EF3 Tornado — Calhoun, Iowa

2021-07-14 · near Lake City, Calhoun, Iowa

Event narrative

This was the first and strongest tornado of the day. It developed west southwest of Lake City and produced tree and power line damage. The tornado moved into and across the southern portion of Lake City. Imagery from UAV's and chasers show that the tornado was multi-vortex as it passed through the city. Up to EF2 damage occurred as it passed through town. As the tornado moved east of the town, it began to consolidate into a larger funnel and strengthen. It passed through a farmstead producing considerable damage to the farmhouse and out buildings with EF3 damage noted on the house. The tornado continued for a few more miles and impacted a confinement facility before lifting to the northwest of Lohrville. Fortunately, no injuries or deaths occurred with this tornado.

Wider weather episode

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.

View location on OpenStreetMap → (42.2605, -94.7834)

Source: NOAA Storm Events Database, event_id 972496. Narrative written by the NWS forecast office that issued the report.