Climate forecast for spring is released by Inmet

Spring in the Southern Hemisphere begins tomorrow (23/9), at 3:50 am; and ends on December 22nd, at 0:27 am. Climatologically, it is a transition period between the dry and rainy seasons in the central sector of Brazil. It is also possible to notice the process of moisture convergence coming from the Amazon, which defines the quality of the rainy season over the Center-West and Southeast regions and in part of the center-south of the North Region (figure 1a). During the season, accumulated precipitation (rain) in the north of the Northeast Region is usually less than 100 millimeters (mm), mainly in the north of Piauí and northwest of Ceará. Temperatures are higher in much of the North Region, the interior of the Northeast Region and in some parts of the central part of Brazil (figure 1b).

In the Equatorial Pacific Ocean, the monthly averages of the reference area for defining the El Niño-Southern Oscillation (ENSO) event, called the Niño 3.4 region (between 170ºW-120ºW), show values ​​of Sea Surface Temperature (SST) anomalies. greater than 0,5ºC since June 2023, indicating El Niño conditions. This condition has persisted over the last three months, with fluctuations in SST anomaly values, varying between 1,1ºC and 1,6ºC, and remaining in the moderate classification category of the El Niño phenomenon.

The ENSO forecast model from the APEC Climate Center (APCC), a research center based in South Korea, points to a probability of 90% or more that El Niño conditions will remain active during the spring and late months of the year. summer 2023/2024 (figure 2). Furthermore, the model also indicates a high probability that the phenomenon will intensify, reaching the strong classification category in the coming months. However, it is worth noting that other international models suggest the continuation of the current El Niño in the moderate classification category for the coming months.

Climate forecast for October, November and December

• North region: The climate forecast, carried out by CPTEC/INMET/FUNCEME for the months of October to December, indicates favorable conditions for the predominance of rain below the climatological average (historical average) in a large part of the North Region due to the action of the El Niño phenomenon (figure 3a).

The trend in average air temperature in the spring months is for warmer conditions to predominate than the climatological average conditions throughout the region (figure 3b). It is worth mentioning that the lack of rain in the south of the Amazon, combined with high temperatures and low relative humidity, tends to favor the incidence of fires and forest fires.

• Northeast Region: The climate forecast indicates favorable conditions for the predominance of rain below the climatological average (historical average) in a large part of the region, mainly in Maranhão and Piauí. In the east of the states of Paraíba and Pernambuco, there is a possibility of rain close to average (figure 3a). As in the North Region, the rain conditions predicted for the Northeast Region are associated with the impacts of El Niño.

The air temperature forecast indicates a predominance of favorable conditions for temperatures above the historical average across the region in the coming months (figure 3b).

• Midwest region: the tendency for spring is for a gradual return of rain, but still irregularly, in which volumes above the historical average are predicted to be favorable for Mato Grosso do Sul and south of Goiás, while in Mato Grosso, central-north of Goiás and in the Federal District, the forecast is for rain below the climatological average (figure 3a). As for temperatures, the forecast indicates favorable conditions of temperatures above the climatological average in the coming months (figure 3b).

• Southeast region: The forecast for the next three months indicates favorable conditions for rain below the climatological average in the northern part of the region. In São Paulo and the south of Minas Gerais and Rio de Janeiro, rainfall may occur above average, with a tendency for more regular rains to return from November onwards (figure 3a). Temperatures tend to remain above average across much of the region (figure 3b).

• South region: the forecast indicates a greater probability of rain above the climatological average (historical average) throughout the southern region due to the impacts that the El Niño phenomenon may cause in the region (figure 3a). The predicted temperatures may present conditions predominantly above the climatological average, except in the south of Rio Grande do Sul, where temperatures may be milder due to the number of consecutive days with rain.

Possible impacts of rain at the beginning of the harvest

With climate models forecasting the persistence of the current El Niño phenomenon until at least the end of summer 2023/2024, the question arises as to what the impact of this event will be on the beginning of the current summer harvest.

In general, in El Niño years, there is an increase in rainfall in the South Region of the country, while in the North and Northeast regions, there is a reduction in rainfall. However, it is important to highlight that the climate in Brazil is not only influenced by the action of this phenomenon, as there are other factors to be considered, which also affect the weather and climate conditions in the country, which can mitigate or intensify the effects of El Niño, factors these are also considered in climate forecasts. In this sense, constant monitoring and attention to observed conditions and climate forecasts are extremely necessary, especially in producing regions.

The climate forecast points to the gradual return of rain in the southern portion of the Central-West and Southeast regions, mainly in November, an important factor for increasing water storage in the soil and the establishment of the initial phases of crops in the field, such as soybeans , corn and cotton. However, in the northern portion of the Central-West and Southeast regions, irregular rainfall, combined with high temperatures, can reduce water levels in the soil.

In the South Region, the forecast of above-average rainfall may benefit the start of the grain harvest in these areas. However, special attention is needed for Rio Grande do Sul, where excessive rain is expected in the coming months, a scenario that could intensify the water surplus, causing the soil to become waterlogged and, consequently, damaging the winter harvest and the beginning of planting of grain crops.