Possibly the single most destructive tornado in U.S. history occurred May 5, 2013 in Moore, Oklahoma. The tornado cut a swath 2 miles wide in places and 12 miles long through the Oklahoma City metropolitan area, basically cutting it in two. The EF-4 tornado hammered the area with winds at 200 miles per hour. Meteorologists said it was 600 times more powerful than the atomic bomb dropped on Hiroshima in World War II.
So far, 105 people were admitted to the hospital and 24 people were killed, including 9 children. The Medical Examiner expects the death toll could rise by another 40 people. At least 50 pets have been found, as well.
This storm is the most expensive in U.S. history, with damage estimates at more than $2 billion, greater than the previous most expensive tornado that hit Joplin, MO in 2011. It's double the damage done by the previous tornado that hit Oklahoma City on May 3, 1999, which destroyed 2,500 buildings and created $1 billion in damage. (Source: NY Daily News, OK Tornado $2 Billion in Damage, Mary 22, 2013; ABC News, Live Tornado Updates)
The largest tornado season occurred April 25-27, 2011. In that week, 305 twisters damaged the Southeast, breaking the 1974 record of 267 tornadoes. The outbreak caused $5 billion in damage. At least two of the storms were EF-5 twisters, producing wind gusts of more than 200 miles per hour.
The tornado outbreak killed 327 people, with 250 dead in Alabama alone. It was the third-deadliest single outbreak in U.S. history. The worst was March 1925, when 747 people died and the second-worst was March 1932, when 332 perished.
That outbreak made April the most active month for tornadoes ever, with 600 tornadoes forming. The previous record was 542 tornadoes in May 2003. It also brought the year's total to 881 tornadoes, almost half the tornado record of 1,817 set in 2004. And May is typically the worst month. (Source: Bloomberg, "Deadly Tornado Outbreak May be Worst in History," May 4, 2011)
Tornadoes usually hit east of the Rockies during the spring and summer. On average, 800 tornadoes hit a year, killing 80 people and injuring 1,500 more. Since 2008, that average has increased to more than 1,300 a year. The most violent tornadoes can have wind speeds of more than 250 mph and leave a damage path a mile wide and 50 miles long.
A tornado is any violently rotating column of air extending from a thunderstorm to the ground. Tornado-producing thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts with dry air, known as a "dryline." The U.S. is the world's "hot spot" for tornadoes, thanks to a combination of large land mass (the Great Plains) that warms on hot days, a cold, dry wind from the Rockies, and warm moist air from the Gulf of Mexico. The earth's jet stream swoosh all these together to create -- Tornado Alley.
Does Global Warming Increase Tornado Damage?
Some say global warming is increasing tornado damage because the Gulf of Mexico is becoming warmer, increasing the contrast when it hits the cold air from the Rockies. Many others argue that global warming warms the cold air even more, which leads to fewer tornadoes.
However, two separate studies in 2007 reported that global warming could increase the type of weather conditions that feed tornadoes. In the Proceedings of the National Academy of Sciences, Jeff Trapp of Purdue University, said the number of days that generate severe thunderstorms could double by the end of the century. NASA research scientist Tony Del Genio agrees that tornado activity may be on the rise. Del Genio developed a computer model to research the impact of global warming on tornado activity. According to his research, global warming increases the likelihood of strong updrafts. This is when the wind moves up and down instead of sideways, which is like an incubator for tornadoes. The computer model predicted that global warming would create the conditions most likely to result in the most damaging tornadoes.