It is well known that tornadoes form within quasi-linear convective systems such as squall lines and bow echoes. The mechanisms responsible for their genesis, however, are not well understood.

On 29 June 1998, a well-defined quasi-linear convective system initiated in central Iowa and subsequently propagated southeastward into Illinois, producing copious straight line wind damage and spawned numerous tornadoes. Observations of this event are presented in Part I of this paper.

Preliminary simulation results from the Weather Research and Forecast (WRF) model of the 29 June 1998 event will be presented. It will be shown that the model is able to reproduce the salient system-scale features of the 29 June event including the mid-level book-end vortices and rear inflow jet (RIJ). The overall evolution and orientation of the simulated bow echo is consistent with observations of the 29 June event. Furthermore, the model produces a zone of enhanced positive vertical vorticity north of the bow apex. Similar to the observed event, low level, short lived, meso gamma-scale vortices are generated north of the bow apex in the zone of enhanced vertical vorticity. The vortices are located in the cool air on the gradient of vertical velocity associated with the leading edge of the bow echo. The evolution, structure, and possible genesis mechanisms of these low-level vortices will be discussed.