Emergency communication system
161 people were killed and at least 990 injured when an EF5 multiple-vortex tornado hit Joplin, Missouri. Because Joplin is located in a tornado-heavy area of the country, many people considered the tornado sirens routine and ignored them. Instead, many residents waited until they received confirmation from another, non-routine, source, such as seeing the tornado, a radio or TV report, or hearing a second siren. In the aftermath, an assessment team recommended that emergency warnings take risk perception into account to convey a sense of urgency. NOAA Officials are considering ways to change the warning system to distinguish smaller tornadoes from more deadly ones.
2011 Hackleburg–Phil Campbell tornado
The 2011 Hackleburg–Phil Campbell tornado was a violent, long-track EF5 wedge tornado that devastated several towns in northern Alabama, United States, before tearing through the northern suburbs of Huntsville and causing damage in rural portions of southern Tennessee on the afternoon and early evening of Wednesday, April 27, 2011. It was the deadliest tornado of the 2011 Super Outbreak, the largest tornado outbreak in United States history. The tornado reached a maximum width of and was estimated to have had peak winds of . The tornado killed 72 people, making it the deadliest tornado in Alabama history, and injured at least 145 others. It was the deadliest tornado to strike the U.S. since the Udall, Kansas tornado of 1955 until the catastrophic tornado on May 22, 2011, which killed 158 people in Joplin, Missouri.