1925 was the deadliest year in the U.S., with 794 killed, according
to the National Oceanic and Atmospheric Administration. That year is
infamous for the Tri-State Tornado, the longest-tracking, deadliest
tornado on record. The tornado's path, over 219 miles long, went
through portions of Missouri, Illinois and Indiana. The twister
killed 695 people along its path.
There were 552 deaths in 1936
and 551 deaths in 1917, ranking as the second- and third-most deaths
caused by tornadoes in a year. According to the Storm Prediction
Center, the yearly average for tornado deaths is around 60.
2011 had an unusually high number of large, destructive tornado
outbreaks as 1,709 tornadoes touched down, a close second to the
record 1,817 tornadoes set in 2004. In comparison, the average
number of tornadoes per year over the past decade is around 1,300.
Why so many tornadoes in 2011?
A key ingredient for the violent severe weather in 2011 was a
very strong jet stream. La Niña, a phenomenon where the sea surface
temperatures in the central and eastern Pacific around the equator
are below normal, helped to cause the strong northern jet stream,
which frequently plunged into the South. This set the stage for
powerful supercell thunderstorms, which are the type of storms that
People typically think of "Tornado Alley" as the corridor from
Texas to Kansas that is frequently hit by tornadoes in the spring.
Warm, humid air from the Gulf of Mexico clashes with drier air from
the Rockies. During 2011, many tornadoes touched down east of the
typical Tornado Alley, which is often the case in La Niña years.
More densely populated areas sit in the path of severe storms
capable of spawning tornadoes.
Tornadoes hit many cities, communities outside of Tornado Alley
"Last year was an exceptionally deadly year because city after
city got hit. Some of them were far outside of Tornado Alley. My
friend Jenna Blum coined the term 'Metronado,' which is what we had
last year," said Mike Smith, senior vice president of AccuWeather
Among the cities where tornadoes touched down in 2011 were
Minneapolis, Minn.; Springfield, Mass.; Raleigh, N.C.; St. Louis,
Mo.; Birmingham, Ala.; Jackson, Miss.; Oklahoma City, Okla.; New
York City, N.Y.; and Philadelphia, Pa.
Two of the most deadly tornadoes touched down in Joplin, Mo., on
May 22, 2011, and Tuscaloosa, Ala., on April 27, 2011.
"No matter how good the warnings are, if you take a densely
populated area and put a F-4 or F-5 tornado in there, tragically,
people are going to lose their lives," Smith added.
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Some strong tornadoes also touched down far outside of Tornado
Alley, where people are less prepared for violent severe weather.
Springfield, Mass., was hit by a rare EF-3 tornado on June 1,
2011. "This was the first major tornado to hit Massachusetts since
1953," Smith said.
Inadequate shelters led to more deaths in 2011
Another factor in how deadly tornadoes were in 2011 was
inadequate shelters, both in solid structure homes and mobile home
The safest place to take shelter during a tornado is in the
lowest interior room of a house or building, preferably in a
basement, but there are areas in the country where people do not
Many people who live in Tornado Alley and other areas of the
country frequently hit by tornadoes do not have basements, while
other communities far outside of Tornado Alley do have basements.
"Places like Massachusetts have basements -- well outside of
Tornado Alley. Oklahoma, almost no one has a basement. It’s local
building customs, soil conditions, etc., that dictate whether people
have basements. In Joplin, almost no one had a basement, but in St.
Louis, same state, almost everyone did," Smith said.
Many mobile homes were devastated by tornadoes in 2011, leaving
many to debate whether mobile home parks should be required to have
[Text from file received from
AccuWeather.com; written by Meghan Evans, meteorologist writer]