Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
256 PM EDT Thu May 21 2026

Forecast Bulletin 21 May 2026 at 1900 UTC:

Mexico and Northern Central America...
On Thursday, and upper level trough extends into the northern
Mexico, tilting slightly negative over Texas, favoring divergence
over northeast Mexico. Expect the region to see a moderate risk of
severe weather with moderate to locally heavy precipitation,
primarily overnight. To the south, a mid to upper level ridge
weakens, giving way to a weaker inversion cap and allowing for
convection to develop over regions that have been seeing high
surface temperatures. The reflection of the mid to upper level
ridge is seen in the lower levels of the atmosphere, over the
Eastern Pacific Ocean, favoring winds from the west to enter into
the Pacific coasts of Oaxaca through El Salvador. On Thursday, the
region can expect light to locally moderate precipitation totals.
On Friday, the pattern from Thursday continues, where expect
moisture from the East Pacific enters into the coasts of Oaxaca
through El Salvador, enhancing moisture convergence, and favoring
light to moderate precipitation totals throughout the day on
Friday. In northeast Mexico, a new upper level trough axis extends
into the region, tilting negatively and favoring severe weather.
As moisture continues entering from the south, expect moderate
precipitation totals in Coahuila and Nuevo Leon. By Saturday, the
base of the upper level trough enters northwest Mexico, continuing
the pattern of severe weather. This region will see the entry of
moisture from the south, favoring heavy precipitation with the
moderate risk of severe weather. Moisture from the Pacific
continues to enter along northern Central America, favoring
moderate precipitation totals.

Southern Central America and Northern South America...
The region is seeing consistent propagation of troughs in the
lower levels with enhanced moisture accompanying these waves as
they move through the region the next few days. A tropical wave is
exiting the Costa Rica and Nicaragua throughout Thursday, while
enhanced cyclonic circulation over Panama is favoring convection
into eastern Costa Rica, Panama, and Colombia. The region can
expect local heavy precipitation on Thursday. To the east, in
Venezuela/Colombia region, another tropical wave is propagating,
favoring heavy precipitation that could exceed 70mm locally. In
the Guianas, another tropical wave is entering the region by the
early morning hours of Friday, but drier conditions will limit
maxima to moderate totals. On Friday, a propagating wave from the
Gulf of Panama region will favor to locally moderate totals of
precipitation from Costa Rica through west Colombia. The tropical
wave to the east has now entered the Lake Maracaibo region and
east Colombia, favoring heavy precipitation particularly along the
foothills of the mountain range. The tropical wave propagating
over the Guianas will likely favor light to moderate precipitation
totals are enhanced by the ridge in the mid to upper levels,
centered just north of the continent. By Saturday, a similar
pattern is expected over northern South America with the passing
of the tropical wave into east Venezuela, interacting with the
Shield of the Guianas. As the other tropical enters the northwest
portion of Colombia, expect heavy precipitation on Saturday.

Caribbean and the Bahamas...
A weakening Tropical Tropospheric Upper Trough is located over
northern Bahamas with the base extending into Hispaniola and Cuba
in the morning of Thursday. Throughout the day, the upper trough
will meander to the east, weakening and making way for the entry
of the periphery of a mid to upper level ridge that will extend
into the northern Caribbean by the end of the day. Alongside this
ridge, expect drier air and subsidence to spread along the
Caribbean, inhibiting deep convection for the next three days.
Daily precipitation totals are expected to remain from trace to
light amounts, with the exception of east Cuba and Hispaniola,
which could see moist plumes with available moisture exceeding
50mm.

TYP SOF INIT 22/00 22/12 23/00 23/12 24/00 24/12 25/00 25/12
TW  08N  46W   49W   52W   55W   58W   60W   63W  65W  68W
TW  12N  69W   71W   73W   75W   77W   79W   81W  82W  84W
TW  12N  88W   90W   92W   95W   98W  101W  103W 105W 108W
TW  13N 115W  118W  EXITS

Castellanos..(WPC)