Meteorologists describe the storms as “dangerous and ferocious” that will hit eastern states this weekend, bringing damaging winds and flash flooding.
There is also a high risk of supercell thunderstorms in western New South Wales, which Sky Weather metrologist Alison Osborne warned, “that means tornadoes”.
The worst weather will be Sunday afternoon, with widespread storms from Tasmania to Queensland. The heaviest falls and strongest storms will occur in New South Wales.
“This is not good news at all for already flooded areas, as destructive winds in soggy soils will make trees more likely to topple and cause flash floods, which will spill into already swollen rivers,” said Ms Osborne.
The pink arrows superimposed over the purple areas on the map below indicate the high risk of thunderstorms and supercell tornadoes.
‘It will be a dangerous day with rain accumulations totaling around 50-100mm between Friday and Sunday,’ Ms Osborne warned.
The heaviest falls are predicted for the central ranges of NSW which extend to northern Victoria.
“That means some of this very heavy rain will flow into rivers like the Murrumbidgee and the Murray,” she said.
Up to 50mm of rain is forecast for Canberra on Sunday. In Albury and Wodonga, up to 60mm is expected.
There are warnings for widespread minor to moderate flooding in Victoria and minor to major flooding in New South Wales.
The Bureau of Meteorology warned on Sunday of possible “life-threatening flash floods” in the NSW interior as rivers rise.
It issued a flood watch on Friday afternoon for parts of the NSW North West, Central West and South West inland rivers.
“A trough is approaching New South Wales from the west and will move across the state on Friday and Saturday, bringing a return to unstable conditions,” the alert said.
“A cold front is then expected to combine with this trough on Sunday and Monday to generate enhanced areas of rain and thunderstorms in parts of the state.
“Moderate to locally heavy rain and severe thunderstorms are forecast for Sunday and Monday.
“This rainfall could cause further minor to major flooding along rivers in parts of the mid-west and south-west inland catchments of New South Wales from Sunday, and in parts of the catchments interiors of the northwest as of Monday, many of which are experiencing continued flooding due to previous rainfall. These last months.”
The Bureau of Meteorology has also issued a flood watch for northern Victoria and parts of southern Victoria.
“For Sunday, widespread totals of 10-20mm are expected, with 20-50mm for the central and eastern ranges, possibly the southwest and Gippsland. Widespread totals of 40-70mm are forecast for the Northeastern Ranges, with isolated totals of 80-100mm with thunderstorms,” this alert said.
Extreme rains intensify in Sydney
New research was published on Friday analyzing extreme rainfall in Sydney over 20 years.
He found that sudden heavy downpours – “rain squalls” – in the city had increased by 40% during this period.
A quick burst of rain is a short period of extreme rain and increases the likelihood and severity of flash floods.
Professor Jason Evans, co-author of the study at UNSW Sydney, warned of big implications.
“If this trend continues in Sydney, the city needs to be better prepared for quick bursts of rain and flash flooding in the future,” he said.
“This should be factored into our urban planning with buildings, roads and communities having to prepare for the likelihood of faster bursts of rain to test the short-term capacity of our drainage, roads and plains. floodable.”
Professor Evans said The Sydney Morning Herald the amount of rain falling during these rain gusts was now typically between 7mm and 20mm in 10 minutes, whereas 20 years ago it was 4mm to 15mm.