The meteorological service of the Australian Government’s Meteorological Department reported on its website on Tuesday 30 March that most of the indicators associated with ENSO (El Niño / Oscilação Sul) La Neena turned from neutral.
In other words, La Nina incident has come to light And the ocean Equatorial pacific Returned to condition Neutrality.
Prospects for climate models suggest that Equatorial Pacific will remain inside The neutral level of ENOS is at least until the end of winter.
“ENOS, or El Niño / South Oscillation, is a phenomenon of ocean-atmosphere interaction, associated with variations in ocean and atmosphere in the equatorial Pacific. The La Niño condition occurs when temperatures in the eastern equatorial Pacific Ocean Value increases. Below average, that is, when we observe a negative anomaly of SST (sea surface temperature) and also when the circulation of winds associated with this pattern changes. “, Meteorologist Bianca Lobo explains.
Sea surface temperature
As Sea surface temperature The tropical Pacific Ocean has maintained neutral ENSO values in recent weeks. Below the surface, most of the tropical Pacific is now with temperatures close to the average.
You Atmospheric indicator, In general, are also indicated Neutral ENSO level. The Southern Oscillation Index (SOI) is close to zero, while the trade winds are being intensified by the Madden – Julian oscillation (MJO). Only the Meghvita near the equator show a weak pattern similar to La Niña.
These changes are consistent with the analysis of climate models that indicate Equatorial Pacific’s return to neutrality during the autumn of the Southern Hemisphere And with little hope of a return to La Nina standards in the coming months.
The return of neutral conditions in the Equatorial Pacific in the fall is also typical of the life cycle of ENSO events. All climate models indicate that ENSO will remain neutral at least until the end of the winter of the Southern Hemisphere.
Impact of MJO and AAO in the fall of 2021
With the neutrality of the equatorial Pacific, without La Nina, Other atmospheric indicators Start doing more and more Relevance to the analysis of variations in weather In Brazil and South America during the fall.
Factors such as Maiden-julian oscillation (Madden-Julian Oscillation, MJO) and The Southeast mode (Antarctic Oscillation, AAO to distinguish from AAO, Artic Oscillation) help predict changes in patterns of precipitation and temperature over the course of a few weeks.
“The Madden-Julian Oscillation can be understood as clusters of convection clouds that normally form near the Earth’s equator in the Indian Ocean, and then travel around the world, increasing or decreasing rainfall on many continents Are. These variations occur in an interval. From 30 to 60 days. “, Meteorologist Ana Clara Marques, explains Climate.
Hey Southeast mode (AAO) is currently neutral and is expected to remain neutral for the next fifteen days.
“South annular mode is basically the pressure level at mid-latitudes, in the range between 45 ° and 60 °, and the difference between high latitudes, which covers the range of latitudes between 60 ° and 90 °. If AAO is negative, it means. More cyclones and more cold fronts coming to Brazil. When AAO is positive, cold fronts leaving Antarctica have difficulty moving over Argentina and reaching Brazil “, Ana Clara Marques explains Huh.
Forecast for april
The month of april begins Positive phase South Annular Mode on South America Cold fronts Proceed more sea route, Without much impact on the inner continent.
“That’s why during First 10 days of april We will observe the predominance of a dry air mass in the center-south of Brazil. Thus, most areas of the South, Southeast, and Midwest will have sunny days and dry seasons, typical of autumn. In this period, by April 10, rain over Brazil will be concentrated in the northern region and the northern coast of the northeast ”, predicts Ana Clara.
A after 10 April Big change in rainfall pattern Should be over Brazil, because of the influence of A. Positive phase from MJO About the country.
“After April 10, the positive phase of MJO starts taking action on Brazil and we will see Cloud cover and increased rain conditions Part of the Southeast, Midwest and Northeast regions. The states said that the most benefit from the rains should be Goias, Minas Gerais, Rio de Janeiro and Espírito Santo. But some areas of Bahia and Sao Paulo, including Greater Sao Paulo, will also experience an increase in rain. Hey Increased rain should be seen by the end of the first half of April. “Ana Clara Marques explains
Hey April begins with the effect of the mass of cold air. Polar origin that relieves heat in the southern states, part of the Midwest and southeast region.
As Capital Porto Alegre, Florianopolis, Curitiba, Campo Grande, Sao Paulo, Rio de Janeiro and Belo Horizonte begin the month Gentle morning And can record 2021 by far the lowest temperature.
But this “fresh autumn” will not last for many days and Summer forecast over easter weekend. Those enjoying the cold weather will have to wait until the end of April to feel the polar air again.
“April should end with the passage of a mass of cool air of moderate to strong intensity, but which will not have much impact on the Brazilian interior. Hopefully, there will be a sharp drop in temperature in the south region and that too. Sao Paulo In areas such as the south and east of the state of K, including Greater Sao Paulo “, Ana predicts Clara Marix.