Numerical Simulations of Derecho-producing Convective Systems

Understanding the environments and mechanisms responsible for the development and maintenance of widespread severe convective windstorms (derechos) remains an important research focus. These environments and 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 low-level wind shear in controlling the strength and longevity of squall lines. However, recent studies describing observed derecho environments have suggested that low-level shear is not a dominant factor.

To address these issues, two main objectives have been defined: 1) produce a reasonably comprehensive set of horizontally non-homogeneous numerical simulations within the range of observed environments associated with derechos, and 2) produce an analogous set of horizontally homogeneous cloud-model simulations. This study will use a detailed classification of the observed wind and thermodynamics profiles in derecho environments as a baseline for the numerical simulations. The intellectual merit of this proposal is that the disparity between the results derived from observed derecho environments and those derived from idealized model simulations largely will be reconciled, and 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 will be increased. The broader impacts are the improved forecasts of convective windstorms, resulting in enhanced public safety and economic benefits to commerce.