Australia is on track to see its fourth La Nina event in five years with almost no chance of another El Nino, Sky News predicts
Wetter than usual weather is on the cards for Australia's east and north as forecasts show a likely La Nina event developing through 2024 and beyond, Sky News can reveal.
Rob Sharpe
January 19, 2024 6:00 am
Australia’s weather patterns are heavily influenced by what is going on in the Pacific Ocean.
From mid-2020 to early 2023 our weather was governed by three periods of La Nina.
Across that three-year stint Australia as a whole saw 17 per cent more rainfall than usual – the country’s wettest spell in a decade.
This was immediately followed by the current El Nino and positive Indian Ocean Dipole events, that included a record dry August-to-October before the wet weather returned.
This four-year stretch has been remarkable for its lack of sustained neutral conditions.
Historically, half of the years in the Pacific Ocean are neutral, with a quarter each for La Nina and El Nino.
What is even more remarkable is that La Nina could take hold before the year is out, extending that run to five years.
And even if it doesn’t, we are still facing strong odds for wetter than usual weather in our east and north.
El Nino to end in autumn
Despite the recent rain in the east, El Nino is still active in the Pacific Ocean.
Much of Australia is expected to return to drier than usual weather for the month of February, although near-normal rainfall could materialise near our populated eastern seaboard.
Through autumn El Nino is very likely to weaken, with the waters in the middle of the Pacific Ocean returning closer to normal in a so-called ‘neutral’ state.
Australia’s weather may return to some semblance of neutrality too, with near normal rainfall the most likely situation in autumn at this stage.
However, from winter to summer, seasonal outlook maps are expected to display a familiar shade of blue.
The return of La Nina
Australia’s most famous climate drivers are El Nino (drier) and La Nina (wetter) in the Pacific Ocean to Australia’s east.
Each event lasts between six months and three years.
But what is less known is that these sibling climate drivers (El Nino means boy and La Nina means girl) have an uncle (let’s call him El Tio) and aunt (La Tia) who hang around for much longer.
El Tio and La Tia remain active across the Pacific Ocean for decades at a time.
That is why climate scientists refer to this pattern as the Interdecadal Pacific Oscillation (IPO).
El Tio brings drier weather and more El Nino phases for sustained periods of time in eastern and northern Australia.
The most recent period of El Tio was from the early 1980s to the early 2000s, culminating in the Millenium Drought.
This drought was broken when the current phase of La Tia began with back-to-back La Ninas from 2010 to 2012.
The current La Tia event strengthened during the triple La Nina event and all forecast models are suggesting it will continue through 2024 and early 2025.
Looking back through the history books and whenever an El Nino has managed to develop within the wet La Tia period, approximately 65 per cent of the time we’ve flipped straight into La Nina.
This is supported by approximately two thirds of forecast models picking the ocean moving into La Nina in the second half of this year.
Therefore, Sky News Weather is giving La Nina a 65 per cent chance of developing this year, a 30 per cent chance of remaining neutral and only a 5 per cent chance of seeing back-to-back El Nino.
Rain and flood risk rising this year
Four years ago, Australia’s dam levels were sitting at just 44 per cent of capacity.
Last year they peaked at 79 per cent, before settling back to the current 74 per cent of capacity.
Essentially, the greatest concern for most regions will be flood rather than drought or fire, although those cannot be ruled out.
The situation is different to the last few years.
The flood concerns are clearly greater than the first La Nina in 2020/2021 off the back drought and Black Summer fires.
The scenario seems similar to the second La Nina in 2021/2022 where we saw the disaster unfold in Lismore.
Hopefully we avoid a flood of that scale in this event.
Thankfully the landscape is not as soggy as it was in advance of the 2022/2023 La Nina that caused many floods across southeastern Australia, including the Murray-Darling.
Even if La Nina doesn’t develop and we are in neutral conditions, the La Tia event covering the Pacific with its warm seas east of Australia still tips the scales slightly in favour of wet weather for eastern Australia.
Therefore, it is wise to plan for a wet end to 2024 and start of 2025.
