Editorial Type:
Article
Article Type:
Research Article

Investigating the Development and Characteristics of Streamwise Vorticity Currents Produced by Outflow Surges in Simulated Supercell Thunderstorms

Kevin T. Gray aDepartment of Atmospheric Sciences, University of Illinois Urbana–Champaign, Urbana, Illinois

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Jeffrey W. Frame aDepartment of Atmospheric Sciences, University of Illinois Urbana–Champaign, Urbana, Illinois

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Online Publication:
05 Dec 2023
Print Publication:
01 Dec 2023
DOI:
https://doi.org/10.1175/MWR-D-22-0309.1
Page(s):
3089–3111
Restricted access

Abstract

Streamwise vorticity currents (SVCs) have been hypothesized to enhance low-level mesocyclones within supercell thunderstorms and perhaps increase the likelihood of tornadogenesis. Recent observational studies have confirmed the existence of SVCs in supercells and numerical simulations have allowed for further investigation of SVCs. A suite of 19 idealized supercell simulations with varying midlevel shear orientations is analyzed to determine how SVC formation and characteristics may differ between storms. In our simulations, SVCs develop on the cold side of left-flank convergence boundaries and their updraft-relative positions are partially dependent on downdraft location. The magnitude, duration, and mean depth of SVCs do not differ significantly between simulations or between SVCs that precede tornado-like vortices (TLVs) and those that do not. Trajectories initialized within SVCs reveal two primary airstreams, one that flows through an SVC for the majority of its length, and another that originates in the modified inflow in the forward flank and then merges with the SVC. Vorticity budgets calculated along trajectories reveal that the first airstream exhibits significantly greater maximum streamwise vorticity magnitudes than the second airstream. The vorticity budgets also indicate that stretching of horizontal streamwise vorticity is the dominant contributor to the large values of streamwise vorticity within the SVCs. TLV formation does not require the development of an SVC beforehand; 44% of TLVs in the simulations are preceded by SVCs. When an SVC occurs, it is followed by a TLV 53% of the time, indicating not all SVCs lead to TLV formation.

Significance Statement

Streamwise vorticity currents (SVCs) are features within thunderstorms hypothesized to strengthen updraft rotation and increase the likelihood of tornado formation. SVCs in a suite of 19 thunderstorm simulations are analyzed to investigate how they develop, if their characteristics differ between storms, and how often they precede tornado production. The rotation in an SVC is amplified as air accelerates toward the updraft, which is the main process contributing to SVC formation. The likelihood of SVCs may vary with differences in the winds 3–6 km above the ground. These findings may aid in developing strategies for better observing SVCs.

© 2023 American Meteorological Society. This published article is licensed under the terms of the default AMS reuse license. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Kevin T. Gray, kevintg2@illinois.edu

Abstract

Streamwise vorticity currents (SVCs) have been hypothesized to enhance low-level mesocyclones within supercell thunderstorms and perhaps increase the likelihood of tornadogenesis. Recent observational studies have confirmed the existence of SVCs in supercells and numerical simulations have allowed for further investigation of SVCs. A suite of 19 idealized supercell simulations with varying midlevel shear orientations is analyzed to determine how SVC formation and characteristics may differ between storms. In our simulations, SVCs develop on the cold side of left-flank convergence boundaries and their updraft-relative positions are partially dependent on downdraft location. The magnitude, duration, and mean depth of SVCs do not differ significantly between simulations or between SVCs that precede tornado-like vortices (TLVs) and those that do not. Trajectories initialized within SVCs reveal two primary airstreams, one that flows through an SVC for the majority of its length, and another that originates in the modified inflow in the forward flank and then merges with the SVC. Vorticity budgets calculated along trajectories reveal that the first airstream exhibits significantly greater maximum streamwise vorticity magnitudes than the second airstream. The vorticity budgets also indicate that stretching of horizontal streamwise vorticity is the dominant contributor to the large values of streamwise vorticity within the SVCs. TLV formation does not require the development of an SVC beforehand; 44% of TLVs in the simulations are preceded by SVCs. When an SVC occurs, it is followed by a TLV 53% of the time, indicating not all SVCs lead to TLV formation.

Significance Statement

Streamwise vorticity currents (SVCs) are features within thunderstorms hypothesized to strengthen updraft rotation and increase the likelihood of tornado formation. SVCs in a suite of 19 thunderstorm simulations are analyzed to investigate how they develop, if their characteristics differ between storms, and how often they precede tornado production. The rotation in an SVC is amplified as air accelerates toward the updraft, which is the main process contributing to SVC formation. The likelihood of SVCs may vary with differences in the winds 3–6 km above the ground. These findings may aid in developing strategies for better observing SVCs.

