A rare sudden stratospheric warming event is beginning to occur above Antarctica, and it may influence Australia’s weather in the coming weeks.


The term sudden stratospheric warming (SSW) refers to an abrupt increase in air temperature high above either of Earth’s polar regions, typically on the magnitude of tens of degrees Celsius in a few days. This warming occurs in a layer of the atmosphere called the stratosphere, roughly 30 to 40km above the surface.


While warming in the stratosphere does not immediately (or always) affect weather patterns near the ground, SSW events can filter down through the atmosphere and influence tropospheric weather in the weeks following the initial SSW.


If an SSW event does make its way down to the troposphere, it can cause the tropospheric polar vortex to weaken, which allows cold polar air to drift further away from Antarctica (or the Arctic if in the Northern Hemisphere) and spread towards the mid-latitudes.


Through this domino effect, SSW events can cause the Southern Annular Mode (SAM) to shift into a negative phase, which can have the following impacts in Australia during winter:



More cold fronts and low pressure systems over southern Australia

Increased rainfall and snow potential in southwest and southeast Australia

Reduced rainfall in parts of eastern Australia

Stronger winds in the southern half of Australia
https://www.weatherzone.com.au/news/sudden-stratospheric-warming-event-underway--heres-what-it-means-for-australian-weather/1889631