• Bluestein, H. B., and M. L. Weisman, 2000: The interaction of numerically simulated supercells initiated along lines. Mon. Wea. Rev., 128 , 31283149.

    • Search Google Scholar
    • Export Citation
  • Bosart, L. F., and G. M. Lackmann, 1995: Postlandfall tropical cyclone reintensification in a weakly baroclinic environment: A case study of Hurricane David (September 1979). Mon. Wea. Rev., 123 , 32683291.

    • Search Google Scholar
    • Export Citation
  • Bunkers, M. J., B. A. Klimowski, J. W. Zeitler, R. L. Thompson, and M. L. Weisman, 2000: Predicting supercell motion using a new hodograph technique. Wea. Forecasting, 15 , 6179.

    • Search Google Scholar
    • Export Citation
  • Craven, J. P., H. E. Brooks, and J. A. Hart, 2002: Baseline climatology of sounding derived parameters associated with deep, moist convection. Preprints, 21st Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor. Soc., 643–646.

  • Davies, J. M., and R. H. Johns, 1993: Some wind and instability parameters associated with strong and violent tornadoes. 1. Wind shear and helicity. The Tornado: Its Structure, Dynamics, Prediction, and Hazards, Geophys. Monogr., Vol. 79, Amer. Geophys. Union, 573–582.

    • Search Google Scholar
    • Export Citation
  • Davies, J. M., C. A. Doswell, D. F. Burgess, and J. F. Weaver, 1994: Some noteworthy aspects of the Hesston, Kansas, tornado family of 13 March 1990. Bull. Amer. Meteor. Soc., 75 , 10071017.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R., 1984: Streamwise vorticity: The origin of updraft rotation in supercell storms. J. Atmos. Sci., 41 , 29913006.

  • Davis, C. A., and K. A. Emanuel, 1991: Potential vorticity diagnostics of cyclogenesis. Mon. Wea. Rev., 119 , 19291953.

  • Davis, C. A., E. D. Grell, and M. A. Shapiro, 1996: The balanced dynamical nature of a rapidly intensifying oceanic cyclone. Mon. Wea. Rev., 124 , 326.

    • Search Google Scholar
    • Export Citation
  • Fujita, T. T., 1981: Tornadoes and downbursts in the context of generalized planetary scales. J. Atmos. Sci., 38 , 15111534.

  • Gold, D. A., and J. W. Nielsen-Gammon, 2008a: Potential vorticity diagnosis of the severe convective regime. Part I: Methodology. Mon. Wea. Rev., 136 , 15651581.

    • Search Google Scholar
    • Export Citation
  • Gold, D. A., and J. W. Nielsen-Gammon, 2008b: Potential vorticity diagnosis of the severe convective regime. Part IV: Comparison with modeling simulations of the Moore tornado outbreak. Mon. Wea. Rev., 136 , 16121629.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps. Quart. J. Roy. Meteor. Soc., 111 , 877946.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Morgan, M. C., and J. W. Nielsen-Gammon, 1998: Using tropopause maps to diagnose midlatitude weather systems. Mon. Wea. Rev., 126 , 25552579.

    • Search Google Scholar
    • Export Citation
  • Nielsen-Gammon, J. W., and D. A. Gold, 2008: Potential vorticity diagnosis of the severe convective regime. Part II: The impact of idealized PV anomalies. Mon. Wea. Rev., 136 , 15821592.

    • Search Google Scholar
    • Export Citation
  • Rasmussen, E. N., 2003: Refined supercell and tornado forecast parameters. Wea. Forecasting, 18 , 530535.

  • Rasmussen, E. N., and D. O. Blanchard, 1998: A baseline climatology of sounding-derived supercell and tornado forecast parameters. Wea. Forecasting, 13 , 11481164.

    • Search Google Scholar
    • Export Citation
  • Roebber, P. J., D. M. Schultz, and R. Romero, 2002: Synoptic regulation of the 3 May 1999 tornado outbreak. Wea. Forecasting, 17 , 399429.