© 2023 American Meteorological Society. This published article is licensed under the terms of the default AMS reuse license. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Kevin T. Gray, kevintg2@illinois.edu
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  • Bartos, E. A., P. M. Markowski, and Y. P. Richardson, 2022: Three-dimensional thermodynamic observations in supercell thunderstorms from swarms of balloon-borne sondes. Mon. Wea. Rev., 150, 1689–1723, https://doi.org/10.1175/MWR-D-21-0122.1.

    • Search Google Scholar
    • Export Citation

  • Beck, J., and C. Weiss, 2013: An assessment of low-level baroclinity and vorticity within a simulated supercell. Mon. Wea. Rev., 141, 649–669, https://doi.org/10.1175/MWR-D-11-00115.1.

    • Search Google Scholar
    • Export Citation

  • Bryan, G. H., and J. M. Fritsch, 2002: A benchmark simulation for moist nonhydrostatic numerical models. Mon. Wea. Rev., 130, 2917–2928, https://doi.org/10.1175/1520-0493(2002)130<2917:ABSFMN>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Coffer, B. E., and M. D. Parker, 2018: Is there a “tipping point” between simulated nontornadic and tornadic supercells in VORTEX2 environments? Mon. Wea. Rev., 146, 2667–2693, https://doi.org/10.1175/MWR-D-18-0050.1.

    • Search Google Scholar
    • Export Citation

  • Coffer, B. E., M. D. Parker, J. M. L. Dahl, L. J. Wicker, and A. J. Clark, 2017: Volatility of tornadogenesis: An ensemble of simulated nontornadic and tornadic supercells in VORTEX2 environments. Mon. Wea. Rev., 145, 4605–4625, https://doi.org/10.1175/MWR-D-17-0152.1.

    • Search Google Scholar
    • Export Citation

  • Davies-Jones, R., 2022: Theory of parcel vorticity evolution in supercell-like flows. J. Atmos. Sci., 79, 1253–1270, https://doi.org/10.1175/JAS-D-21-0178.1.

    • Search Google Scholar
    • Export Citation

  • Davies-Jones, R., and H. E. Brooks, 1993: Mesocyclogenesis from a theoretical perspective. The Tornado: Its Structure, Dynamics, Prediction, and Hazards, C. Church et al., Eds., Amer. Geophys. Union, 105–114, https://doi.org/10.1029/GM079p0105.

  • Davies-Jones, R., R. J. Trapp, and H. B. Bluestein, 2001: Tornadoes and tornadic storms. Severe Convective Storms, Meteor. Monogr., No. 28, Amer. Meteor. Soc., 167–222, https://doi.org/10.1175/0065-9401-28.50.167.

  • Finley, C. A., and B. D. Lee, 2004: High resolution mobile mesonet observations of RFD surges in the June 9 Bassett, Nebraska, supercell during project ANSWERS 2003. Preprints, 22nd Conf. on Severe Local Storms, Hyannis, MA, Amer. Meteor. Soc., P11.3, https://ams.confex.com/ams/11aram22sls/webprogram/Paper82005.html.

  • Finley, C. A., M. Elmore, L. Orf, and B. D. Lee, 2022: Impact of the streamwise vorticity current on low-level mesocyclone development in a simulated supercell. Geophys. Res. Lett., 50, e2022GL100005, https://doi.org/10.1029/2022GL100005.

    • Search Google Scholar
    • Export Citation

  • Goldacker, N. A., and M. D. Parker, 2021: Low-level updraft intensification in response to environmental wind profiles. J. Atmos. Sci., 78, 2763–2781, https://doi.org/10.1175/JAS-D-20-0354.1.

    • Search Google Scholar
    • Export Citation

  • Gray, K., and J. Frame, 2021: The impact of midlevel shear orientation on the longevity of and downdraft location and tornado-like vortex formation within simulated supercells. Mon. Wea. Rev., 149, 3739–3759, https://doi.org/10.1175/MWR-D-21-0085.1.

    • Search Google Scholar
    • Export Citation

  • Houston, A., B. Argrow, M. C. Coniglio, E. W. Frew, E. N. Rasmussen, C. C. Weiss, and C. L. Ziegler, 2020: Targeted observation by radars and UAS of supercells (TORUS): Summary of the 2019 field campaign. Severe Local Storms Symp., Boston, MA, Amer. Meteor. Soc., 1.3, https://ams.confex.com/ams/2020Annual/webprogram/Paper369999.html.

