An “incredibly rare phenomenon” during a wildfire near Lillooet was caught on video last week.
The fire whirl, or “fire tornado,” was caught on video by an overnight ground personnel responding to the Downton Lake wildfire on Aug. 17. Fire whirls are “intensely rotating columns of gas and flames,” BC Wildfire Service explained in a series of tweets Tuesday (Aug. 22).
A cold front passed through the province Aug. 18 after several days of dry hot weather and when it passed through the Gun Lake area in the Bendor Range Complex fires near Lillooet it resulted in the “fire tornado.”
The “unique conditions and extreme fire behaviour” are not experienced in the majority of B.C. wildfires, but BC Wildfire Service explained the conditions that led to the “fire tornado.”
There were strong winds from the southwest, resulting in significant fire growth and intensity, the relative humidity value of 14 per cent at 4 a.m. that BC Wildfire said was “incredibly rare to see overnight” and a reduced measure of how much moisture was in the air of -11 C.
BC Wildfire Service said it was a significant drop – 20 C lower than the day prior to the cold front.
“With this combination of conditions and fire behaviour, fire intensity was more extreme during this overnight period, reaching intensities that hadn’t been seen even during the day.”
With the combination of high fire intensity, strong winds and air mass instability, it led to the formation of a fire whirl over Gun Lake.
Another important factor in the formation of whirls is adequate vorticity, a measure of the atmosphere’s tendency to spin or rotate. Complex terrain, downslope winds and the passing cold front provided the necessary conditions for the formation of this fire whirl over Gun Lake.
— BC Wildfire Service (@BCGovFireInfo) August 22, 2023