• Arakawa, A., , and V. Lamb, 1981: A potential enstrophy and energy conserving scheme for the shallow water equations. Mon. Wea. Rev., 109 , 1836.

    • Search Google Scholar
    • Export Citation
  • Barnes, S. L., 1978: Oklahoma thunderstorms on 29–30 April 1970. Part I: Morphology of a tornadic storm. Mon. Wea. Rev., 106 , 673684.

    • Search Google Scholar
    • Export Citation
  • Beebe, R. G., 1959: Notes on the Scottsbluff, Nebraska tornado, 27 June 1955. Bull. Amer. Meteor. Soc., 40 , 109116.

  • Bluestein, H. B., , and A. L. Pazmany, 2000: Observations of tornadoes and other convective phenomena with a mobile, 3-mm wavelength, Doppler radar. Bull. Amer. Meteor. Soc., 81 , 29392952.

    • Search Google Scholar
    • Export Citation
  • Browning, K. A., 1964: Airflow and precipitation trajectories within severe local storms which travel to the right of the winds. J. Atmos. Sci., 21 , 634639.

    • Search Google Scholar
    • Export Citation
  • Browning, K. A., , and F. H. Ludlam, 1962: Airflow in convective storms. Quart. J. Roy. Meteor. Soc., 88 , 117135.

  • Browning, K. A., , and R. J. Donaldson, 1963: Airflow and structure of a tornadic storm. J. Atmos. Sci., 20 , 533545.

  • Burgess, D. W., , R. A. Brown, , L. R. Lemon, , and C. R. Safford, 1977: Evolution of a tornadic thunderstorm. Preprints, 10th Conf. on Severe Local Storms, Omaha, NE, Amer. Meteor. Soc., 84–89.

    • Search Google Scholar
    • Export Citation
  • Das, P., 1983: Vorticity concentration in the subcloud layers of a rotating cloud. National Science Foundation Final Rep. ATM-8023825, 78 pp.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R. P., 1973: The dependence of core radius on swirl ratio in a tornado simulator. J. Atmos. Sci., 30 , 14271430.

  • Davies-Jones, R. P., 1982a: A new look at the vorticity equation with application to tornadogenesis. Preprints, 12th Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor. Soc., 249–252.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R. P., 1982b: Observational and theoretical aspects of tornadogenesis. Intense Atmospheric Vortices, L. Bengtsson and J. Lighthill, Eds., Springer-Verlag, 175–189.

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

  • Davies-Jones, R. P., 2000: Can the hook echo instigate tornadogenesis barotropically? Preprints, 20th Conf. on Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 269–272.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R. P., , and H. E. Brooks, 1993: Mesocyclogenesis from a theoretical perspective. The Tornado: Its Structure, Dynamics, Prediction, and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 105–114.

    • Search Google Scholar
    • Export Citation
  • Deardorff, J. W., 1972: Numerical investigation of neutral and unstable planetary boundary layers. J. Atmos. Sci., 29 , 91115.

  • Forbes, G. S., 1981: On the reliability of hook echoes as tornado indicators. Mon. Wea. Rev., 109 , 14571466.

  • Fujita, T. T., 1958: Mesoanalysis of the Illinois tornadoes of 9 April 1953. J. Meteor., 15 , 288296.

  • Fujita, T. T., 1973: Proposed mechanism of tornado formation from rotating thunderstorms. Preprints, Eighth Conf. on Severe Local Storms, Denver, CO, Amer. Meteor. Soc., 191–196.

    • Search Google Scholar
    • Export Citation
  • Fujita, T. T., 1975: New evidence from the April 3–4, 1974 tornadoes. Preprints, Ninth Conf. on Severe Local Storms, Norman, OK, Amer. Meteor. Soc., 248–255.

    • Search Google Scholar
    • Export Citation
  • Fujita, T. T., 1979: Objectives, operation, and results of Project NIMROD. Preprints, 11th Conf. on Severe Local Storms, Kansas City, MO, Amer. Meteor. Soc., 259–266.

