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Intense rainfall is expected in parts of eastern Australia over the coming days in a precursor to what is set to be a wetter-than-average spring.
A large cloudband was shifting east on Friday, expected to cause widespread rain over southern and central Queensland and northern New South Wales until Sunday.
Over the past two days, the cloudband had produced more than two months’ worth of rain in south-west Queensland, washing out the opening day of the Birdsville Races.
Ben Domensino, a meteorologist at Weatherzone, said a low-pressure system was likely to form off the east coast on Saturday, interacting with the cloudband to cause heavy rain along NSW’s mid-north coast.
“Over those three days we could see in excess of 100mm falling along the mid-north coast,” he said.
The areas around Coffs Harbour and Port Macquarie are forecast to bear the brunt of the rainfall.
Flood watch warnings were issued on Friday for the Orara, Bellinger and Hastings rivers and residents in low-lying areas nearby have been told to prepare to move if flooding should develop.
Looking to spring, Domensino said Australia’s three main climate drivers are all pointing towards increased rainfall and wet conditions over the coming months.
To the west a negative Indian Ocean dipole event is under way, likely to drive wetter-than-average weather over central and south-eastern Australia this spring.
To the south, a positive southern annular mode will lead to more moisture-laden winds over Queensland and NSW. Slightly less rainfall could be in store for southern coastal areas of Australia, western Tasmania and south-west Western Australia.
Meanwhile, a La Niña alert remains in place with a 70% chance of it forming this spring – around three times the normal likelihood of an event forming in any year.
During a La Niña, changed ocean currents bring cooler, deep water up from below and lead to a cooling of the central and eastern tropical Pacific Ocean. The changed conditions can lead to heavy rainfall.
“We’re very close to exceeding the La Niña thresholds at the moment,” Domensino said.
“Even if the Bureau [of Meteorology] don’t declare it, we are in a La Niña-like pattern and that is expected to increase the chance of rain over eastern Australia this spring.”
Dr David Wilson, a hydrologist with the BoM, said a La Niña event could result in an earlier start to the northern wet season.
He said cooler days are expected across the country this spring, outside the tropics, with an increased risk of flooding in the eastern states.
But parts of southern Australia are expected to be drier than average this season, and there is above normal fire potential in western and central parts of the country.
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