After facing record heat and torrential rains in December, Alaska suffers a series of particularly violent winter storms: wind and ice crippled this US state this week. In question, fluctuations in Jet Stream over the American continent.
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Winds at 146 km / h swept through the Anchorage area last weekend, accompanied by a temperature of -18 ° C. Small planes and trucks were overturned by the power of the storm and 13,000 residents were deprived of electricity. If theAlaska is used to extreme cold, these last weeks have been marked by a succession of phenomena weather report unusual.
An unprecedented series of extreme weather events
In many cities, December 25, 2021 was Christmas Day the sweetest on record, but also the wettest, with 50mm of water recorded that day over Fairbanks. On December 26, Alaska experienced its hottest day on record, nationally this time, in December: 19.4 ° C on Kodiak Island, while the average at this time of year is 3 ° C in the afternoon. In Anchorage, the mercury rose to 15.5 ° C, against an average of -5 ° C at the end of December! A few hours after this record, torrential rains hit the interior of the country. It had never rained so much in such a short time since 1937, leaving many roads flooded. A sudden arrival ofair Cold then hit the country, leading to a historic ice storm. In western Alaska, this ice deprived residents of several cities of drinking water for nearly a week.
While the alaskan climate is generally very cold in winter (from -20 to -40 ° C), but also very dry, at the end of last December and the beginning of January were marked by exceptionally humid weather. If the low temperatures recorded in recent days are classic, the strong wind and humidity are less, leading to several “ice storms”, called “Icemageddon” by the Americans, contraction of ” ice »(Ice cream) and the apocalyptic film Armageddon. This succession of extreme weather events, storms, heat record, torrential rains, ice, is unprecedented since the start of the weather readings according to the Alaska Department of Transportation.
Also, once the ice settles on the road, it is very difficult to remove it. Even though temperatures are rising in Fairbanks, the second largest city in the country, the temperature of the roads remains below -18 ° C. According to Alaska Center for Climate Assessment, the ice could get stuck on the roads until March or April.
Abrupt weather changes caused by the Jet Stream
Fluctuations in the Jet current are at the origin of these abrupt changes in the weather over North America: by forming a very marked “ridge” further north than usual, the Jet Stream let soft, humid air come from Hawaii over Alaska. It was this almost tropical upwelling of air that brought the unusual heat of December and the torrential rains to Alaska. Which were followed by a sudden return to a more classic cold, freezing the humidity in place. the Jet Stream works like a ribbon, which separates cold air from hot air and its fluctuations are normal. However, in winter it usually affects Alaska very little, and has more of an impact in spring, making this totally unusual winter situation.
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