Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD


Forecast Bulletin 08 October 2026 at 1845 UTC:

For the next three days, expect an active precipitation pattern
across Mexico being driven by the presence of multiple surface low
pressure systems. The first low pressure system is Tropical Storm
Isaias, which is starting to move farther into the Gulf. For
Thursday, still expect some feeder bands to be moving along the
coast of the state of Yucatan which will support total
precipitation maxima of 25 to 30mm through Friday morning.
Thereafter, remnant moisture plumes will still be converging into
the continent, particularly across the south gulf states of Mexico
and Guatemala, positively favoring the initiation and sustenance
of precipitation in the region for Friday and Saturday. Also on
Friday, expect the presence of upper divergence across northern
Central America, which will support convective ventilation in the
upper levels. Thus, expect elevated total precipitation maxima
across central Guatemala on Friday and moderate accumulations in
the surrounding region. By Saturday, precipitation impacts will
remain across the region but accumulations will lessen as dry air
is expected to surge into the region from the east.

Across the Pacific, Tropical Storm Simon will continue moving
parallel to the coastline for Thursday and Friday. By Saturday,
the system is expected to move into Jalisco and rainfall
accumulations will increase substantially due to orographic
effects. By day, on Thursday, the region of greatest direct
precipitation impact will be across Guerrero and Michoacan coast.
On Friday, expect the greatest precipitation impacts across
Michoacan, Colima, and south Jalisco coasts. On Saturday, the
greatest impacts will be observed across Jalisco.

Another system of interest is Tropical Storm Rachel, which is
expected to approach Baja California on Saturday. The increase in
moisture and support from the mid-levels will lead to the increase
in precipitation chances. A total precipitation maxima of up to
30mm is likely with the arrival of this system.

A tropical wave is continuing to move across the Greater Antilles
today. It is expected to be exiting Hispaniola today and moving
into Jamaica and Cuba. This tropical wave is interacting with an
upper level trough that will be providing upper divergence across
the region. Additionally, there will be an increase in moisture in
the region with the interaction of these two features. Expect the
development of thunderstorms across southeast Cuba and Jamaica on
Thursday. The tropical wave will be losing its structure on Friday
but the ample moisture will remain in the region. The moisture
plume is expected to arrive in Nicaragua. Overall, expect moderate
total precipitation maxima with the passage of this tropical wave
and its remnants.

In Central America, the monsoon trough will continue to meander
across Costa Rica and Panama, reinforcing daily diurnal convection
across the region. As the tropical wave remnant moves into the
region on Sunday, expect the development of westerly low level
winds into Colombia, leading to enhanced moisture convergence.
This pattern will lead to enhanced total precipitation maxima with
this pattern change on Sunday.

Across the Lesser Antilles, a long-fetch moisture plume will
continue to converge into the windward islands, leading to the
daily development of convection. Meanwhile in the Amazon, dominant
easterly low-to-mid level winds will continue to promote moisture
convergence in the region. Overall, expect diurnal convection to
develop and to support moderate total precipitation maxima for the
next three days.


Tropical Waves Initialized at 12 UTC:
TYPE SOF  INIT  09/00 09/12 10/00 10/12 11/00 11/12 12/00 12/12
TW  15N   32W   34W   35W   37W   39W   41W   42W   44W   46W
TW  19N   73W   75W   78W   80W   82W   84W   85W   87W   89W

Tinoco-Morales...(WPC)