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

  • Haglund, G. T., 1969: A study of the severe local storm of 16 April 1967. ESSA Tech. Memo. ERLTM-NSSL 44, 54 pp.

  • Hookings, G. A., 1965: Precipitation-maintained downdrafts. J. Appl. Meteor., 4 , 190195.

  • Howells, P. A., , R. Rotunno, , and R. K. Smith, 1988: A comparative study of atmospheric and laboratory-analogue numerical tornado-vortex models. Quart. J. Roy. Meteor. Soc., 114 , 801822.

    • Search Google Scholar
    • Export Citation
  • Kamburova, P. L., , and F. H. Ludlam, 1966: Rainfall evaporation in thunderstorm downdrafts. Quart. J. Roy. Meteor. Soc., 92 , 510518.

  • Klemp, J. B., , and R. B. Wilhelmson, 1978: The simulation of three-dimensional convective storm dynamics. J. Atmos. Sci., 35 , 10701096.

    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., , and R. Rotunno, 1983: A study of the tornadic region within a supercell thunderstorm. J. Atmos. Sci., 40 , 359377.

  • Lemon, L. R., , and C. A. Doswell, 1979: Severe thunderstorm evolution and mesocyclone structure as related to tornadogenesis. Mon. Wea. Rev., 107 , 11841197.

    • Search Google Scholar
    • Export Citation
  • Leslie, L. M., , and R. K. Smith, 1978: The effect of vertical stability on tornadogenesis. J. Atmos. Sci., 35 , 12811288.

  • Lewellen, D. C., , W. S. Lewellen, , and J. Xia, 2000: The influence of a local swirl ratio on tornado intensification near the surface. J. Atmos. Sci., 57 , 527544.

    • Search Google Scholar
    • Export Citation
  • Ludlam, F. H., 1963: Severe Local Storms: A Review. Meteor. Monogr., No. 27, Amer. Meteor. Soc., 1–30.

  • Maddox, R. A., 1976: An evaluation of tornado proximity wind and stability data. Mon. Wea. Rev., 104 , 133142.

  • Markowski, P. M., 2002: Hook echoes and rear-flank downdrafts: A review. Mon. Wea. Rev., 130 , 852876.

  • Markowski, P. M., , J. M. Straka, , and E. N. Rasmussen, 2002: Direct surface thermodynamic observations within the rear-flank downdrafts of nontornadic and tornadic supercells. Mon. Wea. Rev., 130 , 16921721.

    • Search Google Scholar
    • Export Citation
  • Marshall, J. S., , and W. M. Palmer, 1948: The distribution of raindrops with size. J. Meteor., 5 , 165166.

  • McCaul Jr., E. W., , and C. Cohen, 2000: The sensitivity of simulated storm structure and intensity to the lifted condensation level and the level of free convection. Preprints, 20th Conf. on Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 595–598.

    • Search Google Scholar
    • Export Citation
  • McCaul Jr., E. W., , and M. L. Weisman, 2001: The sensitivity of simulated supercell structure and intensity to variations in the shapes of environmental buoyancy and shear profiles. Mon. Wea. Rev., 129 , 664687.

    • Search Google Scholar
    • Export Citation
  • Moller, A., , C. A. Doswell, , J. McGinley, , S. Tegtmeier, , and R. Zipser, 1974: Field observations of the Union City tornado in Oklahoma. Weatherwise, 27 , 6877.

    • Search Google Scholar
    • Export Citation
  • Peterson, R. E., 1976: The Sunray tornado. Bull. Amer. Meteor. Soc., 57 , 805807.

  • 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
  • Rotunno, R., 1981: On the evolution of thunderstorm rotation. Mon. Wea. Rev., 109 , 577586.

  • Rotunno, R., , and J. B. Klemp, 1982: The influence of the shear-induced pressure gradient on thunderstorm motion. Mon. Wea. Rev., 110 , 136151.

