923
FXCA20 KWBC 201909
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
309 PM EDT Mon Jul 20 2026

Forecast Bulletin 20 July 2026 at 1915 UTC:

Across the Caribbean...
A persistent upper-level low over the northeastern Caribbean has
induced a surface trough just north of the Leeward Islands. This
trough is forecast to move westward across the northern Caribbean,
promoting warm, moist advection from the Atlantic. A modest amount
of moisture is accompanying the induced trough, which will support
the development of light showers across Hispaniola and Jamaica
mainly on Tuesday and Wednesday. Also expect the development of
localized low level troughs across Hispaniola and Cuba that will
further support precipitation processes in the region.

Another well-defined tropical wave over the tropical Atlantic
Ocean is forecast to enter the Caribbean by Thursday. As it
progresses westward, this wave is expected to weaken the Atlantic
subtropical high-pressure ridge situated east of the Caribbean.
Consequently, the low- to mid-level trade wind inversion is
expected to weaken from Wednesday into Thursday and there will be
a weakening of the Caribbean Low Level Jet (CLLJ). This will
create a more favorable environment for deeper convection,
particularly across the northern Leeward Islands and portions of
the Greater Antilles.

Elsewhere across the Caribbean, relatively dry air and a stronger
low- to mid-level inversion will continue to suppress deep
convection. As a result, any precipitation occurring on Tuesday
and Wednesday is expected to be light, with accumulations
generally ranging from trace amounts to a few millimeters.

In the Guianas and Northern South America...
With the Intertropical Convergence Zone (ITCZ) positioned over
Suriname and French Guiana, easterly trade winds will continue
transporting abundant moisture westward from the Orinoco Delta
toward the Andes.
By Wednesday and Thursday, enhanced moisture advection, combined
with a low-level disturbance, is expected to promote the
development of deep convection over the Cordillera de Mrida and
the northern Andes. Upper-level wind conditions appear favorable
for sustaining organized deep convective activity across this
region, increasing the potential for locally heavy rainfall and
thunderstorms. Meanwhile along the Pacific coast of Colombia,
there will be a resurgance of onshore westerly low level winds
into the coast for Monday and Wednesday that will help favor
moisture convergence. Thunderstorms will be likely during this
period.

Across Mexico and Central America...
A mid-to-upper level ridge will continue to dominate across the
southern United States plains. Its southern periphery will extend
across northern Mexico. The enhancement in easterly winds will
lead to a drying effect in the northeast section of the country
for Tuesday and Wednesday. Meanwhile along the northwest Pacific
coast of Mexico, a  low level ridge will be situated off-shore and
it will support the increase in westerly winds. This will lead to
moisture pooling along the Gulf of California eastern coast. There
will be isolated showers and thunderstorms in this region for the
next three days. A period of interest across Sonora is Monday when
a mid-level trough will be present in the region and support the
development of thunderstorms. Another region of interest is Costa
Rica. For the next three days, there will be ongoing onshore flow
into the region. The presence of the Caribbean low level jet will
also support the increase in cyclonic rotation. Thus, expect the
daily development of thunderstorms in this region. Elevated
precipitation accumulations are expected daily.


SOF INIT 21/00 21/12 22/00 22/12 23/00 23/12  24/00 24/12
21N 39W  42W  44W  46W  49W 54W  56W  61W 64W
12N 74W  77W  79W  82W  85W 89W  91W  95W 99W
11N 86W  89W  91W  93W  95W 97W  99W 101W ABS

Luciano...(MDC)
Murray...(MSJ)
Castellanos...(WPC)


$$