Extreme Pyroconvective Updrafts During a Megafire

Abstract

Airborne cloud radar reveals extreme wildfire updrafts (~60 m s−1) and downdrafts (~30 m s−1) rivaling those in supercell thunderstorms. These extreme vertical velocities occur through a 3-km-deep layer and below the base of a developing pyrocumulonimbus (pyroCb) cloud, which extends to the tropopause at 12 km. In situ aircraft sampling shows updrafts are linked to large temperature and moisture excesses but remain subsaturated at flight level (i.e., below cloud base). Parcel estimates using the in situ data help explain how these “hot-moist” updrafts trigger the overlying pyroCb. The extreme vertical motions observed also pose a previously undocumented aviation hazard.