Why it feels colder than it actually is: Antarctic polar vortex engulfs Melbourne

Suburbs across Melbourne recorded “feel-like” temperatures well into the negatives on Thursday morning, with experts blaming a “destabilised” Antarctic weather pattern for the icy conditions.

A cold fog blankets Melbourne as a polar vortex encircles Victoria. Picture: David Crosling

Melburnians woke to icy conditions on Thursday morning, with many suburbs across the city recording “feel-like” temperatures well into the negatives.

Melbourne’s Olympic Park recorded a low of 1.1C at 7am. But temperatures felt a lot icier than they actually were at -2.4C.

Moorabbin Airport plummeted to -1.2C at 7am, with a feel-like temperature of -3.4C. Melbourne Airport also dropped to 0.8C overnight, with an apparent temperature of -4.5C.

In the city’s northeast, Viewbank recorded -0.8C about 4am, with an apparent temperature of -4.2C.

#Melbourne's satellite today shows a unique clockwise circulation known as the Spillane eddy (or Melbourne eddy) that kept the temperature below 8 °C at 2pm. More: https://t.co/jlOoTZLz8dpic.twitter.com/GweMqM7L3m

— Bureau of Meteorology, Australia (@BOM_au) July 31, 2024

Senior meteorologist from the Bureau of Meteorology Michael Efron said Thursday’s overnight low was just above the coldest morning of the year – on July 3 when Melbourne dropped to 1C.

“A lot of the city felt like it was below 0C – so a very chilly morning. We had some fog patches in the morning but that cleared as the day progressed,” he said.

“It’s turned into a very sunny and settled afternoon, and despite it being only 13 to 14C, it feels warmer in the sun.

“When the winds are light, apparent temperatures don’t vary too much, but like in the case of tomorrow (Friday), it will feel a lot cooler because there will be greater winds.”

Mr Efron said Thursday’s overnight low was just above the coldest morning of the year. Picture: Nicki Connolly

The colder weather has also been brought on by a destabilised polar vortex.

The polar vortex is a circular weather pattern that sits above Antarctica, which usually keeps a ring of icy weather contained to the continent.

But when warmer than average air temperatures creep above Antarctica – as has been observed this year – the vortex weakens and loses stability.

This causes the edges of the circular pattern to push into southern Australia, bringing with it cold conditions and winds.

The colder weather has also been brought on by a destabilised polar vortex. Picture: Luis Enrique Ascui

Mr Efron said the destabilised polar vortex has also resulted in unsettled weather in Western Australia.

“It has altered the short term weather patterns over the southern hemisphere. But it’s not the same pattern everywhere,” he said.

“Western Australia has been really wet – they recorded 170mm in July.”

He said a slow-moving high-pressure system over Tasmania was extending a high-pressure ridge over Victoria, leaving the state with clear skies and light winds overnight.

“With a lack of cloud cover, it’s allowed those temperatures to drop overnight,” he said.

Melbourne will drop to a low of 5C on Friday, reaching a top of 15C.

Every day from Friday to Wednesday is forecasted to reach 15C, with partly cloudy conditions.

The weekend will see showers of up to 4mm and 2mm on Saturday and Sunday respectively.