A large purple stain dances on the Northern hemisphere and the direction of the United States continues to spread. The funny play of color is likely to delight the people in the United States, however little. To see how the currently prevailing cold from Canada to the Midwest has works. The purple color stands for temperatures of minus 40 degrees.

in Addition to the already very low temperatures, strong winds make it difficult to stay Outdoors. The feels like temperature was in some places below minus 50 degrees Celsius. At least 21 people have fallen to the minus temperatures, in the meantime, to the victims. (How the body reacts to the extreme cold, read here).

The American space Agency has satellite images of the cold front from 20. January 2019 to 29. January 2019 selected. Instruments onboard the Nasa satellite “Aqua” captures infra-red radiation, and microwaves, which are radiated from the earth and information about the current weather situation.

you are Fixated with the eyes of the American border, you can see where the extreme temperatures reached in the United States.

MORE on THE TOPIC of down To minus 40 degrees What happens to the body in extreme cold?

trigger: a Sudden stratospheric warming at the end of December?

In the United States, the cold air was drawn from the so-called polar vortex. It is formed in Winter over the Arctic, when in the eternal darkness, especially a lot of cold air accumulates. In the 20 km height and the Mr 70 degrees to the minus. It forms a low-pressure area, reports the German weather service (DWD). This area of low pressure strengthened, strong West winds, all year, labor – the so-called Jetstream.

Strictly speaking, the polar vortex is made up of two air streams:

The ice-cold low-pressure area at a great height, forming only in the Winter over the Arctic and from the underlying, strong West-to-East flowing jet stream (see graphic above).

In most years, this System is stable and stays where the cold collects through the air – at the North pole. The polar vortex weakens, however, the System is out of balance. The ice-cold Arctic air towards the South moves to Canada and the USA.

Meandering winds

it is Still not entirely clear what has slowed down the polar vortex in January. The German weather service, however, has a guess.

at the end of December 2018 has heated sphere of air in the stratosphere – 10 to 50 kilometers altitude – all of a sudden. How exactly it comes to such repeated heat events, researchers have yet to understand in Detail. Since the Jetstream but is driven by temperature differences between the Equator and the Arctic, weakens it, and if these differences are small.

“He tends to stronger and, therefore, further to the North and the South, sweeping wave-like movements,” writes the DWD. Within this meandering jet-stream winds can spread the Arctic air over the North pole to the South (see graph above). Low pressure areas pull, instead of from East to West, with the ice-cold air to the South – the Americans also speak of the “Arctic Outbreak”.

temperatures at the 30. January 2019 in comparison to the long-term average (1979 to 2000)

No Arctic air in Europe

In contrast to the USA, Europe remains by the consequences of such Arctic outbreaks in General, spared. This is partly due to the fact that cold, Arctic air has to overcome on your way to us, the North sea and the North sea and thus the Gulf stream. Icy air masses are warmed up. In Germany, it will be next week, but regardless of the weak Arctic jet stream cold.

Meanwhile, can breathe a sigh of relief, the people in Chicago gradually. Although it should stay on Saturday still frosty, then there is hope for plus grade.


Sam Yoon has many years of experiences in journalism. He has covered such areas as information technology, science, sports and politics. Yoon can be reached at 82-2-6956-6698.