Greenfield tornado

On the afternoon of May 21, 2024, a violent EF4 tornado tracked across southwestern Iowa, United States, devastating the city of Greenfield. The tornado, known most commonly as the Greenfield tornado, destroyed many buildings and wind turbines across its path that stretched through Page, Taylor, Adams, and Adair counties, while also causing more than $31 million in property damage, killing five people and injuring 35 more. The tornado reached peak intensity within Greenfield, where National Weather Service surveyors denoted maximum wind speeds estimated at 185 mph (298 km/h), or EF4 on the Enhanced Fujita scale. However, estimated winds of 309–318 mph (497–512 km/h) were briefly determined from inside the tornado by a Doppler on Wheels portable radar unit, one of only three times that wind speeds exceeding 300 miles per hour (480 km/h) have been determined in a tornado from radar observations.

The tornado formed amidst a week-long period of elevated tornadic activity in an area expected to be strongly conducive for the development of long-tracked and fast-moving tornadoes. Over the next 48 minutes, the tornado was observed by multiple storm chasers and research teams, who would determine the extreme wind figure from a direct radar measurement above the city of Greenfield. In addition to one fatality on a highway in Adams County, four fatalities occurred in Greenfield, with the damage in the city described as "horrific", as surveyors revealed damage consistent with a violent EF4 tornado, contradicting analysis of mobile radar data. The tornado has been noted as an important milestone in the practical efficacy of the Warn-on-Forecast system, which predicted tornadic activity in the vicinity of Greenfield about 75 minutes before the tornado reached the community. State legislation introduced in the aftermath of the Greenfield and Minden tornadoes passed that summer and the following year would fund housing projects and disaster recovery programs throughout Iowa.