The Initiation and Evolution of Multiple Modes of Convection within a Meso-Alpha-Scale Region

Abstract

On 30 March 2006, a convective episode occurred featuring isolated supercells, a mesoscale convective system (MCS) with parallel stratiform (PS) precipitation, and an MCS with leading stratiform (LS) precipitation. These three distinct convective modes occurred simultaneously across the same region in eastern Kansas. To better understand the mechanisms that govern such events, this study examined the 30 March 2006 episode through a combination of an observation-based case study and numerical simulations. The convective mode was found to be very sensitive to both the environmental thermodynamic and wind shear profiles, with variations in either leading to different convective modes within the numerical simulations. Strong vertical shear and moderate instability led to the development of supercells in western Oklahoma. Strong shear oriented parallel to a surface dryline, coupled with dry air in the middle and upper levels, led to the development of the PS linear MCS in central Kansas. Meanwhile, moderate wind shear coupled with high instability and strong linear forcing led to the development of the LS MCS in eastern Kansas. Absent linear forcing, the moderate shear environment in eastern Kansas was supportive of isolated supercells in the numerical experiments. This suggests that the linear initiation mechanism was key to the development of the LS linear MCS. From the results of this study it is concuded that, for this event, localized environmental variations were largely responsible for the eventual convective mode, with the method of storm initiation having an impact only within the weaker shear environment of eastern Kansas.