systems relative to surface fronts and determines the degree to which environmental wind profiles ahead of the convection are in thermal wind balance.
Composite radar images are used to identify MCSs in the central United States from 1 April to 15 May in 2006 and 2007. 92 systems meet our MCS criteria. Each system had their general characteristics, such as duration and orientation recorded. Pre-line wind profiles for each
case are retrieved every hour from operational mesoscale model output. Also, the characteristics of the initiation mechanism as well as the shallow and deep layer shear directions are recorded for each case.
Preliminary results show that MCSs generally acquire the orientation of the boundary that initiates them, and usually maintain this orientation as they move away from the boundary. Mean wind profiles show that ageostrophic shear is dominant in the boundary layer, owing to frictional effects. Ageostrophic shear can also be important in the upper troposphere in association with jet streaks. The middle troposphere is mainly dominated by geostrophic shear. Composite diagrams depict environments conducive for the development of convection in the vicinity of the initiation mechanism, with geostrophic shear generally decreasing downstream of such features. As the MCS moves away from the
boundary, the reduced lifting from the boundary as well as the decrease in geostrophic shear will have implications for storm evolution and maintenance.