Tornado in Butler County, Iowa
Tornado July 14, 2021 · Butler County, Iowa
The path drawn at its surveyed width of 50 yards (0.03 mi) — zoom in and the swath grows to true scale. Other tornadoes recorded nearby that day are shown faint.
What the National Weather Service wrote
Storm Chaser report of a tornado southeast of Allison. Track was determined through use of high resolution satellite imagery. No damage indicators were impacted, therefore the EFU rating.
The wider storm
A surface low pressure system was centered over Kansas and Nebraska with attendant warm front draped across north central Iowa. This was bisected by an outflow boundary from morning convection across western Iowa. As morning activity exited the are the atmosphere quickly recovered steep low and mid level lapse rates exceeded 8 C/km with 0-6 km shear over 40 knots. Near the remnant outflow boundary 0-1 km SRH exceeded 150 m2/s2. Storms developed along this boundary and moved east along the warm front, spawning a number of tornadoes across the state. In fact, this is in the top 5 for tornadoes occurring in a single day for the state of Iowa since reliable records began in the 1980s. By evening convection congealed into an MCS, bringing heavy rain to portions of the state. A line of training storms set up north of the Des Moines metro, resulting in localized flash flooding.
Began near Butler Center (42.7219, -92.7616).
Other tornadoes from the same storm system
10 more tornadoes the National Weather Service filed under this storm episode.
Source: NOAA Storm Events Database, event 972523. Narratives are written by the National Weather Service forecast office that issued the report.
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