Pyrocumulonimbus pair in Wollemi and Blue Mountains National Parks, 22 November 2006

Abstract

On 22 November 2006 a pair of pyrocumulonimbus (pyroCb) storms, roughly 75 km apart, erupted simultaneously in the forests of Wollemi and Blue Mountains National Parks. The so-named Wollemi and Grose Valley fires blew up at an unusual time—late morning—and injected smoke into the uppermost troposphere. This is the first pyroCb event recorded during active pyroconvection by NASA’s A-Train satellite constellation. Hence we show for the first time the pyroconvection column from simultaneous passive imagers, active lidar and radar, and UV backscattering instruments. There are no previous reports of pyroCb activity from Wollemi, and a report of the Grose Valley pyroconvective column limited its vertical extent to 6 km. Here we show, using ground-based radar data, that both fires blew up quasi-simultaneously before local noon. The Grose Valley pyroCb penetrated to the tropopause, the Wollemi pyroCb injection height exceeded the tropopause by 1–3 km. Analysis of a portion of the smoke plume sampled by the A-Train on 23 November confirms tropopause injection altitude. We explore a variety of meteorological observations and analyses to determine that the blow ups on 22 November 2006 (and only on this date in the fires’ lifetimes) were mostly a consequence of anomalous boundary layer warmth and wind speed.