JACKSONVILLE, Fla. – Freezing temperatures are impacting 250 million people today yet the surprising headline is warm air triggered this frigid outbreak.
Extreme temperatures 30 degrees below freezing hit the midwest and this type of cold is very often accompanied by warming somewhere over the Arctic.
The mechanism can be explained by the polar vortex.
Polar air accumulates around the north pole where temperatures routinely average -40° below freezing during the endless dark winter nights.
This air rotates around the northern pole in a broad counterclockwise gyre known as a vortex.
The polar air in the vortex is typically locked up in the polar region bounded by a virgous flow of air called the jet stream.
When jet stream wind slows down, lobes of the vortex dip sending the cold south.
For the same reason jet stream winds weaken in summer due to warm air, the jet stream is affected when weaker temperature gradients ocurre the northern latitudes.
The vortex weakens, in part, because of warming temperatures high above the polar regions.
Evidence points at climate change as the culprit for increasing more erratic polar vortex swings into southern latitudes.