A Polar Vortex is expected to bring a record-breaking cold snap in much of the United States following a major snow storm that has sent North America shivering in bitter cold.
The National Weather Service (NWS) has warned of "dangerously cold wind chills" in the northern and central US. Cold temperatures will remain in place along the East Coast through mid-week.
"Combined with gusty winds, these temperatures will result in life-threatening wind chill values as low as 60 degrees below zero," the weather bureau warned.
Heavy snowfall with up to a foot of accumulation is likely in the eastern plains, it said.
Here is a fact sheet about Polar Vortex, essentially an arctic cyclone.
What is Polar Vortex?
A Polar Vortex rises in the Arctic. It is actually a pattern of winds that resemble that of cyclones and flow around the North Pole year round.
How is a Polar Vortex formed?
According to San Houston State University, a Polar vortex is formed during the polar winter when stratospheric air moves in a circular motion, with an area of relatively still air in its centre.
Why Polar Vortex depletes ozone?
The temperature in the vortex is approximately -130 degrees F (-80 degrees C), which assists in the formation of polar stratospheric clouds.
The polar stratospheric clouds are responsible for the depletion of ozone as they contain chlorine compounds, which in the presence of sunlight destroy ozone.
When is a Polar Vortex strongest?
A Polar Vortex is the most dangerous when it weakens as it creates more acute winter conditions at this phase. In fact, a deteriorating Vortex leads to extreme frigid weather conditions in the eastern US.
NOAA scientist James Overland explains: "When the Polar Vortex — a ring of winds circling the Arctic — breaks down, this allows cold air to spill south, affecting the eastern United States and other regions."
"This can result in a warmer-than-average Arctic region and colder temperatures that may include severe winter weather events on the North American and European continents."
The Polar Vortex is usually circular in August and September, elongates in October stretching towards inhabited areas of South America, and by November it begins to weaken.
"During the winter/spring period, when the polar vortex is strongest, air outside of the vortex cannot enter. So, because the warm air from the mid latitudes cannot mix with the cold polar air, the polar air continues to get colder due to radiative loss of heat," Noaa explains.