By Tom Saunders
On Tuesday temperatures soared to 47C in some parts of Western Australia. Photo: 123 RF
Parts of NSW are facing the hottest temperatures in four years this week as a severe heatwave engulfs central and eastern Australia.
The extreme heat was building across WA last week and is now moving east, bringing the hottest weather in five years to south western South Australia on Tuesday, when maximums soared to 47 degrees.
A north-westerly airstream will spread the hot air across NSW during the next three days, sending both minimum and maximum temperatures up to 12C above average and triggering a heatwave warning for much of the state.
The heatwave is rated as 'severe' for areas north from the Illawarra, an indication the high temperatures could be dangerous to vulnerable groups.
It's even rated as 'extreme' around the lower Mid North Coast, which signals potentially dangerous heat for all groups.
According to NSW Health, groups at risk include babies and young children, pregnant women, people over 65 years old, people who work outside, live alone or are socially isolated, who are homeless or have certain medical conditions.
Temperatures to peak in the high 40s
Hot air is already spreading across inland NSW today, although an onshore breeze will temper conditions along the coastal fringe.
The heat will intensify further on Thursday, leading to maximums in the mid to high forties in the state's far west - the hottest weather anywhere in NSW since 48C was recorded in Walgett in December 2020.
Some modelling even indicates the potential temperatures will spike at around 48 or 49 degrees right near the SA border, just shy of the state's all-time record of 50.1C in Wilcannia way back in January 1939.
While western NSW is baking through near record high temperatures, the hot north-westerly winds will also spread near 40-degree heat to parts of the east through Thursday and Friday.
For several regions around the state, the mid-summer scorcher will bring the hottest day in four years, including:
| Location | Temperature | Day |
|---|---|---|
| Armidale | 35C | Thursday |
| Broken Hill | 44C | Wednesday |
| Ivanhoe | 45C | Wednesday/Thursday |
| Maitland | 42C | Friday |
| Tamworth | 40C | Thursday |
| Taree | 40C | Friday |
| Tibooburra | 47C | Thursday |
| Wilcannia | 47C | Thursday |
Sydney to sweat through warmest night in four years
Most of Sydney is forecast to reach from 35 to 37C on Thursday afternoon, as much as nine above average for January but well below the 40-degree heat observed in early December.
While Thursday's heat won't break any records, the most uncomfortable weather for Sydneysiders should arrive on Friday when the city wakes to a muggy minimum of 25C - the warmest night since late 2020.
A second consecutive maximum in the mid to high 30s will follow on Friday before a cool and thundery southerly change reaches Sydney in the afternoon.
Sydney's heatwave continues an exceptionally warm and humid summer, which has produced an average daytime high of 28C in the CBD, more than two above the long-term average and less than one degree off the December-January record.
Tropical low's enhancing south-east heatwave
One notable feature of the current heatwave is its simultaneous occurrence during an active phase of the monsoon over northern Australia, a common pattern as tropical lows can fuel heatwaves further south.
The heat from a tropical low or cyclone does not blow directly to southern states near ground level, but rather is transported vertically above a tropical system, then moves pole-ward at around 10 kilometres above the surface and eventually sinks back to the surface over the mid latitudes.
Initially, the rising air over the tropics cools and condenses, leading to the thick cloud and heavy rain commonly associated with tropical weather systems, however, by the time the air reaches central and southern Australia it has dried out.
This disparity in moisture levels is what intensifies heatwaves as dry air warms up faster on descent towards the surface relative to the rate the original air-mass cooled during ascent.
When will the heatwave end?
A southerly change will arrive in the south of NSW on Friday, reaching Sydney sometime in the afternoon.
The cool southerly will then sweep through northern NSW on Saturday and, along with an increase in cloud and rain, will help drop temperatures back to average in most regions by Sunday.
- This story was first published by the ABC