Relationship Between CAPE & Air Vertical Velocity- V2

This paper presents the first empirically-derived efficiency coefficient (η) for CAPE-to-updraft velocity conversion in supercell thunderstorms, derived from direct aircraft measurements obtained during STEPS 2000 Flight 761 using the South Dakota School of Mines T-28 armored research aircraft. The conventional assumption of η ≈ 0.5, drawn from generalized atmospheric parcel theory, is shown to systematically underestimate observed updraft velocities in supercell environments. Using T-28 in-situ measurements of vertical wind velocity paired with proximity sounding CAPE values, this study derives an empirically-constrained η range of 0.72–0.96 for mature supercell updrafts — a finding corroborated by supporting cases from the CCOPE (1981) and C3LOUD-Ex (2016–17) field campaigns. The physical mechanisms responsible for supercell efficiency enhancement — including reduced entrainment in rotating updraft cores, dynamic pressure perturbations from storm-relative wind shear, and compensating effects of water loading — are discussed in the context of existing literature. These results carry direct implications for operational severe weather forecasting, hail size estimation, and applied meteorology contexts requiring defensible updraft velocity quantification from standard atmospheric sounding data.