Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
332 PM EDT Tue Sep 08 2026

Forecast Bulletin 08 September 2026 at 1920 UTC:

The Bahamas and Caribbean:

Light precipitation can be expected today through Wednesday over
The Bahamas due to an induced low-level trough, easterly low-level
flow advecting deep moisture, and the proximity of a frontal
boundary increasing moisture convergence in the area. However, a
ridge at mid- and upper-levels should limit convective
development. Accumulations are expected to be around 15mm. From
Wednesday through Thursday, light precipitation is also expected
over the northern Bahamas as slightly stronger southerly low-level
flow advects moisture into the region.
In the Caribbean, the synoptic pattern is dominated by an
upper-level trough south of Cuba and an upper-level ridge north of
Hispaniola, both of which are expected to propagate westward
throughout the forecast period. At mid- and lower-levels,
troughing over Cuba will induce rainfall today through Wednesday
morning, with total accumulation around 15mm. Precipitation will
continue from Wednesday through Thursday as a low-level trough
enhances moisture convergence in the area.

In the Lesser Antilles, an approaching tropical wave will increase
instability and moisture, resulting in rainfall today through
Wednesday, bringing around 15mm of rain. This wave is expected to
reach Puerto Rico, increasing precipitation from Wednesday through
Thursday morning, before propagating westward to bring rain over
Hispaniola from Thursday through Friday. By the end of the
forecast period, another tropical wave will approach the Lesser
Antilles, bringing additional rainfall.

Mexico and Central America:

Over Mexico, rainfall and thunderstorms are expected today through
Wednesday across the Sierra Madre Occidental. Main drivers include
upper-level diffluence, deep moisture, and a shortwave mid-level
trough enhancing instability. Accumulations are expected to reach
25-50mm. Light rainfall is expected today over Baja California due
to low-level troughing and moisture advection, with totals
reaching 10mm. A tropical wave and mid-level trough will enhance
instability over southern Mexico, combining with deep moisture to
bring rainfall today through Wednesday. Accumulations are expected
to range from 15-30mm. Less precipitation is anticipated for
southern Mexico after Wednesday as precipitable water decreases,
though isolated showers remain likely due to low-level troughing.
Heavy rainfall and thunderstorms, however, are expected throughout
the rest of the forecast period along the Sierra Madre Occidental,
driven by persistent low-level troughing, moisture convergence,
and enhanced upper-level diffluence along the periphery of a high
over northwestern Mexico.

Over Central America, primary areas of interest include Costa Rica
and Panama, where the monsoon trough, high precipitable water, and
strong low-level Caribbean winds could bring instability and
precipitation. Additional support exists at upper levels as a
trough propagates westward over the Caribbean. From Wednesday
through Thursday, accumulations will range from 25-50mm over
northeastern Costa Rica.  Elsewhere in Central America, rainfall
will mostly stem from low-level troughs, diurnal heating, and
localized effects.

Tropical South America:

Today through Wednesday, heavy rainfall and thunderstorms are
anticipated over the Amazon region of Colombia, Peru, and Brazil
as low-level troughs advect moisture and winds converge.
Precipitation should continue through the end of the forecast
period toward the northern portion of the continent, particularly
over Colombia and Venezuela, where the strongest moisture
advection is expected. Daily rainfall is also anticipated along
the Pacific coast of Colombia and Ecuador due to deep moisture
advected from the Pacific. Accumulations, however, should remain
on the lower end due to relatively weak low-level winds.
Elsewhere, daily showers are likely from low-level moisture
convergence, diurnal heating, orographic lift, and local effects.


Tropical Waves Initialized at 12 UTC:
TYP SOF  INIT 09/00 09/12 10/00 10/12 11/00 11/12 12/00 12/12
TW  17N  46W  50W  54W  58W  61W  64W  67W  72W  76W  
TW  20N  57W  61W  65W  69W  73W  78W  82W  85W  88W
TW  13N  92W  95W  100W  105W  110W  111W  112W  113W  114W  
TW  20N  110W  113W  115W  117W  Exits  ---  ---



Rivera-Torres...(WPC)