    • Search Google Scholar
    • Export Citation
  • Rotunno, R., , and J. B. Klemp, 1985: On the rotation and propagation of simulated supercell thunderstorms. J. Atmos. Sci., 42 , 271292.

    • Search Google Scholar
    • Export Citation
  • Schlesinger, R. E., 1980: A three-dimensional numerical model of an isolated thunderstorm. Part II: Dynamics of updraft splitting and mesovortex couplet evolution. J. Atmos. Sci., 37 , 395420.

    • Search Google Scholar
    • Export Citation
  • Smagorinsky, J., 1963: General circulation experiments with the primitive equations. Part I: The basic experiment. Mon. Wea. Rev., 91 , 99164.

    • Search Google Scholar
    • Export Citation
  • Smith, R. K., , and L. M. Leslie, 1978: Tornadogenesis. Quart. J. Roy. Meteor. Soc., 104 , 189198.

  • Smith, R. K., , and L. M. Leslie, 1979: A numerical study of tornadogenesis in a rotating thunderstorm. Quart. J. Roy. Meteor. Soc., 105 , 107127.

    • Search Google Scholar
    • Export Citation
  • Soong, S. T., , and Y. Ogura, 1973: A comparison between axisymmetric and slab-symmetric cumulus cloud models. J. Atmos. Sci., 30 , 879893.

    • Search Google Scholar
    • Export Citation
  • Stout, G. E., , and F. A. Huff, 1953: Radar records Illinois tornadogenesis. Bull. Amer. Meteor. Soc., 34 , 281284.

  • Straka, J. M., , and E. N. Rasmussen, 1998: Thirty years of cloud modeling: Does the emperor wear clothes? Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 342–347.

    • Search Google Scholar
    • Export Citation
  • Trapp, R. J., 1999: Observations of nontornadic low-level mesocyclones and attendant tornadogenesis failure during VORTEX. Mon. Wea. Rev., 127 , 16931705.

    • Search Google Scholar
    • Export Citation
  • Trapp, R. J., , and R. P. Davies-Jones, 1997: Tornadogenesis with and without a dynamic pipe effect. J. Atmos. Sci., 54 , 113133.

  • van Tassel, E. L., 1955: The North Platte Valley tornado outbreak of June 27, 1955. Mon. Wea. Rev., 83 , 255264.

  • Wakimoto, R. M., , and H. Cai, 2000: Analysis of a nontornadic storm during VORTEX 95. Mon. Wea. Rev., 128 , 565592.

  • Walko, R. L., 1988: Plausibility of substantial dry adiabatic subsidence in a tornado core. J. Atmos. Sci., 45 , 22512267.

  • Walko, R. L., 1993: Tornado spin-up beneath a convective cell: Required basic structure of the near-field boundary layer winds. The Tornado: Its Structure, Dynamics, Prediction, and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 89–95.

    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., , and J. B. Klemp, 1982: The dependence of numerically simulated convective storms on vertical wind shear and buoyancy. Mon. Wea. Rev., 110 , 504520.

    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., , and J. B. Klemp, 1984: The structure and classification of numerically simulated convective storms in directionally varying wind shears. Mon. Wea. Rev., 112 , 24792498.

    • Search Google Scholar
    • Export Citation
  • Wicker, L. J., , and R. B. Wilhelmson, 1995: Simulation and analysis of tornado development and decay within a three-dimensional supercell thunderstorm. J. Atmos. Sci., 52 , 26752703.

    • Search Google Scholar
    • Export Citation
  • Wicker, L. J., , and W. C. Skamarock, 1998: A time-splitting scheme for the elastic equations incorporating second-order Runge–Kutta time differencing. Mon. Wea. Rev., 126 , 19921999.

    • Search Google Scholar
    • Export Citation
  • Wicker, L. J., , and W. C. Skamarock, 2002: Time splitting methods for elastic models using forward time schemes. Mon. Wea. Rev., 130 , 20882097.

    • Search Google Scholar
    • Export Citation
  • Wicker, L. J., , D. Dowell, , Y. Richardson, , and R. Wilhelmson, 2002: A large eddy simulation of a tornadic supercell: Comparison with observations. Preprints, 21st Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor. Soc., 262–263.

