Australia braces for 'unusual' and historic event with La Niña 'gathering steam fast'

All eyes are on one key indicator as above average rainfall could be set to return for millions of Australians in the coming months.

An Australian weather map showing the predicted rainfall in the coming months.
Aussies might soon see another La Niña weather event hit our shores, making it four in five years. Source: BoM/Getty

Millions of Aussies could soon expect a bout of wild weather as predictive data shows another possible La Niña event on the way. In fact, it's "gathering steam fast," according to one expert who warned of wetter and cooler conditions to once again blanket major parts of the country.

The Bureau of Meteorology (BoM) officially declared the end of El Niño in mid-April with suggestions a wet La Niña event may be coming our way. And if it does, it would then be the first time in history Australia has seen an El Niño or La Niña weather event declared five years in a row.

"It's certainly unusual," Dr Tom Mortlock from UNSW's Climate Change Research Centre, told Yahoo News Australia this week.

Recent BoM data shows the sea-surface temperatures (SST) in the Nino 34 area in the Pacific Ocean — the area that defines whether a La Niña or El Niña event is emerging — rapidly decreasing. And that is a key number that could determine what summer looks like for millions of Aussies.

"We compare the temperatures inside that [area] to the long-term average," he said.

"If they're cooler than the long-term average, then it could be a sign that a La Niña event is emerging. If they're warmer, it could be a sign of an El Niño event," he explained.

According to ABC meteorologist Thomas Saunders, a downward trend on the graph shows La Niña "is gathering steam fast". Higher rainfall for northern, central and eastern Australia "is likely" throughout June and beyond, he said on social media this week.

Speaking to Yahoo News Australia, Milton Speer, an expert in meteorology and extreme weather, agreed Nino3.4 indicates the likelihood of a La Niña developing in late winter or early spring. "Even though the images show the temperatures are currently in the white or neutral area, they continue to head down to the blue or La Niña part of the image," he explained.

"The science is suggesting, at least, that there is the potential for us to be dipping back into a La Niña this coming year," he continued.

"There's a 50 per cent chance at the moment that a La Niña event will form by the end of the year. The bureau defined that based on their watch alert".

Previous to last year, Australia experienced a "triple dip" which refers to three La Niña weather events in a row – something Mortlock said is "relatively rare".

"It's only happened three times in the historical record, and was the first time for the first 20 years," he said.

"I don't think it's unprecedented. It's certainly unusual. We do tend to get more La Niñas than El Niños, But certainly, four La Niñas in five years is unusual, that's for sure. It certainly doesn't happen all the time."

While every La Niña event is different, "we tend to see wetter conditions during La Niña, especially on the East Coast of Australia ... From an extreme weather perspective, certainly we do see more floods and tends to be more cyclones during periods of La Niña, and less of both during periods of El Niño," he said.

The map shows the mean winter–spring rainfall during La Niña years. Source: BoM
The map shows the mean winter–spring rainfall during La Niña years. Source: BoM

However Dr Linden Ashcroft, a lecturer in Climate Science at the University of Melbourne, believes it's too soon to predict and suggests the data currently shows "fairly average conditions for the next few months".

"The Bureau has declared a La Niña watch, which means there's a slightly higher than standard likelihood that we might get it later in the year. But at this time, in this autumn time, it's still too early to tell," she argued. "It's a watch and we're in a watch-and-wait stage.

"We just need to be cautious before we start saying it's going to be La Niña, and it's all going to be a flood. I think we need to look at all the evidence, and the evidence isn't there yet to convince me that La Niña is definitely going to happen."

Watch, we will.

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