A bizarre weather phenomenon known as a fire cloud is likely to form over the fire raging between Lithgow and Bilpin if weather conditions deteriorate from Tuesday, as predicted, say fire analysts.
Andrew Sullivan, a leading bushfire behaviour researcher with the CSIRO, said the phenomenon required a fire generating a significant amount of heat.
As it burned, the hot air it released would rise as a column into the atmosphere. As air moved upwards, it was quickly replaced by cooler air, a process that produced a convection column.
In very large bushfires, these hot-air columns could be ”enormous” and rise high into the atmosphere carrying a large amount of water vapour – one of the main combustion products of fire.
An unstable atmosphere meant that the column could rise higher and higher into the atmosphere, where the temperature was cool enough for the water vapour to condense into a pyrocumulus cloud, said Dr Sullivan, a senior research scientist.
The fires are so large that they may spawn vortices or fire tornados. The clouds may also produce lightning which could potentially spark additional fires. Or, it could cause condensation and rainfall. Let’s hope for the latter.