Central South America to Experience Heavy Rainfall and Strong Winds with Temperature Drop

It is expected that from June 21 to 24, influenced by a low vortex and an upper-level trough (Fig. 1), regions including southern Brazil, Bolivia, central Chile, northeastern Argentina, and eastern Paraguay will experience moderate to heavy rain, with localized downpours. These rains will be accompanied by severe convective weather such as short-duration intense rainfall and thunderstorms with strong winds. The cumulative precipitation in most of these areas is forecasted to be between 25 and 50 mm, with some regions receiving 60 to 80 mm. Localized areas in the Brazilian states of Mato Grosso do Sul, Paraná, and Santa Catarina, as well as in the Paraguayan departments of Canindeyú, Caaguazú, and Alto Paraná, and the Argentine province of Misiones, are expected to see accumulations of 100 to 150 mm (Fig. 2). During this period, central South America will experience a temperature drop of 5 to 8°C, with parts of southern Brazil and northeastern Paraguay facing a more significant drop of 8 to 12°C. These regions will also be affected by winds of 4 to 6 on the Beaufort scale, with gusts reaching 8 to 9 on the same scale (Fig. 3).

Figure 1. 500 hPa Geopotential Height (contours, units: dagpm) and 850 hPa Wind Field (wind barbs, units: m/s) at 1200 UTC on June 23, 2025

Figure 2. Forecasted Accumulated Precipitation from June 21-24, 2025 (Unit: mm)

Figure 3. 24-Hour Maximum Gust Forecast for June 23, 2025 (Shaded, Unit: m/s)

Author: Min Yue                                 Reviewer: Wang Guanlan 

English reviewer:Wang Yi                                                                       Issue approver:Dan Kan