  • Klemp, J. B., and R. Rotunno, 1983: A study of the tornadic region within a supercell thunderstorm. J. Atmos. Sci., 40, 359–377, https://doi.org/10.1175/1520-0469(1983)040<0359:ASOTTR>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Knupp, K. R., and Coauthors, 2014: Meteorological overview of the devastating 27 April 2011 tornado outbreak. Bull. Amer. Meteor. Soc., 95, 1041–1062, https://doi.org/10.1175/BAMS-D-11-00229.1.

    • Search Google Scholar
    • Export Citation

  • Kosiba, K., J. Wurman, Y. Richardson, P. Markowski, P. Robinson, and J. Marquis, 2013: Genesis of the Goshen County, Wyoming, tornado on 5 June 2009 during VORTEX2. Mon. Wea. Rev., 141, 1157–1181, https://doi.org/10.1175/MWR-D-12-00056.1.

    • Search Google Scholar
    • Export Citation

  • Lee, B. D., C. A. Finley, and C. D. Karstens, 2012: The Bowdle, South Dakota, cyclic tornadic supercell of 22 May 2010: Surface analysis of rear-flank downdraft evolution and multiple internal surges. Mon. Wea. Rev., 140, 3419–3441, https://doi.org/10.1175/MWR-D-11-00351.1.

    • Search Google Scholar
    • Export Citation

  • Mansell, E. R., 2010: On sedimentation and advection in multimoment bulk microphysics. J. Atmos. Sci., 67, 3084–3094, https://doi.org/10.1175/2010JAS3341.1.

    • Search Google Scholar
    • Export Citation

  • Mansell, E. R., C. L. Ziegler, and E. C. Bruning, 2010: Simulated electrification of a small thunderstorm with two-moment bulk microphysics. J. Atmos. Sci., 67, 171–194, https://doi.org/10.1175/2009JAS2965.1.

    • Search Google Scholar
    • Export Citation

  • Markowski, P. M., T. P. Hatlee, and Y. P. Richardson, 2018: Tornadogenesis in the 12 May 2010 supercell thunderstorm intercepted by VORTEX2 near Clinton, Oklahoma. Mon. Wea. Rev., 146, 3623–3650, https://doi.org/10.1175/MWR-D-18-0196.1.

    • Search Google Scholar
    • Export Citation

  • Marquis, J., Y. Richardson, P. Markowski, D. Dowell, and J. Wurman, 2012: Tornado maintenance investigated with high-resolution dual-Doppler and EnKF analysis. Mon. Wea. Rev., 140, 3–27, https://doi.org/10.1175/MWR-D-11-00025.1.

    • Search Google Scholar
    • Export Citation

  • May, R. M., and Coauthors, 2020: MetPy: A Python package for meteorological data. Unidata, accessed 1 November 2021, https://doi.org/10.5065/D6WW7G29.

  • Morrison, H., J. A. Curry, and V. Khvorostyanov, 2005: A new double-moment microphysics parameterization for application in cloud and climate models. Part I: Description. J. Atmos. Sci., 62, 1665–1677, https://doi.org/10.1175/JAS3446.1.

    • Search Google Scholar
    • Export Citation

  • Morrison, H., G. Thompson, and V. Tatarskii, 2009: Impact of cloud microphysics on the development of trailing stratiform precipitation in a simulated squall line: Comparison of one- and two-moment schemes. Mon. Wea. Rev., 137, 991–1007, https://doi.org/10.1175/2008MWR2556.1.

    • Search Google Scholar
    • Export Citation

  • Murdzek, S. S., P. M. Markowski, and Y. P. Richardson, 2020: Simultaneous dual-Doppler and mobile mesonet observations of streamwise vorticity currents in three supercells. Mon. Wea. Rev., 148, 4859–4874, https://doi.org/10.1175/MWR-D-20-0239.1.

    • Search Google Scholar
    • Export Citation

  • Naylor, J., and M. S. Gilmore, 2012: Convective initiation in an idealized cloud model using an updraft nudging technique. Mon. Wea. Rev., 140, 3699–3705, https://doi.org/10.1175/MWR-D-12-00163.1.

    • Search Google Scholar
    • Export Citation

  • Orf, L., R. Wilhelmson, B. Lee, C. Finley, and A. Houston, 2017: Evolution of a long-track violent tornado within a simulated supercell. Bull. Amer. Meteor. Soc., 98, 45–68, https://doi.org/10.1175/BAMS-D-15-00073.1.

