Meteorologists have warned there is a strong chance of La Niña forming ahead of summer and bringing heavy rain and flooding to Australia’s east.
Weatherzone’s Joel Pippard said a ‘clear La Niña signal’ was emerging in the central Pacific Ocean in the form of a pool of cold water collecting about 150m below the surface.
‘This is often the first signal that a La Niña could develop in a given year, and this year has been no exception,’ he said.
Mr Pippard explained that La Niña is the cool phase of the El Niño Southern Oscillation (ENSO) which happens when cooler than normal waters push westward along the equatorial Pacific Ocean.
‘This ocean pattern, along with changes to the overlying atmosphere, cause warmer waters and more rising air to occur over northern Australia, typically increasing spring and early summer rainfall.’
Australia has been in the El Niño phase of weather pattern for the last 12 months but was in La Niña between late 2020 and 2022 which contributed to the intense rain that soaked the east coast in those years.
The Bureau of Meteorology has had a ‘La Niña watch’ in place since May, which means it estimates there is a 50 per cent chance of the pattern developing whereas the normal likelihood would be about half that.
In September, the World Meteorological Organization said there was a 60 per cent chance of La Niña conditions emerging by year’s end.
Meteorologists are warning there is a strong chance the La Niña weather pattern could form ahead of summer, bringing with it heavy rain and flooding for Australia’s east
Meteorologists are forecasting Australia will see a wet summer. This map shows that there has already been significantly more rainfall on the east coast this year compared to last year
In the United States, the National Oceanic and Atmospheric Administration put the likelihood at 71 per cent, but the US criteria are less strict than BoMs.
The Bureau could upgrade its watch to a ‘La Niña alert’, which would be a 70 per cent chance, if more signals emerge over the next few weeks including trade winds being stronger than average and further cooling trends in the Pacific are observed.
Other experts are also warning of a wet summer.
Sky News Weather meteorologist Alison Osbourne said the country has been sitting on ‘La Niña watch’ but the weather system does indeed appear to be forming.
‘The reason why we’ve been in that holding pattern over recent months is we haven’t seen any strong shift until now towards an increased likelihood of this phenomenon kicking in,’ Ms Osbourne said.
‘At this stage we are predicting at Sky News Weather that it is looking more likely than that 50 per cent chance but it is developing much later than usual.’
Mr Pippard said the cooler water in the central Pacific combined with warmer waters around Australia indicated an increased rainfall.
‘For nearly the entire year, a pool of very cool water has been sitting about 150m below the surface in the middle of the Pacific Ocean.
‘A tongue of this cold water also extends east to near South America, where it is much closer to the surface, but has not fully reached the surface.
Australia has been in the El Niño phase of weather pattern for the last 12 months but was in La Niña between late 2020 and 2022 which contributed to the intense rain that soaked the east coast in those years
‘Usually, this cold water would have triggered a La Niña by now, but temperamental weather in the region has continually disrupted this final step from occurring so far.’
Mr Pippard said it is at this stage looking ‘evenly balanced’ as to whether or not La Niña could form, but Australia is in for a wet summer either way.
‘Regardless of the declaration, climate forecasts for the next few months are still favouring for wetter than average conditions over northern and eastern Australia due to the warm waters surrounding Australia.’
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