On 14 June 2001, a squall line developed in northern Missouri in a moderate shear, high instability environment. The squall line moved rapidly into eastern Iowa, bowed, then produced two tornadoes in addition to widespread wind damage. One of the tornadoes caused F2 damage and the other F1, and both occurred very near the KDVN WSR-88D. The tornadoes developed near the bow's apex, close to the intersection of the squall line with a synoptic-scale frontal boundary. The frontal boundary was reenforced by differential heating and flash flood producing thunderstorms which occurred earlier that day.

Tornadoes associated with squall lines typically pose a great challenge for meteorologists attempting to provide warning lead time. The circulations developed rapidly and in a non-descending mode (Mode II). Thus, radar sampling limitations, both temporal and spatial, are especially critical in these events compared to classic supercell thunderstorms producing tornadoes in a descending mode (Mode I). Moreover, squall lines seem to produce the majority of tornadoes in eastern Iowa compared to supercells.

This presentation will detail and compare the evolution of the two vortices which occurred within 15nm (~30km) of the radar. We will also discuss sampling limitations and the prospects for improvements with the new VCPs proposed for field use.