EFU Tornado — Winnebago, Iowa

2025-08-17 · near Neils, Winnebago, Iowa

Event narrative

Satellite imagery revealed a track in agricultural fields, just missing a farmstead. No DIs were impacted, resulting in an EF-U rating.

Wider weather episode

A warm front was draped across northern Iowa the afternoon and evening of August 17th. Convection developed along the boundary late in the afternoon in a deeply unstable environment with over 4000 J/kg of MLCAPE. Shear was lacking an prevented storm organization and more robust development, with around 25 kts of effective shear. Low level CAPE was high at over 200 J/kg in the 0-3 km and allowed for stretching of the updraft, resulting in a brief tornado in northern Iowa. This tornado remained over cropland and did not result in tree or structural damage, hence the EF-unknown rating.

View location on OpenStreetMap → (43.2651, -93.7775)

Source: NOAA Storm Events Database, event_id 1297496. Narrative written by the NWS forecast office that issued the report.