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How the La Niña weather event could affect Australia for the rest of 2020

By Meg Bolton and staff, Thursday October 1, 2020 - 05:18 EST
ABC licensed image
La Nina systems increase the risk of cyclones like ex-Tropical Cyclone Owen. - ABC licensed

A La Niña weather pattern could finally put an end to the drought in parts of Australia, but for some it has raised concerns about potential cyclones and flooding.



The last La Niña event stretched from 2010 to 2012 and resulted in one of Australia's wettest two-year periods, but conditions this year are forecast to be less extreme.

Bureau of Meteorology senior forecaster Lauren Pattie said while flooding and cyclones were associated with La Niña, it was too early to predict the severity of the weather pattern.

"Each one is different, but the last significant La Niña we saw, we saw very intense flooding," Ms Pattie said.

"We aren't expecting to see it as strong, however we do expect to see an above average rainfall, which does mean there's an increased risk of flooding."

Ms Pattie said cyclones and an early monsoon for north Queensland were also associated with the weather pattern.

"The average number of cyclones for the Queensland region is four," she said.

"But regardless of the number, it only takes one cyclone to make a season."



National impact

Bureau of Meteorology manager of climate operations Andrew Watkins said south-eastern Australia could expect more rainfall during spring and into summer.

While that would lead to more water in reservoirs, he said, it also brought an increased risk of flooding.

The other side of the country was likely to feel the effects later in the year, he said.

"In south-western Australia we don't typically see a big impact from La Niña during the spring," Dr Watkins said.

"But sometimes in summer we do see some tropical cyclones driving down from the north-west and affecting the south coast."



Dr Watkins said the north-west could expect six to seven tropical cyclones each year, and the La Niña increased the likelihood of getting at least this many, if not more, along with an earlier monsoon.

He said the bushfire season, which occurs every summer in southern Australia, should be milder during La Niña.

"A bit of extra rainfall will keep those fires a little smaller, a little shorter than we have seen in recent years," he said.



No 'magic tap'

Despite his memories of the last La Niña, the prospect of more rain has been welcomed by Greg Hutchinson, who farms cotton in the drought-declared shire of Banana, near Rockhampton.

"It was devastating for us and a lot of irrigators along the Dawson River, because two years in a row people got their cotton crops flooded out, so they had no income for those two years," he said.

"We definitely don't want what happened in 2010-2011 but probably something in between would be nice."



Rick Britton, the Mayor of outback Queensland's Boulia Shire, was optimistic the forecast would eventuate.

"It's the same type of prediction now [that there was] in 1973, 1974 and 2000, and those years were our wettest years on record," Cr Britton said.

"That prediction would be really good for the majority of Australia.

"I've noticed in the last five or six weeks here we've had prominently north, north-west winds, and to me that's a sign that there is something in the wind, and we've just got to sit and wait to get a wet [season]."



Agriculture Victoria seasonal agronomist Dale Grey said farmers had been looking out for the La Niña for months.

"Just because the [Bureau of Meteorology] declares a La Niña doesn't mean the tap suddenly, magically turns on," he said.

"We've been waiting for the tap to turn on for some time in the north of the state, and we've just had average to drier rainfall.

"There would be plenty of crops that would really benefit from a wet October."



Crushing blow?

In the meantime, Australia's sugar millers are concerned the weather pattern could threaten the remainder of the 2020 crush.

One third of an estimated 30.9 tonnes of sugarcane is yet to be harvested and processed, and rain could disrupt the final weeks of the season.

"La Niña-influenced light rain will be manageable and welcome," the Australian Sugar Milling Council's Jim Crane said.

"But heavier falls could be challenging towards the end of the crush.

"[But] spring rain can set the foundation for an improved 2021 crop across most of the cane growing regions."


- ABC

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