Observations of Anomalous Charge Structures in Supercell Thunderstorms in the Southeastern United States

Anomalous thunderstorm charge structures (ACSs), characterized by a dominant layer of positive charge in the lower mixed-phase region, are uncommon and rarely reported outside of the Great Plains region of the United States. This study documents the kinematics, precipitation microphysics, and charge structures of two supercell thunderstorms exhibiting ACSs that were observed in the Southeastern United States. Ground-based three-dimensional total lightning observations, polarimetric Doppler radar observations, and environmental model analysis of these supercells presented the opportunity to evaluate conceptual models of ACS development and characteristics in an atypical parameter space. In both anomalous storms, prominent layers of positive charge were located in lower to middle mixed-phase regions (-10 degrees C to-30 degrees C) of updrafts and were spatially associated with riming hydrometeor types. Simultaneously, negative charge regions were identified above the primary positive charge layers in the upper mixed-phase and glaciated region of updrafts, collocated with graupel and small ice hydrometeors. While coarse charge structure observations were consistent with noninductive charging-based models of anomalous storms, charge structure complexities were also observed that suggested variability in cloud microphysical conditions. Analysis of the environments in which these storms formed indicated that several parameters thought to increase mixed-phase liquid water content in favor of anomalous charging were inconsistent with those documented in the Great Plains region. However, environmental humidity metrics were most comparable. Comparisons between these and other documented anomalous storms identified similarities in kinematic structure and microphysical conditions while motivating ongoing study of the environmental parameter space supportive of ACSs.