An Observational and Modeling Study of Derecho-producing Convective Systems

Understanding the mechanisms responsible for the development and maintenance of widespread severe convective windstorms (derechos), that are responsible for numerous casualties and significant property damage each year, remains an important research focus. These mechanisms have been examined with idealized simulations of strong, line-oriented convection (squall lines) of which derecho-producing convective systems are a subset. These past studies emphasize the importance of environmental wind shear in controlling the strength and longevity of squall lines. While recent studies describing observed derecho environments suggest that low-level shear is not as dominant a factor as some numerical simulations have suggested, the lack of a detailed observational baseline describing derecho environments has hindered the comparison of these ideas to observations.

To address these issues three main objectives have been defined: 1) collect and analyze a large set of proximity soundings from derechos and determine the distribution of wind shear and other parameters associated with these events; 2) produce a set of idealized numerical simulations to examine the sensitivity of line-oriented convection to the range of environments identified in the observational portion of this project; 3) examine the forces responsible for maintaining the strong updrafts and the strong near-surface winds within the numerical modeling experiments.

This study will produce a detailed classification of the observed wind and thermodynamics profiles in derecho environments and will increase our knowledge of the physical mechanisms responsible for the development and maintenance of the line-oriented convection and the strong surface winds within these types of weather systems. Results potentially will lead to better forecasts of these destructive wind storms.