An El Niño event is looking more probable than ever after the Bureau of Meteorology upgraded its status from “El Niño watch” to “El Niño alert” this afternoon.
This means there is about a 70 per cent chance of the weather event developing this year.
“While the models show it’s very likely the tropical Pacific Ocean temperatures will reach El Niño levels during winter, we have seen some movement in the atmosphere towards El Niño conditions,” BoM senior climatologist Catherine Ganter said.
“While our El Niño alert criteria have been met, these changes will need to strengthen and sustain themselves over a longer period for us to consider an El Niño event.”
El Niño describes changes in the tropical Pacific Ocean that affect global weather and it occurs on average every three to five years.
During El Niño, there is a higher chance of drier weather in eastern Australia and it’s more likely to be warmer than usual for the southern two-thirds of Australia.
“The Bureau’s long-range winter forecast is for drier and warmer conditions across almost all of Australia and the climate conditions in the Pacific Ocean are already factored into our forecasts,” Ganter said.
“The long-range forecast for winter also shows an increased chance of below average rainfall for almost all of Australia and the move to El Niño alert does not change this forecast.”
Ganter said even if an El Niño developed, its impact could vary depending on where you are, as well as from event to event.
In Australia, changes during El Niño could include reduced rainfall in the east, warmer temperatures for the southern two thirds of the country, increased risk of extreme heat, increased bushfire danger in the south-east, increased frost risk due to clear night skies, decreased alpine snow depths, a later start to the northern wet season, and reduced tropical cyclone numbers.
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What is El Niño and how is it different to La Niña?
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The cycle of La Niña and El Niño – known as ENSO, or the El Niño-Southern Oscillation index – works a bit like a pendulum.
La Niña occurs when water in the eastern tropical region of the Pacific Ocean is cooler than average as the “trade winds” – the planet’s prevailing east-to-west winds – strengthen, creating warmer-than-normal water around Indonesia and Australia’s east coast.
This leads to increased rainfall and brings the risk of heavy flooding in Australia.
However, when those conditions are reversed – trade winds are weaker, and water is warmer than average in the eastern tropical Pacific but cooler close to Australia – an El Niño is declared, and our continent will experience hot, dry conditions and come under the threat of drought.
When the “pendulum” sits in the middle and ocean temperatures are closer to average, it is referred to as “neutral” ENSO conditions – and it is more likely to bring less extreme weather conditions.
And, if you’re wondering what the two terms actually mean, “La Niña” is Spanish for “the girl” or “little girl”, while “El Niño” translates to “the boy” or “little boy”.
When was the last time Australia had an El Niño?
Australia’s last El Niño event occurred during the summer of 2019/2020.
The country had a severe drought throughout 2019, and the strong El Niño system was partly responsible. The 2019 drought was measured by the Bureau of Meteorology to be Australia’s most intense ever recorded.
It was then followed by one of the most dangerous bushfire seasons.
Before 2019-20, the previous strong El Niño event impacted Australia from 2014 to midway through 2016.
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