Topic: Bushfire dynamics

[Jimmy Deguara]

Given the severe bushfires in Victoria December 2006 with impressive pyrocumulonimbus as well as experiences of other serious bushfires in the past, I think it deserves its own technical discussion - in particular, bushfire dynamics and its similarities and differences to storm behaviour.

I have long suspected since the 2002 Glenorie fires that the dynamics of fire plumes complete with pyrocumulus or pyrocumulonimbus are not too dissimilar to the dynamics of storms. I have video that was not tripoded and you can see rotation along the main front - updraft plume. You could also note that the bushfire was moving left of the mean level flow to a certain extent similar to multicellular flow though this may have been more influence byt topography. Some fire fighters have also noted an inflow wind (updraft) ahead of the fire. I know these observations are arguable but I would seriously like to see studies using doppler on the flow patterns - surely it must have been done with such an extensive doppler radar network in the US!

[Michael Bath]

A similar weather setup occurred on 22nd December 2001, though the fire was on a smaller scale. Nevertheless, it was responsible for significant pyrocumulonimbus clouds south of Woodburn.






Report:

http://australiasevereweather.com/storm_news/2001/docs/200112-02.htm


The soundings for Brisbane on 22/12/2001 and Wagga on 06/12/2006 are fairly similar I believe.





I guess the bushfires enhance the low level moisture (which was pretty marginal pre-storm environment) and provide additional lift.

Michael

[australiasevereweather]

John,

I am not sure I fully understand what you are trying to suggest in the previous statement - perhaps elaborate further and also expand the jargon and abbreviations. It seems that if I had to respond in the way I understand it, it seems you and I for instance may be on a similar line of thought.

Also, have you read the literature in relation to fire behaviour?

Regards,

Jimmy Deguara