Surface Analysis of the Rear-Flank Downdraft Outflow in Two Tornadic Supercells

Abstract

The rear-flank downdraft regions of two tornadic supercells were sampled on 12 June 2004 and 9 June 2005 using four “mobile mesonet” probes. These rear-flank downdraft outflows were sampled employing two different data collection routines; therefore, each case is described from a different perspective. The data samples were examined to identify variations in measured surface equivalent potential temperature, virtual potential temperature, and kinematics. In the 12 June 2004 case, the tornadic circulation was accompanied by small equivalent potential temperature deficits within the rear-flank downdraft outflow early in its life followed by increasing deficits with time. Virtual potential temperature deficits modestly increased through the duration of the sample as well. The 9 June 2005 case was highlighted by heavy precipitation near the tornado itself and relatively small negative, or even positive, equivalent and virtual potential temperature perturbations. Large horizontal variations of surface thermodynamic properties were also noted within several regions of this rear-flank downdraft outflow.