Tornado debris signature

A tornadic debris signature (TDS), often called a debris ball, is a special area that shows up on weather radar when a tornado lifts pieces of things from the ground high into the air. This happens because the strong winds of a tornado pick up dust, dirt, and other objects and throw them upward. When these pieces get high enough, they change the way the radar waves bounce back, making a bright spot that scientists can see.

Weather tools that use something called dual-polarization radar can also find these debris balls. These special radars help experts tell the difference between normal weather things, like raindrops, and things that are not part of the weather, like pieces of debris from a tornado. When they see this special sign on the radar together with the bright spot from the debris, they know for sure that a tornado is happening.

This helps weather experts warn people faster when a tornado is on the ground, giving everyone more time to stay safe.

Overview

When strong winds from a tornado lift pieces of buildings, trees, or other objects into the air, these pieces can show up on weather radars. This is called a debris ball. Debris balls are more common when a tornado moves through places with lots of objects, like forests or towns. Stronger tornadoes are more likely to create debris balls because they have the power to pick up and throw objects high into the air.

Weather radars can spot debris balls as small, round areas that look brighter than the surrounding areas. These bright spots help scientists confirm that a tornado is happening about 70–80% of the time. Special radar tools can also help find debris balls, making it easier to know when a tornado is nearby.