DISCUSSION: The intense heat generated by wildfires causes air to rise. To replace the rising air at the surface, air must converge. Sometimes as it converges, it begins to rotate. Similar to an ice skater pulling in her arms, as this rotation gets squeezed smaller, it speeds up. Nevertheless, most rotation generated by fires (called fire whirls by the National Weather Service) is relatively weak and/or occurs far from populated centers such that they don't cause much additional damage already generated by the fire itself. Such was not the case for a fire whirl generated by the Carr Fire in California on July 26, 2018 (pictured above). This particular whirl (dubbed a "fire tornado" by the California Department of Forestry and Fire Protection) had wind speeds of up to 165 mph, equivalent to an EF-3 tornado, that destroyed homes, trees, and transmission towers. In addition, two fatalities were attributed to this fire whirl. It also lasted a lot longer than typical fire whirls of ~80 minutes.
There were a lot of pictures, videos, and data collected near this fire whirl that scientists are now combing through to try to better understand the conditions that spawned this intense whirl and perhaps better predict their occurrence in the future. However, small, transient circulations in the atmosphere are very difficult to predict when only atmospheric dynamics are at play. But, here there is an interplay between atmospheric and fire dynamics, making understanding this fire whirl even more challenging. In addition, documentation of fire whirls this intense are rare, further complicating our understanding of these events. What scientists do know is that while damage caused by this whirl is comparable to a tornado, the conditions and forces that generated it are far different that those governing the more typical formation of tornadoes from supercell thunderstorms. Hence, the National Weather Service is hesitant to call this event a "fire tornado." In addition, we cannot say this event was caused by climate change. Climate change occurs on a much larger space and time scale than this fire whirl. In addition, it is possible that these types of events occur more often in rural areas where they are more difficult to observe, and there is less to damage, thus inhibiting an accurate estimation of intensity. Nevertheless, there is still much to be learned about fire whirls, in particular these high-intensity ones.
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© 2018 Meteorologist Dr. Ken Leppert II