A tornado family is a series of tornadoes spawned by the same supercell. These families form a line of successive or parallel tornado paths and can cover a short span or a vast distance. Tornado families are sometimes mistaken as a single continuous tornado, especially prior to the 1970s. Sometimes the tornado tracks can overlap and expert analysis is necessary to determine whether or not damage was created by a family or a single tornado. In some cases, different tornadoes of a tornado family merge, making discerning whether an event was continuous or not even more difficult.
Some tornado damage remains a mystery even today due to a lack of evidence. The Tri-State Tornado was one such tornado. It could either have been the longest single tornado recorded or a family of tornadoes. New re-analyses suggest that it was one continuous tornado, however, many other very long track tornado events were later found to be tornado families, notably the Woodward, Oklahoma tornado family of April 1947 and the Charleston-Mattoon, Illinois tornado family of May 1917.
Tornado families can be a result of satellite tornadoes, cyclic tornadogenesis, or some combination thereof. Intense downbursts may also cause damage paths to appear continuous, although this was more an issue for historic tornadoes.
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