Weather bureau says torrential downpours expected along coast between Sydney and Wollongong for six to 12 hours

This article is more than 1 year old

This article is more than 1 year old

Swathes of coastal New South Wales will likely be deluged with more than a month’s worth of rainfall in less than a day, with the State Emergency Service preparing to mobilise thousands of volunteers and police warning commuters to stay off the roads.

The Bureau of Meteorology has warned of possible flash flooding amid torrential downpours in an intense six to 12-hour burst expected to hit along the coast between Sydney and Wollongong on Wednesday.

On Tuesday, the bureau’s severe weather forecaster, Simon Louis, told reporters in Sydney that a low-pressure system expected to develop over western NSW today would hit the coast “somewhere between Sydney and Wollongong” early on Wednesday.

He said “quite heavy and intense rainfall” – potentially as much as 200mm in some locations – would begin falling early on Wednesday, “potentially sometime around the morning commute”.

The low-pressure system is expected to move off the coast “fairly quickly” but would be replaced by strong southerly winds in the afternoon, with gusts of damaging winds, averaging 60km/h to 70km/h likely along the coast.

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Louis said there was “still some uncertainty” about where the heaviest falls would occur but warned of the potential for flash flooding for the Nepean, Hawkesbury and Georges rivers.

The State Emergency Service deputy commissioner, Scott Hanckel, warned that some communities – particularly around the Nepean – could experience “short-term isolation” as a result of the rain.

He said the morning and afternoon commutes would be “particularly dangerous”.

“As families try to get to work, drop kids off, pick kids up, things are going to get really problematic,” he said. “Businesses need to expect people to be late both getting in or getting home.”

He said the SES was working to have most of its 3,000 Sydney-based volunteers available.

“Last weekend with a relatively small wind event we had well over 1,000 requests for assistance,” he said.

The bureau had earlier forecast that Sydney could see up to 50mm of rainfall over a two-day period beginning on Wednesday, but on Tuesday that prediction was updated to between 50mm and 100mm in some areas, and as much as between 150mm and 200mm for the areas worst hit.

Chief Inspector Phillip Brooks from the NSW police urged people to consider not driving on Wednesday.

“With severe rain predicted tomorrow after what has been very warm weather, roads will become slippery and unpredictable,” he said. “We’re asking all road users to perhaps reconsider the need to be on the roads throughout what will be a severe rain event.”