In November, 2012 we wrote about some of the research that was conducted to study and document what can only be described as a fire tornado in Australia, a tornado-like event that can be generated by a wildfire. In recent years a new term has been coined — firenado — which seems appropriate.
It occurred near Chapman in the Australian Capitol Territories during the McIntyres Hut Fire January 18, 2003. After studying the event, Rick McRae of the ACT and others discovered that it traveled across 25 kilometers at 30 kph (19 mph), had horizontal winds of 250 kph (149 mph), and vertical winds of 150 kph (93 mph). Damage that occurred to trees and structures is much like what you would see after a tornado in Oklahoma.
Australia’s ABC TV produced an excellent video that goes surprisingly deeply into some of the scientific principles of this phenomenon, including fire behavior when a strong wind pushes a fire up a slope. This can result in spot fires at the bottom of the slope on the other side, the lee slope, which can be pushed rapidly up the lee slope by a wind eddy in the opposite direction of the prevailing wind (see the screen grab above from the video). They also documented how a fire at the top of the ridge can travel across the ridge at 90 degrees to the direction of the prevailing wind.
Knowledge about this kind of fire behavior is something that wildland firefighters should retain in their “slide file”, in the unfortunate event that they find themselves in danger of being entrapped and are considering using the lee side of a ridge as an escape route or a sheltering location.
Check out our November, 2012 article for more information about this 2003 event. The video below illustrates some of the findings developed by the fire researchers.
The information in the video can be even more interesting when considered along with the winds at the site of the Yarnell Hill Fire entrapment, as modeled by WindWizard. The image below is from page 79 of the Yarnell Hill Fire SAIT report. Click the image to see a slightly larger version.
While new to a generation, this is not a new phenomenon. Residents of Hinkly, Minnesota and Peshtigo, Wisconsin probably encountered this phenomenon as well. First hand reports and anecdotal evidence would seem to support that “firenadoes” obliterated both towns.