Tornado outbreak

A tornado outbreak or tornado swarm is the occurrence of multiple tornadoes. At least six to ten tornadoes have to touch down for it to be a tornado outbreak. Most commonly in New England, they are called tornado swarms. For example this was used for the 1787 Four State Tornado Swarm. In most other uses, it is called a tornado outbreak. If there are enough tornadoes and casualties in a tornado outbreak, it could be called a Super outbreak. This has only occurred in 1932, 1974, and 2011. Some tornado outbreaks could be rather weak, such as the May 16-17, 2015 tornado outbreak. Some could also be rather lengthy and strong, such as the May 21-26, 2011 tornado outbreak sequence.