Observations of turbulent kinematics and lightning-inferred electric potential structure in a severe squall line

Recent work by Bruning and MacGorman (2013) proposed an energetic measure of lightning flashes based on flash size (area) and rate. The resulting energy spectrum as a function of flash size had a consistent shape, and had an apparently linear scaling regime at the same length scales where a turbulent thunderstorm's inertial subrange would be expected. They hypothesized that electrical potential was organized by the (possibly turbulent) character of the convective flow. Since then, flash extent has also been applied to the energy available for NOx production by lightning, and the geometric, space-filling character of the lightning channel itself. A severe squall line that moved across West Texas on the night of 5 June 2013 caused extensive dam- age, including much that was consistent with 80-90 mph winds in the vicinity of Lubbock. The storm was samplednear Pep, TX during the onset of severe winds by two Ka-band mobile radars operated by Texas Tech University (TTU), as well as the West Texas Lightning Mapping Array (WTLMA). In-situ observa- tions by TTU StickNet probes verified the severe winds. Vertical scans with the radars were taken ahead of the storm and continuously for one hour behind the line in conditions consistent with the conceptual model for the transition zone of a mesoscale convective system. Doppler velocity observations from the radars (every 10 s at 0.33 deg beamwidth and 10 m gate spacing) clearly resolve the turbulent kinematics, includ- ing overturning eddies in front-to-rear flow just behind the squall line. Lightning energetics are inferred from WTLMA-derived flash size and rate, allowing for a test of the idea that the turbulent structure of the convection controls the distribution of electric potential energy discharged by lightning.