Tornado outbreak sequence of May 21–26, 2011
The tornado outbreak sequence of May 21–26, 2011 was one of the largest tornado outbreaks on record which affected the Midwestern and Southern regions of the United States. Most of the tornadoes developed in a corridor from Lake Superior southwest to central Texas; isolated tornadoes occurred in other areas. An especially destructive tornado destroyed one-third of Joplin, Missouri, resulting in 158 deaths and over 1,000 injuries. The Joplin tornado is the deadliest in the U.S. since April 9, 1947, when an intense tornado killed 181 in the Woodward, Oklahoma area. Tornado-related deaths also occurred in Arkansas, Kansas, Minnesota, and Oklahoma. Overall, the tornado outbreak resulted in 184 deaths, 6 of those non-tornadic, making it second only to the 2011 Super Outbreak as the deadliest since 1974, and the second costliest tornado outbreak in U.S. history behind that same April 2011 outbreak, with insured damage estimated at $4–7 billion.
Tornadoes of 1973
Notable scientific milestones toward understanding the life cycle of tornadoes occurred in Oklahoma on May 24, 1973, when researchers exploited primitive Doppler weather radar, then under development by the National Severe Storms Laboratory (NSSL), to examine a tornado vortex signature, or TVS, for the first time in history. The scientists, in one of the earliest successful cases of storm chasing, were able to study the evolution of a violent tornado near Union City, and to generate clear visual photography of its entire life cycle, from birth to decay. The successful deployment of Doppler radar to detect tornado formation also pointed the way to the development of a nationwide Doppler radar system, and helped precipitate funding for studies on tornadogenesis.
At the beginning of the year, one of the strongest El Niño episodes since 1950, as defined by sea surface temperatures, was in progress but gradually diminishing, according to the Oceanic Niño Index (ONI). Peak trimonthly anomalies, measured in moving averages, were +1.7 °C above normal for the period December–February 1972 – 1973. The month of January featured clusters of tornado activity along the Gulf Coast, primarily in Texas and Louisiana, as well as part of the Florida peninsula—a pattern not inconsistent with that of El Niño winters in general. The deadliest and strongest tornado of the month was an F3 that struck Caldwell Parish, Louisiana, on January 18, killing one person and injuring two others. It was part of a larger outbreak on the same date that spawned five other significant tornadoes near the Gulf Coast, with 20 total injuries. A smaller outbreak affected Central Florida ten days later, causing damaging F2 tornadoes in the Campbell–Orlando area, with 24 injuries. February featured much less activity, with 10 confirmed tornadoes compared to 33 in January, and no destructive or deadly tornadoes occurred. Outside the U.S., a catastrophic tornado, believed to be an F5, ravaged a small town in Argentina on January 10, causing more than 50 deaths.