Family of tornadoes
From AMS Glossary
family of tornadoes
A sequence of long-lived tornadoes produced by a "cyclic" supercell storm.
Tornadoes touch down at quasi-regular intervals (typically 45 min). Usually a new tornado develops in a new mesocyclone just after an old tornado has decayed in an old, occluded neighboring mesocyclone. Sometimes, two successive tornadoes may overlap in time for a few minutes. The two mesocyclones may rotate partially around each other. If the damage tracks of the tornadoes appear to form a wavy broken line, the family is classified as a series mode. In the more common parallel-mode family, the damage tracks are parallel arcs with each new tornado forming on the right side of its predecessor. The parallel mode is subcategorized into left turn and right turn, according to the direction in which the paths curve.
Davies–Jones, R. 1986. Tornado dynamics. Thunderstorm Morphology and Dynamics. E. Kessler, Ed., Univ. of Okla. Press, . p. 223.