Southern Brazil is under an orange alert for severe storms as an extratropical cyclone forms, bringing risks of hail, flooding, and intense winds. According to the National Institute of Meteorology, known as Inmet, the orange alert for danger remains in effect until late Thursday night.
Extratropical Cyclone Triggers Orange Alert Across Southern Brazil
The advisory covers the southern and southeastern parts of Paraná, nearly all of Santa Catarina, and the northern, central, eastern, and southern regions of Rio Grande do Sul, including the greater Porto Alegre area. Forecasters warn of potential hail, flooding, and strong winds reaching up to 100 km/h. In the Rio Grande do Sul coastline and metropolitan region, the Civil Defense also issued a wind gust warning of up to 80 km/h.
According to Inmet, the system originated from an extratropical cyclone that formed during the early hours of Thursday in the western part of Rio Grande do Sul. Meteorologists note the system is organizing in an area known as cyclogenesis, which is favorable for cyclones and cold fronts due to atmospheric pressure changes and temperature contrasts.
Heavy Rains, Coastal Flooding, and Wind Hazards
Rio Grande do Sul is experiencing some of the most delicate conditions, with storms forecasted across all regions and potential hail in various spots. Maximum rainfall volumes could reach 80 millimeters in the western, campanha, and southern regions of the state. Additionally, rivers and streams near the border with Uruguay face flooding risks.
In Santa Catarina, coastal areas face severe maritime impacts. Epagri/Ciram issued a specific forecast for coastal flooding and shrinking beach sand strips due to persistent southwest winds and southern waves peaking between 2.0 and 3.0 meters. Affected locations along the Santa Catarina coastline include SC 405 near Rio Tavares, the Centro-Sul event center, Avenida da Saudade, beaches in southern Santa Catarina Island, Barra Velha, Araranguá, Itajaí, and Joinville. Oceanographer Argeu Vanz and meteorologist Marcelo Martins noted that coastal flooding peaks will coincide with astronomical high tide times.
Across the broader southern region, wind gusts are forecasted to vary between 70 km/h and 90 km/h. In areas near Camaquã, the Civil Defense issued a storm and gale warning. Authorities advise residents to avoid risk areas near hillsides and riverbanks, avoid parking near trees or towers, and unplug electrical appliances. Citizens can contact the Civil Defense by calling 199 or the Fire Department at 193.
Cold Air Mass and Temperature Drops
As the extratropical cyclone begins to move away from the continent, an associated cold front is driving a sharp drop in temperatures across southern Brazil. Minimum temperatures are expected to fall below 10 °C in southern Paraná, western Santa Catarina, and much of the interior of Rio Grande do Sul.
On Friday, winds will remain intense in the eastern strip of Rio Grande do Sul, particularly in the mountain and coastal regions, accompanied by rough seas and heavy surf. By Saturday, the cold air mass will intensify further, bringing possibilities of frost and fog across various areas of Rio Grande do Sul, Santa Catarina, and Paraná.
The instability and cooler air will also reach parts of the Southeast. São Paulo and Rio de Janeiro face potential winds of up to 60 km/h, with Inmet issuing a yellow alert for potential gale hazards, though no significant rainfall volumes are expected in that region.
