Quasi-stationary convective systems forming perpendicular to, and above the cold pools of, strong bow echoes

The accurate prediction of warm-season convective systems, and the heavy rainfall and severe weather associated with them, remains a challenge for numerical weather prediction models. This study looks at one such circumstance in which back-building convection forms perpendicular to, and above the cold pool region behind strong bow echoes. We refer to this phenomenon as a “bow and arrow” because, on radar imagery, the two convective lines resemble an archer's bow and arrow. The “arrow” can extend over hundreds of kilometers and can cause damage from high winds, hail and flooding. Events of this nature pose a particular challenge to forecast because they require an accurate forecast of the earlier convection and the effects of that convection on the environment. In this study, radar and surface observations of several events are presented to identify common environmental conditions prior to the development of the back-building convection. Additionally, simulations of several cases using the Weather Research and Forecasting (WRF) model are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line.