New Zealand Local Weather Forum
Weather Discussion => International => Topic started by: Mark on July 21, 2024, 09:39:39 AM
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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
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Stratospheric warming above Antarctica is expected to persist into August. This warming event could have significant atmospheric implications, particularly influencing the Southern Annular Mode (SAM).
The SAM is a climate driver for the north-south movement of the westerly wind belt that circles Antarctica. It influences weather patterns in the Southern Hemisphere, particularly in Australia, New Zealand, and parts of South America, and oscillates between positive and negative phases.
https://electroverse.substack.com/p/bc-wineries-get-support-after-devastating