In early May 2003, a series of devastating tornado outbreaks affected much of the Central and Eastern United States. Environmental conditions were unusually conducive to a prolonged period of severe weather, driven by a persistent upper-level trough across the Intermountain West. This feature in the upper atmosphere provided significant wind shear during each day of the outbreak series. Meanwhile, moist air from the Gulf of Mexico surged northward across the country, providing the moisture and instability needed to fuel tornadic activity. This combination of factors persisted every day from May 3 to May 11.
The most significant day of the severe weather event was May 4, when a votaile atmospheric setup produced numerous strong to violent tornadoes across Arkansas, Kansas, Missouri, Oklahoma, and adjacent areas. A total of 79 tornadoes were documented that day, the second most on record at the time, behind only the 1974 Super Outbreak.
A total of 42 people were killed, and an additional 652 people were injured. In all, 363 tornadoes were confirmed over an eight-day period. Further analysis of the event suggested an extended outbreak of that magnitude occurs roughly every 10–100 years. May 2003 would remain the month with the most tornado activity on record, until it was surpassed by April 2011.
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