The Doppler Radar
The Doppler Radar is the system that detects the weather system and what the atmosphere is like. It can tell if atmospheric motion is moving toward or away from the radar. The Doppler Radar is the leading radar system in warning of the coming of tornados.
Doppler Screenshots

The way the Doppler works is that it sends out signals into the atmosphere and when it hits something, it displays a color corresponding to what was hit. The more severe the atmosphere it hits, the redder the color is.
Find a Doppler Radar near you.
HOME HOW THE FORM CLASSIFICATIONS TORNADO ALLEY DOPPLER MAKE A TORNADO