Severe Winter Storms Hit Eastern US Due to Polar Vortex

Severe winter storms are impacting over 60 million people in the eastern United States, with temperatures expected to drop as low as -50°C (-60°F). This extreme cold is caused by the polar vortex.   

Here's a simplified explanation:

What is the polar vortex? It's a large area of very cold air and low pressure that sits over the North and South Poles. It spins like a giant whirlpool.   

How is it affecting the US? The polar vortex has expanded southward from the Arctic, bringing extremely cold air to the eastern US.   

What are the two types of polar vortexes?

• Tropospheric: This is in the lowest layer of the atmosphere and affects most of our weather.   
• Stratospheric: This is higher up in the atmosphere (10-30 miles above the ground). It forms in the fall and weakens in the spring. When it's strong, it keeps the cold air at the North Pole. When it weakens, the cold air can move south.   

What makes the polar vortex weaken? Warm air rising from lower parts of the atmosphere can weaken it. This warm air can be caused by different weather patterns or climate changes.   

How often do these events happen? They are seasonal (happen in winter) but don't happen every year.   

What happened in 2013-14? There was a very strong polar vortex event that brought record cold and snow to Canada and the eastern US. Cities like New York, Philadelphia, and Chicago had record snowfalls.   

What was the impact on the Great Lakes in 2013-14? They froze over almost completely (92.5%), which was the second-highest ice coverage ever recorded. Lake Michigan had a record 93.3% ice coverage.

How does climate change relate to the polar vortex? Scientists are studying how climate change is affecting the polar vortex. Some think that as the Arctic warms faster than other areas, it reduces the difference in temperature between the Arctic and more southern areas. This can weaken the jet stream (a fast-flowing air current that helps keep the cold air contained), allowing the polar vortex to move south.   

Key Facts:

• The term "polar vortex" became widely known after the 2013-14 winter.
• The 2013-14 event caused record ice on the Great Lakes.   
• Lake Michigan had record ice coverage (93.3%).
• The polar vortex can have wind speeds of about 155 mph (250 km/h).   
• Climate change may weaken the polar vortex.   

In simple terms: A mass of very cold air that usually stays over the North Pole has moved south, bringing extremely cold weather to the eastern US. This is called the polar vortex. Scientists are looking into how climate change might be making these events more common