Dozens of Australian heat records were smashed over the weekend, as the Bureau of Meteorology forecasts a warmer than average autumn ahead.
Miriam Bradbury, a senior meteorologist at the weather bureau, said many locations in New South Wales recorded their hottest March day ever on Sunday.
“We saw dozens of temperature records broken,” she said.
On Saturday, records were set at various locations in South Australia, as well in Mildura in Victoria, Bradbury said. “But [on Sunday] the heat really contracted into New South Wales.”
Bradbury noted that top temperatures reached about 44C in parts of the south-eastern states. Records set included:
NSW: Wagga Wagga (39.9C), Dubbo (39.6C), Goulburn (37.6C)
Victoria: Mildura (42.5C)
South Australia: Roxby Downs (43.3C), Leigh Creek (42.3C)
Canberra hit 37.4C on Sunday, its hottest March day in 25 years, and 0.1C off the March record of 37.5C.
Sydney’s March daily high temperatures are averaging higher this year (29.1C) than the historical March mean (24.8C), but Bradbury said no individual temperature records had been set in the city.
“Towards the south-west suburbs, we did have a couple of late-season maximum temperature observations for certain stations,” she said. “Basically it means this is the latest we’ve ever seen it this hot. But it’s not a record either annually or for the month.”
Bradbury said the hot weather arose from a combination of a high pressure system across Australia’s south-east, and a trough that extended from the Kimberley region in Western Australia towards the south-east of the country, which deepened during the week.
“A lot of heat that was sitting over central parts of the country, even over parts of Western Australia, started to shift eastward and southward,” she said.
Bradbury predicted there would be a reprieve for the south-eastern states over the next fortnight, with slightly below average temperatures forecast.
“But if we look further ahead, on a one-to-three-month basis, we do see that trending the opposite direction,” she said. “We’re more likely to see warmer than average conditions as we move through that April-to-June period.
“The impact of climate change in general is a warming trend,” Bradbury said. “But on a month-to-month or even week-to-week basis, we do see this natural variation in the temperatures across the whole country.”
Historic late-season heat in NSW today, with temperatures up to 14ºC above average and these places enduring their hottest March day on record (old record in brackets):
— Ben Domensino (@Ben_Domensino) March 19, 2023
- West Wyalong 42.2ºC (40.6)
- Mudgee 38.3ºC (37.2)
- Goulburn 37.6ºC (36.9)
- Mount Boyce 34.2ºC (32.5) pic.twitter.com/N5i2w0WSiG
Joel Pippard, a meteorologist at Weatherzone, said the late blast of heat was largely driven by a negative swing in a climate driver called the southern annular mode (Sam), which refers to the north-south movement of the strong westerly winds.
“In a positive phase, cold fronts contract closer to the south pole and provide more high pressure near Australia, and during a negative phase, cold fronts more regularly cross southern Australia,” Pippard said in a statement.
“For the entirety of 2022, the Sam was in a predominantly positive phase, leading to more high pressure and increased easterly winds over the nation’s east coast.”
Pippard said the Sam had recently swung to a strong negative phase, which, during summer and early autumn, could mean “more cold fronts crossing Australia, but with less cold air in them”.
“For the eastern states, the increased frontal activity causes westerly winds to become more common, allowing hot, dry desert air from the interior to blow across the region.
“The good news for the eastern states is that the Sam is starting to move back to a neutral phase, meaning temperatures will start to return to normal over the next few weeks.”
But Pippar said with the the strength of El Niño forecast to build, a more persistent negative Sam might return later in the year.
The bureau noted last week that the Pacific Ocean La Niña had officially ended, and said there was a 50% chance an El Niño would develop in 2023.
