Key Takeaways:
- A record heatwave is sweeping across south-east Australia, with temperatures expected to reach up to 50 degrees Celsius in multiple states.
- The heatwave is expected to last for seven to eight consecutive days, making it the longest stretch of high temperatures in parts of New South Wales since the 1930s.
- Melbourne is expected to see its highest maximum temperature in 17 years, with a forecasted high of 45 degrees Celsius on Tuesday.
- The heatwave is driven by a stationary high-pressure system anchored above NSW, which is forcing hot air down towards the surface.
- Fire danger is expected to peak on Tuesday, with extreme danger ratings in 14 districts across southern Australia.
Introduction to the Heatwave
A record heatwave is currently sweeping across south-east Australia, with temperatures expected to reach extreme levels over the coming days. The heatwave is expected to peak on Tuesday, with temperatures forecasted to reach up to 50 degrees Celsius in multiple states. The longevity of the heatwave is also notable, with some areas expected to experience seven to eight consecutive days of temperatures above 40 degrees Celsius. This is the longest stretch of high temperatures in parts of New South Wales since the 1930s.
Record-Breaking Temperatures
The current heatwave has already driven temperatures up to 21 degrees Celsius above average, with some areas experiencing record-breaking highs. On Monday, temperatures reached 49.5 degrees Celsius in Ceduna, the hottest day on record for the town. Other areas, such as Wudinna and Trangie, also experienced their hottest days on record, with temperatures reaching 48.6 degrees Celsius and 47.3 degrees Celsius, respectively. The heatwave is expected to continue, with temperatures forecasted to reach even higher levels over the coming days. For example, Melbourne is expected to see its highest maximum temperature in 17 years, with a forecasted high of 45 degrees Celsius on Tuesday.
Causes of the Heatwave
So, what is behind the unprecedented heat this week? A glance at a basic weather map offers no explanation, as there is a weak surface trough over the south-east inland, which is a semi-permanent feature in summer. However, the actual cause of the record high temperatures is what is happening higher in the atmosphere. A stationary high-pressure system has anchored itself a few kilometers above NSW, and since winds blow away from high pressure, its elevated position is forcing air down towards the surface. This compression process leads to a rapid warming of the air mass by about 10 degrees Celsius per kilometer of descent, resulting in a dome of hot air over the surface.
Fire Danger and Weather Forecast
The fire danger is expected to peak on Tuesday, with extreme danger ratings in 14 districts across southern Australia. The fire threat will be enhanced by dry lightning and an approaching south-westerly wind change, due to reach the SA coast around lunchtime and western Victoria through Tuesday afternoon and evening. The fire danger will also be elevated by the hot weather and low humidity, with temperatures forecasted to reach up to 48 degrees Celsius in some areas. For the remainder of the week, lighter winds will lower the fire danger one level to the "high" range across most of south-east Australia, although extreme danger will return on Wednesday to a handful of SA districts along with the Wimmera.
Prolonged Heatwave
The heatwave is expected to linger, with cooler air from the south not eroding the heat dome until the weekend. This will lead to a prolonged run of 40-degree days across most of inland SA, northern Victoria, and western NSW. For many towns, the heatwave will deliver the longest stretch of 40-degree temperatures since the Black Summer. However, for the eastern Riverina, it is the longest in nearly a century. This includes Wagga Wagga and Albury, both on track for seven consecutive days at or above 40 degrees Celsius for the first time since 1939. The region of maximums in the high 40s will make an anti-clockwise rotation, traveling to north-west NSW on Wednesday, then to north-east SA on Thursday, and finally to western SA on Friday.
