Simulated Effects of an Isolated Supercell on the Evolution of a Nearby Squall Line
Past studies have shown that in cases of squall line-supercell mergers, there was a weakening of the squall line near the onset of the merger due to the outflow from the supercell cutting off inflow to the squall line. In these cases the two storms were in close proximity, and it is unclear how the effect may change for a supercell further ahead of the line. In cases of supercell-supercell interactions, the outflow from one supercell has been shown to enhance the tornado production in a trailing supercell. This study hypothesizes that the cold pool produced in the wake of an isolated supercell will be strong enough to promote localized heterogeneity along the nearby squall line, and may favor the development of mesovortices or small bowing segments. The effect of the supercell's outflow is, however, expected to vary based on its intensity due to the range from the squall line or type of supercell (high precipitation, low precipitation, and classic).
To examine these effects, squall line-supercell interactions have been simulated using the Bryan Cloud Model (CM1) configured with a double moment microphysics scheme, convection-resolving grid spacing, and an environment favorable for supercell structures and bow echoes. The Base-State Substitution method was used to effectively simulate both convective modes in the same horizontally homogeneous environment. A pair of benchmark simulations will be discussed that compare the squall line in isolation to one in close proximity to a supercell. Special attention will be paid to the effects that the presence of the supercell has on the squall line's cold pool and low-level lifting, along with the development of any mesovortices. These results will be compared with a series of sensitivity tests run to explore the effects of the proximity of the two storm types, as this is likely to impact the depth and strength of the supercell's outflow.