1974 Guin tornado

The tornado first touched down in eastern Mississippi near the town of Caledonia, before crossing state lines into Alabama. It would move to the northeast, rapidly intensifying as it neared the town of Guin. The tornado obliterated numerous brick buildings in Guin, claiming the lives of twenty-three residents before exiting the town, which lay in ruins. The tornado would produce extreme damage as it moved over forests and other rural areas; this damage was visible from satellite imagery that was conducted after the outbreak. The tornado dissipated over an hour and a half after touching down, having reached a maximum width of 1,350 yards (1,230 m).

The tornado was so powerful that Ted Fujita considered assigning the tornado an F6 rating; the tornado was eventually rated by Fujita as "F5+".

Meteorological synopsis

Earlier on April 3rd, three bands of convection would develop, the third developing at about 16:00 UTC, extending from near St. Louis into west-central Illinois. Based upon real-time satellite imagery and model data, differential positive vorticity advection coincided with the left exit region of an upper-level jet streak, which reached wind speeds of up to 130 kn (150 mph) (66.9 m/s (241 km/h)), thereby enhancing thunderstorm growth. Storms grew rapidly in height and extent, producing baseball-sized hail by 17:20 UTC in Illinois and, shortly thereafter, in St. Louis, Missouri, which reported a very severe thunderstorm early in the afternoon that, while not producing a tornado, was the costliest storm to hit the city up to that time. By 19:50 UTC, supercells producing F3 tornadoes hit the Decatur and Normal areas in Illinois. As thunderstorms moved into the warmer, moister air mass over eastern Illinois and Indiana, they produced longer-lived tornadoes—one of which began near Otterbein and ended near Valentine in Indiana, a distance of 121 miles (195 km).

Meanwhile, by 00:00 UTC the southern half of the first convective band became indistinguishable from new convection that had formed farther south over Alabama and Tennessee in connection with convective band two. In this area, increasing west-southwesterly wind shear at all levels of the troposphere, juxtaposed over near-parallel outflow boundaries, allowed successive supercells, all producing strong, long-tracked tornadoes, to develop unconstrained by their outflow in a broad region from eastern Mississippi to southern Tennessee. These storms, forming after 23:00 UTC, produced some of the most powerful tornadoes of the outbreak, including a large and long-tracked F4 that struck the western and central portions of Alabama, tracking for just over 110 miles (180 km), two F5s that both slammed into Tanner, causing extensive fatalities. One supercell in Mississippi from this group of storms would produce the Guin F5 at about 8:25 p.m.