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The Southern Annular Mode (SAM) is one of the “main mechanisms influencing our climate” and meteorologists say it’s just reached one of its strongest positive levels on record.
An index that measures the north-south displacement of the westerly winds that flow between Australia and Antarctica, SAM carries the “cold fronts and low pressure systems that bring seasonal rain, snow and wind to southern Australia”.
When the SAM is in a positive phase – as it is now – the belt of circumpolar westerly winds seeps away from Antarctica and heads towards Australia, meaning rain and snow-bearing cold fronts and easterly winds are set to increase over the nation’s east.
“This typically reduces rainfall and snowfall over parts of southern Australia and allows more rain to fall in parts of Queensland and New South Wales,” Weatherzone said.
“There has been an observed trend towards more positive phases of the SAM in recent decades.
“So, while this week’s strong positive phase may be short-lived, we may see more positive swings of the SAM in the coming weeks and months.”
The announcement comes as the Bureau of Meteorology issued severe weather warnings up and down the eastern seaboard for intense marine winds.
Residents in Queensland, New South Wales, the ACT, Victoria and Tasmania have all been put on alert over the winds, which are forecast to be particularly strong in coastal areas.
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Meanwhile, our Kiwi neighbours are set to cop a battering headed into the weekend, with “several days of severe weather about to lash parts of New Zealand as a powerful low pressure system, and associated front, barrel across the country between Thursday and Saturday.”
“A low pressure system that formed near southeast Queensland earlier this week is expected to gain strength as it crosses the Tasman Sea on Wednesday and Thursday,” Weatherzone said.
“Prior to the arrival of this dangerous weather system, a slow-moving low pressure trough will cause heavy rain and snow over parts of the South Island on Wednesday into Thursday.
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“This South Island soaking will be followed by several days of severe weather in New Zealand’s North Island and parts of the South Island.”
Back on home soil, Sydney’s metro will reach a chilly top of 16 degrees today, with lows of just seven, while in Melbourne it’s expected to reach just 13 degrees today with lows of seven.
In Brisbane city, a pleasant 22 degrees is expected, in both Adelaide and Canberra, it’ll be just 14 today, while in Perth, residents will enjoy a balmy 26 degrees with lows of 12.
