843
AXPZ20 KNHC 211526
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 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 1200 UTC surface analysis and satellite imagery through
1500 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 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.

...TROPICAL WAVES...

A tropical wave has its axis along 109W from 07N to 18N, moving
westward at 10-15 kt. A 1006 mb low pres is within the wave,
centered near 15N109W. Scattered moderate convection is from 10N
to 17N between 107W and 112W.

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

The monsoon trough extends from 13N88W to a 1006 mb low near
13N109W 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.

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

A broad surface ridge extends SE to just west of the Baja California
offshore waters. Moderate to fresh 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, except
for moderate to fresh W winds over the outer S and SW Mexican
offshore waters.

For the forecast, the surface ridge will remain in place and
fluctuate through the weekend. Moderate to fresh NW winds will
continue over the Baja California offshore waters through late
tonight, then diminish to gentle to moderate speeds afterward
into Wed night. Ongoing moderate to fresh SW winds in the
northern Gulf of California will diminish to gentle speeds today
and then prevail 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, 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
northward 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.

...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 extending from a pair of high pressure centers
located well NW of the area reaches ESE to just W of the Baja
California Peninsula offshore waters and south to about 20N. 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 10N to 20N and W of 132W. Gentle to moderate
NE to E winds and moderate seas are elsewhere N of 10N and W of
110W. South of the monsoon trough and between 102W and 120W SW
winds are fresh to strong and seas are 7-8 ft. SW winds are
moderate to fresh between 82W and 102W with seas are 5-7 ft.

For the forecast, fresh winds and rough seas to 9 ft are
forecast to develop today in association with a 1008 mb low
located near 10N138W. The low 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 northward 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