El Niña weakens and signals the arrival of La Niña – 04/06/2024 – Environment

Atmospheric anomalies in the equatorial Pacific have been weakening since the beginning of the year, which indicates a transition from the El Niño phenomenon to La Niña in a “very rapid” way, according to the most recent weekly meteorological bulletin from Noaa (the US weather and climate agency). United States government).

El Niño is a natural meteorological phenomenon, which corresponds to the warming above the historical average of a large part of the equatorial Pacific. It appears every two to seven years, lasting nine to 12 months.

La Niña, in turn, has opposite characteristics. It manifests itself as an abnormal cooling of the ocean’s surface waters. Therefore, some of the impacts tend to be different, but a region affected by El Niño does not always experience significant changes in weather and climate due to La Niña.

El Niño and La Niña are parts of the same phenomenon, called Enos (El Niño Southern Oscillation; or Enso, for its acronym in English). The change in the temperature of the Pacific Ocean has effects on temperature and precipitation around the world.

In Brazil, for example, La Niña tends to cause an increase in the volume of rain in the North and Northeast regions. In the South, the trend is towards more drought and heat, while, in the Central-West and Southeast, the impacts fluctuate.

Understand the phenomena

According to the most recent NOAA bulletin, the transition from El Niño to the so-called neutral Enos (neither La Niña nor El Niño) will occur between April and June, with an 83% chance. The La Niña phenomenon has an increasing 62% chance of developing between June and August.

According to the Metsul Meteorologia platform, which analyzes Noaa data, the sea surface temperature anomaly in the so-called “Niño 3.4” region (Central-Eastern Equatorial Pacific) was at 1°C, which indicates the presence of El Niño in the weak to moderate range. This is the officially designated region to check for El Niño or La Niña.

Also according to the platform, another region monitored with great attention is the Eastern Equatorial Pacific, on the coasts of Peru and Ecuador, known in climatology as “Niño 1+2”. In this part of the ocean, the sea temperature is already colder than average: -0.4°C.

“This, in practice, is an indication that colder waters from the depths of the Pacific have begun to emerge on the surface, through a phenomenon called upwelling, starting the process that should lead to a La Niña event”, assessed the Metsul.

Meteorologists have emphasized that this incipient cooling in the East Pacific is not yet the beginning of La Niña, but rather the beginning of a complex process of changes in the ocean and atmosphere that is expected to lead to a La Niña event later this year.

For the May to July quarter, the probabilities are 3% for El Niño, 65% for neutrality and 32% for La Niña.

For the winter quarter of June to August, 1% probability of El Niño, 37% neutrality and 63% La Niña. In the July to September quarter, 1% El Niño, 24% neutral and 75% La Niña.

In the quarter from August to October, 1% El Niño, 17% neutrality and 82% La Niña. In the spring quarter, finally, between September and November, 1% El Niño, 14% neutral and 85% La Niña.