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weather forecast. Frost USA and Canada, an exceptional event in the era of climate change «3B Meteo

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Severe frost at Christmas for North America

A severe frost has begun to affect North America. Extremely cold air coming in from Siberia already includes Canada with values ​​reaching -52°C between the Yukon and Northwest Territories, above -40°C in Montana. Temperatures are lower than in Siberia as values ​​begin to move above the multi-day average. But the frost will soon spread across most of the United States to include unusually temperate regions like Mexico, Cuba and the Bahamas. Likely historic, according to Ecmwf’s Highest Expectations Index, The Arctic is separating in Canada and in large areas of the United States, so much so that it could break thermal records in the past 10 to 30 years. The cold will also be “very cold” in those usual areas at very low temperatures. The simulations show how temperature values ​​can be 20–25 °C below the typical mean for the period.

Maximum temperatures expected in many regions according to Ecmwf's EFI standard
Maximum temperatures expected in many regions according to Ecmwf’s EFI standard

In addition to the strength of the freezing outage, the wave of bad weather is also accentuated by weather parameters outside of climatology such as minimum low pressure

Minimum pressure outside the statistical range
Minimum pressure outside the statistical range

Using the HYSPLIT model, it can be seen that the air mass comes first from eastern Siberia, Where the coldest December was recorded in the last 38 years, then from the North Pole.

Siberian origin of the air mass - Source Noaa Hysplit
Siberian origin of the air mass – Source Noaa Hysplit

Why does that happen? The formation of an anti-eddy bridge between Alaska and Siberia causes a lobe of the tropospheric polar vortex to sink. However, despite the presence of non-canonical dynamics, this situation could be affected by the elongation of the stratospheric polar vortex after the wave reversal event. Therefore, stratospheric inversion events are relevant from the perspective of tropospheric predictability.

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stratospheric polar vortex
stratospheric polar vortex

The episode is set in the context of unusual weather events with potentially dangerous effects. So millions of people will be affected by this freezing and potential negative entry which is comparable in severity to the February 2021 episode. More than 50 million people are being alerted to the physical discomfort caused by the effects of freezing winds. Although it is still a topic under discussion, in a study published in the journal Science It shows how events like extreme cold snaps like those that occurred now or in February 2021 may actually become more likely with global warming: the Arctic is warming faster than any other region at a rate more than twice the global average. However, it must be said that the Arctic swell does not cause colder North American winters, after all the winter warming trend is increasing. However, warming in the Arctic is associated with extreme cold spells like these.

Thermal trend for American winters
Thermal trend for American winters

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