Is a Cold Pool Necessary for the Maintenance of a Squall Line Produced by a Cold Front Aloft?

Abstract

Abstract On 19–20 June 1979 a cyclone moved through the central United States. This cyclone contained a squall line associated with a cold front aloft (CFA), which caused significant damage. The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) was used to diagnose the role of the cold pool in the maintenance of the squall line. A control simulation with “full physics” was run, at 18- and 3.6-km grid spacing. Both simulations produced a squall line that was similar in location, orientation, and speed to the observed squall line, and displayed several characteristics that differed from the “leading line–trailing stratiform” paradigm for midlatitude squall lines. Sensitivity test simulations were run for both grid spacings, with diabatic cooling due to evaporation and melting of precipitation withheld to prevent the formation of a cold pool. These simulations produced a squall line similar to that in the control simulation, in terms of the location, orientation, and movement of the s...