Tornado strikes, such as the one in Joplin, Mo., this week, hit U.S. cities with relative frequency, says University of Minnesota geographer Kenny Blumenfeld, so emergency planners need to make sure they prepare for the worst. With about 300 urban tornadoes on record since 1990, and twisters occurring at an unusually high rate this year, it's only a matter of time before the next damaging urban strike. "If the ingredients are right, a tornado can hit just about anything, and cities are no exception," Blumenfeld said.

Related Summaries