Late season La Niña forms

Late season La Niña weather event forms, but not an officlal event as yet


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There is a heightened chance of wetter than average summer conditions due to a La Niña forming, but the Bureau of Meteorology add it is far from a fait accompli.

There is a heightened chance of wetter than average summer conditions due to a La Niña forming, but the Bureau of Meteorology add it is far from a fait accompli.

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It's official! The Pacific Ocean has entered La Niña territory, after coming within a whisker of El Niño earlier in the year.

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A TOPSY turvy year in terms of climate drivers has culminated with the Bureau of Meteorology (BOM) officially declaring a late season La Niña has begun.

This week the BOM said the tropical Pacific Ocean had officially passed La Niña levels.

To be declared an official La Niña for the records, the Pacific must stay in excess of La Niña thresholds for three months now.

The BOM is forecasting a weak La Niña to last until the early autumn.

It comes after an early season flirtation with an El Niño event where the key elements in the Pacific Ocean came close to El Niño levels.

The agriculture sector will monitor the situation with interest.

While not unheard of, late season La Niña events are relatively rare and the weakness of the current, combined with the timing, mean the event may not lead to the classic La Niña pattern of heavier than average rainfall.

The BOM says La Niña in the early summer typically brings above average rainfall, and many parts of eastern Australia have already seen a wetter than average start to the summer, but it was also noted the event could see higher than average temperatures and prolonged heatwaves.

Abnormal sea surface temperatures (SSTs) and Indian Ocean indicators, anomalous for a La Niña also raise the doubt of the event delivering typically wet conditions over summer.

In terms of the climatic indicators that have changed, the central to eastern tropical Pacific Ocean has cooled steadily since winter, and is now at La Niña thresholds (0.8 °C below average).

Atmospheric indicators, including the Southern Oscillation Index (SOI), trade winds and cloud, also show clear La Niña patterns.

The story Late season La Niña forms first appeared on Farm Online.

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