Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
955 AM EST Thu Feb 13 2025

Weekly Discussion for Puerto Rico and the USVI 13 February 2025

In general, the rainfall pattern across PR/USVI over the next
several days will be that of isolated to scattered trade wind
showers, though possibly enhanced with land interactions across
eastern PR. Any convection that may occur during the daytime
hours, over the next several days, is expected to be shallow and
very isolated. A trade wind inversion is expected to dominate most
of the time over the local area, and the available moisture is
expected to be limited to the lower levels most of the time. This
will favor a rainfall pattern where eastern PR observes the
highest amounts of rain relative to the rest of the local area,
with south central to southwestern PR expected to observe the
lowest amounts of rain. The USVI are also expected to observe
brief showers, generally amounting to a few hundredths of an inch
of rain each day. Most of the rainfall is expected to occur in the
nighttime and the morning hours. This general pattern is fairly
typical for the time of year.

In the upper levels there is a ridge over the Caribbean and a
trough to the northeast of the northeast Caribbean. This ridge
will remain over the area until Saturday, as an upper level
positively-tilted trough approaches the area, with its axis
expected to be from northeast of PR/USVI to the Mona Passage by
Saturday afternoon. This trough will move east and over PR on
Saturday, then another shortwave trough will move through on
Sunday. The local islands will be in the subsident side of the
troughs by Monday. Thereafter and through midweek, a high pressure
will dominate over the local islands. The mid-levels seem to be
behaving a bit different, with a trough to the ESE of PR today
that will retrograde, with its axis being positioned over
Hispaniola by Friday morning. A weak mid-level trough will pass
near or over the local islands early on Saturday and Sunday, but
these too will be retrograding over the area. A mid-level high
pressure will also remain over the local area from Monday onward
into at least midweek.

In the lower levels, there are a few troughs in the 850 mb level
that could be contributing to some moisture convergence in the
lower levels, and possibly some enhanced rainfall as they move
west and over the tropical Atlantic into the Caribbean. One of the
weak lower level troughs is expected to move through on Friday,
which will then cause an increase in moisture and rainfall
activity over the local islands. Even weaker low level troughs
could pass over the local islands on Sunday and on Tuesday. In
terms of overall moisture, the precipitable water values will be
really up and down over the next several days, though the
available moisture is forecast to be very close to above normal
levels on Friday, then gradually decreasing between normal and
below normal thereafter, though still showing peaks of moisture
over the local islands during the overnight hours. The increase in
moisture on Friday is reflected through the lower levels, with RH
values being above normal at 850 and 700 mb. That said, the signal
of increased moisture is very weak at the 500 mb level, therefore
most of the moisture, even when it peaks, it is expected to be
generally in the lower levels. Another possible increase in
moisture across the area could be early on Tuesday into Wednesday,
as an area of moisture develops in the Caribbean waters. The model
guidance suggests that the deeper moisture will remain mainly
across the Caribbean waters, but some areas of higher moisture may
clip St Croix and southeast PR for brief periods. The rest of the
local islands could remain fairly dry. That said, confidence
really starts to decrease so far out, especially with these
relatively small features.

In terms of rainfall, as previously mentioned, eastern PR is
expected to receive the highest amounts of rain relative to the
rest of the local area. Given that today and Friday could be the
days with the most rainfall out of the next week, we can expect
general areas across eastern PR to observe near 0.5 inches of rain
each day including today, but perhaps under a quarter of an inch
thereafter. Other areas in PR and across the USVI can expected
generally 0.25 inches or less of rain each day, especially across
south central to southwestern PR, where little to no rain is
expected each day.

Alamo...WPC(USA)