Note that the storm is not an object, rather it is a process (e.g., flow in a stream analogy, although not exactly). Determining the mean wind layer is not necessarily a simple thing to do-no universally accepted layer (gets complicated rather quickly). What about pressure-weighting? This mechanism affects all convection. Advection becomes increasingly important as the mean wind speed increases. When advection is zero, you only have propagation. The key for this slide is knowing whether you have surface-based convection or elevated convection. In general, the mean wind depth equals the lowest half of the thermodynamic profile. Rich Thompson, Roger Edwards, and other SPC people have done some nice work here (22nd SLS).