South America Forecast Discussion - International Desks
NWS Weather Prediction Center College Park MD
128 PM EST Wed Feb 19 2025

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

South America Forecast Bulletin 19 Feb 2025 1900UTC:

In Mid - Latitude South America...

In Chile, a series of negatively tilted upper troughs and jet
streaks will traverse the region through the forecast cycle.
Expect upper divergence to be favorable across central Chile
during this period. At the low levels, the wind flow is
anticipated to increase in speed starting Wednesday evening
through Thursday evening , favoring moisture convergence and
enhancing orographic effects across this region. The period of
greatest impact will begin Thursday morning through Friday
morning. On Thursday evening, a mid-level shortwave trough,
associated with vorticity advection, will help yield to a total
precipitation maximum of 30 - 60mm from Thursday morning through
Friday morning.

In Tropical South America...

In the upper levels, a feature of interest is the Bolivian High,
centered at 21S 75W on Wednesday afternoon, which will retain its
strength through the next two days. Model guidance is that the
Bolivian High will begin to lose definition after Friday morning.
Another feature of interest is a weakening upper trough located in
west-central Brasil on Wednesday afternoon and will have minimal
precipitation impacts. In north Tropical South America, enhanced
upper easterly flow will be associated with some speed divergence
across northwest Brasil, Peru, Ecuador, and south Colombia for the
next three days.

In South Brasil, at the upper levels, a shortwave upper trough,
with an axis from 28S 56W to 46S 38W on Wednesday afternoon, will
move off the coast of Brasil by Thursday morning. Through
Wednesday evening, upper divergence will be favorable across
Paraguay and south Brasil. However, the highest precipitation
impacts will occur on Wednesday morning through Thursday morning
as moisture convergence will be most favorable along Santa
Catarina, where expected total maximum precipitation totals of 20
- 45mm during this time period. Moisture convergence along the
southeast Brasil coast will persist through the remainder of the
forecast cycle, yielding to maximum precipitation totals of 20 -
40mm/Day after Thursday morning.

In northwest Paraguay, from Wednesday morning through Thursday
morning, a shortwave trough will meander across portions of north
Argentina and Paraguay, enhancing upper divergence along central
Paraguay. This trough will quickly lose its definition by Thursday
afternoon. An accompanied mid-level trough with a vorticity maxima
will also be located across this region through Thursday evening.
These conditions, coupled with low level moisture convergence,
will yield to a total precipitation maxima of 30 - 60mm from
Wednesday morning through Thursday morning. From Thursday morning
through Friday morning, expect a decreasing total precipitation
maxima, of 20 - 35mm, for this region. A drying trend is expected
region thereafter.

In Bolivia, the aforementioned Bolivian High will continue to
drive upper diffluence and divergence across central Bolivia
through Thursday morning, where an increase in low level moisture
will yield to maximum precipitation totals of 20 - 40mm from
Wednesday morning through Thursday morning. After Thursday
morning, the Bolivian High will begin to lose definition, and an
upper jet streak will develop across central Bolivia, sustaining
upper divergence. Moisture convergence will still be favorable in
the lower levels and will yield a total precipitation maxima of 30
- 60mm for Thursday Morning through Friday morning.

Elsewhere in Tropical South America, the ITCZ, NET, and Southern
ITCZ will continue to favor diurnal convection. A series of
moisture plumes will continue to traverse across the region,
helping increase precipitation chances. Starting on Friday
evening, to the east of the Colombian - Ecuadorian - Peruvian
Andes, low level wind flow will become more easterly and will help
in increasing moisture convergence across the Amazon Basin.Expect
total precipitation maxima of 30 - 60mm across in this region from
Friday morning through Saturday morning. To the west of the Andes,
ongoing moisture convergence associated with the ITCZ and Southern
ITCZ will continue to favor orographic enhancement, yielding to
higher total precipitation maxima across Colombia, Ecuador and
Peru. Elsewhere, in the Amazon delta and northeast Brasil, the
ITCZ and Southern ITCZ will be the main driving force for
convection in this region. Incoming low level troughs will help
increase moisture convergence and yielding to higher total
precipitation maxima for the next three days.



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