570
AXPZ20 KNHC 212035
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Sat Sep 21 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.

...SPECIAL FEATURE...

A Central American Gyre is gradually developing this weekend and
will continue through the middle of next week. This scenario,
combined with daytime heating and orographic lifting, is expected
to generate periods of excessive rainfall over southern Mexico
and Central America, as well as the adjacent W Caribbean and E
Pacific waters between 80W and 95W. This activity could produce
dangerous flash flooding and mudslides across the area.
Furthermore, strong to near gale force winds, rough seas and
tstms are forecast to affect the offshore waters between Costa
Rica and El Salvador from Mon night through mid week. Please
follow the forecasts from your local weather offices for more
detailed information.

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

The monsoon trough extends from 12N87W to 15N110W to 10N140W.
Aside from the convection associated with the tropical wave/low
described above, scattered moderate convection is noted within
150 nm on either side of the boundary, with the highest coverage
W of 135W.

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

A broad surface ridge extends SE to just west of the Baja California
offshore waters. Moderate NW winds prevail over the Baja
California offshore waters with moderate seas. Along the Gulf of
California, light to gentle winds are ongoing. Light to gentle
winds and slight to moderate seas are elsewhere.

For the forecast, the surface ridge will remain in place and
fluctuate through the weekend. Moderate to fresh NW winds will
develop over the Baja California offshore waters through late
tonight, then diminish to gentle to moderate speeds afterward
into Wed night. Gentle NW winds will prevail across the Gulf of
California through the middle of next week. An active monsoon
trough will support moderate to fresh W to SW winds across the
outer SW Mexican offshore waters through Mon. Looking ahead, disorganized
showers and thunderstorms located a few hundred miles south of
the coast of southern Mexico are associated with a trough of low
pressure. Some gradual development of this system is possible
while it meanders offshore through early next week, then moves
slowly eastward or northeastward toward the coast of southern
Mexico during the middle part of next week. Regardless of
development, strong to near-gale force winds and rough seas are
forecast to affect the S and SW Mexican offshore waters starting
Mon night and continuing through the end of the week.

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

Moderate to fresh SW to W winds are ongoing south of the monsoon
trough and across the offshore waters from Colombia to Costa
Rica along with moderate seas. Gentle to moderate winds and
slight to moderate seas prevail elsewhere. Scattered showers and
tstms are over the majority of the Central America offshore
waters due to an active monsoon trough. Strong winds and rough
seas are likely in the regions of strongest convection.

For the forecast, moderate to fresh southwest to west winds
south of the monsoon trough will change little through the
weekend, then increase to fresh to near gale force speeds across
the offshore waters from Costa Rica to Guatemala late Mon
through Wed night. Seas will build during this time in mixed
swell. The monsoonal flow is expected to become very active, and
dominate the region through next week. This pattern will
generate increasing westerly wind waves moving into the area
waters. Periods of very active weather are also expected across
the Central America offshore waters through at least mid week.

...REMAINDER OF THE AREA...

Surface ridging prevails across the area. The pressure gradient
between the ridge and the monsoon trough to the south is
resulting in moderate to fresh NE trade winds and moderate seas
from 08N to 21N and W of 130W. An area of fresh to strong winds
and seas to 9 ft prevails along the monsoon trough from 12N to
15N between 103W and 118W. Another area of fresh to strong winds
and seas to 8 ft are noted within a 1010 mb low pres, analyzed
near 11N137W. Gentle to moderate NE to E winds and moderate seas
are noted elsewhere.

For the forecast, the low near 137W will move W of 140W tonight.
Southwest monsoonal winds will continue to become well
established through the remaining weekend as the monsoon trough
lifts slowly northward. Looking ahead, an area of low pressure
could form well to the southwest of the southwestern coast of
Mexico during the next couple of days. Environmental conditions
appear conducive for some slow development of this system, and a
tropical depression could form during the early or middle part of
next week while the system moves slowly eastward or
northeastward. Regardless of development, strong to near-gale
force winds and rough seas are forecast to affect the S and SW
Mexican offshore waters starting Mon night and continuing through
the end of the week.

$$
ERA