The Role of Downward Momentum Transport in the Generation of Convective   Downbursts
  A downburst index has been developed to assess the magnitude of convective downbursts associated with heavy precipitation-producing (HP) convective systems. The index, designed for use during the warm season over the central and eastern continental United States, is composed of relevant parameters that represent the simultaneous physical processes of convective updraft development and downburst generation, incorporating positive buoyant energy or convective available potential energy (CAPE) and the vertical equivalent potential temperature gradient between the surface and the mid-troposphere. In addition to large CAPE and the presence of a vertical equivalent potential temperature gradient gradient, previous research has identified other favorable conditions for downburst generation during cold-season convection events. A primary mechanism in downburst generation associated with synoptically forced convective systems is the downward transport of higher momentum possessed by winds in the mid-troposphere. 
Kenneth Pryor