London rain tower storm alert weather Paraná — Photo: RPC Londrina
The advance of an extratropical cyclone is expected to keep the weather unstable in the Center-South and increase the area that could be hit by tornadoes this Friday (11).
🌀Extratropical cyclones are low atmospheric pressure systems – regions that cause large-scale adverse weather – that typically arise in middle latitudes. They are formed by the temperature contrast between different air masses (hot and cold).
According to Climatempo, northern Santa Catarina, the entire state of Paraná, southern São Paulo, and southern Mato Grosso do Sul could register the phenomenon. (see map below)
Risk of tornadoes this Friday (11). — Photo: Art/g1
Between Wednesday (9) and Thursday (10), tornadoes have already caused damage in some cities in Paraná. The phenomena hit the municipalities of Francisco Alves, in the northwest of the state, and Espigão Alto do Iguaçu, in the west.
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On Friday, the scope of the phenomenon may be larger because the cyclone combines with an already highly unstable atmosphere.
According to meteorologists, two factors had already been contributing to keeping the weather rainy in the Center-South and increasing the chance of tornado formation:
A warmer and more humid air current coming from Northern Brazil, passing through areas of the Center-West, and arriving in areas of Paraná, which favors instability in the region.
The presence of a wind circulation known as a trough, about five kilometers high, which favors the formation of heavily loaded clouds.
🌧️Troughs are elongated areas of low pressure. This meteorological phenomenon happens when there is a wind current that helps in the formation of storm clouds.
These two components are essential for the configuration of what meteorologists call a supercell.
"A supercell is a truly massive storm cloud that, due to the characteristics of its formation, can give rise to tornadoes," details César Soares, a meteorologist at Climatempo.
⛈️In short, a supercell is a storm featuring a rotating updraft inside the cloud. This type of formation can generate heavy rain, hail, strong winds, and tornadoes.
Meteorologists also detail that the atmosphere needs to gather a few specific components for this type of cloud to form:
Low atmospheric pressure
High moisture availability across multiple layers of the atmosphere
Large differences in wind speed and direction between the surface and the middle and upper layers of the atmosphere – a condition that fuels cloud rotation
Strong temperature contrast
Favorable conditions to drive significant vertical cloud development
Unstable weather throughout the Center-South
In addition to increasing the chance of tornado formation, the cyclone and, subsequently, the cold front are expected to keep the weather unstable across much of the Center-South this Friday (11).
With heavy rain forecasted, the National Institute of Meteorology (Inmet) maintained storm warnings for eight states for this Friday:
Rio Grande do Sul
Santa Catarina
Paraná
São Paulo
Rio de Janeiro
Minas Gerais
Espírito Santo
Mato Grosso do Sul
According to Inmet, the far north of Rio Grande do Sul, along with the central-west regions of Santa Catarina and Paraná, are the areas expected to continue recording the highest rainfall volumes. (see map below)
⚠️These locations are under a high danger warning for storms this Friday, with forecasts of more than 100 millimeters of rain per day and winds exceeding 100 km/h. There is also a risk of flooding and falling trees.
Storm forecast for the Center-South this Friday (11). — Photo: Art/g1
How the weather will be in each region
Friday will bring unstable weather to the South and Southeast, with rain, thunderstorms, and the possibility of severe storms in various areas. In the North and Northeast, showers should occur mainly in coastal areas, while the interior should see periods of sun and heat.
In the North, Amazonas concentrates the main areas of instability, with rain and thunderstorms in the northern part of the state. Isolated showers may also occur in central-southern Amazonas, western Roraima, northern Rondônia, northern and eastern Amapá, and the Pará coast. Tocantins and most of Pará will see predominantly sunny skies with few clouds.
In the Northeast, rains are concentrated mainly along the coast, reaching areas of Bahia, Sergipe, Alagoas, Rio Grande do Norte, Ceará, Piauí, and Maranhão.
The region's interior will have more sunshine, especially in central-southern Maranhão, Piauí, southern Ceará, western Paraíba, central-western Pernambuco, and northern and western Bahia. In other areas, the sky will be cloudier, with no rain forecasted.
In the Center-West, Mato Grosso do Sul will have the most unstable weather, with rain and thunderstorms in the central-southern and eastern parts of the state. Goiás may also register rain, especially in the far south.
Cloudiness increases in central Goiás and the Federal District, while Mato Grosso will see predominantly sunny weather across most of its territory.
The Southeast will also have a rainy day. São Paulo, Rio de Janeiro, and the southern parts of Minas Gerais and Espírito Santo may experience rainy periods accompanied by thunderstorms.
In the Triângulo Mineiro, Belo Horizonte, and Vitória, isolated showers are forecasted. In other areas, the sky will be cloudy, but without rain.
In the South, instability will be widespread. The forecast indicates rain, thunderstorms, wind gusts, and hail, as well as the possibility of severe storms. The environment also favors the formation of squall lines and supercells.
