Simplify the following text for a Grade 8 native English-speaking person.
Original: If there is no break in activity , this is considered a tornado outbreak , although there are various definitions . A period of several successive days with tornado outbreaks in the same general area ( spawned by multiple weather systems ) is a tornado outbreak sequence , occasionally called an extended tornado outbreak .
Simplified: A `` tornado warning '' is issued if someobdy has actually seen a tornado or if a tornado has shown up on radar .