Influence of Balanced Motions on Heavy Precipitation within a Long-Lived Convectively Generated Vortex

Stanley B. Trier National Center for Atmospheric Research, Boulder, Colorado

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Christopher A. Davis National Center for Atmospheric Research, Boulder, Colorado

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Abstract

The forcing of heavy precipitation within a long-lived convectively generated mesoscale vortex (MCV) is investigated with the aid of diagnoses from Rapid Update Cycle gridded analyses. Organized convection within the MCV followed a distinct diurnal cycle, which featured organized mesoscale convective systems (MCSs) that matured overnight near the MCV center on successive days. The MCV was typically most intense in the middle troposphere, but intensified within the lower troposphere during the episodes of organized nocturnal convection.

The lower-tropospheric vertical shear was an important organizing factor in MCS development and sustenance, in the sense that its interaction with the cold temperature anomaly beneath the MCV center determined where balanced lower-tropospheric ascent occurred. From trajectory analyses, we estimate that balanced ascent accounted for approximately half of the total vertical displacement of the thermodynamically unstable air that eventually composed elevated saturated layers immediately upstream of areas of active deep convection within the MCS. Flooding occurred overnight during a portion of the MCV life cycle when the balanced ascent became located toward the rear flank of the MCS (i.e., opposite to the orientation of the mean flow). This evolution served to focus the propagation of the region of intense convection toward a direction opposite to the overall MCS movement, thereby slowing the envelope of heavy precipitation.

Corresponding author address: Dr. Stanley B. Trier, NCAR/MMM, P.O. Box 3000, Boulder, CO 80307-3000. Email: trier@ucar.edu

Abstract

The forcing of heavy precipitation within a long-lived convectively generated mesoscale vortex (MCV) is investigated with the aid of diagnoses from Rapid Update Cycle gridded analyses. Organized convection within the MCV followed a distinct diurnal cycle, which featured organized mesoscale convective systems (MCSs) that matured overnight near the MCV center on successive days. The MCV was typically most intense in the middle troposphere, but intensified within the lower troposphere during the episodes of organized nocturnal convection.

The lower-tropospheric vertical shear was an important organizing factor in MCS development and sustenance, in the sense that its interaction with the cold temperature anomaly beneath the MCV center determined where balanced lower-tropospheric ascent occurred. From trajectory analyses, we estimate that balanced ascent accounted for approximately half of the total vertical displacement of the thermodynamically unstable air that eventually composed elevated saturated layers immediately upstream of areas of active deep convection within the MCS. Flooding occurred overnight during a portion of the MCV life cycle when the balanced ascent became located toward the rear flank of the MCS (i.e., opposite to the orientation of the mean flow). This evolution served to focus the propagation of the region of intense convection toward a direction opposite to the overall MCS movement, thereby slowing the envelope of heavy precipitation.

Corresponding author address: Dr. Stanley B. Trier, NCAR/MMM, P.O. Box 3000, Boulder, CO 80307-3000. Email: trier@ucar.edu

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  • Bartels, D. L., and R. A. Maddox, 1991: Midlevel cyclonic vortices generated by mesoscale convective systems. Mon. Wea. Rev., 119 , 104–118.

    • Search Google Scholar
    • Export Citation
  • Bartels, D. L., J. M. Brown, and E. I. Tollerud, 1997: Structure of a midtropospheric vortex induced by a mesoscale convective system. Mon. Wea. Rev., 125 , 193–211.

    • Search Google Scholar
    • Export Citation
  • Benjamin, S. G., J. M. Brown, K. J. Brundage, B. Schwartz, T. Smirnova, and T. L. Smith, 1998: The operational RUC-2. Preprints, 16th Conf. on Weather Analysis and Forecasting, Phoenix, AZ, Amer. Meteor. Soc., 249–252.

    • Search Google Scholar
    • Export Citation
  • Blackadar, A. K., 1957: Boundary-layer wind maxima and their significance for the growth of nocturnal inversions. Bull. Amer. Meteor. Soc., 38 , 283–290.

