La Nina more likely than El Nino or neutral conditions by spring this year 2024

[Mark]

It was only last year that we came out of a 3-year La Niña but there is a significant chance that the Pacific Ocean returns to a La Niña state by spring this year, increasing the chances of wet weather across eastern Australia in spring and summer. The 2010/2011 La Niña event demonstrates that such a short turnaround can happen, and computer models have been consistently predicting La Niña as more likely than either El Niño or neutral conditions.


Firstly, it appears that La Niña is currently the more common phase of the El Niño Southern Oscillation (ENSO). We can see that by looking at the multi-variate ENSO index (MEI) for the past several decades from 1979 to 2023. The MEI considers atmospheric variables (cloud, pressure and wind patterns), in addition to the Pacific Ocean’s surface temperature pattern, giving a more wholistic index than other indices.
https://www.weatherzone.com.au/news/la-nina-more-likely-than-el-nino-or-neutral-conditions-by-spring-this-year/1722122

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[Mark]

The current El Niño event peaked during the Southern Hemisphere’s summer and is now weakening, with forecast models suggesting the Pacific Ocean should return to a neutral state (neither El Niño nor La Niña) by the end of the Southern Hemisphere’s autumn.


What happens after that is difficult to predict. Some forecast models suggest the Pacific Ocean will remain in a neutral phase through the middle of the year, while others are more bullish with predictions of a rapid transition to La Niña in the Southern Hemisphere’s winter or spring.
https://www.weatherzone.com.au/news/pacific-ocean-cold-pool-emerges-hinting-at-la-nina/1835932

[Mark]

The likelihood of La Niña occurring in 2025 has increased due to a change in the way the Bureau of Meteorology calculates sea surface temperature anomalies in the tropical Pacific Ocean.


What is La Niña?

La Niña refers to a distinct pattern of sea surface temperatures across the tropical Pacific Ocean. When La Niña is occurring, it affects weather patterns on a global scale.


La Niña occurs when cooler than average water develops at the surface of the central and eastern equatorial Pacific Ocean, and warmer than average water sits at the surface of the western tropical Pacific Ocean.


This pattern of sea surface temperature anomalies typically enhances cloud and rainfall over the western Pacific, including part
s of Australia. It also changes how weather behaves in other parts of the world.
https://www.weatherzone.com.au/news/la-nina-more-likely-this-year-after-bom-switches-to-new-index/1890871