Tornado
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Tornado activity in 2014 so far is at its lowest level since 1953, according to the National Weather Service's (NWS) Storm Prediction Center (SPC). "2014 has likely established a new low in tornado activity through the 21st of April," according to SPC warning coordination meteorologist Greg Carbin.

Carbin also pointed out that the time gap between the worst tornadoes is also the fourth largest since 1953. "At 152 days on April 18, 2014, the span between EF-3 or stronger tornadoes is the 4th longest span... in the last 60 years," Carbin noted. The longest gap was 249 days in 2004.

The NWS defines an EF-3 (Enhanced Fujita scale) tornado as one with winds between 158 and 207 mph capable of causing "severe damage," including blowing off roofs, overturning trains, and uprooting trees.

Between 2001 and 2010, 563 Americans were killed by tornadoes, which occur 1,200 times a year on average.

Although Texas experienced the highest number of twisters per year (142 on average) between 1981 and 2010, compared to less than five in 15 Northwest and Western states, Alabama had the nation's highest annual number of tornado fatalities (6 per year), the NWS reported.

The deadliest tornado day in U.S. history was March 18, 1925 when 695 people were killed by twisters in Missouri, Illinois and Indiana.