Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
326 PM EST Wed Mar 05 2025

Forecast Bulletin 5 March 2025 at 2020 UTC:

In the upper levels, there is a trough axis north of the Leeward
Islands, with a ridge to the west over and north of the Bahamas.
There is a weak trough over the central Caribbean, with an axis
across Nicaragua and Honduras. By Thursday night an upper high
pressure will move into central to southern Mexico, while a weak
trough develops across the western Caribbean. A broad upper trough
over the western Atlantic, and southwestern flow over the southern
Caribbean, will cause an area of upper level confluence across the
northern Caribbean Islands, with relatively stronger winds over
the western tropical Atlantic, causing some divergence aloft. By
Friday night, the upper high pressure over Mexico will move east
and will be centered over Yucatan. The trough axis will move east
and tilt forward, with its axis then extending from Hispaniola to
Jamaica into Nicaragua and Honduras. The upper-level confluence
will continue from the central Caribbean, east and over the
Leeward islands by Friday night, with the relatively stronger
winds over and east of the leeward islands.

In the mid levels, a low pressure centered near 24N/63W has an
associated trough that will amplify to its south-southeast, just
east of the Lesser Antilles by tonight. Most of the Caribbean into
the Bahamas will be under the influence of a ridge, associated
with a mid-level high pressure over southern Mexico. By Thursday
night, the high pressure in the mid levels continues to dominate
most of the Caribbean into central America, though a weak trough
will have an axis over the eastern Caribbean, just west of the
lesser Antilles. By Friday night, essentially the entire
Caribbean, as well as central America, most of southern and
eastern Mexico, as well as the Bahamas will be under a mid level
high pressure, which will cause generally stable conditions. The
EGDI and GR02T algorithms agree, and suggest generally shallow
convection over the area.

The main low-level feature in the Tropics is a cold front that is
currently extending from the western Atlantic to the Yucatan
peninsula. This frontal boundary will continue to move east as its
southern portion starts to fragment with each passing day. By
Friday night, the cold front will extend from the central Atlantic
to Hispaniola, remaining north of Puerto Rico. Some enhancement of
precipitation can be observed ahead of the frontal boundary, but
the mid and upper level conditions, although somewhat favorable
with some diffluence, are not particularly favorable for deep
convection. In addition, the mid level moisture is very limited
over the area, therefore, generally shallow convection would be
expected across most areas in the basin. That being said, there is
a low-level trough in the western tropical Atlantic, just
north-northeast of Puerto Rico and north of the Leeward Islands,
that is causing moisture convergence over the area. This is
interacting with a mid-level trough in the area, which may cause
enhanced convection over the western to central tropical Atlantic,
and therefore allowing for brief thunderstorms from the Atlantic
waters into the northeastern Caribbean islands.

Once again, 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 and Peru were bumped up for the rest of
today into tonight, as deep convection is occurring. Overall, the
generalized diurnal convection over tropical South America will be
influenced by the combination of the available moisture, daytime
heating, and local effects, but the deeper convection will be
influenced by favorable mid and upper level troughs, as well as
low level convergence. 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 southern Mexico and Hispaniola may observe up to
25mm today, while the Leeward Islands may observe a rainfall
maxima of 35mm, due to the aforementioned low level trough causing
moisture convergence and combining with the mid-level low. Lower
amounts of rain are expected on Thursday and Friday across the
Basin.


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)