Recent radar observations of wave-like features interacting with quasi-linear convective systems

The environmental set-up for quasi-linear convective systems (QLCS's) is one that is also often conducive to wave generation, such as gravity waves. During the months of February, March and April, 2011, at least 4 separate cases of potential wave interactions with QLCS's was observed via the WSR-88D network in the Southeastern United States. During and after the wave interaction, some or all of the following was observed:

1). a localized change in the reflectivity structure of storm cells within the QLCS,

2). a localized change in the speed and direction of the linear system,

3). the formation (or strengthening if already present) of a low-level mesocyclone and at least one case of tornadogenesis

4). a clustering of damaging wind reports.

Changes in the reflectivity structure, speed, and direction of the linear system were often manifested as the formation of localized bowing segments or the development of a line-echo wave pattern.

Previously, Coleman and Knupp (2008) found that the interactions of ducted gravity waves with preexisting mesocyclones can increase the vorticity of the mesocyclone through the convergence-divergence and perturbation wind shear associated with the gravity wave. The observations here give further validity to their findings, but also paint an important picture of the role of wave interactions with localized changes in the QLCS's reflectivity and velocity structure. For example, it is hypothesized that wave interactions are an important component for some “spin-up” tornadoes along the leading edge of linear systems.

One case (28 Feb 2011) will be described in detail during a separate presentation to be given at this conference.