Understanding the interplay between lightning activity and hydrometeor distribution is crucial for advancing knowledge of thunderstorm electrification processes. Using three-dimensional lightning mapping and dual-polarization radar observations, this study investigates the spatiotemporal correlations between low-frequency (LF) lightning sources and hydrometeors during a severe thunderstorm on 11 June 2014, in North Carolina, USA. The results reveal that lightning sources are predominantly observed above 6 km (near the −10 °C isotherm) and stabilize into a dual-peak vertical distribution as the storm progresses into its mature stage, with peaks located at 6–7 km (−10 °C to −15 °C) and 10–11 km (approximately −40 °C). Low-density graupel (LDG) and aggregates (AGs) dominate at lightning locations. Stronger updrafts lead to higher proportions of LDG and high-density graupel (HDG), and lower proportions of AG. LDG exhibits the strongest positive correlation with LF lightning sources, with a peak correlation coefficient of 0.65 at 9 km. During the vigorous development stage, HDG and hail (Ha) also show positive correlations with LF lightning sources, with peak correlation coefficients of 0.52 at 7 km and 0.42 at 8 km, respectively. As the storm reaches its mature phase, the correlation between LDG and lightning sources also displays a dual-peak vertical distribution, with peaks at 7–8 km and 13–14 km. Both the peak correlation coefficient and its corresponding height increase with the strengthening of updrafts, underscoring the critical role of updrafts in microphysical characteristics and driving electrification processes.

This study investigates the diversity of the impact of the North Pacific Meridional Mode (NPMM) on western North Pacific (WNP) tropical cyclone (TC) genesis during June–November from 1961 to 2024. We consider preceding springtime NPMM events driven by tropical and extratropical forcings, and classify them as successive and stochastic events, respectively. In successive positive NPMM years, TC genesis changes only slightly over the entire WNP. In successive negative NPMM years, significant increases (decreases) in TC genesis are observed over a region spanning 20°–140°E, 0°–20°N (140°–160°E, 0°–20°N). In stochastic NPMM years, there are significant increases in TC genesis over a region spanning 135°–160°E, 5°–25°N. These changes in TC genesis can be explained by the anomalous environmental conditions in different NPMM years, which can be further linked to the NPMM's strength as well as sea surface temperature anomalies over the tropical western Pacific.