This video explains how an unusual combination of weather systems caused an extreme winter storm that froze a large part of North America. Normally, the polar vortex is a strong circle of winds that keeps the coldest air near the North Pole. However, during this winter, the Arctic was much warmer than usual. This weakened the polar vortex and allowed very cold air to move far south into the United States and Canada.
At the same time, a powerful storm formed over the Pacific Ocean and moved toward California. This storm connected with an atmospheric river, a long and narrow flow of warm, moist air coming from the tropics. When this warm air collided with the cold polar air already in place, it was forced upward, creating large storm clouds. The strong temperature contrast provided a huge amount of energy, resulting in heavy snow and ice.
The storm affected over 260 million people across North America. Some regions experienced extreme snowfall, with up to 60 centimeters of snow in certain areas. In southern regions, temperatures near freezing caused rain to turn into ice, damaging power lines and leaving many people without electricity. Cities like Toronto recorded historic snowfall levels, making it one of the snowiest months ever recorded.
Vocabulary:
• polar vortex (noun) : a large area of very cold air rotating around the North Pole
• atmospheric river (noun) : a narrow band of moist air transporting water vapor
• weakened (adj) : made less strong or less effective
• spill south (verb) : to move or flow toward southern areas
• moisture (noun) : small amounts of water in the air
• hover (verb) : to stay at or near a certain level
• swath (noun) : a wide area or path
Source: CBC News