How Did Updraft Variations in the Geary Supercell Influence Local Electrification?

The Geary, Oklahoma high-precipitation supercell storm of 29-30 May 2004 provides a unique opportunity to examine in detail the evolution of storm electrification regions surrounding the storm updraft during the complete cycle of formation, maturation, and dissipation of a mesocyclone. A previous study (Betten et al. 2018) used a 1.5-hour period of continuous dual-Doppler radar data to analyze the evolving kinematics during this cycle in detail. The present study adds data from the Oklahoma Lightning Mapping Array (OKLMA) throughout that period to analyze the origins of lightning flashes and the charge regions inferred from the OKLMA data relative to the evolving mesocyclone. Furthermore, the fields of temperature, supercooled cloud water, cloud ice, graupel/hail, and snow, all of which are highly relevant to mixed-phase noninductive graupel/hail-ice collisional charging, have been inferred by applying a diabatic Lagrangian analysis to the synthesized wind fields throughout the period. This storm had a complex charge structure during the intensification of the supercell, studied by Calhoun et al. (2013, 2014). The charge regions inferred from OKLMA data continued to be complex and varied considerably in time and space near the updraft during the whole mesocyclone cycle and replacement studied by Betten et al. For an example of the variability, the narrow lightning-producing region on the southwestern edge of both the weak lightning region and weak echo region produced net positive charge at 8-10 km MSL from 0016 to 0022 UTC during the organization phase of the second-observed mesocyclone during the observation period, followed by a transition to net negative charge in the same layer by 0033 UTC during its mature phase and returning to net positive by 0102 UTC during the organization of the following mesocyclone cycle. To the north along the weak lightning region the charge structure varied from a traditional normal-polarity charge structure containing net negative charge at 7-10 km MSL with net positive above and below to more complicated structures containing up to 6 identifiable charge layers. Meanwhile, the 6-9 km MSL layer immediately east of the primary updraft in the forward flank region consistently contained net positive charge throughout the study period, but with significant temporal variations in flash initiation regions. This paper presents several aspects of how the inferred charge regions evolved with respect to local and temporal variations in the updraft and microphysics of the supercell, focusing on what the inferred charge region morphology may reveal about the storm morphology.