Mammatus clouds were spotted about 50 miles outside of Greenfield, Iowa on Tuesday as strong supercells eventually spawned deadly tornadoes in the state. (Video courtesy: Alex Hall)
VILLISCA, Iowa — Skies painted ominous clouds in Iowa ahead of devastating severe storms that swept through the region on Tuesday.
Alex Hall saw dramatic mammatus clouds in the town of Villisca while storm chasing that afternoon.
Mammatus clouds are identified by their trademark bumps. They are most commonly found drooping from the underside of a cumulonimbus cloud’s anvil as the cloud reaches a later stage of development, but they can also accompany non-severe weather.
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They are also usually a sign of strong turbulence.
In this case, they were attached to supercells that would unfortunately spawn deadly tornadoes in Iowa, including Greenfield, about 50 miles to the northeast. The National Weather Service rated that tornado an EF-4