Characterizing The Severe Turbulence Environments Associated With Commercial Aviation Accidents

A 44 case study analysis of the large-scale atmospheric structure associated with development of accident-producing aircraft turbulence is described. Categorization is a function of the accident location, altitude, time of year, time of day, and the turbulence category, which classifies disturbances. National Centers for Environmental Prediction Reanalyses data sets and satellite imagery are employed to dang- nose synoptic scale predictor fields associated with the large-scale environment preceding severe turbulence. These analyses indicate a predominance of severe accident-producing turbulence within the entrance region of ajet stream at the synoptic scale. Typically, a flow curvature region is just upstream within the jet entrance region, convection is within 100 krn of the accident, vertical motion is upward, absolute vorticity is low, vertical wind shear is increasing, and horizontal cold advection is substantial.