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Abstract This study utilizes mobile Doppler wind lidar (DWL) observations collected by the National Severe Storms Laboratory throughout recent collaborative field experiments. Using data from 50 deployments on 36 supercells between 2017 and 2023, this work compares the kinematic environments of tornadic and nontornadic right-moving supercells. The DWL observations provide the unique opportunity to sample the subhourly evolution of the storm inflow wind profile, especially below 500 m. DWL observations are combined with surface and radiosonde observations using optimal estimation to create complete vertical wind profiles for the quantification of severe weather forecasting parameters. Supplemental Rapid Refresh model profiles are used to estimate the near-storm environmental perturbations. The tornadic supercells show larger ground-relative winds, and ground-relative wind perturbations, than nontornadic supercells. Differences in storm-relative wind are less consistent but are larger above 1 km in tornadic environments with a signal for larger winds 10–20 min after tornadogenesis. Low-level storm-relative helicity (SRH) discriminates tornadic from nontornadic cases better than deep-layer SRH but does not show a tendency to increase leading up to tornadogenesis, nor does the wind shear or storm-relative wind (SRW). The tornadic environments have greater near-ground horizontal vorticity (both streamwise and crosswise) with vorticity maximized very close to the ground (≤100 m), indicating the potential importance of frictionally generated vorticity and related processes. Overall, this work demonstrates the utility of DWL for sampling near the ground in storm environments while providing clarity on results from recent literature. Significance StatementForecasters and researchers continue to search for ways to differentiate between supercells that produce tornadoes and those that do not. Most previous studies have used vertical profiles of the atmosphere derived from models or radiosonde observations. Mobile deployments of Doppler wind lidars allow for new observations not widely used in severe storm research. Analysis of the resulting wind profiles provides a more detailed understanding of supercell environments. Findings from this work support many past results including the best layers over which to diagnose various severe parameters. A detailed look into near-ground observations reveals how tornadic storms modify their environments differently from nontornadic storms and supports studies that show how the stronger near-ground wind speeds may contribute to the rotation supporting tornado potential in the storm.
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This content will become publicly available on March 1, 2027
Will a Worm Turn? Observations of Coherent Surface-Layer Vertical Vorticity in Supercell Inflow
Abstract A recent supercell modeling study showed that coherent turbulent structures associated with significant near-surface vertical vorticity in the ambient environment may serve as seeds for tornadoes. These structures, colloquially coined “vorticity worms” owing to their elongated and meandering appearance, develop within the surface layer in strong flow and are distinct from the larger-scale horizontal convective rolls often seen in the mixed layer. Elongated coherent turbulent structures are a common feature of the atmosphere and have been heavily studied by the boundary layer community, but before the recent simulation, they have not been previously implicated as facilitators of tornadogenesis. Observations of these structures around supercells have been limited, and historically, the observing platforms most often used in storm-focused data collection have not prioritized the precipitation-free inflow surface layer especially at the spatial and temporal resolution required to capture these structures and their interactions with storms. In recent field deployments, the National Severe Storms Laboratory used a truck-mounted pulsed Doppler lidar to perform near-ground scans to search for vorticity worms in real supercell inflow to compare with the simulation findings. Multiple deployments revealed vorticity worms and near-surface horizontal vorticity in supercell inflow that were consistent with the recently published supercell simulations that motivated this work. In two presented cases, vorticity worms were associated with the development of pretornadic, near-ground vortices, although neither circulation reached tornadic strength. These observations provide credibility to the recent simulations and suggest that continued observations of these coherent structures and research into their role in tornadogenesis are worth pursuing. Significance StatementNew simulations suggest that a source of rotation for tornadoes may originate in the ambient environment in the form of streak-like coherent structures near the ground. We used a mobile Doppler lidar to document the existence of these streak-like structures around storms and present cases where these structures developed into regions of enhanced rotation when they moved near the storm’s updraft. These observations provide credibility to the recent simulations and suggest that more research and observations of these structures around storms are needed to confirm if these structures play a role in tornado formation.
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- Award ID(s):
- 2150792
- PAR ID:
- 10691368
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Bulletin of the American Meteorological Society
- Volume:
- 107
- Issue:
- 3
- ISSN:
- 0003-0007
- Page Range / eLocation ID:
- E675 to E695
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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