662
AXPZ20 KNHC 231610
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Mon Sep 23 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
1530 UTC.

...SPECIAL FEATURE...

Tropical Storm John is centered near 14.8N 98.5W at 23/1500 UTC,
moving north at 3 kt. Estimated minimum central pressure is 992
mb. Maximum sustained wind speed is 60 kt with gusts to 75 kt.
Tropical storm force winds are occurring within 30 NM of the
center, except within 40 NM of the center in the NE quadrant.
Seas 12 ft or greater are occurring within 45 NM in the northern
semicircle, and within 75 NM in the southern semicircle, with
peak seas of 15 ft. Scattered strong convection is occurring
within 150 NM in the east semicircle of the center, and within
250 NM in the west semicircle. Rapid strengthening is forecast,
and John is expected to become a hurricane by this afternoon,
with additional strengthening expected before the center reaches
the coast of southern Mexico. John will move to near 15.2N 98.3W
this evening, move to 15.7N 97.9W Tue morning, inland to 16.0N
97.6W Tue evening, move inland and weaken to a tropical storm
near 16.2N 97.4W Wed morning, and dissipate Wed evening. Through
Thursday, John is expected to produce 6 to 12 inches of rain with
isolated totals around 15 inches across the coastal areas of
Chiapas. In areas along and near the Oaxaca coast to southeast
Guerrero, between 10 and 20 inches of rain with isolated totals
near 30 inches can be expected through Thursday. This heavy
rainfall will likely cause significant and possibly catastrophic,
life-threatening flash flooding and mudslides to the Mexican
States of Chiapas, Oaxaca, and southeast Guerrero, particularly
in areas near the coast. A dangerous storm surge is expected to
produce significant coastal flooding near and to the east of
where the center makes landfall. Near the coast, the surge will
be accompanied by large and destructive waves. Please see local
statements for more information.

Please read the latest HIGH SEAS FORECAST issued by the National
Hurricane Center at website -
https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest
John NHC Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

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

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

The monsoon trough axis extends from 15N111W to 12N140W. Aside
convection related to Tropical Storm John, scattered moderate
convection is occurring from 08N to 11N between 127W and 136W.

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

Please refer to the Special Features section above for
information on both Tropical Storm John and on the developing
Central American Gyre (CAG).

A broad surface ridge extends southeastward to just west of the
Baja California offshore waters. The related gradient is allowing
for generally gentle to moderate northwest winds to exist over
the Baja California offshore waters, with locally fresh winds and
moderate seas north of Punta Eugenia. Light to gentle winds are
ongoing along the Gulf of California with slight seas. Fresh to
strong winds are noted in the vicinity of Tropical Storm John,
with seas to 10 ft. Otherwise, light to gentle winds and slight
to moderate seas are occurring elsewhere.

For the forecast, away from Tropical Storm John, high pressure
will remain in place through mid-week. Gentle to moderate
northwest winds will continue over the Baja California offshore
waters through Wed night, with moderate to fresh winds occurring
Thu into the weekend. Light to gentle winds will continue over
the Gulf of California through the period, with occasional
instances of gentle to moderate winds in the central section.
Looking ahead, a trough of low pressure located several hundred
miles west-southwest of southwestern Mexico is producing limited
shower and thunderstorm activity. Environmental conditions only
appear marginally favorable for gradual development of this
system while it moves slowly eastward to the south of the coast
of Mexico through the middle of this week.

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

Moderate to fresh southwest to west winds are occurring 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 thunderstorms are
over the offshore waters between northern Costa Rica through
western Panama. Strong winds and rough seas are likely in the
regions of strongest convection.

For the forecast, moderate to fresh southwest to west winds will
continue through Wed morning, becoming moderate speeds Wed
afternoon through the end of the week. Increasing westerly wind
waves are likely in the wake of Tropical Storm John, moving into
the waters off of Guatemala today, expanding farther east toward
El Salvador on Tue, and toward Nicaragua Wed. Periods of very
active weather are also expected over most of the Central America
offshore waters through at least mid week.

...REMAINDER OF THE AREA...

High pressure is generally present north of about 15N and west of
115W. Moderate to fresh trade winds and moderate seas are north
of 15N and west of 135W. An area of fresh to strong winds and
seas of 8 to 9 ft prevails near the monsoon trough from 08N to
15N between 98W and 108W. Gentle to moderate trade winds along
with moderate seas are noted elsewhere north of the monsoon
trough.

For the forecast, southwest monsoonal winds will continue to
become well established through the next couple of days as the
monsoon trough lifts slowly northward. Looking ahead, a trough
of low pressure located several hundred miles west-southwest of
southwestern Mexico is producing limited shower and thunderstorm
activity. Environmental conditions only appear marginally
favorable for gradual development of this system while it moves
slowly eastward to the south of the coast of Mexico through the
middle of this week.

$$
ADAMS