Regional Adaptation and Convergent Thresholds: Environmental Controls on Extreme Thunderstorm Duration in Pakistan and Kazakhstan

Extreme-duration thunderstorms (≥9 hours) produce catastrophic flooding across Pakistan and Kazakhstan, yet atmospheric conditions enabling persistent convection across diverse climatological regimes remain poorly understood. This study analyzes 56 extreme-duration storms and 200 control storms (0.5–3 hours) from 2010 to 2023 using lightning observations and ERA5 reanalysis to compare environmental requirements in Pakistan's monsoon-influenced regime versus Kazakhstan's continental interior. Control storms reveal fundamental regional differences: Pakistan exhibits higher baseline moisture (32.6 versus 26.5 kg m⁻²), instability (793 versus 241 J kg⁻¹ CAPE), and shear (11.7 versus 9.3 m s⁻¹). Extreme-duration storms emerge through regionally distinct pathways shaped by these baselines. In Pakistan, where western disturbances (February to April) account for 62.5% of extremes and supply strong ambient shear, extreme persistence is distinguished by pronounced moisture (67%) and instability (291% CAPE) enhancement relative to season-matched controls, while shear is already near ambient levels. Kazakhstan shows broad enhancement including CAPE (400%) and moisture (39%), occurring exclusively during warm-season moisture intrusions (May to August). Extreme storms also yield greater total precipitation than controls in both regions. Despite these distinct pathways, extreme storms from both regions converge on a common moisture regime near 37 kg m⁻², with formal statistical equivalence established through two one-sided tests (TOST, p = 0.031), while CAPE, shear, and propagation speed show consistent point estimates with sample-limited statistical power. These convergent thresholds provide operational benchmarks across climatologically diverse regions, while the contrasting pathways suggest that warming-driven changes in extreme convection frequency will differ systematically between moisture-rich and moisture-limited regimes.