The BC Wildfire Service has published a video of a fire tornado spotted at the Downton Lake wildfire last week.
Last week’s cold front moved over B.C. causing strong winds and sending many wildfires in the Southern Interior on large runs.
At the Downton Lake wildfire near Gun Lake and Lillooet, the relative humidity reaches 14% at 4 a.m, a figure the BC Wildfire Service says is extremely rare overnight.
There was also a reduced dew point (a measure of how much moisture is in the air) of -11C on August 18. This was a significant drop, 20C lower than the day, prior to the cold front, said BCWS.
“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,” BCWS said in a social media post.
“As shown in the video, the combination of high fire intensity, strong winds and air mass instability resulted in the formation of a fire whirl (otherwise known as a fire tornado) over Gun Lake. These fire whirls are vertically oriented, intensely rotating columns of gas and flame.”
“Another important factor in the formation of these whirls is adequate vorticity, a measure of the atmosphere’s tendency to spin or rotate. The complex terrain, downslope winds and impact of the passing cold front provided the necessary conditions for the formation of this fire whirl over Gun Lake.”
The BC Wildfire Service says fire whirls are an “incredibly rare phenomenon” and are not experienced on the majority of fires in B.C.