A Three-Dimensional Numerical Analysis of Colliding Microburst Outflow Dynamics

Abstract

A parameter study of colliding microburst outflows is performed using a high-resolution three-dimensional model. The colliding microburst pairs me simulated in a domain of 18 km ? 16 km ? 4.25 km with 50-m resolution. Microburst pairs are examined in varying space and time separations, and the authors find that for certain geometries strong elevated wind fields are generated from the interactions between outflows. For a narrow range of space-time geometries, this elevated wind field is extremely divergent. An examination of the F-factor aircraft hazard parameter reveals that both the divergent wind fields and microburst downdraft cores are regions of danger to jet aircraft. Trajectory analysis reveals that the air composing the elevated jets can be traced back to the shallow outflow formed beneath each microburst core. An analysis of the parcel kinetic energy budget indicates that the pressure domes beneath and between the microbursts are the primary mechanisms for directing energy into the elevated jets.