Analysis of information sources in references of the Wikipedia article "1974 Super Outbreak" in English language version.
In total, 148 tornadoes spanned 13 states producing about 900 square miles (2,300 square kilometres) of tornado damage in less than 18 hours. ... Most of the tornadoes were produced by individual thunderstorm cells within these lines. The individual tornadoes moved northeastward at 40–60 mph (64–97 km/h), while the larger scale squall-line systems advanced toward the southeast. ... Many of these tornadoes were part of 'families' or a sequence of tornadoes spawned in succession by a single thunderstorm cell. Dr. Ted Fujita identified 30 such tornado families that accounted for 74% of the Outbreak's tornadoes and resulted in 98% of the 315 deaths. The longest-lasting tornado family existed for nearly five hours, while the average life was approximately two hours.
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: CS1 maint: bot: original URL status unknown (link)In total, 148 tornadoes spanned 13 states producing about 900 square miles (2,300 square kilometres) of tornado damage in less than 18 hours. ... Most of the tornadoes were produced by individual thunderstorm cells within these lines. The individual tornadoes moved northeastward at 40–60 mph (64–97 km/h), while the larger scale squall-line systems advanced toward the southeast. ... Many of these tornadoes were part of 'families' or a sequence of tornadoes spawned in succession by a single thunderstorm cell. Dr. Ted Fujita identified 30 such tornado families that accounted for 74% of the Outbreak's tornadoes and resulted in 98% of the 315 deaths. The longest-lasting tornado family existed for nearly five hours, while the average life was approximately two hours.