Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
1246 PM EDT Fri Mar 20 2026

Forecast Bulletin 20 March 2026 at 1645 UTC:

A frontal boundary in the Atlantic, currently extending into the
Bahamas and Cuba, along with a strong mid- to upper-level trough
east of the United States extending into the western Caribbean,
will continue to be the main drivers of precipitation and
convective activity throughout the forecast period by favoring
low-level moisture convergence, the presence of low-level
pre-frontal troughs, and upper-level divergence.

Today through Saturday morning, the mid- to upper-level trough
will enhance upper-level divergence over the Bahamas, Turks and
Caicos, and northern Hispaniola. At lower levels, the frontal
boundary and pre-frontal troughs will favor onshore moisture
advection and low-level moisture convergence over the Bahamas,
Turks and Caicos, and Hispaniola. This will result in periods of
convective activity, thunderstorms, and heavy precipitation for
that region. A slight risk for severe weather exists for the
Bahamas through Saturday morning. Precipitation accumulations are
anticipated to exceed 50mm, particularly over northwestern
Hispaniola and Turks and Caicos. Light to moderate precipitation
is expected over eastern Cuba and southwestern Hispaniola, with
the low-level flow favoring moisture convergence in the area.
Total precipitation is anticipated to be around 15-25mm, with
localized higher values possible.

As the frontal boundary propagates and reaches Hispaniola from
Saturday through Sunday, an enhancement of low-level convergence
is anticipated mainly over the Dominican Republic, increasing
precipitation in the area. This will result in rainfall
accumulations around 35-70mm. Over Puerto Rico, expect an increase
in precipitation as the low-level flow shifts to southerly and
southwesterly, advecting moisture from the Caribbean into the
region. Strong winds aloft will also aid the development of
thunderstorms in the region. Totals will range from 20-35mm.

Precipitation associated with the frontal boundary will continue
over Puerto Rico as it approaches the region from Sunday through
Monday, and low-level moisture convergence continues over the
area. An additional 20-35mm of rainfall is expected. Over the rest
of the Caribbean, a drying trend is anticipated with anticyclonic
flow dominating at low levels and relatively low values of PWAT
prevailing over the region.

Over Mexico, expect stable conditions, particularly over northern
Mexico, with a mid- to upper-level ridge over the northwest and
dry air in the region throughout the forecast period. Light
rainfall is likely over Veracruz today through Saturday morning
with the presence of some low-level troughs in the region, with
totals around 15mm. Light precipitation is also anticipated for
the Pacific coast over the next three days, particularly over
Guerrero, due to low-level winds being perpendicular to the coast
and some low-level troughs advecting moisture. Accumulations are
expected to remain on the lower end, ranging from 15-20mm, with
the low-level winds being relatively weak and the lack of deep
moisture in the area.

In Central America, low- and mid-level troughing will bring light
precipitation over Guatemala and northern Honduras today through
Saturday morning. Over Guatemala, the highest totals will be
around 15-25mm. Heavier rainfall is anticipated over the Caribbean
coast of Costa Rica and Panama over the forecast period. Today
through Saturday, the main drivers of precipitation will be strong
low-level flow, the presence of a low-level trough, and an
increase in moisture associated with the frontal boundary in the
Caribbean. This will result in totals from 20-45mm. Low-level
troughing is expected to continue through the end of the forecast
period, and northerly flow perpendicular to the coast will favor
the advection of moisture into the region. Accumulations will be
around 20-35mm from Saturday through Sunday morning, and another
20-40mm are expected from Sunday through Monday.

Over tropical South America, expect relatively dry conditions from
today through Saturday morning, with most of the precipitation
over the Amazon Delta and the Para region in Brazil due to the
presence of a low-level trough, deep moisture being advected from
the Atlantic, and low-level winds converging in the area with a
low further south in Brazil. Additional support for the
development of convection and strong thunderstorms is anticipated
from upper-level wind diffluence and the presence of mid-level
troughs. Total accumulation will be around 35-70mm, with the
possibility of higher values in isolated regions. Light rainfall
is also anticipated in western tropical South America,
particularly over Colombia and Ecuador, mainly due to low-level
moisture convergence. Stable conditions are expected to continue
through Monday over most of central tropical South America, with
dry air prevailing and a lack of upper-level support for
convective activity. Most of the rainfall activity will continue
over Colombia, the Amazon Delta, the Guianas, and the Eastern
Amazon region. The daily highest totals will range from 20-45mm.
An increase in precipitation is expected for Peru and the
southwest Amazon from Saturday through Monday, with moisture
availability improving and low-level winds converging in the
region, with accumulations of 20-35mm each day.


Rivera-Torres...(WPC)