South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
331 PM EST Mon Feb 10 2025

GFS data at ftpprd.ncep.noaa.gov/data/nccf/com/gfs/prod/

SOUTH AMERICAN FORECAST BULLETIN FOR 10 FEB 2025 AT 2030 UTC:

In the climate scale, the Madden-Jullian Oscillation phase will
become more divergent beginning this week through the end of the
week. This will favor more widespread rainfall where conditions
are favorable for development.

In mid-latitude South America...

In the upper levels, a positively titled upper trough will help
induce a cut-off upper high by mid-day Tuesday around 99S51W and
is expected to be over Austral Chile by Wednesday evening. This
pattern will yield to the acceleration of the upper winds to the
south and will enhance a pre-existing jet streak after Wednesday
evening. In addition, a mid-level shortwave trough, accompanied
vorticity advection, and low level moisture plume will yield to
maximum rainfall totals of 15-20mm for Tuesday morning through
Wednesday morning and totals of 20-35mm for Wednesday morning
through Thursday morning.

In northern Argentina and Uruguay, a cold front is currently
located across La Pampa and Buenos Aires states and will continue
to propagate northwards. By Monday evening, it will be located
across central Argentina. By Tuesday evening, expect the front to
be across northern Uruguay through northwest Argentina. By
Wednesday evening, the front will be across northern Argentina and
southern Brasil. A combination of mid-level shortwave troughs and
increasing moisture convergence will yield to maximum rainfall
totals of 30-60mm for Tuesday morning through Wednesday morning
and totals of 25 - 50mm for Wednesday morning through Thursday
morning.

In tropical South America...

In the upper levels, the Bolivian High is currently located off
the coast of central Chile. By Wednesday, it will begin
restructuring over northern Chile and southwest Bolivia. Another
feature of interest is an upper cut off low over south-central
Brasil on Monday afternoon, which is expected to meander across
the region through the next three days. These features will help
enhance upper level diffluence and divergence across this region.
One of the areas of interest is the Western Amazon Basin, where
favorable moisture convergence and upper level dynamics will
assist in enhancing rainfall totals. Enhanced upper level
divergence, limited shear, and the proximity to the Near
Equatorial Jet (NET) will yield to maximum rainfall totals of 30 -
60mm through Tuesday morning, 35 - 75mm for Tuesday morning
through Wednesday morning, and 30 - 60mm for Wednesday morning
through Thursday morning.

In Ecuador, heavy precipitation is anticipated daily through the
next three days. In the low-levels, moisture convergence will be
most favorable today through Tuesday morning as northwest flow
continues to affect the region. Though the wind speeds remain low,
long fetch moisture will continue to be driven into the coast of
Ecuador through Thursday morning. Additionally, weak mid-level
wind speeds and upper level divergence associated with a
semi-stationary trough, with an axis across 04S 81W to 17S 96W,
will enhance the potential for higher rainfall totals through the
forecast cycle. Expect the highest maximum rainfall totals to
occur today through Tuesday morning, with totals of 30 - 60mm and
decreasing for Tuesday morning into Wednesday morning. By
Wednesday morning through Thursday morning, an increase in upper
level easterlies will yield to an increase in maximum rainfall
totals, which are expected to be 30 - 60mm.

In northern South America, a series of low level troughs, the
Intertropical Convergence Zone (ITCZ), and the NET will be the
main driving force for precipitation through the next three days.
Note, a secondary ITCZ will form over the Atlantic basin after
Tuesday morning and will influence precipitation patterns in the
Amazon Delta and the Brasilian North Coast.



Morales...(WPC)
Castellanos...(WPC)