Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
1225 PM EST Wed Feb 12 2025

Forecast Bulletin 12 February 2025 AT 1700 UTC

For the rest of the workweek, the MJO pattern is forecast to be
favorable for upper divergence across the region, which will play
a role in the expected convection across the region over the next
few days. That said, it may have a more significant impact across
northern South America, as the Caribbean region will remain with a
relatively dry and stable atmosphere. Isolated to scattered brief
showers amounting to modest rainfall accumulations each day are
expected, with daily accumulations near 10-20mm across some areas,
but even lower accumulations in most areas of the Caribbean and
Central America. Across eastern Mexico, an increase in moisture
will be observed over the Veracruz region and nearby Mexican
states on Thursday into Friday as a cold front moves south into
the region, which will increase the chances of showers, with up to
45mm of rain across the area. Across tropical South America over
the next three days, a mean low-level westerly flow into the
coasts of Colombia and Ecuador is expected, which will play a role
as moisture will interact with the local terrain and the favorable
mid and upper level divergence, enhanced by the divergent MJO.
Note that this pattern is similar to what they have observed over
the past few days. On top of everything observed in the synoptic
and large scale oscillations, using persistence as a forecast
method, showers and thunderstorms are expected each day for the
rest of the workweek, with rainfall maxima forecast to be around
25-50mm each day over western Colombia and Ecuador. 

In terms of the synoptic pattern, a ridge will persist over the
Caribbean in the mid and upper levels through the end of the
workweek. A weak mid to upper level trough could develop over the
Tropical Atlantic on Thursday, but the axis will be to the east of
the Lesser Antilles, and therefore the islands will remain on the
subsident side. This pattern will keep a fairly stable atmosphere,
allowing only shallow convection across isolated areas, depending
on the moisture availability and other factors over any one area.
The dry air in the mid levels continues moving over the Caribbean
region and will persist for the next few days. That said, there
are some patches of moisture at the 700 hpa level, with pockets of
above normal RH values moving through quickly across the Caribbean
into the Gulf. The 500 hpa level has a very widespread below
normal RH values across the region, however. This suggests that
the available moisture will be limited to the lower levels over
the region. Across most of tropical South America, the RH values
at the 700-500 hpa levels are relatively high, contrary to the
Caribbean. That said, eastern Brasil will have dry air at the 500
hpa level for the next few days. In terms of winds aloft, the mid
and upper levels will continue to cause divergence across western
Colombia and Ecuador, promoting convection over the area.  The mid
levels will have relatively light winds over most of tropical
South America, but will be diffluent across the central to western
portions of Brasil into Peru, allowing for isolated deep
convection. Eastern Brasil will have some convergence, however.

At the surface, a high pressure over the central Atlantic will
continue to dominate the Caribbean and the tropical Atlantic. This
surface high pressure center is expected to remain in place today
and Thursday, but drift slowly west on Friday into the western
tropical Atlantic. A weak surface low pressure will move south
over the east coast of Mexico tonight into Thursday, a high
pressure will move into eastern Mexico by Friday. The low level
winds are still expected to be relatively strong for the next
several days across the Caribbean, tropical Atlantic and into the
Gulf. The model guidance continues to insist that the surface
winds will be near or over 20 KT over much of the Tropical region,
especially over the waters.

In terms of rainfall, the Caribbean will have minimal to modest
amounts over the next few days due to the drier air and stable
atmosphere, combined with the breezy conditions pushing shower
activity quickly over any one area. Mexico is expected to observe
a dry day today and on Friday, with essentially fair weather
across the country. However, an increase in moisture across
eastern Mexico on Thursday will cause an increase in shower
activity, with forecast rainfall maxima up to 45mm from Thursday
into Friday morning over areas in and around Veracruz. The Guianas
and Amapa of Brasil are expected to observe showers and
thunderstorms over the rest of the workweek as low level moisture
moves in with the trade winds and the proximity to the ITCZ, with
rainfall maxima near 25-50mm today, 20-45mm on Thursday, and
20-35mm on Friday. Dry air will move in over Venezuela into
northeastern Colombia with the nocturnal LLJ bringing dry air each
day. Once again, the area with the best chance of significant
rainfall is the tropical region of South America, especially
western Colombia and Ecuador, where daily maxima of 25-50mm is
forecast.  Northern Peru, into the Amazonas and Para states of
Brasil will have diurnal convection, with daily maxima ranging
between 20-35mm today, but as much as 50mm across some areas on
Thursday and Friday.


Alamo...(WPC