W from 04N to 20N moving
westward at about 10 kt. Scattered moderate to isolated strong
convection within 120 nm west of the wave from 09N to 12N.

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

The monsoon trough axis extends from northwest Colombia to
11N86W to 12N102W to 10N119W to 09N125W to 10N140W. Numerous
moderate to strong convection is seen from 10N to 14N between
91W and 97W. Scattered moderate to isolated strong convection is
from 03N to 09N between 77W and 83W, within 60 nm of the trough
between 123W and 126W and within 60 nm south of the trough
between 126W and 131W. Scattered moderate convection is within
60 nm either side of the trough west of 135W.

...OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A broad surface ridge extends southeastward into the region
through 27N130W to offshore of southwestern Mexico near 21N108W.
Gentle to moderate northwest to north winds are over the
offshore waters of Oaxaca. Gentle northwest to north winds are
south and southwest of Baja California, including the vicinity of
the Revillagigedo Islands and east-southeastward from there to
the coasts of Jalisco and Michoacan, Mexico. Seas are generally 4
to 5 ft in moderate period northwest swell. Light to gentle
southwest to west winds are over the remaining waters eastward to
Tehuantepec. Seas south of 20N are to 4 to 5 ft in long-period
southwest swell east of 105W, and in long-period northwest swell
west of 105W. Numerous showers and thunderstorms moving westward
are over the offshore waters of Oaxaca.  Gentle to moderate
south to southwest winds are over the northern and central
portions of the Gulf of California. Light to gentle variable
winds are over the southern part of the Gulf, except for gentle
to southwest to west winds north of 25N. Seas are 1 to 3 ft over
the Gulf of California, except 3 to 4 ft in southwest swell over
the entrance to the Gulf.

For the forecast, the present Pacific ridge will remain in place
and fluctuate into the upcoming weekend. Gentle to moderate
northwest to north winds over the Baja California offshore waters
will increase to fresh speeds Fri evening and continue through
late Sat night, then diminish to gentle to moderate speeds
afterward into early next week. Variable winds less than 15 kt
are expected across the Gulf of California, except for pulses of
moderate west gap winds across southern portions and fresh
southwest gap winds north of 30N each evening and night through
Fri. Looking ahead, an area of low pressure could form well to
the southwest of the southwestern coast of Mexico late this
weekend. Environmental conditions appear conducive for some slow
development of this system thereafter as it slowly moves
generally northward.

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

Gentle to moderate southwest to west winds prevail south of the
monsoon trough, along about 10N-11N. North of the monsoon trough,
moderate or weaker winds are observed. Seas are 4 to 5 ft in
long-period south to southwest swell, except to 6 ft south
through west of the Galapagos Islands. Scattered to numerous
showers and thunderstorms are over the majority of the offshore
waters of Costa Rica. Scattered showers and isolated
thunderstorms are over the offshore waters of northern Panama.

For the forecast, moderate to fresh southwest to west winds
south of the monsoon trough will change little through Sun night,
then increase to fresh to strong speeds Mon through Tue night.
Seas will build during this time in a mix of southwest swell and
westerly wind swell. North of 11N, moderate or weaker winds are
expected through this evening before the monsoon trough begins to
lift northward, and winds shift to westerly and gradually
increase to gentle to moderate by Sat. The monsoonal flow is
expected to become very active, and dominate the region Fri into
early next week. This pattern will generate increasing westerly
wind waves moving into the area waters. Periods of very active
weather are also expected across area waters north of 06N through
the weekend and possibly into next week.

...REMAINDER OF THE AREA...

Surface ridging extending from a 1028 mb high that is centered
well northwest of the area near 39N156W extends east-
southeastward through 27N130W to offshore of SW Mexico near
17N108W. The pressure gradient between the ridge and the monsoon
trough to the south is resulting in moderate northeast trade
winds south of about 24N and west of 130W. Seas are 5 to 6 ft in
mixed northeast and southeast swell south of 25N west of 125W, 5
to 8 ft in long-period southeast swell south of the monsoon
trough from 03N to 10N between 90W and 120W, and 4 to 6 ft in
long-period southerly swell elsewhere as noted in recent
altimeter satellite data passes.

For the forecast, little overall change is expected over the
open Pacific waters west of 120W for the next several days as
the aforementioned ridge dominates the region. A dissipating
frontal trough extends from southeastern California
southwestward to far northern Baja California and to
near 30N120W. Latest ASCAT satellite data passes indicate
light to gentle northwest winds near the trough. Southwest to
west monsoonal winds will continue to become well established
through the weekend as the monsoon trough lifts very slowly
northward. Moderate to fresh southwest to west winds, with small
areas of locally strong winds near active thunderstorms will
generally develop from 05N to 12N and east of 120W through the
weekend. Seas within this wind regime will build to around
7 to 10 ft east of 120W during that time.

$$
Aguirre