Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
432 PM EST Thu Feb 27 2025

Forecast Bulletin 27 February 2025 at 2130 UTC:

The latest CFS model guidance continues to suggest that a
divergent MJO phase should continue into the weekend across the
Atlantic, Caribbean, Central America and Mexico. The latest MJO
observations suggest a weak convergent phase across most of South
America, including the tropical region, and the latest CFS
guidance does suggest a weak divergent pattern for extreme
northwestern South America, but a weak convergent pattern for
Brasil and the Guianas through the weekend.

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

In general for the rest of the workweek and into the weekend, the
rainfall totals over the region are forecast to be modest. The
latest guidance continues to suggest that brief showers are to be
expected over the Caribbean islands. Daily rainfall over the
Caribbean islands, Central America, and Mexico are expected to be
generally under 25mm, although very isolated areas could observe
up to 25mm. Once again, the global models suggest a mid to upper
level trough over Hispaniola today into Friday. Although the
latest model guidance does favor a slight chance of strong storms
over Hispaniola, the latest satellite imagery does not indicate
that deep convection is occurring, therefore the forecast for the
area was adjusted considering the latest observations.

In the upper levels, a trough, with axis west of Hispaniola will
move east, and will be over the Greater Antilles for the rest of
today into Friday. This upper trough could provide some
instability over Hispaniola this evening, which could combine with
with slightly higher than normal moisture to cause isolated
thunderstorms. As previously mentioned, the latest satellite
imagery does not indicate deep convection being currently
developed over the area, but the potential for isolated
thunderstorms is still there for tonight. By Friday night, the
upper trough will be over the northeastern Caribbean but will be
weaker, and the impact on rainfall development will be very
minimal, in part because the mid-levels will not be favorable for
deep convection to break through during that time. That said, the
mid-levels will also have a trough moving through Hispaniola
tonight into Friday, but the northeastern Caribbean islands will
remain under the influence of a mid-level high pressure that will
extend from the central tropical Atlantic into the northeastern
Caribbean into the weekend.

In the lower levels, there is a cold front moving south from the
US into the northern Gulf Coast and the western Atlantic by this
evening. There is also a weakening stationary front across the
western tropical Atlantic. Even though this stationary front is
weakening, leaving a trough in its place by this weekend, there
will be a line of higher moisture extending south from the
Atlantic into the Caribbean, mainly over Hispaniola into the
Central Caribbean from tonight into the weekend. The Caribbean
will have patches for moisture and dry air moving through the area
over the next few days. A low-level trough will move into the
Caribbean on Friday into Saturday, causing a jump 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...

Colombia and Ecuador will continue observing showers and
thunderstorms in their respective Pacific coasts for the next few
days. The latest guidance keeps suggesting that the conditions
will be favorable for development over the area, with deep
moisture over the area. The presence of the southern ITCZ ending
in the west coast of Ecuador, combined with low-level onshore flow
will play a role in the development of showers and thunderstorms
as the warm moist air rises with the topography and is ventilated
with the mid and upper level diffluence. The available moisture is
expected to be deep in the atmosphere, and the relative humidity
values in the low and mid levels will be above normal for portions
of northwestern South America. This means that for the rest of
today into Friday, western Colombia and Ecuador is forecast a
rainfall maxima at around 30-80mm with some areas receiving more
or less than that. A slight decrease in rainfall potential is
forecast for Ecuador on Friday into Saturday, but a jump in
rainfall amounts is forecast again for Saturday into Sunday. 

Across Brazil and surrounding countries, higher than normal
moisture is expected, with the exception of the Guianas,
Venezuela, and portions of northern Brasil. However, the drier
than normal air is moving south into portions of Amazonas for the
next few days. That said, the deep moisture that is available,
will continue to interact with the ITCZ/NET to cause diurnal
showers and thunderstorms over the area. In general, the diurnal
shower and thunderstorms expected will cover a widespread area.
Most of the area is expected to observe daily rainfall maxima in
the order of 15-35mm each day for the rest of the workweek and
into 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)