Despite the shallow nature of the convective layer and a relatively cold environment (surface temperature=10 o C), this squall line exhibited characteristics typical of many squall lines in warmer environments. These included a line of strong reflectivity cores followed by a trailing stratiform precipitation region and rear inflow jet. The leading gustfront remained within 3 km of the high reflectivity cores, a feature typical of intense squall lines observed and modeled in warmer environments. However, this squall line also exhibited a slight forward tilt of the core and a more extensive forward anvil overhang with respect to its motion. In an environment consisting of greater than 50 kts of shear in the convective layer, and a CAPE of around 500 j/kg, this study will attempt to answer how this squall line retained its upright character.
For the 30 minutes prior to the first observed tornado, a quasi-two-dimensional bounded weak echo region (BWER) was observed by radar underneath a forward-tilted elevated core. This linear BWER exhibited 3-D variations in intensity, as inferred by the changes in minimum reflectivity at a constant altitude, along its length. This BWER structure suggests that a strong linear updraft was in progress from near cloud base up to 3 km above radar level with local along-line variations in strength. This background updraft with the along-line variations in intensity above a gustfront with intense convergence may have allowed locally enhanced tilting of horizontal vorticity in the lowest two kilometers above ground level to produce small 1-2 km diameter tornadic circulations.