Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
218 PM EST Thu Mar 06 2025

Forecast Bulletin 6 March 2025 at 1915 UTC:

In the upper levels, there is a trough axis near the central
tropical Atlantic, which is quickly flattening and is expected to
dissipate by Friday morning. The trough axis will tilt positively
by Saturday, having its axis along the northern Leewards into
Venezuela. An upper high pressure currently over central to
southern Mexico will gradually move east, and its center may reach
the western Caribbean by Sunday morning.

In the mid levels, there is a mid -level trough  northeast of the
Lesser Antilles, which is causing a low-level trough to develop
over the area, and may cause shower and thunderstorm development
over some of the islands in the northeast Caribbean. However, most
of the Caribbean and the Bahamas will be under the influence of a
ridge, associated with a mid-level high pressure over southern
Mexico. By Friday night, the Caribbean region, as well as central
America, most of Mexico, and the Bahamas will be under the
influence of the mid-level high pressure, which will cause
generally stable conditions.

In the low levels, there is a cold front that is currently
extending from the western Atlantic, across the southern Bahamas,
into southern Cuba. This cold front will continue to move east as
its southern portion fragments a little each day. By Friday night,
the cold front will extend from the central Atlantic to
Hispaniola, remaining north of Puerto Rico. Enhanced precipitation
potential will be observed ahead of the frontal boundary, but the
mid and upper level conditions are not particularly favorable for
deep convection. The mid level moisture is generally limited, with
the exception of the area near the troughs in the tropical
Atlantic, elsewhere near the Caribbean, the moisture does not
reach the mid levels, and therefore, generally shallow convection
would be expected. That being said, the aforementioned low-level
trough is interacting with a mid-level trough in the area, which
may cause enhanced convection over the western to central tropical
Atlantic, and therefore could allow brief thunderstorms from the
Atlantic waters into the northeastern Caribbean islands for the
rest of today and  Friday.

With regards to widespread rainfall potential, most of the
significant showers and thunderstorms expected over the next few
days will be over the tropical region of South America. The latest
satellite imagery is indicating that some global models are
handling the deep convection better than others. Therefore, the
precipitation forecast considered a combination of model solutions
and consensus as well as ensembles. Considering the latest
satellite imagery, the rainfall forecast for portions of Colombia,
Peru and western Brasil were adjusted for the rest of today into
tonight, as deep convection is already occurring. Overall, the
generalized diurnal convection over tropical South America is
still expected to be influenced by the combination of the
available moisture, daytime heating, and local effects. The deeper
convection will be influenced by favorable mid and upper level
troughs, as well as low level convergence, however. The Caribbean
region is still expected to observe some shower activity over the
next few days, but the amounts are modest, which is typical for
the time of year. Isolated areas of the Caribbean region and
Mexico may observe some rainfall, but mainly under 15mm today,
while the northern Leeward Islands, west into PR and the VI may
observe a rainfall maxima of 25mm on Friday, due to the
aforementioned low level trough in the area causing moisture
convergence.


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)