    • Search Google Scholar
    • Export Citation

  • Roberts, B., M. Xue, A. D. Schenkman, and D. T. Dawson II, 2016: The role of surface drag in tornadogenesis within an idealized supercell simulation. J. Atmos. Sci., 73, 3371–3395, https://doi.org/10.1175/JAS-D-15-0332.1.

    • Search Google Scholar
    • Export Citation

  • Rotunno, R., and J. Klemp, 1985: On the rotation and propagation of simulated supercell thunderstorms. J. Atmos. Sci., 42, 271–292, https://doi.org/10.1175/1520-0469(1985)042<0271:OTRAPO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Schenkman, A. D., M. Xue, and M. Hu, 2014: Tornadogenesis in a high-resolution simulation of the 8 May 2003 Oklahoma City supercell. J. Atmos. Sci., 71, 130–154, https://doi.org/10.1175/JAS-D-13-073.1.

    • Search Google Scholar
    • Export Citation

  • Schueth, A., C. Weiss, and J. M. L. Dahl, 2021: Comparing observations and simulations of the streamwise vorticity current and the forward-flank convergence boundary in a supercell storm. Mon. Wea. Rev., 149, 1651–1671, https://doi.org/10.1175/MWR-D-20-0251.1.

    • Search Google Scholar
    • Export Citation

  • Shabbott, C. J., and P. M. Markowski, 2006: Surface in situ observations within the outflow of forward-flank downdrafts of supercell thunderstorms. Mon. Wea. Rev., 134, 1422–1441, https://doi.org/10.1175/MWR3131.1.

    • Search Google Scholar
    • Export Citation

  • Skinner, P. S., C. C. Weiss, M. M. French, H. B. Bluestein, P. M. Markowski, and Y. P. Richardson, 2014: VORTEX2 observations of a low-level mesocyclone with multiple internal rear-flank downdraft momentum surges in the 18 May 2010 Dumas, Texas, supercell. Mon. Wea. Rev., 142, 2935–2960, https://doi.org/10.1175/MWR-D-13-00240.1.

    • Search Google Scholar
    • Export Citation

  • Skinner, P. S., C. C. Weiss, L. J. Wicker, C. K. Potvin, and D. C. Dowell, 2015: Forcing mechanisms for an internal rear-flank downdraft momentum surge in the 18 May 2010 Dumas, Texas, supercell. Mon. Wea. Rev., 143, 4305–4330, https://doi.org/10.1175/MWR-D-15-0164.1.

    • Search Google Scholar
    • Export Citation

  • Vande Guchte, A., and J. M. L. Dahl, 2018: Sensitivities of parcel trajectories beneath the lowest scalar model level of a Lorenz vertical grid. Mon. Wea. Rev., 146, 1427–1435, https://doi.org/10.1175/MWR-D-17-0190.1.

    • Search Google Scholar
    • Export Citation

  • Weiss, C. C., A. Schueth, and A. L. Houston, 2020: TORUS 2019 highlights from the TTUKa mobile Doppler radars. Severe Local Storms Symp., Boston, MA, Amer. Meteor. Soc., 1.4, https://ams.confex.com/ams/2020Annual/webprogram/Paper366442.html.

  • Wurman, J., D. Dowell, Y. Richardson, P. Markowski, E. Rasmussen, D. Burgess, L. Wicker, and H. B. Bluestein, 2012: The Second Verification of the Origins of Rotation in Tornadoes Experiment: VORTEX2. Bull. Amer. Meteor. Soc., 93, 1147–1170, https://doi.org/10.1175/BAMS-D-11-00010.1.

    • Search Google Scholar
    • Export Citation

  • Xu, Q., M. Xue, and K. K. Droegemeer, 1996: Numerical simulation of density currents in sheared environments within a vertically confined channel. J. Atmos. Sci., 53, 770–786, https://doi.org/10.1175/1520-0469(1996)053%3c0770:NSODCI%3e2.0.CO;2.

    • Search Google Scholar
    • Export Citation

  • Xue, M., 2000: Density currents in two-layer shear flows. Quart. J. Roy. Meteor. Soc., 126, 1301–1320, https://doi.org/10.1002/qj.49712656506.

    • Search Google Scholar
    • Export Citation

  • Ziegler, C. L., 1985: Retrieval of thermal and microphysical variables in observed convective storms. Part I: Model development and preliminary testing. J. Atmos. Sci., 42, 1487–1509, https://doi.org/10.1175/1520-0469(1985)042<1487:ROTAMV>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
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