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What drove the sudden cyclone that left southern Brazil in ruins this November?

  • Julieta Mendez
  • Dec 2
  • 3 min read

During the first week of November 2025, meteorologists started tracking the strengthening of winds that moved across the southern coast of Brazil. However, what most people didn’t expect was that it would turn out to be one of the most damaging extratropical cyclones the region has experienced in years. By the time the storm made landfall, neighborhoods were underwater, power lines lay tangled in the streets, and entire communities were cut off from the rest of the country. 


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You're probably wondering right now: What turned an ordinary weather system into a destructive force that reshaped areas of Rio Grande do Sul, Santa Catarina, and Paraná? The answer actually lies in a chain of atmospheric events both familiar and unexpectedly intense.  


What first distinguished the cyclone from previous storms was the sharp contrast between two opposing air masses. A cold, dense polar front pushed northward over the continent just as another warm, humid tropical air advanced from the Amazon and the Atlantic. These clashes are usually typical in the South, according to the UEPG, yet this time, the temperature gradient between them was extreme. As meteorologists would later explain, the greater the contrast, the more explosive the storm’s potential.


As these air masses collided, the atmosphere destabilized rapidly. Within hours, pressure levels dropped sharply, fueling a system capable of producing not only intense windstorms but also tornadoes. The result was a sequence of extreme events that unfolded across all three southern states. In Rio Grande do Sul, windstorms surpassed 100 km/h, and rainfall totals exceeded 150 millimeters in less than 12 hours in several municipalities. This incident overwhelmed drainage systems and eventually flooded entire neighborhoods. Cities like Camaquã, Taquari, Tramandaí, General Câmara and Dom Pedrito reported severe structural damage, while more than 200,000 residents temporarily lost power as transformers failed and electric towers collapsed. 


In Santa Catarina, the cyclone triggered widespread hailstorms, landslides and coastal flooding. Emergency reports indicated damage across the Planalto Sul, Vale do Itajai, and Grande Florianópolis, with intense rainfall drenching slopes already vulnerable from previous storms. According to local residents, several scenes of submerged cars, blocked highways and collapsed retaining walls became usual as authorities struggled to reach these isolated communities. 


Unfortunately, Paraná faced the most violent conditions of the cyclone's passage. The atmospheric instability intensified as the system moved inland, producing multiple tornadoes, including an F3 tornado in Rio Bonito do Iguaçu with estimated winds of up to 330 km/h. The tornado destroyed nearly 90% of homes and businesses, left 80% of the town’s population affected, and resulted in six fatalities and hundreds of injuries. At the state level, Paraná recorded more that 4,700 homes damaged or destroyed, 23,300 people were affected, and economic losses reached an estimated R$ 335.4 million which is now considered to be the highest weather-related loss in the state’s history. 


Overall, the cyclone’s most devastating impact came from how quickly these events have unfolded in the past week. Many communities had little to no warning; alerts often arrived minutes before tornadoes formed or before floodwaters reached. For thousands of families, the storm did not just disrupt their daily life, it completely erased it. Homes, small farms, schools, and local business disappeared in a matter of hours, only leaving behind waste and uncertainty. 


Despite the large scale of destruction already gone, it's unfortunate to say that the dangers are not over yet. According to the Instituto Nacional de Meteorologia, a new intense cold front is expected to sweep across the region around November 16-17, bringing the possibility of extra flooding, strong winds, and further instability to communities still trying to recover. As southern Brazil prepares once again for worsening conditions, this month’s events can serve as a reminder of how vulnerable the region has become to natural disasters and how urgently long-term protection and climate awareness is needed.


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