South America Forecast Discussion - International Desks NWS Weather Prediction Center College Park MD 318 PM EST Tue Feb 18 2025 GFS data at ftpprd.ncep.noaa.gov/data/nccf/com/gfs/prod/ South America Forecast Bulletin 18 Feb 2025 2030UTC: On the Climate Scale... The Madden Julian Oscillation (MJO) has become disorganized, with models indicating that some upper level divergence is still present over the east Pacific and will likely retrograde west. Although uncertainty remains in the propagation of the MJO, expect a general convergent phase. In Mid - Latitude South America... In Chile, a series of upper to mid level troughs will continue to migrate across central Chile through the next three days. From Monday through Tuesday morning, a potent jet streak will traverse across southern Chile, favoring upper divergence. Thereafter, upper divergence will be sustained by an amplifying upper trough, which will impact the region after Wednesday morning. At the lower levels, a long fetch moisture tongue accompanied by strong winds will enhance orographic effects across south-central Chile starting Monday through Wednesday. Though the wind direction is expected to shift to a more northerly component by Wednesday evening, increasing wind speeds during this time will continue to favor moisture convergence across central Chile. From Monday morning through Tuesday morning, expect a maximum precipitation total of 15 - 30mm and increasing to 20 - 40mm/Day for Tuesday and Wednesday. Note, after Thursday morning, another upper trough, enhanced mid-level vorticity advection, increasing wind speeds, low level wind speeds, and a long fetch moisture tongue may favor higher precipitation totals through the day. In Tropical South America... In the upper levels, the Bolivian High, centered at 21S 77W Monday afternoon, will continue to drive upper divergence across its periphery. To the east, an upper trough has developed across central Brasil, centered at 13S 52W Monday afternoon. By mid-week, this trough is anticipated to lose its structure. A stationary front will be located across south Brasil into north Paraguay by Monday evening and weakening into a trough thereafter. In the upper levels, an upper trough accompanied by speed divergence will help enhance ascent in this region. This upper trough will remain semi-stationary across this region through Thursday evening and will assist in weakening the structure of the aforementioned upper trough across central Brasil. In the low levels, moisture convergence will also be more favorable through Monday evening, which will yield a total precipitation maxima of 35 - 70mm across south Bolivia, north Paraguay, and south Brasil from Monday morning through Tuesday morning. Note, a developing low pressure system off the coast of southeast Brasil will help increase precipitation accumulations from Monday morning through Tuesday morning in this region and is expected to propagate out to sea after Tuesday morning. From Tuesday morning through Wednesday morning, a total precipitation maximum of 20 - 45mm is possible across north Paraguay, where a mid - level trough, accompanied by vorticity advection, and low level moisture convergence will move across this region. Elsewhere in Tropical South America, a series of surface troughs will continue to move across north South America, where moisture convergence will persist. Expect the highest total precipitation maxima to occur for Monday morning through Tuesday morning and decrease thereafter as low level moisture and upper divergence decrease in parts of the region. Elsewhere, expect an enhancement in diurnal convection along the ITCZ / NET / Southern ITCZ. Regions of interest include the Amazon Delta, where expect daily maxima precipitation totals of 20 - 45mm/Day, and northeast Brasil, where expect totals of 20 - 35mm/Day. In Ecuador, expect daily maxima precipitation totals of 30 - 60mm/Day, enhanced by orographic effects and increased moisture convergence. In east Peru, the day of greatest precipitation impact will be from Monday morning through Tuesday morning, when moisture convergence and upper divergence will be most favorable. Expect decreasing maxima precipitation totals from Tuesday to Thursday morning. Morales...(WPC) Castellanos...(WPC)