    • Search Google Scholar
    • Export Citation
  • Bluestein, H. B., and M. H. Jain, 1985: Formation of mesoscale lines of precipitation: Severe squall lines in Oklahoma during the spring. J. Atmos. Sci., 42 , 1711–1732.

    • Search Google Scholar
    • Export Citation
  • Bonner, W. D., and J. Paegle, 1970: Diurnal variation in boundary layer winds over the south-central United States in summer. Mon. Wea. Rev., 98 , 735–744.

    • Search Google Scholar
    • Export Citation
  • Bosart, L. F., and F. Sanders, 1981: The Johnstown flood of July 1977: A long-lived convective system. J. Atmos. Sci., 38 , 1616–1642.

    • Search Google Scholar
    • Export Citation
  • Brandes, E. A., 1990: Evolution and structure of the 6–7 May 1985 mesoscale convective system and associated vortex. Mon. Wea. Rev., 118 , 26–49.

    • Search Google Scholar
    • Export Citation
  • Bryan, G. H., and J. M. Fritsch, 2000: Moist absolute instability: The sixth static stability state. Bull. Amer. Meteor. Soc., 81 , 1207–1230.

    • Search Google Scholar
    • Export Citation
  • Carbone, R. E., J. D. Tuttle, D. A. Ahijevych, and S. B. Trier, 2002: Inferences of predictability associated with warm season precipitation episodes. J. Atmos. Sci., in press.

    • Search Google Scholar
    • Export Citation
  • Chappell, C. F., 1986: Quasi-stationary convective events. Mesoscale Meteorology and Forecasting, P. Ray, Ed., Amer. Meteor. Soc., 289–310.

    • Search Google Scholar
    • Export Citation
  • Colby, F. P. Jr,, 1984: Convective inhibition as a predictor of convection during AVE-SESAME II. Mon. Wea. Rev., 112 , 2239–2252.

  • Cotton, W. C., M-S. Lin, R. L. McAnelly, and C. J. Tremback, 1989: A composite model of mesoscale convective complexes. Mon. Wea. Rev., 117 , 765–783.

    • Search Google Scholar
    • Export Citation
  • Davis, C. A., and M. L. Weisman, 1994: Balanced dynamics of mesoscale vortices produced by mesoscale convective systems. J. Atmos. Sci., 51 , 2005–2030.

    • Search Google Scholar
    • Export Citation
  • 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 , 3–26.

    • Search Google Scholar
    • Export Citation
  • Davis, C. A., D. A. Ahijevych, and S. B. Trier, 2002: Detection and prediction of warm season midtropospheric vortices by the rapid update cycle. Mon. Wea. Rev., 130 , 24–42.

    • Search Google Scholar
    • Export Citation
  • Frank, W. M., and E. A. Ritchie, 1999: Effects of environmental flow upon tropical cyclone structure. Mon. Wea. Rev., 127 , 2044–2061.

    • Search Google Scholar
    • Export Citation
  • Fritsch, J. M., J. D. Murphy, and J. S. Kain, 1994: Warm core vortex amplification over land. J. Atmos. Sci., 51 , 1780–1807.

  • Fulton, R. A., J. P. Breidenbach, D-J. Seo, D. A. Miller, and T. O'Bannon, 1998: The WSR-88D rainfall algorithm. Wea. Forecasting, 13 , 377–395.

    • Search Google Scholar
    • Export Citation
  • Hertenstein, R. F. A., and W. H. Schubert, 1991: Potential vorticity anomalies associated with squall lines. Mon. Wea. Rev., 119 , 1663–1672.

    • Search Google Scholar
    • Export Citation
  • Houze, R. A. Jr,, S. A. Rutledge, M. I. Biggerstaff, and B. F. Smull, 1989: Interpretation of Doppler weather radar displays of midlatitude mesoscale convective systems. Bull. Amer. Meteor. Soc., 70 , 608–619.

