Storm damage at Kiama. Image supplied by SES NSW.
The wet and wild weather that caused flooding in much of eastern NSW is likely to continue for much of this week.
Communities from Kempsey in the state's north to eastern suburbs of Sydney and Kiama south of Wollongong are assessing damage from heavy rain and strong wind over the weekend.
The Bureau of Meteorology is considering sending severe weather experts to several areas, including Kiama, where many houses were damaged.
Experts debate whether the Kiama event was a tornado or a downburst from a thunderstorm. Josh Fisher, head meteorologist at Weatherzone, said the storm had the characteristics of a tornado from the radar observations: “It was a rotating storm over Kiama.”
Mohammed Nabi, severe weather forecaster at the weather bureau, though, said the straight-line nature of the event suggested it was a thunderstorm downburst. More investigation will be needed to be sure, he said.
Warragamba spills
The north-east corner of the state can expect 25-50mm of rain today, potentially complicating recovery efforts for some towns.
The Weather Bureau and State Emergency Service expect the heavily populated Nepean-Hawkesbury valley to Sydney's north and west will face minor flooding later today, in part because the giant Warragamba Dam has hit capacity and is automatically releasing water.
A spokeswoman for the Sydney Catchment Authority said the dam, which has spilled 53 times in its 53 years, will continue releasing water for several days. The dam's water total increased 6 per cent in the past week alone.
“When the water continues to rise 80mm above its full storage level, the central drum gates on the dam automatically open to let that floodwater through,” she said.
“If the water continues to rise to 230mm above that fall storage, (four) side radial gates start to open.”
The side radial gates were last open on February. The NSW government is reviewing flood risks for the Nepean-Hawkesbury valley and whether it should alter the dam's operating procedures to give it the power to release water earlier when flood risks intensify.
The rainfall outlook suggests inflows into the Warragamba will continue to be high for days to come.
“For the next days, we are going to see thunderstorms over parts of western Sydney,” Weatherzone's Mr Fisher said.
“These thunderstorms could impact the Warragamba Dam and the flows into that.
“There is the potential for another significant band of rain to move through on Thursday.”
Insurers
Despite the widespread floods hitting towns including Kempsey, insurers are yet to declare the event a catastrophe based on current claims.
The industry has already declared catastrophes for floods three weeks ago stretching from central Queensland to the mid-NSW coast, and bushfires in Tasmania and NSW, with total claims approaching the $1 billion mark for summer.
Yarras, west of Port Macquarie, had the highest rainfall during the past week. It recorded 415mm in the 24 hours to 9am on Saturday, breaking a daily record for the area that had stood for 64 years, the bureau said.
Weatherzone is owned by Fairfax Media, publisher of this website.
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