Science Source

Tornado outbreak variability follows Taylor's power law of fluctuation scaling and increases dramatically with severity

States the largest tornado impacts come from ‘outbreaks’ consisting of multiple tornadoes closely spaced in time
Finds an upward trend in the annual mean number of tornadoes per US tornado outbreak for the period 1954–2014
Finds the variance of this quantity is increasing more than four times as fast as the mean
States the mean and variance of the number of tornadoes per outbreak vary according to Taylor’s power law of fluctuation scaling (TL), with parameters that are consistent with multiplicative growth
Finds tornado-related atmospheric proxies show similar power-law scaling and multiplicative growth
States path-length-integrated tornado outbreak intensity also follows TL, but with parameters consistent with sampling variability
Results show observed TL power-law scaling of outbreak severity means that extreme outbreaks are more frequent than would be expected if mean and variance were independent or linearly related