Autumn begins this Monday in the Southern Hemisphere

Autumn in the Southern Hemisphere begins at 18:25 pm next Monday (20). A transition season between the hot, humid summer and the cold, dry winter, mainly in Central Brazil, autumn is characterized by scarcer rain in the interior of the country, especially in the semi-arid northeast, according to the National Institute of Meteorology (Inmet) .

In the northern part of the Northeast and North regions, it is still a time of heavy rain, especially if the Intertropical Convergence Zone (ZCIT) persists south of its climatological position.

Autumn is also characterized by incursions of cold air masses coming from the south of the continent, which cause a drop in air temperatures, mainly in the South Region and part of the Southeast Region.

During the season, it is possible to observe the first formations of adverse phenomena, such as fogs in the South, Southeast and Central-West regions; frosts in the South and Southeast regions and in Mato Grosso do Sul; snow in the mountainous areas and plateaus of the South Region, and cold in the south of the North Region and in the states of Mato Grosso do Sul, Mato Grosso and even in the south of Goiás.

Observed ocean conditions and trend

Since last year, Sea Surface Temperature (SST) anomalies

in the area of ​​the Equatorial Pacific Ocean, called Niño 3.4 (between 170°W-120°W), it has been showing values ​​below -0,5°C, a situation in which the La Niña phenomenon exists. This fact has contributed to the occurrence of more frequent rains in the North and Northeast regions, as well as the lack of rain in the South Region of Brazil, especially in Rio Grande do Sul, during the 2022/2023 summer.

However, in the first two months of 2023, La Niña conditions have been losing intensity, as SST anomaly values ​​have gone from -0,7°C to -0,4°C, indicating a transition to neutral conditions.

Considering the coming months, the ENSO forecast model from the APEC Climate Center (APCC), a research center based in South Korea, points to a probability greater than 80% that neutral conditions will remain until the beginning of autumn/2023 , with a possible transition to the formation of the warm phase (El Niño) between the end of this season and the beginning of winter. In this sense, it is recommended to monitor future updates on the progress of ENSO by monitoring the SST in the Pacific so that the persistence of the phenomenon can be verified.