US: Migrating tornadoes are the nation's deadliest disasters

By Thomas Frank

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The mortal storms illustrate an alarming trend that is overlooked amid concern about hurricanes, wildfires and floods: Tornadoes are increasingly occurring in the Southeast, where they are twice as deadly as tornadoes elsewhere in the United States, according to an E&E News analysis.

A shift of tornado activity from the Great Plains to the Southeast has brought heightened danger by concentrating twisters in a far more perilous landscape — one covered by forest that conceals tornadoes and is filled with mobile homes that are easily demolished.

NOAA records dating to 1950 show that tornado activity has increased in the Southeast since the late 1990s and that the trend — and death toll — has accelerated in recent years.

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'The shift is real'

Studies have suggested possible links between global ocean temperatures and U.S. tornadoes but are inconclusive about the effect of climate change. Tornado activity is difficult to link to climate change because tornadoes are small and spontaneous compared with hurricanes and cannot generally be produced in large-scale climate models.