Parts of Australia are about to get a month’s worth of rain in just a few days as an “atmospheric river” of tropical moisture stretches from the Top End to Tasmania.
Already this week, the thick north-west cloud band stretching almost the width of the country has already brought the heaviest October rain in 120 years of records to parts of South Australia, prompted a flood watch in central Australia, and produced the coldest day in four years at Alice Springs.
The weather bureau said the weather system could dump up to 120 millimetres of rain and potentially cause flash flooding in parts of Victoria – hitting western and central parts of the state late on Wednesday and the north-east ranges early on Thursday.
“My latest update was that there’s significant rainfall expected in the north-east of the state, but everybody should be aware of those circumstances,” Victorian Premier Daniel Andrews said on Wednesday.
Bureau of Meteorology senior forecaster, Kevin Parkyn said the weather pattern heralded the start of La Nina.
During a La Nina phase, Australia’s northern waters are warm, typically resulting in increased rain for eastern and northern Australia.
“The atmospheric conditions are just ripe for that system to intensify tonight over Victoria,” Mr Parkyn told the ABC.
Weatherzone meteorologist Ben Domensino said rain and thunderstorms would fall in parts of the Northern Territory, South Australia, NSW, the ACT and Victoria in the next several days.
Rain and storms will continue across a broad area of northern, central and south-eastern Australia on Wednesday, with falls of up to 30 millimetres predicted for Melbourne by Thursday afternoon.
Mr Domensino said there would be storms and increasingly windy weather in south-eastern states by Friday.
“This dynamic low could cause damaging winds and flooding in parts of SA, Victoria, Tasmania and southern NSW, so be sure to check the latest warnings later in the week,” he said.
The weather bureau has issued a severe warning for heavy rain in Victoria’s Mallee, northern country, north central, Wimmera and parts of the central, south-west and north-east forecast districts.
It said the low-pressure system would deepen over north-western Victoria on Wednesday night, before tracking south on Thursday, possibly causing some flash flooding.
There is also strong wind warning for the Gippsland lakes, west coast, central coast, central Gippsland coast and East Gippsland coast.
NSW and ACT
Heavy rain is expected in NSW’s south-east, although most of the rest of the state will escape the worst.
Sydney has a medium chance of rain later on Wednesday.
Similar conditions are expected in the ACT, although it has a very high chance of rain later on Wednesday.
There are minor flood warnings for many rivers, and it is also likely to be fairly cool across the island state.
Hobart is forecast to reach up to 17 degrees on Wednesday.
There is a strong wind warning in place for Tasmania’s far north-west coast, central north coast and east of Flinders Island.
More rain is forecast for Wednesday, particularly in SA’s west and north.
Adelaide will be cloudy on Wednesday, with a very high chance of showers.
Drier weather will return to most of Australia by the weekend as a broad area of high pressure develops over the continent.