Extract from ABC News
Thunderstorms are expected to bring some relief from the heat to South Australia and Victoria. (Supplied: Troy Wilson)
The weather is heating up across Australia, both figuratively and literally.
South-east states are currently baking in temperatures up to 17 degrees above average, while a near nationwide outbreak of thunderstorms is brewing through the final days of spring.
For South Australia and Victoria, the thundery change will bring cool relief this weekend, however, the heatwave is set to linger across New South Wales into the middle of next week.
Ultimately, the rainband will win the battle, intensifying into a major thunderstorm outbreak through the week from the Top End, through the interior to southern Victoria, eventually spreading east to Queensland and NSW.
This broad spread of storms along with the slow-moving nature of the system will result in up to 100mm of rain across multiple states by next weekend, heralding a wet and stormy finish to 2024.
A wet end to spring as a solid soaking hits most of Australia, with pockets even seeing around 100mm through the next eight days. (ABC News)
Heatwave to shift east this weekend
The burst of late spring heat is due to a hot northerly airstream being squeezed south between a high-pressure system in the Tasman Sea and a trough of low pressure approaching from central Australia.
This set-up has already produced the hottest November temperatures in more than a decade across parts of south-east Australia, including maximums on Friday of:
- Melbourne 37C — hottest spring day in five years
- Mortlake 37.1C — hottest spring day in 12 years
- Warrnambool 36.9C — hottest spring day in 12 years
- Mount Gambier 37.7C — hottest spring weather in 42 years
Rain and cooler southerlies will start to filter through SA on Saturday, however, an even hotter day is predicted for Victoria and Tasmania as the northerly winds freshen.
Melbourne is again forecast to reach around 37C on Saturday, 15 above the city's November average and just 4C off an all-time spring record.
The combination of heat, winds to 35kph and dry air will also raise the fire danger to extreme levels in north-west Victoria before a cool south-westerly change arrives in the late afternoon and evening.
A tight temperature gradient on Saturday afternoon as a cool south-westerly change pushes through western Victoria. (ABC News)
Relief should reach Melbourne from about 4pm, leading to a temperature drop from the mid-30s to the mid-20s in about 60 minutes.
Typically, cool changes take around 24 hours to move from Melbourne to Sydney, however, the change will stall on Sunday and lead to a continuation of a heatwave across southern and central NSW into the new week.
Sydney's west is likely to reach the mid to high 30s until at least Wednesday, potentially even recording four consecutive days above 35C for the first time in spring in 15 years — enough to warrant a low-intensity heatwave warning.
A slightly milder north-easterly breeze off the Tasman (not quite a classic sea breeze) will keep Sydney's east closer to about 30C over the coming days, peaking at 32C in the CBD on Tuesday —the hottest day in at least eight months
Away from the coast, a severe heatwave warning is in force for south-east NSW where temperatures will climb about 10 degrees above average for up to four days.
A low-intensity to severe heatwave is forecast to continue into early next week across south-east and central-east NSW. (ABC News)
So, when will NSW finally cool down?
Modelling is currently showing a wide variety of scenarios of when cooler weather will arrive in eastern NSW, with a range from Thursday to even as far out as next Sunday.
Thundery finish to spring brings nationwide soaking
The trough responsible for the cool change is also generating a band of thundery rain as tropical moisture feeds south across the nation
Earlier this week, the system brought near-record falls to Western Australia, including 65mm at Kalgoorlie, about four times their monthly average.
A separate weather system has also brought a deluge to Queensland, which included up to 170mm on the Gold Coast in 24 hours to 9am Friday.
The rainband from the west will gradually work its way east through SA, Victoria, and central Australia this weekend before stalling and bringing additional stormy days in a broad band from Darwin to southern Victoria through Monday and Tuesday.
A band of rain and storms will edge east across central and eastern Australia this week.
Through the next four days, most of the Northern Territory, SA, Victoria and far western NSW can expect about 10 to 30mm, with a few pockets closer to 50mm.
The trough is then likely to deepen into a full-blown low-pressure system by Wednesday — and with a continued influx of humid air from the north will result in more intense rain and storms, which will eventually spread east through Queensland and NSW by the end of the week.
The outcome of this sustained soaking is the majority of Australia will see significant rainfall at some point through the next eight days with multiple areas across several states likely to receive close to 100mm.
Severe thunderstorms are also likely, particularly from Tuesday onwards once the low begins forming, and the main threat appears to flash-flooding due to the abundant atmospheric moisture streaming in from the tropics.
November rain a taste of a stormy December
The pendulum has clearly swung to favour a wet December across most of Australia due to numerous wet climate drivers. (ABC News)
The thundery finish to spring is not just random weather variability, but rather, is a likely indication of the probable prevailing weather patterns through December.
This outlook for above-average rain is thanks to numerous climate drivers swinging to a wet phase including, a positive SAM, a negative IOD, near-record high global sea temperatures and pulse of the MJO.
The latest monthly forecast from the Bureau Of Meteorology shows all regions of Australia apart from western Tasmania are likely to see above-median rain next month, including a greater than 70 per cent risk in many parts of WA, the northern tropics and eastern inland.
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