CALHOUN COUNTY – The National Weather Service (NWS) in St. Louis confirmed a tornado did in fact touch down in Calhoun County Tuesday evening – and it was a rare sort.
Called a “land spout,” the tornado, which was rated at F-0 with 60 m.p.h. winds, was not connected to the thunderstorms slamming the Riverbend in the late afternoon and evening hours Tuesday. Instead, it was part of a boundary around the storms. NWS St. Louis Senior Meteorologist Fred Glass said the land spout was on the ground from 6:21-6:23 p.m., and traveled approximately eight or nine 10ths of a mile before ultimately dissipating.
Glass said land spouts are caused by vortexes inside of boundaries around thunderstorms, but are not inside of thunderstorms like most tornadoes would be.
“A land spout tornado is what happens when it is removed from a thunderstorm,” he said. “Typically, when we have tornadoes, they are a part of a thunderstorm. This was part of a boundary around a thunderstorm. Vortexes get updrafts along that boundary, which can lead to these land spouts. It's really a pretty complicated process.”
He described the Calhoun land spout as the “most noteworthy” part of Tuesday's thunderstorms, adding it did not produce any significant damage.
More thunderstorms are in the forecast today, Glass said, but they are expected to be scattered and isolated from St. Louis to the south Wednesday afternoon. These storms are being caused by a warm, humid air mass currently atop the region.
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