An extratropical cyclone in the ocean is associated with a cold front marking the beginning of October, promoting a climatic change in the Southeast and Central-West regions. According to Inmet, this change should begin on Thursday, the 1st, with forecasts for rain, thunderstorms, and possible hail, extending until Friday, the 2nd.
Although Thursday starts warm in certain parts of the Southeast, the arrival of the cold front throughout the day rapidly alters conditions. In the South, a high-pressure system helps reduce cloudiness, making way for cold weather. Instability also affects the agricultural area known as Matopiba, which includes portions of the states of Maranhão, Tocantins, Piauí, and Bahia.
Detailed forecasts for the Southeast
In the Southeast, the climatic change first manifests in western and southern São Paulo, where rain accompanied by thunderstorms is expected early in the morning. In the afternoon and evening, instability shifts to southern Minas Gerais, Rio de Janeiro, and to the center and south of Espírito Santo. There are also reports of possible hail in various locations, with a special focus on Rio de Janeiro and southeastern Minas Gerais.
In the Central-West regions, Mato Grosso do Sul, Mato Grosso, and parts of Goiás are expected to record rain and thunderstorms. The risk of hail is higher in Mato Grosso do Sul during the morning. In Brasília and Goiânia, the day remains hot, with maximum temperatures reaching 35°C.
Conditions in the South and changes in the Central-West
The change is also noted in the South. Paraná and Santa Catarina will have rain and thunderstorms in the morning, but clouds tend to decrease throughout the day. In Rio Grande do Sul, the sky progressively clears, and the cold begins to be felt during the night.
On Friday, the cold front will persist with rain over the Southeast. Minas Gerais, Espírito Santo, Rio de Janeiro, and areas in northern São Paulo may experience rain with thunderstorms. In the capital of São Paulo, the temperature will drop even further, recording a minimum of 13°C and a maximum of only 16°C. In Rio de Janeiro, thermometers will range between 20°C and 24°C.
Instability in the Central-West and South
The Central-West will remain unstable, although the heat will lose intensity. Campo Grande will have a minimum of 19°C and a maximum of 25°C. Cuiabá may reach 28°C, while Brasília and Goiânia are expected to reach 30°C.
In the South, the cold will gain more strength. Mountainous regions of Santa Catarina and Rio Grande do Sul may register temperatures close to 5°C during the early morning hours. Porto Alegre will have a minimum of 10°C and a maximum of 21°C. Curitiba will reach 17°C and Florianópolis, 18°C.
Impacts on the Northeast and North
While the cold consolidates in the South, instability systems formed inland advance towards the Northeast. On Friday, southern Maranhão and western and southern Bahia may present isolated rains with thunderstorms. Western Piauí also has the potential to record precipitation.
In the North, Friday will remain unstable in most of the region, with showers and thunderstorms forecast for Acre, Amazonas, Rondônia, Roraima, as well as areas of Pará and Tocantins. In the Northeast, rain will be more concentrated in some areas, while others will remain sunny and hot.