Tornado Alley: Why is the Great Plains a tornado hotspot of the world?

Forecasting the weather would be far simpler if Earth’s major weather systems followed a constant path and did not vary in size or strength. That is very much not the case on our planet with its complex terrain features, a mosaic of uneven land and sea distribution, changing sun angles (daily and seasonal), and an atmosphere in perpetual flux trying to balance all the forces, big and small, acting upon it.

There are particular geographical regions across the planet that do seem to favor destabilizing the atmosphere enough to yield explosive thunderstorm severity. The Great Plains of central United States, also known as Tornado Alley, is one of the prime candidates! This is true based on the annual high frequency for tornado outbreaks and potential for the most destructive tornadoes (up to EF5) on the Enhanced Fujita Scale to occur.

First, let’s introduce the essential meteorology giving rise to an active Tornado Alley. Tornadoes are not whipping across the plains every day, of course! The ingredients still have to come together in the right combination. Here, we can start to breakdown the overarching considerations.

The lay of the land: Sometimes it is not necessarily where you are at, but what is around you to account for. In this case the Great Plains are bordered to the west by the Rocky Mountains (or Rockies) and the expansive warm waters of the Gulf of Mexico to the south and southeast. Both the influence of mountains on atmospheric behavior and warm, humid air masses associated with the Gulf of Mexico within reach contribute to an ideal severe thunderstorm setup. The flatter terrain between the mountains and Gulf of Mexico is also fantastic for unimpeded air mass clashes. That really is the severe weather setup in a nutshell, surface warm and humid air masses from the south interacting with mid/upper tropospheric cold and drier air masses flowing out of the Rockies carried by the prevailing Westerlies (west to east jet stream winds).

We can get more specific, though! How do we get warm, humid air masses from the Gulf of Mexico to move north into the Great Plains in the first place? Next, I will go over cyclogenesis. Stay tuned!

Photo Credit: Jonny William Malloy