The Super Outbreak: Outbreak of the Century

In a span of 16 hours on 3-4 April 1974, nearly 150 tornadoes touched down over the east central United States. An unprecedented 95 of these were classified significant (F2 strength or greater), and 30 were rated violent (F4-5). At one point at least 15 different tornadoes were occurring simultaneously. The combined path length of destruction exceeded 2500 miles, and the storms were responsible for 335 deaths.

The 1974 Super Outbreak will be compared to other major tornado outbreaks which have affected the Midwestern United States in the last 50 to 100 years. It will be shown that the Super Outbreak is by far the most significant such event on record. The associated meteorological conditions will be discussed to provide some insight as to why the outbreak was so unprecedented. It will also be shown that no single factor was responsible for the intensity and extent of the event, but that the outbreak was the result of a fortuitous combination of meteorological factors which proved favorable for the development of numerous, long-lived discrete supercells. Output from a 29 km version of the Eta model, similar to that now used operationally, will be examined to investigate how today’s numerical guidance might have handled the event.