This week and throughout the month of February, we should see worsening rainfall in the northern part of Minas Gerais, the interior of Bahia and a large area of Tocantins due to the dissipation of the Madden-Julian oscillation, which is a climate phenomenon characterized by the eastward propagation of large areas of convection and precipitation in the tropics, influencing weather patterns in several regions, including Brazil. It has eight distinct phases, each with specific impacts on weather conditions.
In addition, a negative rainfall anomaly will be observed in the most central part of Brazil, as in the case of the north of MT and the south-central part of Pará, as seen in image 1, below. The negative rainfall contradicts the current La Niña condition.
Image 1 – 30-day accumulated precipitation anomaly, valid for February 26, 2025.
On the other hand, much more rain than expected may occur in the southeast, especially between the Paraíba Valley in São Paulo, extending to the metropolitan region of Belo Horizonte, MG. The Angra region may also be affected.
Similarly, a very positive anomaly can occur in a large area of Roraima, in Amapá and in a smaller area of Pará, such as the capital Belém and the region of Santarém. In Amazonas, pay attention to the region of São Gabriel da Cachoeira, for maximum values of the precipitation anomaly.
Finally, let's now look at the week's forecast, which marks the return of dynamics (similar to the Monsoons that occur in Asia) in Brazil, with a greater occurrence of intense rains in the Central West and Southeast regions, which are influenced by the movement of humidity through existing "flying rivers" thanks to medium and low level jets, transporting humidity from the Amazon.
Firstly, a heat bubble in Argentina influences temperatures in the South and Southeast regions. However, the entry of humidity and high air temperatures results in large convective formations, causing disturbances. The heat is influenced by the neutrality of the Antarctic Oscillation (AAO).
ing that the AAO, also known as the Southern Annular Mode, is a climate pattern that significantly influences the climate in the Southern Hemisphere, including the Brazilian territory. A positive phase indicates a reduction in the age of frontal systems, while a negative phase indicates the opposite.
Finally, as mentioned, pay attention to the Southeast region, including the Paraíba Valley – SP, and central Minas Gerais, such as Belo Horizonte, for high accumulations of rain this week, with the possibility of major disruptions. Heavy rains may occur starting this Wednesday, leading to a peak on Friday. Only Espírito Santo has lower accumulations.
What happens is a trough in the South Atlantic, which keeps large volumes of water over the Southeast, as it attracts the humid and hot winds from the Amazon to itself, transported by medium and low level jets, as seen in image 2, making water available in the atmosphere for convection.
Image 2 – Wind circulation at 10.000ft, valid for Friday, 6st.
In the North region, the ITCZ remains active, bringing constant rain to the extreme north of Brazil, including the capital Belém – PA, which has the peak in accumulated precipitation on Thursday, in addition to the entire state of Amapá, throughout the week. Some convections may break away from the ITCZ and cause rain also in the interior of Maranhão, Piauí, Ceará and Rio Grande do Norte.
In the South region, with the exception of Paraná and the coast of Santa Catarina, there will be greater atmospheric stability.
Image 3 – Total accumulated rainfall for the week.
Below, pay attention to this week's alerts:
- Throughout the state of São Paulo for large volumes, especially from Wednesday afternoon;
- Northern coast of São Paulo, such as Ubatuba, for large volumes of water.
- São Paulo capital for large volumes of water, especially between Thursday and Saturday (higher volumes on Friday and Saturday).
- Western São Paulo, such as São José do Rio Preto, from Friday onwards for high accumulations;
- Central-southern portion of Minas Gerais, ing through the capital Belo Horizonte, for large volumes of water, with potential for storms from Thursday onwards (chances of flooding and disruptions in cities);
- Mining triangle for accumulated highs until the 31st;
- State of Goiás, including Brasília, for high accumulations.
- Belém – PA, for high accumulations on Friday.
- The interior of the northeast region, such as Juazeiro do Norte, will experience higher than expected rainfall, despite volumes lower than what will occur in the south and southeast of Brazil.
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