Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
230 PM EST Fri Feb 28 2025

Forecast Bulletin 28 February 2025 at 1930 UTC:

The latest CFS model continues to suggest that a divergent MJO
phase should continue through the weekend across the Atlantic,
Caribbean and Central America. However, the model suggests a weak
divergent pattern for extreme northwestern South America and a
weak convergent pattern for Brasil and the Guianas through the
weekend. The latest MJO observations suggest a strong divergent
phase across the Caribbean and western tropical Atlantic, while a
weak convergent phase was observed across most of South America,
including tropical South America.

Across the Atlantic Basin, Caribbean, Central America, and
Mexico...

Throughout the weekend, rainfall over the region is forecast to be
generally under 25mm each day, and no rain in some areas.
Considering the latest guidance and observations, brief showers
are expected over the Caribbean islands, central America and
portions of Mexico. That said, a persistent line of moisture,
associated with a low-level confluence will extend from the west
central Atlantic, southwest through the southern Bahamas, Turks
and Caicos, and into Hispaniola and eastern Cuba. This constant
moisture will allow for daily shower development over the area,
though the daily accumulations are still expected to be generally
under 25mm each day, today being the day with highest
accumulations and Saturday being the driest day. It is worth
noting that a cold front will move east-southeast through the
western Atlantic late this weekend, enhancing convection ahead of
the boundary, but this convection enhancement will favor areas
north of the Caribbean islands and to the northeast of the
southern Bahamas and Turks and Caicos.

In the upper levels, a shortwave trough moved north of the
Caribbean islands as it weakened, and its axis is now to the
northeast of the Leeward Islands. Another upper trough is forecast
to develop across the Caribbean region this weekend, though it
will be broad and its impact on rainfall development and
instability will be limited, until perhaps very late Sunday into
early Monday, when the trough is expected to amplify over
Hispaniola and cause some instability over the area. This may
combine with the available moisture and a shortwave mid-level
trough, which may increase the chances of isolated thunderstorm
development. That being said, the mid levels across the eastern
Caribbean may remain fairly stable this weekend. This is because
there is a mid-level high pressure to the northeast of the
Leewards that its extending southwest into the northeast Caribbean
islands, keeping things stable in the mid levels. Therefore, the
chances of brief thunderstorms late Sunday into Monday are higher
across Hispaniola than further east in the Caribbean. Elsewhere, a
trade wind inversion will keep the area stable with mainly shallow
convection expected throughout the weekend.

In the lower levels, a weakening stationary front across the
western tropical Atlantic will dissipate by Saturday, then a cold
front will start moving into the western Atlantic from the
southeast US, which is expected to move into the west-central
Atlantic into the central Bahamas by Sunday. As previously
mentioned, there will be a line of higher moisture extending south
from the west-central Atlantic into Hispaniola and Cuba this
weekend. The Caribbean will have patches for moisture and dry air
moving through the area over the next few days. A low-level trough
is moving into the Caribbean on tonight into Saturday, causing an
increase in moisture over the area and enhancing the chances of
rainfall. However, the mid-level ridge expected over the northeast
Caribbean will keep convection shallow over the area.

Across Tropical South America...

The enhanced chance of showers and thunderstorms across western
Colombia and Ecuador will continue this weekend. The model
guidance insists that the conditions will be favorable for
thunderstorm development over the area. The low-level onshore
flow, which has higher than normal moisture, will play a role in
the development of showers and thunderstorms as the air rises with
the topography and is ventilated with the mid and upper level
diffluence. For the rest of today into Saturday, western Colombia
and Ecuador is forecast a rainfall maxima at around 25-60mm with
some areas receiving more or less than that. Saturday into Sunday,
the forecast suggests maxima of 25-50mm, as well as Sunday into
Monday, though the latter has less rainfall in the forecast for
northwestern Colombia. 

Across Brazil and surrounding countries, near normal moisture is
expected, with the exception of the Guianas, Venezuela, and
portions of northern Brasil, where drier than normal moisture is
expected through the weekend. That said, available moisture will
combine with the diurnal heating and local effects to cause
diurnal showers and thunderstorms over the area. Most of the area
is expected to observe daily rainfall maxima in the order of
15-35mm throughout the weekend.

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

Alamo...(WPC)