    • Search Google Scholar
    • Export Citation
  • Johnston, E. C., 1981: Mesoscale vorticity centers induced by mesoscale convective complexes. M.S. thesis, Dept. of Meteorology, University of Wisconsin—Madison, 54 pp.

    • Search Google Scholar
    • Export Citation
  • Jones, S. C., 1995: The evolution of vortices in vertical shear. I: Initially barotropic vortices. Quart. J. Roy. Meteor. Soc., 121 , 821–851.

    • Search Google Scholar
    • Export Citation
  • Jones, S. C., . 2000: The evolution of vortices in vertical shear. III: Baroclinic vortices. Quart. J. Roy. Meteor. Soc., 126 , 3161–3186.

    • Search Google Scholar
    • Export Citation
  • Loehrer, S. M., and R. H. Johnson, 1995: Surface pressure and precipitation life cycle characteristics of PRE-STORM mesoscale convective systems. Mon. Wea. Rev., 123 , 600–621.

    • Search Google Scholar
    • Export Citation
  • Maddox, R. A., 1983: Large-scale meteorological conditions associated with midlatitude, mesoscale convective complexes. Mon. Wea. Rev., 111 , 1475–1493.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., and R. A. Houze Jr., 1995: Diabatic divergence profiles in western Pacific mesoscale convective systems. J. Atmos. Sci., 52 , 1807–1828.

    • Search Google Scholar
    • Export Citation
  • Menard, R. D., and J. M. Fritsch, 1989: A mesoscale convective complex-generated inertially stable warm core vortex. Mon. Wea. Rev., 117 , 1237–1261.

    • Search Google Scholar
    • Export Citation
  • NCDC, 1998: Storm Data, Vol. 40, No. 5, 408 pp. [Available from National Climatic Data Center, 151 Patton Ave., Asheville, NC 28801-5001.].

    • Search Google Scholar
    • Export Citation
  • Parker, M. D., and R. H. Johnson, 2000: Organizational modes of midlatitude mesoscale convective systems. Mon. Wea. Rev., 128 , 3413–3436.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., 1992: Nonlinear balance and potential-vorticity thinking at large Rossby numbers. Quart. J. Roy. Meteor. Soc., 118 , 987–1015.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., and H. Jiang, 1990: A theory for long-lived mesoscale convective systems. J. Atmos. Sci., 47 , 3067–3077.

  • Rogers, R. F., and J. M. Fritsch, 2001: Surface cyclogenesis from convectively driven amplification of midlevel mesoscale convective vortices. Mon. Wea. Rev., 129 , 605–637.

    • Search Google Scholar
    • Export Citation
  • Rotunno, R., J. B. Klemp, and M. L. Weisman, 1988: A theory for strong, long-lived squall lines. J. Atmos. Sci., 45 , 463–485.

  • Skamarock, W. C., M. L. Weisman, and J. B. Klemp, 1994: Three-dimensional evolution of simulated long-lived squall lines. J. Atmos. Sci., 51 , 2563–2584.

    • Search Google Scholar
    • Export Citation
  • Trier, S. B., C. A. Davis, and W. C. Skamarock, 2000a: Long-lived mesoconvective vortices and their environment. Part II: Induced thermodynamic destabilization in idealized simulations. Mon. Wea. Rev., 128 , 3396–3412.

    • Search Google Scholar
    • Export Citation
  • Trier, S. B., C. A. Davis, and J. D. Tuttle, 2000b: Long-lived mesoconvective vortices and their environment. Part I: Observations from the central United States during the 1998 warm season. Mon. Wea. Rev., 128 , 3376–3395.

    • Search Google Scholar
    • Export Citation
  • Young, G. S., and J. M. Fritsch, 1989: A proposal for general conventions in analyses of mesoscale boundaries. Bull. Amer. Meteor. Soc., 70 , 1412–1421.

    • Search Google Scholar
    • Export Citation
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