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Heatwave update: Where and when is the heat expected to hit and what records could fall?

Kate Doyle, Monday December 16, 2019 - 18:31 EDT
ABC image
The heat that has been baking Perth over the last few days is making it's way east. - ABC

Heatwave conditions will see much of the continent swelter this week, with records set to tumble.

Western Australia is just starting to get a little relief, but South Australia is next to feel the heat as a hot air mass moves slowly east — dragging the bushfire danger up with it.

A delayed monsoon and widespread drought means heat has been brewing over central Australia.

That heat has been making its presence felt over WA in recent days and is heading east as the week continues.

Who is in the firing line?

today, but it hit 41.2C at 1:40pm (AEST).

That equals the December record from 1981, but the annual record of 41.7C from February 2004 still stands ... for now.

It is the result of north-easterly winds associated with a trough to the east of the high bringing the heat to the centre and south.

Brisbane, south-east Queensland and northern New South Wales, will likely see relief this evening as the trough moves over, bringing cooler south-westerly winds.

Adelaide is forecast to be 40C and above from Tuesday, with temperatures peaking on Friday at 44C.

The highest temperature recorded at Adelaide (West Terrace) was 46.6C on January 24 this year.

Its hottest December day on record is 44.2C, recorded on December 31, 1904.

Widespread temperatures above 40C are expected in SA over the next few days, as well as for large parts of inland NSW, Victoria and Queensland later in the week.

Hot air in Canberra

Temperatures in Canberra are forecast for the high 30s and low 40s from Wednesday and into Saturday, which is tipped to reach 43C.

This would blitz the record of 41.6C measured at Canberra Airport's new weather station multiple times in 2017 as well as in January this year.

The highest temperature recorded at the airport's old comparison weather station (which closed in 2010) was 42.2C in 1968.

It is a similar story in surrounding areas.

For northern Australia, Darwin is expected to reach up to 36C with the chance of a storm for the rest of the week, while Alice Springs should peak on Thursday at 45C.

So far, it is looking like the south-east coast could avoid the worst of the prolonged heatwave conditions, although it will still be hot.

Melbourne is headed for a rollercoaster week — Wednesday should hit 39C before a cool change brings 23C on Thursday, then back up to 41C on Friday, before again dropping to the mid-20s on Saturday.

The peak day for NSW Saturday is expected to be the peak day.

According to BOM meteorologist Sarah Scully, the top temperatures for parts of Sydney will differ because of their proximity to a sea breeze.

In the west, Penrith is forecast to reach 46C on Saturday while Bondi on the coast is only expected to get to 29C.

What other records could go?

Perth just broke its , both in total and consecutive, recording 40.1C on Friday, 41.0C on Saturday, 40.9C on Sunday and 41.6C on December 3.

The big record in peril this week could be Australia's hottest day on record, calculated by averaging temperatures across the country.

The current record is 40.3C, recorded on January 7, 2013.

Blair Trewin, senior climatologist at the BOM, said it was looking like we would be at least a degree above this on Wednesday and Thursday.

There has been the suggestion that Australia's hottest recorded daytime temperature — 50.7C at Oodnadatta, SA on January 2, 1960 — could be in danger during this heat event.

But at the time of writing, none of the likely locations are forecast to reach this in the current seven-day forecast.

Instead, it is forecast to reach 47C in Oodnadatta for Wednesday, Thursday and Friday — not exactly pleasant, and summer still has a long, long, way to go.

Dr Trewin also noted that it wasn't just places around the ACT that could break overall records.

There are also opportunities for record highs on the Nullarbor on Thursday and from the Eyre Peninsular to north-west Victoria on Friday.

Heading towards our hottest year

The January-to-November mean temperature for Australia was its second highest on record.

A normal December would see us finishing the year at second highest on record, just below 2013, the current hottest year.

But an above-average December has the potential to push us over the line into the top ranking.

January to November was also the second driest on record for Australia.

It is hot, but what makes it a heatwave?

The Bureau of Meteorology defines a heatwave as "three days or more of high maximum and minimum temperatures that is unusual for that location".

It takes into account both overnight and daytime temperatures, as well as what the weather has been like in the lead-up so a heatwave is truly "unusually" hot for that location at that time of year.

John Nairn, the BOM's national heatwave project director, describes heatwave severity levels using a cricket analogy:
During a low-intensity heatwave, the whole family can be out playing and enjoying the sun, grandparents included, providing you take normal conditions like drinks and hats;
When it becomes severe, it is not a good idea for the grandparents to be outside;
When you get to an extreme heatwave, why are you even playing cricket?

Heatwaves may not appear extreme, but they are Australia's deadliest natural disaster, claiming more lives than bushfires, cyclones and floods put together.

This week is likely to be record-breaking, but it is unlikely to be the end.

Until there is widespread rain, the heatwave and fire conditions will continue — this is the time to check in on your granny and keep the kids in the shade.


© ABC 2019

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