It is winter in the Southern hemisphere, but that alone does not account for recent temperatures in Argentina, Chile, and across parts of other nations in the southern half of South America, being well below normal for extended periods this winter.
The German international public broadcaster Deutsche Welle (DW) explains that a weak
Antarctic polar vortex is responsible for multiple extended periods of below freezing temperatures, freezing ponds, and the deaths wildlife and livestock across a wide swath of southern South American. DW wrote:
When Patagonia was hit by a wave of unusual, extreme weather, it recorded temperatures as low as minus 15 degrees Celsius (five degrees Fahrenheit). It is winter in the Southern Hemisphere, but those temperatures were beyond normal.
Ducks froze to death in ponds, sheep were stuck in piles of snow, and military personnel transported food to affected areas for people and livestock.
“This is an unusual phenomenon,” said Raúl Cordero, a climatologist at the University of Santiago de Chile. But he added it was not the first of the season and “may not be the last.”
The low temperatures in Patagonia and the Southern Cone of Latin America (Argentina, Chile, Uruguay, Paraguay, and southern Brazil) are due to the arrival of cold air from Antarctica.
High pressure at the southern tip of the continent pulled polar air northwards. That happens when the polar vortex — a belt of strong winds that keeps cold air over the South Pole — is weak.
“The unusual weakness of the Antarctic polar vortex increases the likelihood of polar air masses escaping to inhabited areas in the southern hemisphere. In other words, the likelihood of cold waves increases,” said Cordero.
The sustained cold weather has kept ski runs open in Argentina and Chile even as blue skies have limited snow in recent weeks. Pre-season record setting snow is providing for a successful ski season.
Most Argentinian ski areas have enjoyed another dry, sunny week, except for more southerly latitudes, including the most southerly of them all, Cerro Castor in Tierra del Fuego province, which has seen some snow most days and temperatures remaining below freezing. Chapelco (115/330cm / 46/132”) continues to post the deepest snow in the world right now, while Catedral (50/140cm / 20/56”) near ski town Bariloche, the continent’s largest ski area by uplift, continues to report the most runs open at a single area in the world. … Most of Argentina’s ski areas have all or nearly all of their runs open, thanks to the huge pre-season snowfalls the country enjoyed.
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It has been a cold but largely dry and sunny week in the Chilean Andes. It’s been about a month since the heavy snowfall that saw Chilean centers start their season with as much snowfall as they get in an average season already fallen. Since then, it has been mostly dry. Temperatures have remained below freezing in the -4 to -12°C range on higher slopes, more like -5 to +5°C at base levels. Thanks to all that early snowfall, most of the country’s centers remain fully open or nearly so.
The dry period may be coming to and end with weather authorities forecasting snow for the southernmost Andes in Argentina and parts of Chile in the coming week. With temperatures remaining below freezing, the new snow will add to the existing deep base.