Numerical Simulation and Analysis of a Prefrontal Squall Line. Part I: Observations and Basic Simulation Results

Abstract

An observational and numerical study of the squall line that occurred on 17?18 June 1978 is presented. This squall line was initially triggered by the strong surface convergence along a cold front and stretched from Illinois to the Texas Panhandle. The squall line was aligned with the 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. The Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) is used to model the squall-line development and propagation. Results are described from several experiments that tested the sensitivity to the use of the Kuo-type cumulus parameterization scheme and grid-scale microphysical processes. The simulations that included the cumulus parameterization scheme accurately modeled the initial development of the squall line and its subsequent movement away from the front.