The Instituto Nacional de Meteorologia (Inmet) issued a weather alert for thunderstorms in Southern Brazil and heavy rains in the Northeast this week [1, 2].
These alerts signal a period of high atmospheric instability that could lead to significant flooding and infrastructure damage in vulnerable regions. The timing is critical as the South transitions from a period of dry weather to intense precipitation.
According to Inmet, the current weather patterns are driven by the influence of the El Niño climate phenomenon [1, 3]. This shift is expected to increase precipitation chances and atmospheric instability across the country. In Rio Grande do Sul, the effects of El Niño are expected to be particularly pronounced this week [3].
Meteorologists forecast that rainfall could reach up to 400 mm in Rio Grande do Sul between July 16 and July 25 [4]. This volume of rain increases the risk of river overflows and urban flooding. An Inmet spokesperson said, "Chuva deve se prolongar durante a próxima semana e elevar o risco de alagamentos e cheias de rios" [1].
The alert also extends to the Northeast region, where heavy rains are anticipated [2]. In addition to the precipitation, Inmet warned of strong winds and low air humidity in certain areas [2]. Specific risks of storms and frost were highlighted for Wednesday, July 17 [5].
Local authorities are monitoring the situation as the weather system moves through the South. The transition follows a "veranico" — a period of unseasonably warm and dry weather — which can often leave soil conditions less prepared for sudden, heavy rainfall [1].
“Rainfall could reach up to 400 mm in Rio Grande do Sul between July 16 and July 25.”
The convergence of El Niño and a sudden shift from dry to wet conditions in Southern Brazil creates a high-risk scenario for flash flooding. When a region experiences a 'veranico' followed by extreme rainfall, the soil may not absorb water efficiently, increasing the likelihood of landslides and rapid river rises that threaten urban centers and agricultural productivity.