    • Search Google Scholar
    • Export Citation
  • Thompson, R. L., R. Edwards, J. A. Hart, K. L. Elmore, and P. M. Markowski, 2003: Close proximity soundings within supercell environments obtained from the Rapid Update Cycle. Wea. Forecasting, 18 , 12431261.

    • Search Google Scholar
    • Export Citation
  • Thorpe, A. J., 1986: Synoptic-scale disturbances with circular symmetry. Mon. Wea. Rev., 114 , 13841389.

  • Thorpe, A. J., and C. H. Bishop, 1995: Potential vorticity and the electrostatic analogy: Ertel-Rossby formulation. Quart. J. Roy. Meteor. Soc., 121 , 14771495.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1978: On the interpretation of the diagnostic quasi-geostrophic omega equation. Mon. Wea. Rev., 106 , 131137.

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Potential Vorticity Diagnosis of the Severe Convective Regime. Part III: The Hesston Tornado Outbreak

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  • 1 Department of Atmospheric Sciences, Texas A&M University, College Station, Texas
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Abstract

Nonlinear balance potential vorticity (PV) inversion is used to diagnose the sensitivity of the severe convective parameter space to the amplitude of a subsynoptic-scale PV anomaly on 13 March 1990, a day on which a significant tornado outbreak impacted the Great Plains. PV surgery is used to both amplify and remove the PV anomaly, and the contemporaneous impact on various convective parameters is subsequently quantified by using piecewise PV inversion to compute the changes in those parameters attributable to each PV alteration. It is found that amplifying the anomaly increases the CAPE by amounts typically ranging from 20% to 30% within the atmospheric columns experiencing the maximum PV increase. Ascent is increased slightly downshear of the PV anomaly, consistent with extant conceptual models governing synoptic-scale forcing for vertical motion. Amplifying the PV anomaly increases deep-layer shear over the southern half of the outbreak region and reduces storm-relative helicity over the northern half, primarily through changes in the estimated storm motion vector. Removing the anomaly produces complementary changes of the opposite sign. Thresholds of several commonly used convective parameters are chosen on the basis of prior empirical studies, and the horizontal displacement of these threshold contours produced by the PV alterations reveals that relatively modest subsynoptic-scale PV changes would not likely change the predominant convective mode during the Hesston outbreak.

* Current affiliation: PPM Energy, Inc., Houston, Texas

Corresponding author address: David A. Gold, P.O. Box 420898, Houston, TX 77242. Email: dr_david_gold@earthlink.net

Abstract

Nonlinear balance potential vorticity (PV) inversion is used to diagnose the sensitivity of the severe convective parameter space to the amplitude of a subsynoptic-scale PV anomaly on 13 March 1990, a day on which a significant tornado outbreak impacted the Great Plains. PV surgery is used to both amplify and remove the PV anomaly, and the contemporaneous impact on various convective parameters is subsequently quantified by using piecewise PV inversion to compute the changes in those parameters attributable to each PV alteration. It is found that amplifying the anomaly increases the CAPE by amounts typically ranging from 20% to 30% within the atmospheric columns experiencing the maximum PV increase. Ascent is increased slightly downshear of the PV anomaly, consistent with extant conceptual models governing synoptic-scale forcing for vertical motion. Amplifying the PV anomaly increases deep-layer shear over the southern half of the outbreak region and reduces storm-relative helicity over the northern half, primarily through changes in the estimated storm motion vector. Removing the anomaly produces complementary changes of the opposite sign. Thresholds of several commonly used convective parameters are chosen on the basis of prior empirical studies, and the horizontal displacement of these threshold contours produced by the PV alterations reveals that relatively modest subsynoptic-scale PV changes would not likely change the predominant convective mode during the Hesston outbreak.

* Current affiliation: PPM Energy, Inc., Houston, Texas

Corresponding author address: David A. Gold, P.O. Box 420898, Houston, TX 77242. Email: dr_david_gold@earthlink.net

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