The "Quad State" supercell.
This storm formed in eastern Kansas, then tracked across the
entire length of Missouri AND Illinois into Indiana. In total,
it lasted over 10 hours and travelled almost 500 miles. This
image shows a clearly visible "hook echo" indicating
strong rotation in the storm. When this image was captured, the
storm had just spawned a tornado that ripped through Springfield,
Illinois causing widespread destruction.
Twin supercell thunderstorms
with hook echoes in Missouri. These two storms were both producing
tornadoes at the same time as one of them tracked near Springfield,
Missouri and the other approaches the state line between Arkansas
and Missouri, near Branson.