Extreme Pyroconvective Updrafts During a Megafire

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. Plain Language Summary Massive wildfires (i.e., megafires) produce enough heat to generate powerful updrafts that are as strong as those observed during tornadic supercell thunderstorms. Weather radar data show that these updrafts are as strong as 130 mph (209 km/hr) and extend for miles above the surface. These updrafts can trigger fire‐generated thunderstorms and pose a threat to aircraft flying in the vicinity of large wildfires. Key Points Megafires produce extreme updrafts rivaling those in supercell thunderstorms. These updrafts help trigger pyrocumulonimbus clouds that reach to the tropopause