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The city of São Paulo broke heat records on Wednesday (09/30), with the second highest temperature recorded in the city (37.1 ° C), according to the National Institute of Meteorology (Inmet) and the second highest average . maximum temperature (36.8 ° C), according to records of the Climate Emergency Center of the City of São Paulo.
The sweltering heat is not exclusive to the city of São Paulo: it hit the southeast and midwest of the country hard in the last week of September. Cuiabá registered 43.7 ° C on Wednesday and reached 44 ° C on Thursday (10/01)? the highest temperature ever recorded by Inmet in the city since the start of the measurement, in 1910, and the third highest temperature ever recorded in Brazil.
According to meteorologists, the end of spring is getting warmer in these two regions of the country, but that does not necessarily mean that we will have a hotter than average summer. Understand.
Why is it so hot?
The main reason for the heat this early spring is what meteorologists call atmospheric blockage when strong winds in the upper layers of the atmosphere (about 12,000 meters high) prevent the cold fronts that are reaching the south of the country from going to the Southeast and Midwest, explains Francisco de Assis, an Inmet meteorologist.
“The winds in the upper atmosphere that are over the center of Argentina and reach part of Rio Grande do Sul (move) from west to east. Whenever a cold front arrives in the southern region, they do not let the cold front pass. to the north, they push it into the ocean, “explains Assis.” We have had this block for two months.
The atmospheric blockade prevents humidity from reaching the southeast and midwest and causes a “persistence of a mass of dry air over these regions,” explains Thomaz García, meteorologist at the Center for Climatic Emergencies (CGE) of the Municipality of San Pablo.
“When this persists for many days, which is the case now, we have these temperature records, because the humidity helps lower the temperature.”
“This year it only rained 20% of the average for that season,” says Garcia.
Looking at the historical series of temperatures in the city, García explains, it can be seen that the beginning of spring has been warmer since the 2000s. And, according to Inmet’s Assis, it is a pattern that is repeated in other states, like Mato Grosso. , Mato Grosso do Sul, Goiás, Minas Gerais and Rio de Janeiro.
“We are having much less cold days than 15 years ago, 20 years ago, we are having suffocating winters and heat waves, with several days in a row of heat, increasingly frequent,” explains García.
More heat and less humidity in the air can cause respiratory problems and dehydration, in addition to unbalancing the ecosystem, which can lead to an increase in pests. Health authorities, such as the São Paulo State Secretariat of Health, warn about the importance of drinking water, trying to keep the home environment humid (with humidifiers, for example) and seeking health services in case of respiratory problems.
São Paulo recorded its second highest average maximum temperature (36.8 ° C)
Image: Getty Images
It is also important to take care that pets do not suffer from the heat: they need fresh water and ventilated environments, as well as care when walking so as not to burn their legs.
The atmospheric lockdown should last another two weeks, until around October 12-13, Inmet’s Francisco de Assis says.
On these dates, the wind should change and break the block, causing rain and softening temperatures in Mato Grosso, Mato Grosso do Sul, southern Goiás and Minas Gerais.
“We will have at least two more weeks of heat, until it starts to rain. So the tendency is to have a lot of storms.”
What will summer be like?
Warmer springs do not necessarily mean that this year we will have a summer with record heat in the Southeast and Midwest, meteorologists explain, because by early summer the atmospheric blockage that keeps this mass of dry air over the regions will have been broken. .
“The phenomenon that increases the temperature in early spring has nothing to do with summer,” explains Francisco de Assis.
“We still do not have a precise forecast, but the trend is that we will have a summer with average temperatures or even lower than normal in São Paulo, we may have some cold days until December due to late cold waves,” he says. García, from the CGE.
Assis also explains that “the summer in the center-west and southeast is rainy, then the temperature drops a bit (in relation to what we have now). In the south, the situation is reversed. Here it rains more, there is no humidity in the south, and there the temperatures can rise a lot ”.
This year we will also have the La Niña phenomenon, which should affect the country.
La Niña occurs when the water surface temperature of the Pacific Ocean becomes colder than normal. Due to the size of the body of water, the drop in temperature changes the atmospheric circulation in that region. The phenomenon creates a variation in the intensity of the winds that, consequently, alters the distribution of hot and cold air masses around the world.
This year, according to the World Meteorological Organization (WMO), La Niña is expected to be of low intensity and last until November.
If the phenomenon affects the Southeast and Midwest regions, it will make the air drier than normal during the summer and milder temperatures.
Drier-than-normal air in summer, however, can exacerbate burning in the Pantanal, which has already destroyed nearly 3 million hectares in the biome.
In the south of the country, the trend is for the effects of La Niña to be felt in the form of less rain. And in the northeast and north, the trend is for the weather to be more rainy.
