With wind chill temperatures as low as -45 degrees Celsius, North America shivers towards Christmas. Many Americans filmed themselves throwing boiling water into the air on Friday. Within a second of leaving the pan, the drops had already solidified into ice.
Extreme cold covers almost the entire region between the Rocky Mountains in the west and the Appalachians in the east. Even states with normally temperate climates like Florida, Louisiana and Alabama were hit hard over the weekend. The NWS weather agency concluded Saturday that storms are slowly winding down in the southern United States, although Americans there are looking forward to their coldest Christmas Eve in decades.
In North American states and Canada, the problems are severe. The New York Times He writes that people in the city of Buffalo (on Lake Erie near Niagara Falls) were unable to leave their homes after another night of heavy snow. Thousands of homes in Nashville are without power. Meanwhile, every Canadian province has issued a safety alert.
The weather has resulted in flooding, power outages and difficult access to roads and runways in recent days. 12 people died in road accidents. On Friday, there was a major accident in the state of Ohio in which fifty vehicles overturned. Two people on the motorcycle have died.
Nearly 1,400 flights departing or arriving in the US were canceled on Saturday morning, following 6,000 canceled flights on Friday. Many affected travelers will have to celebrate Christmas without their families.
According to Peter Siegmond, a climatologist at the Royal Netherlands Meteorological Institute (KNMI), the current weather in the US is the result of a so-called ‘depression’: a low-pressure system that rises in the border region with polar cold from the north and warm air from the north. Subtropics.
Why does the collision between these air types cause such a violent reaction?
Siegmund: ‘Because warm air is light and cold air is heavy. Imagine a container of water and oil, with a shot in between. When you take that shot, the heavy water settles under the light oil and the fluids begin to move. The same thing happens in the creation of wind.
Due to temperature differences, pressure differences are created, and thus wind speed increases with height. If the wind speed is high, the air becomes unstable and a depression is formed.
“Every winter there are lows. In fact, they are a stirring scoop of the atmosphere. Once temperature differences become too large, they rise to compensate. A large low pressure system is now forming over northeastern Canada, and its western side is pushing deep into the southern United States with cold air.
So why isn’t America this cold every year?
Because the location of depression varies. If the collision of warm and cold air takes place in Newfoundland, the depression in Europe is headed our way. We are lucky that the wind comes from the sea. In North America, air now moves over land, where it is cooler. It also cools the air.’
“It’s interesting how wide these depressions are now. Normally they’re about 2000 kilometers long and wide, but this one goes from northeastern Canada down to Florida. I think it’s more intense now because the temperature variations are greater than ours. That’s typical of the US. That’s why you have more hurricanes there. ‘
Does climate change play a role in how severe this cold is?
‘Without climate change, I think it would have been more extreme because the air from the Arctic would have been even colder. Climate change does not ultimately make storms lighter or heavier. Some factors make them weaker, some make them lighter, but ultimately you see no real effect.’
Will Europe be subject to these types of ice storms?
‘Just. Because of the ocean currents coming to us from the south, we have a warmer start than North America. Even though it’s at the same latitude as Barcelona, it’s pretty normal to freeze in New York in the winter.
If Scandinavia has a high pressure area with winds from Siberia, the colder climate of Europe. At one time the temperature in the Netherlands was -27 degrees. We have calculated whether this will happen again in the current climate. That chance is almost nil, but overnight temperatures of -20 could occur in our area.’