Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
108 PM EDT Wed Mar 19 2025

Forecast Bulletin 19 March 2025 at 1710 UTC:

...Mexico...Central America...and Caribbean Basin...

On Wednesday, the majority of Mexico into Central America and the
west Caribbean is seeing the effects of upper level ridging that
is favoring drier conditions due to the subsidence associated with
ridges. This ridging is also present in the mid levels of the
atmosphere, which is favoring a trade wind inversion over most of
the region. To the east, the base of a mid to upper level trough
extends to just north of the ABC Islands by Wednesday evening,
favoring the presence of a stationary frontal boundary over the
Greater Antilles by Wednesday evening. Additionally, a frontal
shear line associated with a weakening front over the Central
Atlantic remains over the east Caribbean Sea, just west of the
Lesser Antilles. To the north, an upper trough over the central
United States is propagating over the country and strengthening a
cold front that is expected in over north Veracruz and along the
Sierra Madre Occidental by the evening on Wednesday. Due to the
lack of moisture over the region, precipitation values are
expected to remain low. On Thursday, the cold front over Mexico is
expected in just north of the Yucatan Peninsula and enters
southern Veracruz and becomes stationary along the Sierra Madre
Occidental. A prefrontal boundary develops over the Yucatan
Peninsula and central Guatemala, favoring lift in the region and
moderate precipitations. To the east, the stationary frontal
boundary over the Greater Antilles weakens by Thursday evening,
yet a prefrontal shear line remains to the south of Puerto Rico
and meanders over the north Leeward Islands. On Friday, the
western cold front reaches the central Bahamas and enters Cuba,
where it becomes stationary and weakens over the northern Yucatan
Peninsula. The eastern frontal boundary weakens over the Central
Atlantic Ocean and behind remains a shear line that extends from
Puerto Rico to the southwestern Caribbean Sea, which the speed
shear in the lower levels of the atmosphere reaches just off-shore
Panama. With the enhanced Caribbean Low Level Jet, moisture is
being advected into the Caribbean shores of Panama and Costa Rica
and interacting with the terrain. Precipitation totals could
become locally moderate in Panama on Friday. Elsewhere in the
region moisture in the easterly trade winds enters regions such as
Guatemala and Nicaragua.

In terms of precipitation, on Wednesday, east Nicaragua can expect
maxima of 15-25mm and south Haiti, the Leeward Antilles, and the
central Lesser Antilles can expect maxima of 10mm. On Thursday,
expect maxima of 20-45mm in Veracruz and east Chiapas, while
maxima of 20-35mm in central Guatemala. Maxima of 15-25mm are
expected in east Oaxaca/south Veracruz. East Costa Rica into
northwest Panama can expect maxima of 10mm. On Friday, maxima
below 15mm are expected in the Isthmus of Tehuantepec
region,Puerto Rico, and central Guatemala. Generalized maxima of
15-25mm are expected in east Nicaragua and east Panama, while
north-central Panama can expect maxima of 20-35mm.

...Tropical South America...

The presence of the upper level systems interacting over and
around South America is dominating where the diffluence that can
assist with ventilating convection over the northern region of the
continent. The strengthening of the Bolivian High will play a big
factor over the northwest portion of the continent, while to the
east, drier air is being advected along the easterly trade winds
and enhanced subsidence is expected over the next three days as
the subtropical ridge over the Central Atlantic meanders near the
Guianas on Thursday and Friday. Additionally, moist plumes are
traveling along the ITCZ/NET, that will be interacting with the
upper level diffluence in the western Amazon Basin. A they
converge and interact with the Andes regions of Colombia and
Ecuador, enhanced moisture convergence is expected and favor
moderate to heavy precipitation. Along the western coasts of
Colombia and Ecuador, the presence of moist onshore flow will
favor deep convection, primarily on Wednesday and Thursday,
decreasing on Friday.

For precipitation values, on Wednesday, expect maxima of 35-70mm
in west Ecuador, while maxima of 30-60mm are expected in
south-central Colombia and into north-central Ecuador and the
Central Amazon Basin. Expect west Colombia to see maxima of
20-40mm, north Colombia into the Lake Maracaibo Region and the
Amazon Delta can expect maxima of 20-35mm. On Thursday, maxima of
30-60mm are expected in west Ecuador, and maxima of 25-50mm in the
west Amazon Basin. West Colombia can expect maxima of 20-45mm,
while the Andean regions of Ecuador can expect maxima of 20-35mm.
On Friday, expect maxima of 25-50mm in the Lake Maracaibo region
into northeast Colombia, as well as in north Peru and east
Ecuador. Generalized maxima of 20-45mm are expected in south
Colombia, west Ecuador, and east-central Amazon Basin.

For a graphical representation and details of the areas with
forecast rainfall:
https://www.wpc.ncep.noaa.gov/international/crb_day1-3.shtml

Castellanos...(WPC)