The January climate reserves temperatures above average in much of Brazil with temperatures above the historical climatology between the Central-West and the South-East | PAULO PINTO/AGÊNCIA BRAZILE/EBC
According to historical climatology, January is the warmest month of the year in most areas of south-central Brazil. The second month of the climatic summer (from the quarter December to February) therefore marks the peak of the season with many hot days and rains mainly of a convective nature, that is, associated with hot and humid conditions.
In southern Brazil, historically, the month does not tend to be very rainy in most areas. The exceptions are the east of Santa Catarina, Paraná and sometimes the extreme north-east of Rio Grande do Sul, due to the action of the South Atlantic Convergence Zone, a humid channel that originates in the Amazon, crosses the Centre-West and reaches the South-East. . At times, the slope of the ZCAS brings heavy rainfall to the easternmost areas of southern Brazil, except the southern coast of Rio Grande do Sul.
Porto Alegre has the highest average temperatures of the year in January. According to the 1991-2020 standards, the average minimum temperature is 20.7ºC, identical to that of February and higher than the 19.4ºC in December or the 19.5ºC in March. The historical average maximum for the month in the capital of Rio Grande do Sul is 31.0ºC, the highest among the months of the year, higher than the 30.5ºC in February and the 30.0ºC in December.
In Sao Paulo, the historical average minimum for Mirante de Santana is 19.4ºC, the second highest of the year, behind only February’s 19.6ºC. In turn, the average monthly maximum of 28.6ºC is the second highest in the annual climatology, being lower than February’s 29.0ºC.
The historical average rainfall in January in Porto Alegre is 120.7 mm. This is the fifth highest among the months of the year, surpassed only by the winter and spring months.
In Florianópolis the average monthly rainfall in January is 241.3 mm, the highest among the months of the year; In Curitiba the average monthly rainfall was 226.3 mm, the highest value in the annual climatology.
In the city of Sao Paulo, an average of 292.1 mm, the highest rainfall of the year. In Belo Horizonte, January is the wettest month of the annual climate with 330.9 mm. It is the height of the rainy season in many cities of Southeastern Brazil, which record the wettest January of the year due to the influence of tropical instability with warm and humid air bringing thunderstorms, in addition to the influence of episodes of South Atlantic Convergence Zone.
Pacific conditions
The month of January will begin with the El Niño phenomenon around its peak in the equatorial Pacific Ocean, which does not result in its maximum impact. The effects of El Niño are greatest, for example, in southern Brazil, during the spring. As the month progresses, the trend is for El Niño to begin to weaken.
The US climate agency’s latest weekly State of the Pacific bulletin indicated that the sea surface temperature anomaly was 2.0ºC in the so-called Niño 3.4 region in the east-central equatorial Pacific.
NOAA
This region is officially used in meteorology as a reference to define whether there is an El Niño and also evaluate its intensity. The positive value of 2.0ºC is in the transition range from a strong El Niño (+1.5ºC to +1.9ºC) to very strong (equal to or greater than 2.0ºC which is Super El Niño).
On the other hand, the Niño 1+2 region has a +1.6ºC anomaly. The coastal El Niño along the coasts of Peru and Ecuador began in February and reached its maximum intensity during the winter. The largest coastal El Niño anomaly in the Niño 1+2 region this year occurred the week of July 19 at 3.5ºC.
Rain in January
January, being the peak summer month, has the common rainfall irregularity with significant variability in rainfall totals from one area to another. In a month, a point in a municipality can have a lot of rain and other low volumes of precipitation. Volumes are determined too much by isolated hits.
This January, in southern Brazil, precipitation is expected to follow this pattern. It is difficult to establish a regional trend in precipitation above or below average because there will be places within the same microregion where volumes in the month may end up above or below, such is the unevenness in the distribution of the expected rainfall.
The sectors west of Rio Grande do Sul and east of Santa Catarina have a greater probability of precipitation with above-average values. On the other hand, some areas could suffer from the lack of more voluminous rainfall, causing some concern in the agricultural sector.
The maps below show the weekly trend of precipitation anomalies for the month of January from the European Weather Model. The maps are merely illustrative and do not necessarily represent MetSul Meteorology’s final prognosis.
MetSul forecasts below-average rainfall across much of the central-west, except parts of Mato Grosso and Goiás, while in the southeast, most of São Paulo is expected to continue to suffer below- or much-below-average rainfall. It is expected to rain more, even in excessive quantities, in Minas Gerais, in the north of Rio de Janeiro and in Espírito Santo.
An event in the South Atlantic Convergence Zone in the first week of the month will contribute to the largest accumulations in these areas. Heavy rains are expected to ease drought in northern Minas Gerais. More abundant rainfall is also expected in the northeast of Brazil, especially in Bahia, for part of the month.
Precipitation anomaly projection from the North American CFS model for January. The map is merely illustrative and does not necessarily represent the final forecast of MetSul Meteorologia | METSUL
Being in the middle of summer, very high and even extreme volumes are frequent at short intervals and in a very isolated way, accompanying localized thunderstorms that occur mainly from afternoon to evening, especially on days of more intense heat.
These summer storms can come with hail, windstorms and in the most extreme cases even tornadoes. In the case of Rio Grande do Sui, the worst storm in Porto Alegre’s recent history, for example, occurred in January 2016 due to El Niño, causing extensive damage.
Temperature in January
Much of southern, central-western and southeastern Brazil is expected to have temperatures above or well above normal. The largest deviations are expected for the south-east and central-west areas, in particular Mato Grosso do Sul, the interior of São Paulo and the west of Minas Gerais (Triângulo Mineiro). In southern Brazil, Paraná will be the state where the temperature is most likely to be above average.
The maps below show the weekly trend of precipitation anomalies for the month of January from the European Weather Model. The maps are merely illustrative and do not necessarily represent MetSul Meteorology’s final prognosis.
Rio Grande do Sul is expected to repeat December’s trend, with temperatures above or well above the average for much of Brazil. Once again, incursions of cooler air into Uruguay and Argentina should provide fewer days of excessive heat than normal, although some days in January are expected to be very hot and even scorching.
Temperature anomaly projection from the North American CFS model for January. The map is merely illustrative and does not necessarily represent the final forecast of MetSul Meteorologia | METSUL
Therefore, in January, such an extreme heat wave is not expected to be repeated in the month, as seen in 2022. This was an extraordinary historical anomaly with 15 consecutive days of highs above 40ºC in Rio Grande do Sul, favored by a strong drought, a condition absent this summer.
The first week of January will have mostly pleasant temperatures with less hot weather than usual on most days in Rio Grande do Sul, but from the second week onwards more intense heat is expected with a greater risk of summer storms in the state of Rio Grande do Sul.
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2023-12-31 14:35:00
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