Rains and storms are expected to lash central and eastern Australia in the coming days, bringing another sodden end to the week as tropical moisture flows down from the north.
South Australia, the Northern Territory, Tasmania, western Victoria, western New South Wales and western Queensland will see falls of up to 100mm in hard-hit areas as Australia edges closer to declaring an official La Niña.
Senior forecaster at the Bureau of Meteorology Jonathan Howe said it would be “one of the wettest weeks” coming into summer for every mainland state and territory as a trough extended from the Great Australian Bight to the tropics.
“Across central and eastern Australia it will be muggy, rainy and stormy,” he said.
“Every state and territory will be hit by thunderstorms and rain over the next week, with showers coming past before the storms arrive.”
A Severe Thunderstorm Warning has been issued for parts of northwestern Victoria for heavy rainfall: https://t.co/HLs2UYFQyQ pic.twitter.com/91Eavlmvne
— Bureau of Meteorology, Victoria (@BOM_Vic) November 3, 2021
Howe said Western Australia, western Queensland and New South Wales, northern Victoria and much of the Northern Territory would be hit the hardest on Thursday and Friday, before storms gradually shifted to the east coming into the weekend.
The heaviest rain – between 50mm and 100mm –is expected across remote Western Australia, the Kimberley and the Top End, while parts of north-east Victoria and south-east New South Wales were predicted to see rain of up to 50mm.
“It depends on where the thunderstorms fall, but there are heavy rain warnings in place in northern Victoria and western New South Wales and there’s already the risk of flash flooding in remote areas,” Howe said.
“Some places are soaked already, so there is a risk of some marine flooding.”
Howe said an active tropical moisture front was causing the storms, with steamy waters in the north of Australia sitting at temperatures between one and three degrees hotter than normal.
“It’s generally in the high 20s but water is getting to 33 degrees, like a warm bath,” he said.
“That’s causing evaporation, and the tropical moisture is dragged across continent, leading to humid days and instability.”
A Severe Thunderstorm Warning has been issued for heavy rain in parts of the Upper and Lower Western districts and far west of the Riverina. Check https://t.co/PJoJsMgKPN for more details. pic.twitter.com/vIAJq21s5L
— Bureau of Meteorology, New South Wales (@BOM_NSW) November 2, 2021
While La Niña hadn’t been officially declared, Howe said forecasters were “on the cusp” of doing so in the coming days or weeks, and predicted the continuation of above-average rainfall lasting into summer.
“You need an above-average temperature over a consecutive period, and we’re almost meeting all criteria. It’s the warm waters that would lead us to declare it,” he said.
“Usually you see weather like this at the start of the active rain and cyclone period, but what is unusual is the timing. You see this in summer, at peak warmth, but it’s quite early in the season which was unexpected.”
Howe said one silver lining may be the lowered risk of severe bushfires like those seen during Black Summer in 2019.
“It was getting really hot [in 2019] but because we’re seeing so much rain across western and central Australia, it’s not giving the heat a good chance to build and we’re unlikely to see big heatwaves over the next few weeks,” he said.
“It’s looking to be an average season coming into summer, but that doesn’t mean we won’t get any bushfires as all you need is a few hot days.
“There’s an above normal chance of bushfires in south-east Queensland and northern New South Wales because of how dry it’s been, but across eastern Victoria and New South Wales it’s below normal, which comes back to the wet weather.”
