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


Forecast Bulletin 07 October 2026 at 1900 UTC:

Across the Caribbean...
A tropical wave is currently traversing south of the Mona Passage
and is expected to continue moving into the northwest Caribbean
through Thursday. Simultaneously, an Tropical Upper Tropospheric
Trough (TUTT) is currently situated across the west Caribbean Sea.
The presence of this TUTT will enable the increase in propagation
speed of the tropical wave as it approaches Hispaniola. Starting
on Wednesday evening, the upper level winds will become diffluent
and will help in the development of divergence across west
Hispaniola. The coupling of these two features will lead to the
development of convection in the region starting Wednesday evening
across the southern regions of the island and continuing through
Thursday morning. Expect moderate total precipitation maxima
across south Hispaniola with the passage of this tropical wave.

The tropical wave will be moving across Jamaica and southeast Cuba
on Thursday and losing its structure on Friday morning. Moist air
advection into the region will favor the development of showers
and thunderstorms across Jamaica, particularly after Thursday
afternoon. Additionally, due to the presence of the TUTT, the
environment will remain unstable. These conditions will promote
moderate total precipitation maxima across Jamaica and Cuba for
Thursday and Friday.

On Friday, another weaker moisture plume will be arriving into
Puerto Rico and the Virgin Islands. The mid-level moisture content
is expected to increase subtly, giving way for the development of
showers and thunderstorms. Meanwhile in the windward Lesser
Antilles and Trinidad & Tobago, the long fetch moisture plume
extending from the central Atlantic will be converging into this
region for the next three days, supporting the daily development
of thunderstorms with light rainfall accumulations.

Across south Central America and South America...
The aforementioned tropical wave will reflect into northern South
America, where a weak cyclonic perturbation will exist in the
low-to-mid level wind flow. This feature will be accompanied with
a moisture plume. Upper level diffluence will also be present
overhead, which will support ventilation for convection. Thus,
expect moderate to elevated total precipitation maxima along the
eastern foothills of the Colombian Andes on Wednesday and elevated
maxima across central Colombia for Thursday in association with
this tropical wave.

In Costa Rica and Panama, the surface to low level monsoonal
trough will be overhead for the next three days and precipitable
water values will remain above 50mm. At the same time, the base of
the TUTT will extend into this region which will support
destabilization. Overall, expect the daily development of showers
and thunderstorms in the region that will favor daily total
precipitation maxima of up to 25mm.

Another region of interest is the Pacific coast of Colombia and
Ecuador. Daily moderate total precipitation maxima is expected for
the next three days, primarily associated with diurnal convection.
East of the Andes, dominating low-to-mid level easterlies will
assist in moisture pooling along the foothills. The environment
will thus contain high instability and adequate moisture to
sustain convection for the next three days.

Across Mexico and north Central America...
Two low pressure systems will continue to influence the
precipitation regime across the country for the next three days.
The first is Tropical Storm (TS) Isaias, which currently sits near
22.2N 92.9W. This system will sustain feeder bands that will
converge into the states of Tabasco, Campeche, and Yucatan for
Thursday and Friday. Elevated total precipitation maxima is
expected in these states for Thursday and Friday. Isolated
thunderstorms are likely to develop across the interior of
Campeche and Yucatan as TS Isaias continues moving into the
central Gulf, leading to enhanced total precipitation maxima for
Thursday and Friday.

By Saturday, expect the transport of moist air into Chiapas (MX),
Tabasco (MX), and Guatemala. Simultaneously, an upper level trough
will be located overhead, leading to an increase in ventilation
for convection. Elevated total precipitation maxima is likely in
this region for Friday.

The second system of interest is Tropical Depression Twenty-E ,
which is currently situated off the southwest coast of Mexico.
This system will continue to move parallel to the coast line for
the next three days. Moisture convergence will be ongoing along
the coast as the surface to low level winds interact with the
local terrain/orography. Elevated total precipitation maxima is
likely for the next three days, with the region of greatest
precipitation impact shifting relatively northward as the system
gains latitude.

Additionally, the dominating southeasterly low level wind will
help transport moisture into south-central Mexico and local and
diurnal effects will help develop isolated showers and
thunderstorms across the interior of the country. Daily moderate
total precipitation maxima is likely in this region.

Tropical Waves Initialized at 12 UTC:
TYPE SOF  INIT  08/00 08/12 09/00 09/12 10/00 10/12 11/00 11/12
TW  15N   29W   31W   33W   34W   36W   38W   40W   42W   44W
TW  19N   68W   71W   73W   75W   78W   80W   82W   84W   86W

Tinoco-Morales...(WPC)