Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
234 PM EDT Fri May 15 2026

Forecast Bulletin 15 May 2026 at 1830 UTC:

The Bahamas and Caribbean:

A frontal boundary extending north of the Bahamas will bring
precipitation over The Bahamas and northern Cuba by increasing the
precipitable water availability in the region, enhancing low-level
moisture convergence and generating troughs. Over Hispaniola, a
westward propagating low-level trough will enhance moisture
advection, producing showers. Additionally, an eastern propagating
upper-level trough is expected to approach the Greater Antilles,
generating upper-level divergence which will support the
development of thunderstorms and convective activity. Given the
synoptic pattern, expect showers over The Bahamas, Cuba, and
Hispaniola today through Saturday morning. Over the eastern
Caribbean, light isolated showers are possible with easterly
low-level prevailing today. From Saturday through Sunday, similar
conditions are expected with the frontal boundary stationary north
of The Bahamas. Most of the precipitation is expected again over
The Bahamas and Cuba. From Sunday through Monday remnants of the
frontal boundary and prefrontal trough will aid the advection of
moisture over Turks and Caicos and portions of The Bahamas,
bringing some light precipitation into the region. Over the
Greater Antilles and Lesser Antilles, easterly flow and the
presence of troughs will bring localized showers. An enhancement
in thunderstorm activity is likely over Hispaniola, particularly
Sunday afternoon with the axis of the upper-level trough moving
into the region, enhancing upper-level divergence.

Mexico and Central America:

Relatively calm conditions are expected today across Mexico, with
a ridge prevailing at mid to upper-levels. Light rainfall is still
expected today through Saturday over Sierra Madre Occidental and
portions of the Yucatan Peninsula into southern Mexico, mainly due
to diurnal heating, moisture advection and local effects. From
Sunday through Monday morning, rainfall activity can be expected
along the Sierra Madre Oriental with the presence of the American
Low-Level Jet advecting moisture into the region, in addition to
orographic enhancement. Some upper-level divergence is also
expected over central-eastern Mexico as an upper-level trough,
reflected at mid-levels, approaches.

Over Central America, daily showers are anticipated in Costa Rica
and Panama with the presence of the monsoon trough and propagating
low-level troughs that will support the development of rainfall in
the region. With strong low-level easterly flow, advection of
moisture will also generate rainfall over the Caribbean coast of
Nicaragua, with the highest accumulations forecast from Saturday
through Sunday. Light rainfall is also expected from Sunday
through Monday over Guatemala and El Salvador light rainfall is
expected as a low-level trough moves along the Pacific coast of
Central America. Deep convection, however, is not expected with
the presence of a mid- to upper-level ridge prevailing in the
region.

Tropical South America:

Precipitation is expected each day over the western coast of
Colombia and northwestern Ecuador with moisture advection from the
Pacific, but with the low-level flow remaining fairly disorganized
and relatively weak accumulations will remain around 20-40mm.

Heavy precipitation and thunderstorms are expected today through
Saturday morning over the Central and Northwest Amazon, and
portions of the Orinoquia. This rainfall activity is primarily
caused by the convergence of low-level winds in the region,
propagation of a low-level trough increasing advecting deep
moisture, and diffluence of winds at upper-levels. A similar
pattern in precipitation is forecast from Saturday through Sunday,
with the heaviest precipitation over the Northwest Amazon and
Orinoquia region in Colombia and portions of Venezuela, where
upper-level divergence is expected with a trough propagating
eastward over the Caribbean, causing diffluence aloft. More
convective activity and rain is anticipated over Colombia and
western Brazil from Sunday through Monday morning, with the
enhancement of upper-level divergence, mid-level troughing, and
instability at lower-levels with the presence of a tropical wave
advecting moisture and increasing low-level convergence in the
region. More support for rainfall and thunderstorms is also likely
with diurnal heating and orographic lifting over the Andes region.

Daily rainfall is also expected over the Guianas, as moisture is
advected from the Atlantic into the region. A tropical wave is
anticipated to enter the region on Sunday, advecting moisture and
increasing instability over northeastern Brazil, and the Guianas
where showers and thunderstorms are expected. Accumulations over
the coast will range from 20-45mm, with higher isolated maxima
possible.


Positions of Tropical/Easterly Waves Initialized at 12 UTC
Type SOF INIT  16/00 16/12  17/00  17/12 18/00 19/12 20/00 20/12
TW   12N  53W   60W   65W   68W   70W  73W  78W  81W  86W
TW   13N  33W   36W   41W   46W   48W  50W  55W  60W  64W



Rivera-Torres...(WPC)