During the early afternoon of 29 June 1998, a severe squall line traversed central Iowa producing widespread straight-line wind damage (gusts exceeding 50 m/s) and several weak to moderate tornadoes (F0-F2). During the early stages of the mesoscale convective system's evolution, it was found to contain several embedded hybrid high-precipitation supercells. Multi-scale analyses were performed utilizing traditional upper-air and surface data as well as profiler and WSR-88D Doppler data. Archived level II data from the Des Moines, Iowa Doppler radar was used to examine the complex storm morphology and velocity structures as the system approached the Des Moines metropolitan area.

One particularly intense portion of the convective line was responsible for producing numerous mesocyclones, some of which spawned tornadoes. These storm-scale vorticies were examined in detail. Several differences were noted between those vorticies that were non-tornadic and those that resulted in tornado touchdown.