Numerical simulation and analysis of a prefrontal squall line. Part II: propagation of the squall line as an internal gravity wave

Abstract

The squall line was collocated with a surface front during its initial development (at 0000 UTC 18 June 1978), but then propagated faster than the front, resulting in a separation of approximately 200 km by 0300 UTC and 300-400 km by 0600 UTC. In this paper (Part II), the movement of the squall line in the model is shown to be due to the propagation of a deep tropospheric internal gravity wave in a wave-CISK-like (Conditional Instability of the Second Kind) process. The thermal and dynamic perturbations associated with the hypothesized wave are shown to be consistent with internal gravity wave theory, and the characteristics of the wave are compared to similar results from other wave-CISK studies. -from Authors