January 2024 was marked by above-average rainfall in several regions of the country

This week, the National Institute of Meteorology (Inmet) published a survey of the main meteorological phenomena that occurred in Brazil in January 2024.

The month was marked by episodes of rain that caused flooding, landslides and impacts on agribusiness. The rains that occurred in the states of Bahia, Rio de Janeiro, Pará and Minas Gerais stand out, as the accumulated rainfall exceeded the historical average.

In areas of São Paulo, Mato Grosso, Piauí and Goiás, the rain that occurred was not enough to reach the average. 

January was also marked by heat, typical of summer, and the influence of El Niño. 

Rain

In January, the greatest accumulation of rain occurred in a band that runs from the northwest of the North Region, passes through the central area of ​​the country and reaches the east of the Southeast and South Regions (figure 1). 

The extreme events in these regions of Brazil were caused by the organization of the humidity channel, in addition to the presence of the South Atlantic Convergence Zone (ZCAS).

This month, two episodes of ZCAS were observed: the first between days 3 and 7 and the last between days 23 and 29.

In the North and Northeast Regions, rain showers were observed in areas of Pará, Ceará and Bahia. Highlight for Iguatu (CE), with 107,0 mm; Paragominas (PA), with 101,0 mm; both on the 1st and Barra (BA), with 130,2 mm, on the 2nd. The influence of the ZCAS also contributed to the heavy rains in Boca do Acre (AM), which accumulated 214,6 mm on the 4th. The combination of heat and high humidity, reinforced by the influence of the ZCIT, caused rainfall in Belém (PA), with 116,9 mm and Castanhal (PA), with 99,2 mm, both on the 7th.

The ZCAS caused rain in the Center-West and Southeast regions, increasing instability in the municipalities of Rio Claro (RJ), with 133,6 mm, on the 4th and Sorriso (MT), with 104 mm, on the 5th. Soon after, the advance of a cold front favored the occurrence of significant rain in Duque de Caxias - Xerém (RJ), with 162,2 mm; Rio de Janeiro - Vila Militar (RJ), with 151,8 mm; Rio de Janeiro - Jacarepaguá (RJ), with 126 mm, all on the 14th. On the 23rd, the organization of a humidity channel caused accumulations of rain in São José do Xingu (MT), with 138,6 mm and Vila Bela da Santíssima Trindade (MT), measuring 101,2 mm.

Finally, the combination of meteorological systems such as cold fronts and low pressure caused rain in the South Region along with the effects of the El Niño phenomenon, which is ongoing and forecast to weaken in the coming months. On the 18th, Cruz Alta (RS) accumulated 112,7 mm; Ibiruba (RS) reached 104,2 mm, with strong gusts of winds in some areas reaching values ​​above 100 km/h. Furthermore, on the 21st, Itapoá (SC) accumulated 162,0 mm and Campina da Lagoa (PR) reached 106,4 mm.

Figure 2a shows the satellite image from the 4th, at 5:30 am (Brasília time), highlighting the heavy rain in Boca do Acre (AM) which, in just 5 hours, accumulated 182,4 mm due to the actions of the ZCAS – system typical weather conditions of the season. Furthermore, on the 23rd it was exceptionally rainy in the central part of the country due to moisture channeling (figure 2b). It should be noted that areas in red indicate regions that are more favorable for the occurrence of intense rain.