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An extratropical cyclone forms between Rio Grande do Sul and Santa Catarina starting Tuesday with gusts of wind above 100 km/h and a risk of hail, while a cold front advances over the entire Southeast starting Wednesday, with continuous rain expected until the second week of May.
The week starting this Monday (6) promises to bring severe weather phenomena to the South and Southeast of Brazil. The formation of an extratropical cyclone between Rio Grande do Sul and Santa Catarina is expected for Tuesday (7), bringing storms with a risk of hail and gusts of wind above 100 kilometers per hour that should affect the three states of the South region by Wednesday (8). The expectation is that the accumulated rainfall in these areas will exceed 70 millimeters in just a few days.
Shortly after, a cold front advances over the entire Southeast starting Wednesday (8), bringing storms and rain to the four states of the region. The expected precipitation volume for the week is between 30 and 40 millimeters, with maximum temperatures around 25 degrees. The trend, according to meteorologists, is that the rain will only cease more generally in the second week of May. For those living in the South or Southeast, the week requires extra attention and preparation for a prolonged period of instability.
What is the extratropical cyclone and why is it so concerning for the South of Brazil
The extratropical cyclone is a low-pressure atmospheric system that forms outside the tropics and gains strength from the contrast between warm and cold air masses.
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Unlike tropical cyclones, which feed off the temperature of the oceans, the extratropical cyclone intensifies due to the temperature difference between two fronts, which explains why it frequently forms in the South region of Brazil, where polar air masses collide with warmer air coming from the interior of the continent.
The extratropical cyclone expected this week originates from a low-pressure system over Paraguay that begins to act already on Monday, increasing instability in Rio Grande do Sul with a risk of storms. Starting Tuesday, the system organizes between RS and Santa Catarina and rapidly gains intensity.
The gusts of wind above 100 kilometers per hour expected for this extratropical cyclone represent a real risk of roof damage, falling trees, and interruption of electricity supply in cities across the three southern states.
The storms with hail and destructive winds that the extratropical cyclone is expected to bring
The forecast for Tuesday and Wednesday is for severe storms throughout the South region. The extratropical cyclone is expected to bring heavy rain with accumulations exceeding 70 millimeters, gusts of wind above 100 km/h, and a risk of hail to areas of Rio Grande do Sul, Santa Catarina, and Paraná.
These conditions require special attention from those living in areas vulnerable to flooding, landslides, and roof damage.
After the passage of the extratropical cyclone, cold air is expected to dominate the South region. Minimum temperatures in low-lying areas are expected to range between 10 and 14 degrees on Thursday (9) and Friday (10), but without a risk of frost.
The sharp drop in temperature after the storms is a typical characteristic of the passage of extratropical cyclones, which push polar air behind the cold front and cause a marked change in weather conditions in just a few hours.
The cold front that advances over the Southeast right after the extratropical cyclone
The Southeast is not left out of the week of instability. A cold front advances over the four states of the region starting Wednesday (8), bringing storms and rain to São Paulo, Rio de Janeiro, Minas Gerais, and Espírito Santo.
The expected precipitation volume is between 30 and 40 millimeters throughout the week, with maximum temperatures around 25 degrees in the coming days.
The most concerning trend is that the rain in the Southeast will not stop anytime soon. According to meteorological projections, instability is expected to remain almost continuously until the second week of May.
This means that cities with a history of flooding and landslides, such as mountainous areas of Rio de Janeiro and Greater São Paulo, need to remain alert for an extended period. The combination of the extratropical cyclone in the South and the cold front in the Southeast creates a scenario of attention that encompasses half of Brazilian territory.
What to expect in other regions of Brazil during the week
While the extratropical cyclone hits the South and the cold front advances over the Southeast, the Midwest is expected to receive showers with accumulations between 30 and 40 millimeters, which will relieve temperatures to around 31 degrees and benefit second-crop corn and pastures.
The expected humidity is positive for the fields, and the trend is that the rain in the region will cease only in the second week of May.
In the North, the highest rainfall accumulations are expected in Amazonas, Roraima, Amapá, and northern Pará, with up to 100 millimeters during the week. In the Northeast, the Intertropical Convergence Zone maintains instabilities along the northern coast, with moderate to heavy rain in Maranhão, Piauí, Ceará, and Bahia.
Heavy rains between 40 and 50 millimeters are expected to predominate in the coming days in western Bahia and several northeastern states. Starting in the second half of April, easterly waves are expected to bring more rain to the region.
How to prepare for the extratropical cyclone and the cold front this week
With winds above 100 km/h and a risk of hail expected for the South, the recommendation is to reinforce roofs, store loose objects in outdoor areas, and avoid taking shelter under trees during storms.
For those living in areas with a history of flooding, keeping documents in a safe place and knowing the evacuation routes in the neighborhood can make a difference in an emergency.
In the Southeast, where rain is expected to persist until May, care should be continuous. Urban slopes, riverbanks, and areas with saturated soil require special attention because the risk of landslides increases as the accumulated rainfall grows over the days.
The extratropical cyclone in the South and the cold front in the Southeast represent distinct but connected events that will require constant monitoring by authorities and the population throughout the week.
Do you live in the South or Southeast and are you already preparing for the extratropical cyclone and the cold front? How is the situation in your city with this rain forecast until May? Share in the comments. Information about severe weather needs to circulate so that more people can protect themselves in time.
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