Fire Lab Seminar Series
The Missoula Fire Sciences Laboratory has been hosting an annual seminar series since 1998. Hour-long seminars are presented by Fire Lab employees and other researchers from throughout the world. Seminars cover current research and management about the natural world from a broad range of disciplines, but most seminars usually have a wildland fire theme. The Fire Lab Seminar Series provides a platform for researchers and managers to present their work in an environment that encourages critical thought, the free exchange of ideas, and knowledge discovery.
December 3: The potential role of a downslope windstorm and associated hydraulic jump in the formation of a tornado-scale fire whirl during the 2018 Carr Fire
Thursday, December 3, 2026, 10am PT/1pm ET
Presenter: Natalie S. Wagenbrenner
This presentation will discuss the meteorological conditions leading up to and during the 2018 Carr Fire tornado-scale fire whirl. A fire whirl is a vertically-oriented rotating column of air, typically comprised of hot gasses and aerosols, generated in or near a fire. Fire whirls can range in size from less than 1 m in diameter with wind speeds less than 10 meters per second up to 3 km in diameter with wind speeds in excess of 50 meters per second. Fire whirls on the small end of the spectrum, similar in size and appearance to dust devils, are routinely observed during wildland fires. Large-scale fire whirls approaching the size of tornados are less commonly observed than their dust devil-size counterparts; however, when they do occur, they pose serious risks to property and human safety.
Two recent examples of tornado-scale fire whirls include one that formed on the 2025 Deer Creek Fire and one on the 2018 Carr Fire. The Deer Creek fire whirl was categorized as an EF2 vortex by the National Weather Service. The 2018 Carr fire whirl, which is the focus of this work, was categorized as an EF3 tornado with a diameter of 300 m and wind speeds over 64 meters per second. The whirl caused damage to roofs, vehicles, power infrastructure, and property. A firefighter and two civilians were killed by the whirl.
Fire whirls can develop wherever and whenever eddies can be expected. The wildland fire environment provides ample vorticity and buoyancy for fire whirl generation. Often the source of vorticity for a fire whirl is the ambient atmosphere and not the fire itself. We hypothesize that vorticity associated with a downslope windstorm and hydraulic jump along with intense fire behavior provided the necessary ingredients for generation of the EF3-scale Carr fire whirl. This work expands on previous analyses of the event that used satellite and radar data to investigate the role of pyroCb formation as a stretching and vorticity concentrating mechanism that facilitated growth of the fire whirl into a tornado.
We will provide a detailed analysis of the meteorological conditions leading up to and during the fire whirl through high-resolution numerical weather prediction simulations along with observations of surface winds and soundings to corroborate the numerical simulations. The goals of this work are to 1) provide a quantitative description of the atmosphere during the formation of the fire whirl; 2) characterize the presence of a downslope wind storm and associated hydraulic jump in the vicinity of the observed fire whirl; 3) provide a theory for why the Carr fire whirl formed where and when it did; and 4) summarize a list of watch out conditions that may be conducive to formation of similar large-scale fire whirls in the future.
