Bow echoes during BAMEX: Assessing transitions in surface wind damage using WSR-88D data

The Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) was conducted from 20 May to 6 July 2003 to study the life cycle of Mesoscale Convective Systems (MCSs) and associated bow echoes and mesoscale convective vortices (Davis et al. 2004). Of the missions that were investigated during BAMEX, nine produced bow echo MCSs with trailing stratiform precipitation, one produced a bow echo with leading stratiform precipitation, ten focused on mesoscale convective vortices (MCVs), and three were frontal squall lines that exhibited both parallel and trailing stratiform precipitation. The analysis in this study was performed on those events whose convection began as initial cells, developed into a quasi-linear system, and finally into a bow echo with well developed trailing stratiform precipitation. Ten events met these criteria and are summarized in Table 1. This investigation considers whether the type of wind-produced damage in bow echoes demonstrates a temporal transition during the MCS life cycle. Specifically, it is examined whether the type of windproduced damage early in bow echo producing MCSs transitions from tornadoes and downbursts early in the MCS lifetime to predominantly straight-line winds once rear inflow has developed. The widespread availability of Weather Surveillance Radar-1988 Doppler (WSR88D) level II and level III radar data, in conjunction with BAMEX damage surveys (Atkins et al. 2005; Wheatley et al. 2005) and concomitant public damage reports, provides an opportunity for a systematic assessment of the radial velocity data at each damage report and survey location. The radar radial velocity data was scrutinized at each damage report and survey location to classify a radar-determined source of damage. Three types of radar signatures were examined: straight-line winds from rear inflow as well as rotational and downburst couplets.