    • Search Google Scholar
    • Export Citation
  • Wurman, J., , J. M. Straka, , and E. N. Rasmussen, 1996: Fine-scale Doppler radar observations of tornadic storms. Science, 272 , 17741777.

    • Search Google Scholar
    • Export Citation
  • Wurman, J., , J. M. Straka, , E. N. Rasmussen, , M. Randall, , and A. Zahrai, 1997: Design and deployment of a portable, pencil-beam, pulsed, 3-cm Doppler radar. J. Atmos. Oceanic Technol., 14 , 15021512.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 266 266 17
PDF Downloads 155 155 14

Tornadogenesis Resulting from the Transport of Circulation by a Downdraft: Idealized Numerical Simulations

View More View Less
  • 1 Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania
  • | 2 School of Meteorology, University of Oklahoma, Norman, Oklahoma
  • | 3 Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, and National Severe Storms Laboratory, Norman, Oklahoma
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

Idealized numerical simulations are conducted in which an axisymmetric, moist, rotating updraft free of rain is initiated, after which a downdraft is imposed by precipitation loading. The experiments are designed to emulate a supercell updraft that has rotation aloft initially, followed by the formation of a downdraft and descent of a rain curtain on the rear flank. In the idealized simulations, the rain curtain and downdraft are annular, rather than hook-shaped, as is typically observed. The downdraft transports angular momentum, which is initially a maximum aloft and zero at the surface, toward the ground. Once reaching the ground, the circulation-rich air is converged beneath the updraft and a tornado develops. The intensity and longevity of the tornado depend on the thermodynamic characteristics of the angular momentum-transporting downdraft, which are sensitive to the ambient low-level relative humidity and precipitation character of the rain curtain. For large low-level relative humidity and a rain curtain having a relatively small precipitation concentration, the imposed downdraft is warmer than when the low-level relative humidity is small and the precipitation concentration of the rain curtain is large. The simulated tornadoes are stronger and longer-lived when the imposed downdrafts are relatively warm compared to when the downdrafts are relatively cold, owing to a larger amount of convergence of circulation-rich downdraft air. The results may explain some recent observations of the tendency for supercells to be tornadic when their rear-flank downdrafts are associated with relatively small temperature deficits.

Corresponding author address: Dr. Paul Markowski, 503 Walker Building, The Pennsylvania State University, University Park, PA 16802. Email: pmarkowski@psu.edu

Abstract

Idealized numerical simulations are conducted in which an axisymmetric, moist, rotating updraft free of rain is initiated, after which a downdraft is imposed by precipitation loading. The experiments are designed to emulate a supercell updraft that has rotation aloft initially, followed by the formation of a downdraft and descent of a rain curtain on the rear flank. In the idealized simulations, the rain curtain and downdraft are annular, rather than hook-shaped, as is typically observed. The downdraft transports angular momentum, which is initially a maximum aloft and zero at the surface, toward the ground. Once reaching the ground, the circulation-rich air is converged beneath the updraft and a tornado develops. The intensity and longevity of the tornado depend on the thermodynamic characteristics of the angular momentum-transporting downdraft, which are sensitive to the ambient low-level relative humidity and precipitation character of the rain curtain. For large low-level relative humidity and a rain curtain having a relatively small precipitation concentration, the imposed downdraft is warmer than when the low-level relative humidity is small and the precipitation concentration of the rain curtain is large. The simulated tornadoes are stronger and longer-lived when the imposed downdrafts are relatively warm compared to when the downdrafts are relatively cold, owing to a larger amount of convergence of circulation-rich downdraft air. The results may explain some recent observations of the tendency for supercells to be tornadic when their rear-flank downdrafts are associated with relatively small temperature deficits.

Corresponding author address: Dr. Paul Markowski, 503 Walker Building, The Pennsylvania State University, University Park, PA 16802. Email: pmarkowski@psu.edu

Save