Editorial Type:
Article
Article Type:
Research Article

A Comparison of Near-Surface Buoyancy and Baroclinity across Three VORTEX2 Supercell Intercepts

Christopher C. Weiss Department of Geosciences, Texas Tech University, Lubbock, Texas

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David C. Dowell NOAA/Earth System Research Laboratory, Boulder, Colorado

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John L. Schroeder Department of Geosciences, Texas Tech University, Lubbock, Texas

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Patrick S. Skinner Department of Geosciences, Texas Tech University, Lubbock, Texas

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Anthony E. Reinhart Department of Geosciences, Texas Tech University, Lubbock, Texas

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Paul M. Markowski Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania

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Yvette P. Richardson Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania

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Print Publication:
01 Jul 2015
DOI:
https://doi.org/10.1175/MWR-D-14-00307.1
Page(s):
2736–2753
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Abstract

Observations obtained during the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2) are analyzed for three supercell intercepts. These intercepts used a fleet of deployable “StickNet” probes, complemented by mobile radars and a mobile mesonet, to map state quantities over the expanse of target storms.

Two of the deployments occurred for different stages of a supercell storm near and east of Dumas, Texas, on 18 May 2010. A comparison of the thermodynamic and kinematic characteristics of the storm provides a possible explanation for why one phase was weakly tornadic and the other nontornadic. The weakly tornadic phase features a stronger horizontal virtual temperature gradient antiparallel to the forward-flank reflectivity gradient and perpendicular to the near-surface flow direction, suggesting that air parcels could acquire more significant baroclinic vorticity as they approach the low-level mesocyclone.

The strongly tornadic 10 May 2010 case near Seminole, Oklahoma, features comparatively small virtual and equivalent potential temperature deficits, suggesting the strength of baroclinic zones may be less useful than the buoyancy near the mesocyclone for assessing tornado potential. The distribution of positive pressure perturbations and backed ground-relative winds within the forward flank are consistent with the notion of a “starburst” pattern of diverging winds associated with the forward-flank downdraft.

Narrow (~1 km wide) zones of intense baroclinic vorticity generation of O(~10−4) s−2 are shown to exist within precipitation on the forward and left sides of the mesocyclone in the Dumas intercepts, not dissimilar from such zones identified in recent high-resolution numerical studies.

Denotes Open Access content.

Current affiliation: National Severe Storms Laboratory, Norman, Oklahoma.

Corresponding author address: Christopher C. Weiss, Department of Geosciences, Texas Tech University, Box 41053, Lubbock, TX 79409. E-mail: chris.weiss@ttu.edu

Abstract

Observations obtained during the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2) are analyzed for three supercell intercepts. These intercepts used a fleet of deployable “StickNet” probes, complemented by mobile radars and a mobile mesonet, to map state quantities over the expanse of target storms.

Two of the deployments occurred for different stages of a supercell storm near and east of Dumas, Texas, on 18 May 2010. A comparison of the thermodynamic and kinematic characteristics of the storm provides a possible explanation for why one phase was weakly tornadic and the other nontornadic. The weakly tornadic phase features a stronger horizontal virtual temperature gradient antiparallel to the forward-flank reflectivity gradient and perpendicular to the near-surface flow direction, suggesting that air parcels could acquire more significant baroclinic vorticity as they approach the low-level mesocyclone.

The strongly tornadic 10 May 2010 case near Seminole, Oklahoma, features comparatively small virtual and equivalent potential temperature deficits, suggesting the strength of baroclinic zones may be less useful than the buoyancy near the mesocyclone for assessing tornado potential. The distribution of positive pressure perturbations and backed ground-relative winds within the forward flank are consistent with the notion of a “starburst” pattern of diverging winds associated with the forward-flank downdraft.

Narrow (~1 km wide) zones of intense baroclinic vorticity generation of O(~10−4) s−2 are shown to exist within precipitation on the forward and left sides of the mesocyclone in the Dumas intercepts, not dissimilar from such zones identified in recent high-resolution numerical studies.

Denotes Open Access content.

Current affiliation: National Severe Storms Laboratory, Norman, Oklahoma.

Corresponding author address: Christopher C. Weiss, Department of Geosciences, Texas Tech University, Box 41053, Lubbock, TX 79409. E-mail: chris.weiss@ttu.edu
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