Heavy rain and storms expected in Australia’s south-east as severe weather warning issued for Tasmania

Bureau of Meteorology says thunderstorms could bring widespread rainfalls and flash flooding while there are ‘signs of El Niño development’

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Severe thunderstorms could bring heavy rainfall and flash flooding to eastern and south-eastern Australia in coming days, according to the weather bureau.

On Tuesday afternoon, the Bureau of Meteorology (BoM) said a low-pressure system over South Australia combined with moisture being pushed down the eastern seaboard from the tropics, would bring widespread rainfalls.

The forecast coincides with a separate update from the bureau saying there were now “signs of El Niño development” in the tropical Pacific. The system can increase the chance of hotter and warmer conditions, particularly in the Australian spring.

In the 24 hours to Tuesday afternoon, thunderstorms brought rainfalls of up to 60mm in New South Wales , 70mm in Tasmania, 20mm in Victoria and 40mm in south-east South Australia.

Meteorologist Ilana Cherny said severe weather warnings were in place for parts of eastern Tasmania on Wednesday and Thursday, and severe thunderstorms were predicted to hit the central west of NSW before extending south towards to Victoria on Thursday evening.

“In addition to heavy falls tomorrow, we could also see areas or storms with damaging winds and large hail through parts of southern Queensland,” Cherny said.

“And on Thursday, that area contracts to the east, focusing on south-east Queensland and parts of central and north-eastern New South Wales.”

Cherny said the low-pressure stream and moisture from the tropics were being enhanced by a trough through the upper levels of the atmosphere, which “is really bringing that enhanced rain activity”.

She said heavy falls in southern Queensland and northern NSW were predicted on Wednesday and Thursday.

“We also have this trough system developing through Tasmania, bringing that moisture and easterly flow and that risk of heavy falls.

The low-pressure system was expected to move offshore on Friday, “however, plenty of moisture will still be wrapping around that system, bringing that ongoing risk of heavy falls to coastal parts of New South Wales,” she said.

The eastern seaboard could expect accumulated totals of about 25-100mm through southern Queensland, with some of those heavier falls about the Darling Downs, 50-100mm through the NSW western slopes, falls of 100-150mm around parts of the NSW coast, and 50-100mm in eastern Tasmania, she said.

Meanwhile, there had been “substantial warming” in the central tropical Pacific region in recent weeks and all climate models reviewed by the bureau, including its own, forecasted sea surface temperatures reaching El Niño thresholds by winter.

The bureau said: “There remains some uncertainty in the likely strength of this El Niño event. Models indicate it will be at least moderate in strength, with the possibility of a strong event, based on the extent of warming in the central tropical Pacific.”

The bureau said the strength of the El Niño – assessed by the sea surface temperatures – would “not necessarily mean strong impacts on Australia’s climate” because there were other factors that influenced Australia’s weather.