With dangerously cold temperatures expected this weekend the term 'Polar Vortex' is popping up, once again.
To clarify, the polar vortex is a real meteorological event that's ongoing throughout the year, but often the term is incorrectly used.
The polar vortex is the convergence of air over or very near to the north and south poles in the mid to upper-troposphere.
Simply put, the Earth's poles receive very little sunlight compared to the equator or even the mid-latitudes.
Due to the lack of sunlight, or incoming energy, the air receives little warmth and therefore will nearly always be cooler than locations closer to the equator.
During the winter months, the polar vortex is strengthened due to the lack of sunlight in the arctic circle.
Conversely, the polar vortex weakens during the summer months, but always remains present.
As cold air moves away from the poles, that air is replaced by air from the atmosphere, specifically in the upper-troposphere or even the lower-stratosphere (roughly the height where you find commercial airplanes flying).
At that height, the air flows together (convergence) and slowly sinks towards the surface, similar to water going down a drain over and near the pole.
That area of convergence and sinking is what is called the polar vortex.
Once the air is near the surface, it's deemed as arctic air due to its location and origin near the pole, and cold temperature relative to equatorial locations.
When a lobe of that cold air breaks away and moves south out of the arctic, we consider that an arctic air outbreak.
So, when the temperatures plunge well below zero this weekend, remember that it's due to a pool of arctic air moving to the south across our region, and that the polar vortex is where it always will be - over the pole.