A multiple-vortex tornado is a tornado that contains several vortices rotating around, inside of, and as part of the main vortex. These multiple vortices are somewhat similar to eyewall mesovortices found in intense tropical cyclones. The only times multiple vortices may be visible are when the tornado is first forming or when condensation and debris is balanced enough so that subvortices are apparent without being obscured. They are responsible for most (if not all) cases where narrow arcs of extreme destruction lie right next to weak damage within tornado paths.
Suction vortices (or suction spots) are really substructures of many, perhaps all, tornadoes but are not always easily visible. These occur, usually, at the base of the tornado vortex where the tornado makes contact with the surface. Subvortices tend to form after vortex breakdown reaches the surface and are resultant from the ratio of cyclonically incoming and rising air motions. Multivortex structure is not unique to tornadoes, occurring in other circulations such as dust devils, but is a natural result of the physics of vortex dynamics.
Multivortex tornadoes should not be confused with cyclically tornadic supercells. These systems can have the tendency to produce many, and very separate tornadoes, called tornado families, existing either at the same time or in succession. A phenomenon similar in nature to multiple vortexes is the satellite tornado. It is different from a multiple-vortex tornado in that it exists outside of the main tornado and forms via a different mechanism.
The May 2011 destructive EF5 Joplin tornado is an example of a multiple-vortex tornado.[1]