EF3 Tornado — Monona, Iowa

2011-04-09 · near Mapleton, Monona, Iowa

Event narrative

A tornado caused extensive damage in the Mapleton area with about 100 houses destroyed and many others severely damaged in a 12 to 15 block area on the southwest side of town. This caused the displacement of around 500 to 600 people. Most garages and stand alone structures were destroyed. In addition, large trees were uprooted and windows blown out of vehicles. Twelve to 14 people sustained minor injuries, the most severe a broken leg. The worst property damage was noted to be on the lower end of the EF3 category. The tornado started about 2 miles west southwest of Mapleton, moved into town, then turned north and ended 1 mile north of town. The path length was around 3.5 miles and the maximum width was around 3/4 of a mile.

Wider weather episode

A large upper level trough of low pressure moved from the Rockies east toward the central U.S. on Saturday April 9th. As it did, it caused a warm front to lift into eastern Nebraska and western Iowa. Temperatures south of the front were in the 80s with dew point temperatures in the 60s. Meanwhile, readings north of the boundary were in the 50s and 60s. Moderate instability south of the front combined with high levels of wind shear allowed for supercell development over eastern Nebraska and southwest Iowa during the late afternoon and early evening of April 9th. A few of the storms that were near the front turned tornadic while the other supercells were prolific hail producers, in some cases producing very large hail.

View location on OpenStreetMap → (42.1535, -95.8283)

Source: NOAA Storm Events Database, event_id 283803. Narrative written by the NWS forecast office that issued the report.