Studies of the Internal Structure and Dynamics of Convective Weather Systems

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The Principal Investigator will investigate the internal structure and dynamics of the convective region of mesoscale convective systems. The main goal is to determine why moist convection appears as discrete thunderstorms in some situations and as solid mesoscale swaths (slabs) of overturning in others. Specific objectives include 1) constructing characteristic inflow environments for discrete-thunderstorm events and for slab events, 2) determining the local (within the convective region) differences in the dynamic and thermodynamic conditions that accompany cellular vs. slab convection, and 3) determining how differences in the convection (slab vs. cellular) affect the mesoscale dynamics and structural properties of the convective system.The research methodology is composed of three parts: 1) construction of a composite environment for observed cases of predominantly cellular convective systems and for systems exhibiting solid-slab overturning, 2) numerical experiments on the composite environments to determine whether or not the model is able to generate the two types of organizational modes, and 3) numerical sensitivity experiments on idealized (analytically specified) initial conditions using the results of items (1) and (2) as a guide.It is expected that the knowledge gained from these investigations will a) help to identify the factors that establish the organizational mode of the convection and the depth and strength of moist absolutely unstable layers, and b) elucidate how those factors affect the overall structure and evolution of mesoscale convective systems. The results may also provide practical benefits, such as improvements in the ability to discriminate among the types of severe weather that will occur for various types of large-scale environments. Differentiating among the possible modes of convective organization is extremely important from a forecasting perspective since it is these differences that often determine whether or not severe weather will occur and, if so, whether it will be characterized by individual, possibly rotating, storms or by strong straight line winds associated with slab convection.