An Examination of Small Lightning Flashes in Mixed Storm Modes

The dependency of electrification structures on mixed-phase microphysics allows lightning properties to respond to and reflect the rapid changes that occur in thunderstorm updraft regions.The comprehensive information provided by Lightning Mapping Array (LMA) observations, including lightning flash altitude, frequency, size, and three-dimensional spatial distribution, reveal unique characteristics in these regions that provide additional insight into the evolution of the updraft. Specifically, the flashes responding to the most rapid evolution are often limited in spatial extent, which may not be detected by operational lightning networks and limits their ability to inform about convective intensity. The data collections from the Propagation, Evolution and Rotation in Linear Storms (PERiLS) project give us a unique opportunity to study such lightning flashes in both tornadic Quasi-linear Convective Systems (QLCSs) and preceding convection. Their relative contribution to the total flash rates measured by the LMA varied from storm to storm. For example, in the mixed-mode storms of 22-23 March 2022 there were relatively few small flashes at any point in time – typically fewer than 30% of the flashes for any storm cell had areas smaller than 4 km². Conversely, at the maximum of lightning-production in the Rolling Fork supercell on 25 March 2023, roughly half of the flashes were smaller than 4 km². We will examine how these small flash distributions evolved alongside other lightning characteristics in the PERiLS cases; where we did, and didn’t, see significant proportions of them in the sampled storms; and the potential operational implications of these results considering the higher sensitivity of the LMA to such small flashes than the operational lightning observing platforms.