A summary of the recent presentation by Karen A. Kosiba (University of Alabama Huntsville), Joshua Wurman, and Paul Robinson, “DOW Radar Studies of the Mechanisms for Tornadogenesis, Maintenance, and Dissipation,” presented at the 41st International Conference on Radar Meteorology, August 25-29, 2025, Toronto, Ontario, Canada. Click the link above for the abstract and recorded presentation.
Understanding the processes that contribute to tornado evolution is necessary for
better prediction of tornado hazards. Critically, our studies focus on identifying
mechanisms for generating, concentrating, and maintaining tornado-strength
vertical vorticity at the surface, and on how the evolution of these mechanisms
can be used to predict tornado intensity evolution. Compared to single-Doppler observations of tornadic storms, coordinated observations from two or more mobile radars
for dual-Doppler analyses are relatively infrequent, but they are essential to providing
additional insight into the processes contributing to tornado intensity changes. Using rapid
update single- and dual-Doppler analyses, we examine the environmental and sub-stormscale
features and processes that contributed to the evolution of a strong tornado.
As part of the Boundary-layer Evolution and Structure of Tornadoes (BEST) project, the Doppler on Wheels (DOW) radars collected an exemplary dual-Doppler dataset during the EF-2-rated, Duke, Oklahoma, tornado on May 23, 2024. Over 30 minutes of every-7-second dual-Doppler data collection, with a 4.2-km baseline, allowed for unprecedented temporal and spatial resolution—literally thousands of vector-wind snapshots—of quickly evolving small-scale features associated with vertical vorticity production during the intensification, maintenance, and dissipation phases of the tornado. During the intensification and maintenance phases, we observed regions of substantial vertical vorticity along the forward and rear flank convergence zones. During the dissipation phase, the tornado essentially loses its immediate source of vertical vorticity. The forward flank convergence boundary weakens and vertical vorticity along the convergence zone decreases. The rear flank convergence boundaries “detach” and move away from the tornado. Changes in intensity appear to be linked to changes in vertical vorticity surrounding the tornado, with a lag between the magnitude of the 1-km circulation and tornado intensity. This suggests a causal link, which may assist
in predicting intensity changes.
DOW Data and Dual-Doppler Analysis
vertical vorticity features (cyan contours) present in the single-Doppler data.
Exactly how appreciable vertical vorticity is produced along the convergence zones is an ongoing investigation. Similar to many previous DOW observations of supercells, single-Doppler data revealed the presence of boundary layer streaks / rolls in the near-ground near-storm environment. These have been hypothesized to contribute to vertical vorticity production, and will be evaluated in the context
of possible production mechanisms along the convergence zones. Additionally, there is an ongoing effort to intercompare the ~20 dual-Doppler cases collected by the DOWs at different stages of tornado evolution and evaluate the commonalities that contribute to tornado intensity changes.
