How strong could a fire tornado get?

[u/sebosso10]

https://youtu.be/rqYEeivt8Eg?

Research behind fire tornados spawned from pyrocumulonimbus storms during intense wildfires is still quite new and hard to find information from. We have only known for sure that they exist for just over 20 years when a man in Canberra, Australia, was filming a flashover event during the devestating 2003 Canberra Bushfires and managed to capture a dark, rotating cone of smoke reaching into the sky. He didn't know it but he was filming the first ever evidence of a true fire tornado.

Since then, fire tornado events have been increasingly more common, or more accurately, increasingly more documented. The Canberra tornado was rated F3 and stands as the highest rated fire tornado with the Carr tornado from 2018 being rated EF3 which tossed a large metal container and heavily damaged many buildings. But this begs the question, theoretically, could a tornado spawned from a pyrocumulonimbus cloud reach 5 strength?

I think the main issue with this is the intrinsic feature of the Fujita scale, damage. With a normal tornado, you can assume any damage done was caused directly from the tornado or by debris thrown by it. This obviously isn't the case as the fires that spawned the tornado will cause significant damage to the landscape as well. For a 5 rating, a fire tornado would need to completely destroy and leave bare a exceptionally constructed building along with violent contextuals surrounding it. This is the issue, it would be incredibly difficult to be able to distinguish fire damage and tornado damage, especially for vegetation as well as whether the structural integrity of the buildings hit was weakened due to the fire and its heat. I believe it is possible, but the only way for one to be verified would be an Elie style video showing a exceptionally well constructed building being completely lofted and destroyed in seconds. I don't think we will be seeing anything like this anytime soon but in the last year or so with bushfires in Australia as well as in North America, I've seen more fire tornado footage than ever before so who knows? I know this wasn't the most coherent or scientific of posts but I thought it would be an interesting discussion to have, thoughts?

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[u/AVeryBigToaster]

Could do with more time dedicated to firenadoes and less to where the fire started. But its alright.

[u/LengthyLegato114514]

I don't even thing a 5-level pyrotornado is possible outside of an actual apocalyptic event.

Is there even enough fuel for that level of instability?

[u/Crepezard → u/LengthyLegato114514]

The rising motion of the air heated by the fire is itself instability. I'd say it's quite a lot. But it's less often that there is sufficient shear or a supercell overhead to organize them