Tornado Debris Ball
On rare occasions you'll hear the term "debris ball" mentioned when a meteorologist refers to a round "ball" of relatively high reflectivity values on Doppler Radar, typically located at the end of a hook echo. These high reflectivity values are not large hailstones, which aren't even found in this particular area of a supercell thunderstorm, but instead are pieces of debris being lifted up into the air around a tornado. All other factors aside, the larger the object the higher the reflectivity value. The debris can be anything from pieces of broken glass and shingles from roofs, or larger objects such as trees, parts of houses and even motor vehicles. A debris ball usually indicates a large, destructive tornado.
The above radar scan is from the WSR-88D (Doppler Radar) in Jackson, KY of a supercell thunderstorm at the time it was producing an EF-3 tornado. The tornado was estimated to be a mile wide with peak winds of 140 mph. Eight people lost their lives, as the twister cut a path of destruction across Menifee and Morgan Counties in eastern Kentucky on March 2, 2012.