Meteorologists at MetSul Meteorologia report that a chaotic, high-intensity weather pattern is developing across South America, threatening Chile, Argentina, Uruguay, Paraguay, and Brazil with extreme conditions. The event, driven by simultaneous large-scale atmospheric phenomena, includes excessive rainfall, extreme temperature swings, and massive snow accumulations in the Andes, breaking the cold-dominant patterns observed over the last three months.
Atmospheric Rivers and Flash Flood Risks
The primary driver of this event is the interaction of two distinct atmospheric rivers. According to MetSul, one system originates in the Pacific, targeting Chile, while a second forms within the South American continent, stretching from Bolivia to Rio Grande do Sul in Brazil.
In Chile, the impact is expected to be historic. MetSul warns that areas of the Atacama Desert—one of the driest places on Earth—could see 100 mm to 150 mm of rain, while other regions may face cumulative totals between 300 mm and 500 mm. Such volumes are comparable to annual rainfall averages, raising significant concerns regarding landslides and major flooding, potentially mirroring severe weather events from the 1980s and 1990s.
Did you know? Atmospheric rivers are narrow corridors of concentrated moisture in the atmosphere. When they make landfall, they can release massive amounts of precipitation, often leading to the extreme flooding currently projected for the Chilean coast.
Severe Storms and Tornado Potential in the Southern Cone
As the weather systems progress eastward, the focus shifts to Uruguay, Northeast Argentina, and Southern Brazil. MetSul predicts a period of highly volatile weather characterized by large hail, destructive winds, and a heightened risk of tornadoes and microbursts.
Rio Grande do Sul is identified as a primary hotspot. Forecasters expect seven-day rainfall totals to reach 100 mm to 200 mm, with isolated areas potentially exceeding 300 mm. This moisture, combined with a deep low-pressure center—recorded at 990 hPa in Northern Argentina—will fuel a powerful low-level jet (LLJ). This jet is expected to transport intense heat and moisture, creating the instability required for severe convective storms.
Heat and Wind Anomalies
The low-pressure system in Northern Argentina acts as a catalyst for a surge of warm air from Bolivia and the Brazilian Center-West. MetSul notes that this low-level jet will reach its peak intensity with wind speeds at 1,500 meters altitude hitting 130 km/h.
Surface temperatures are expected to climb to 10ºC above the historical average for July. In parts of Rio Grande do Sul, thermometers may reach 30ºC to 33ºC. Beyond the heat, the pressure gradient will drive strong northerly winds across the region. Most cities can expect gusts between 40 km/h and 70 km/h, though higher terrain and valleys may see gusts exceeding 100 km/h, risking power outages and structural damage even in the absence of thunderstorms.
Andean Snowfall and the Zonda Wind
The Argentine National Meteorological Service has issued a special alert for the Cordillera de los Andes, covering the period from July 15 to 20. Persistent, heavy snowfall is expected to blanket the range, with accumulations reaching up to 3 meters in the higher reaches of Mendoza and Southern San Juan.
The event also triggers the “Zonda,” a hot, dry downslope wind. Authorities warn that the Zonda may produce gusts exceeding 100 km/h in the foothills of Mendoza and San Juan, creating hazardous conditions for residents and complicating travel through mountain passes.
Pro tip: During extreme weather events involving high-speed winds and heavy rain, secure outdoor furniture and clear drainage paths near your home to mitigate the risk of localized flooding and wind damage.
Frequently Asked Questions
Why is this weather event considered “chaotic”?
MetSul classifies this as chaotic because it involves the simultaneous interaction of multiple large-scale systems, including two atmospheric rivers, a deep low-pressure center, and an unusually intense low-level jet, which together create conflicting weather extremes across the continent.
What is a low-level jet (LLJ) and why does it matter?
An LLJ is a fast-moving current of air in the lower atmosphere. In this case, it is acting as a “conveyor belt” for heat and moisture, driving both the unseasonal warmth and the fuel necessary for severe thunderstorms in Southern Brazil.
Is this weather pattern common for July?
No. According to MetSul, this sequence of events breaks the pattern of persistent cold that has dominated the Southern Cone for the past three months, leading to temperatures significantly higher than historical averages for mid-winter.
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