Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
306 PM EDT Tue Aug 04 2026

Forecast Bulletin 4 August 2026 at 1910 UTC:

Over the next three days, significant rainfall accumulation is
forecast for portions of the Colombian Pacific coast and central
Colombia to southern Nicaragua, with daily maxima of 25 - 50 mm.
Significant rainfall is also expected across portions of Cuba,
Mexico, and Guatemala, with daily maxima ranging between 20 - 45
mm.

In the upper levels, two low-pressure systems, one south of the
Baja California Peninsula and the other over southern Mexico, will
provide favorable conditions for ascent. Another low-pressure
system, currently centered over northern Hispaniola, will track
across the Greater Antilles. Over the next three days, a ridge of
high pressure will strengthen over northeastern Mexico as the
western low continues to move northwestward. The southern low will
shift slightly westward, reducing its influence over western
Mexico. The Caribbean low-pressure system will move westward north
of the Caribbean Sea, favoring dynamical forcing across the region
from The Bahamas to Nicaragua and Colombia. In the mid-levels, a
well-defined trough remains over the southern Baja California
Peninsula with an associated low-pressure anomaly. A noticeable
low-pressure anomaly also persists over the Caribbean basin,
particularly over Colombia and Panama. Over the next three days,
high-pressure anomalies will dominate the region, driven by
strengthening centers over Bermuda and the southwestern U.S.

In the lower levels, elevated precipitable water (PWAT) values are
expected along Mexico's western and southeastern coasts, driven by
humidity advection. PWAT anomalies will remain modest, except over
the northern Sierra Madre Oriental, where values are expected to
exceed two standard deviations above normal. Nonetheless, the
highest rainfall accumulations are anticipated along the western
coast and southern portions of Mexico extending into northern
Central America. A southeasterly moisture flux will support
rainfall over Cuba and The Bahamas over the next three days, while
a plume of Saharan dust limits precipitation over Jamaica,
Hispaniola, Puerto Rico, and the Lesser Antilles. Across southern
Central America and western Colombia, the interaction between the
monsoon trough, regional dynamics, and a passing tropical wave
will sustain significant daily rainfall. The primary area of
precipitation will shift westward from Colombia to Costa Rica and
eastern Nicaragua as the tropical wave propagates. Elsewhere in
northern South America, precipitation will be supported by
low-level moisture advection and orographic lifting over the
Orinoquia and northwest Amazon regions.

Tropical Waves Initialized at 12 UTC:
Typ SOF INIT 05/00  05/12   06/00  06/12   07/00    07/12  08/00 
08/12
TW 14N  21W  24W    27W     30W    34W     38W      42W   46W   
51W
TW 24N  37W  40W    43W     46W    49W     52W      56W   60W   
64W
EW 13N  42W  46W    50W     53W    57W     61W      65W   69W   
72W
TW 26N  56W  60W    64W     68W    73W     77W      80W   83W   
85W
TW 18N  74W  77W    80W     83W    86W     88W      90W   92W   
96W
TW 20N  98W  101W  105W     108W   111W    115W     EXIT   - - -



Sanchez-Perez...(WPC)