Thunderstorms could affect parts of every Australian state except Western Australia in the next 24 hours with forecasters expecting a wet week for large parts of the country.
Only minor flooding is predicted, but the rain will keep catchments saturated ahead of a spring expected to see a third La Niña in a row, increasing the risk of above-average rainfall.
In Sydney, the rain gauge topped 2 metres for the year late on Friday making it the earliest date the 2,000mm mark has been reached since records started in 1858.
Dean Narramore, a senior forecaster at the Bureau of Meteorology, said on Monday a band of showers and storms was hitting many areas in the east, with a second rain band expected across central Australia on Wednesday.
But flood-affected areas along the Murrumbidgee River and in the New South Wales Riverina region may only get another 10 to 20mm of rain.
The heaviest falls were expected in southern Queensland and north-east NSW, with up to 50mm predicted between now and Saturday.
“All this rain is going to keep things wet and saturated as we head into spring,” Narramore said.
The main driver of the rainfall for the next two months will be the Indian Ocean Dipole (IOD), he said.
In its current negative phase, the IOD is characterised by warmer ocean waters closer to Australia’s north-west coast, making more moisture available for rain across the country.
Showers and #thunderstorms will develop across a broad stretch of eastern inland #Aus on Mon, moving east on Tue. Storms may tend severe in some areas 🌩️
— Bureau of Meteorology, Australia (@BOM_au) August 28, 2022
Rain across saturated catchments may cause renewed flooding.
Check latest forecasts and warnings: https://t.co/ZR4Tca9Vkv pic.twitter.com/RTJEnUtZvT
A La Niña was expected to return by spring – a pattern influenced by ocean temperatures in the Pacific – which increases the risk of above-average rainfall for northern and eastern parts of the the country in spring and summer.
Ben Domensino, a meteorologist with Weatherzone, said the thunderstorm outbreak would stretch from the NT to Tasmania, with a potential for super-cell storms bringing gusts above 120 kph and hail bigger than 5cm across.
He said the worst storms were likely to hit south-west Queensland, far western NSW and western Victoria.
#BREAKING - #Sydney has just surpassed 2,000 mm of rainfall so far this year. This is the city's first two-metre year since 1963, and by far its earliest date to exceed two metres in annual records dating back to 1859. pic.twitter.com/YNFIXvz4vb
— Ben Domensino (@Ben_Domensino) August 26, 2022
Domensino has been watching the 2022 year-to-date rainfall totals for Sydney’s Observatory Hill weather station. On Friday, the gauge topped two metres – the first time it has hit 2000mm since 1963.
Before this Friday’s rain, the earliest in a year the gauge had hit the 2 metre-mark mark was 19 October 1950 – a year that turned out to be Sydney’s wettest on record with 2,194mm.
But Domensino said as well as smashing the “earliest to two metres” record, only a further 185mm was now needed to break the wettest year on record. The annual average from September to December was 305.7mm.
“Even if we only get average rainfall, we will break that record comfortably. But with a La Niña-like pattern and a negative IOD, the outlook is for above average rain. We have a good chance to break that [rainfall] record.”
At the end of last week the bureau said for the next two weeks there was a high chance of above-average rainfall for most of the eastern half of the country with the only exceptions being western Tasmania and south-west WA.
Chances of “unusually high rainfall” – that is, a fortnight among the 20% wettest of the last 37 years – had also doubled for most of the NT, Queensland, NSW and northern Victoria.
