Fire-generated tornado confirmed in BC
An extensive NTP investigation has resulted in the confirmation and documentation of a rarely observed fire-generated tornado in southwest British Columbia.
In August of this year, NTP became aware of a video that clearly depicted an intense vortex over a lake near a raging nighttime wildfire somewhere in southwestern BC. NTP has been investigating this event since that time – very carefully, given this was potentially the first fire-generated tornado that we have recorded.
First, we needed to confirm the exact location and the time of the occurrence of the vortex. After many weeks of investigation, and with the help of various witnesses and various types of weather observations and analyses, we were able to confirm that the vortex occurred on the north shore of Gun Lake, at the northeast end of the lake near Gold Bridge, and that the time was approx. 4:45 AM on 18 August 2023.
Next, we needed to confirm that the vortex met the definition of a tornado. We knew from the video that a spray vortex was generated at the base of rotation over the lake, so that criterion was met. Using the location and time information, as well as high-resolution satellite imagery, photos and webcam video, we were also able to determine that the vortex occurred in the updraft region of a deep convective cloud composed of water doplets (not just a cloud of smoke and ash), again meeting the tornado definition criteria. We also noted that the anti-cyclonically rotating vortex occurred in the rear-left quadrant of the main fire area, matching the published literature on the development of fire-generated tornadoes.
Of interest, however, is that the parent deep convective cloud - or pyroCu - had not developed to the intensity of a fire-generated thunderstorm - or pyroCB. That is, an anvil area at the top of the thunderstorm was not apparent in satellite imagery, nor were any lightning flashes detected.
Though the terminology in this area of science is still developing, it should be pointed out that this intense vortex was not a brief, fire-filled 'fire whirl' but an actual tornado that is sometimes referred to as a pyro-tornado (or pyrotornado). This is the first such fire-generated tornado recorded by NTP, and appears to be the most thoroughly documented fire-generated tornado so far in Canada.
The story doesn’t quite end there though. There is evidence of tree damage in the fire zone onshore. We are still working to determine the exact location and scale of the damage and whether it is directly associated with the tornado, but the evidence is trickling in slowly. It may be some time before we know the answer to that question. For now, the event is being classified as a Tornado (over water) with a default rating of EF0.
If you have any further information related to this event, feel free to contact us as ntp @ uwo.ca.
Below is the event summary for this tornado, and a map showing the location where it occurred. They can be plotted via our NTP Dashboard as well.
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Event Name: Gun Lake, BC
Date: August 18, 2023
Start Time: 4:45 AM PDT (1145 UTC)
Final Classification: Tornado (Over Water)
Final EF-Scale Rating: EF0-Default
Estimated Tornado Location: 50.885N, 122.855W
A witness captured video of a tornado over Gun Lake (near Gold Bridge) that developed near an intense overnight forest fire. While the vortex (and spray vortex at the water surface) is visible in the video, darkness and heavy smoke obscure a clear view of cloud above. In order to confirm vortex contact with a parent storm aloft, NTP reviewed satellite imagery to determine if convective cloud was present in the area. While no evidence of a pyrocumulonimbus cloud was found in satellite imagery or lightning data, pyrocumulus (pyroCu) cloud was visible and determined to be the parent storm. As the pyroCu was associated with the active fire, this is considered a fire-generated tornado (often referred to as a 'pyro-tornado' or 'pyrotornado'). An area of snapped and uprooted trees at the shoreline near the tornado was reported. However, it is unclear if the tornado was over land at any point and caused the tree damage. NTP continues to seek out additional information for this event.
