You've probably heard it countless times during severe weather: “A tornado touched down.”

Despite how it may look, a developing tornado isn't dropping out of a cloud and reaching toward the ground. In fact, the air within a developing tornado is rising.

Why Does a Tornado Look Like It's Coming Down?

A tornado's visible funnel can create a bit of an optical illusion.

As pressure decreases and humidity increases within a developing funnel, water vapor can condense into cloud at progressively lower levels.

To someone watching from a distance, that visible funnel may appear to be extending downward toward the ground.

But that doesn't mean the tornado itself is moving downward. The air within the rotating column is still rising rapidly.

Tornadoes Spin Up From the Ground

Mobile radar research has shown that supercell tornadoes can develop through an extremely fast spin-up process from the ground upward.

That's very different from the popular image of a tornado descending from the base of a thunderstorm until it finally “touches” the ground.

Direct observations, videos, radar measurements and numerical modeling have all helped meteorologists better understand what's happening during tornado formation.

What Is a Funnel Cloud?

Here's another weather term worth knowing.

A rotating funnel extending from a cloud before it connects with the ground is called a funnel cloud.

Once that rotating column is associated with the ground, it's considered a tornado.

And here's an important safety note: you don't necessarily need to see a fully condensed funnel extending all the way to the ground for a tornado to be occurring.

What Should We Say Instead of “Touched Down”?

“Touched down” remains an extremely common phrase, but there are several simpler descriptions that more accurately represent what's happening. Instead, you can say a tornado:

So the next time you hear someone say a tornado “touched down,” you'll know there's a lot more happening than what your eyes might suggest.