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Abstract Radar and satellite observations document the evolution of a destructive fire‐generated vortex during the Carr fire on 26 July 2018 near Redding, California. The National Weather Service estimated that surface wind speeds in the vortex were in excess of 64 m/s, equivalent to an EF‐3 tornado. Radar data show that the vortex formed within an antecedent region of cyclonic wind shear along the fire perimeter and immediately following rapid vertical development of the convective plume, which grew from 6 to 12 km aloft in just 15 min. The rapid plume development was linked to the release of moist instability in a pyrocumulonimbus (pyroCb). As the cloud grew, the vortex intensified and ascended, eventually reaching an altitude of 5,200 m. The role of the pyroCb in concentrating near‐surface vorticity distinguishes this event from other fire‐generated vortices and suggests dynamical similarities to nonmesocyclonic tornadoes.
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This content will become publicly available on September 22, 2026
Counter Rotating Vortices during Northern California’s 2021 Dixie Fire
Scanning Ka-band Doppler radar observations reveal the development and intensification of a counter-rotating vortex pair (CVP) embedded in an advancing fire-front during California’s Dixie Fire in August 2021. The observations show that an initially isolated plume associated with a new spot fire develops flow splitting and a fire-generated inflow wind on the plume’s lee side. This inflow retards the fire progression and enhances the lateral wind shear along the plume flanks. The lateral shear evolves into quasi-symmetric cyclonic and anticyclonic vortices with winds >40 m s−1. This counter rotating vortex pair (CVP) spreads perpendicular to the wind direction, yielding a “y-shaped” fire perimeter, with fire intensity and direction of spread strongly linked to the vortices. Detailed snapshots of the vortices reveal associated radar hook echoes and orbiting sub-vortices of tornado-like intensity. Some vortices remain attached to the fire, while others shed downstream. Additional lidar observations show the structure and development of the fire’s inflow. We discuss the observed vortex evolution in the context of existing conceptualizations for CVPs in wildland fire, including their preferential occurrence on lee slopes and their role in generating lateral fire spread.
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- Award ID(s):
- 2114251
- PAR ID:
- 10639786
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Monthly Weather Review
- ISSN:
- 0027-0644
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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