Top 6: Worst Fall Tornado Outbreaks

As many as 12 tornadoes struck Nebraska and Iowa Oct. 4-5, 2013, injuring 15 people and causing millions of dollars of damage. The October storms underscore the fact that spring is not the only season for dangerous tornadoes. Fall is considered the second tornado season of the year, with storm systems historically spawning strong, deadly outbreaks that can span a dozen or more states.

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This photo shows damage from a tornado, Saturday, Oct. 5, 2013 in Wayne, Neb. As many as nine tornadoes hit an area covering northeast Nebraska and northwest Iowa, causing structural damage and injuries but no fatalities, the National Weather Service said Saturday. (AP Photo/Nebraska State Patrol)

The Weather Channel's tornado expert Dr. Greg Forbes examined the storm statistics and found six of the largest 55 known tornado outbreaks occurred in October and November.

"The second half of October and especially November can often be a second season for tornadoes and severe thunderstorms," said Dr. Forbes. "In many ways, this is the counterpart to spring, when strong fronts and upper-air systems march across the United States. When enough warm, moist air accompanies these weather systems, the unstable conditions yield severe thunderstorms and sometimes tornadoes."


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