Lightning Outbreaks at the Mature Stage of Tropical Cyclone: Case Study for Hurricane Dorian (2019)

Abstract The relationship between tropical cyclone (TC) lightning activity and intensity change has been examined for nearly 30 years, yet a clear consensus remains elusive, reflecting the complexity of the processes governing TC lightning. This study investigates the physical mechanisms that triggered inner‐core lightning outbreaks during the mature stage of Hurricane Dorian (2019) using multiple observational data sets. Compared with the rapid intensification period, substantially more inner‐core lightning flashes were detected during the mature stage. Airborne radar and dropsonde observations revealed that, immediately before the outbreak, small‐scale (∼5 km horizontal extent) isolated updrafts exceeding 10 m s −1 developed at ∼2.5 km altitude in the eyewall. The lightning outbreak coincided with these updrafts penetrating into the mid‐to‐upper troposphere. The low‐level updraft maxima were accompanied by isolated relative vorticity maxima of a similar scale—indicative of a mesovortex—and were associated with enhanced low‐level convergence. Flight‐level data and TC‐specific atmospheric motion vectors derived from geostationary satellite observations indicated that angular velocity and vorticity distributions across the eye–eyewall interface became homogenized during lightning outbreaks, suggesting that mesovortex generation was associated with barotropic instability. These findings suggest a possible link between Dorian's inner‐core lightning outbreaks, enhanced convective updrafts, and barotropic instability, allowing their relationship to TC intensity and structural changes to be discussed from a dynamical perspective. This study not only explores the potential role of barotropic instability in lightning outbreaks but also underscores the importance of linking lightning activity to the underlying TC dynamics.