Editorial Type:
Article
Article Type:
Research Article

Observational Analysis of the 27 May 1997 Central Texas Tornadic Event. Part I: Prestorm Environment and Storm Maintenance/Propagation

Adam L. Houston Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana

Search for other papers by Adam L. Houston in
Current site
Google Scholar
PubMed Close
and
Robert B. Wilhelmson National Center for Supercomputing Applications, and Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

Search for other papers by Robert B. Wilhelmson in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Mar 2007
DOI:
https://doi.org/10.1175/MWR3300.1
Page(s):
701–726
Restricted access

Abstract

A detailed analysis of the 27 May 1997 central Texas tornadic storm complex is undertaken in an attempt to document the prestorm environment and identify the roles played by preexisting boundaries on storm maintenance/propagation and rotation. Analysis is carried out using a broad suite of synoptic and subsynoptic data but focuses on the level-II and -III Weather Surveillance Radar-1988 Doppler (WSR-88D) data from three Texas radars. The 27 May 1997 event was characterized by a back-building (propagation against the mean flow) storm complex that produced at least 12 tornadoes including the F5 Jarrell, Texas, tornado. Furthermore, five of the eight longest-lived cells during the analysis period are shown to contain midlevel mesocyclones. However, one-dimensional metrics calculated using representative vertical profiles of state variables reveal that, despite the extreme values of CAPE in place (>6500 J kg−1), the (1D) environment associated with this event is best classified as only marginally favorable for supercells and unfavorable for significant, supercellular tornadoes. Furthermore, the observed wind shear values are shown to be more in line with the vertical shear values typically associated with nonsevere back-building storms. Examples of propagation controlled by quasi-continuous maintenance of a single cell as well as successive discrete cell redevelopment are found. In all situations, two preexisting boundaries in place during this event (a cold front and a dryline) are found to have been necessary for the maintenance/propagation of the storm complex. Specifically, it is argued that the “zippering” of the cold front and dryline (the collision of the dryline and cold front that allowed the cold front to overtake the dryline and penetrate into the most unstable air to the east) was essential for the back-building of the storm complex in this event since it resulted in new cell development at points farther south. While midlevel mesocyclones were present in five of the eight longest-lived and well-sampled cells, analysis of the relationship between observed cell motion, expected cell motion, expected supercellular deviation, and boundary motion for the longest-lived and well-sampled cells reveals little evidence that deviate motions generated through supercellular dynamics governed cell motions. Instead, it is shown that boundary motions largely controlled the propagation of individual cells.

* Current affiliation: Department of Geosciences, University of Nebraska at Lincoln, Lincoln, Nebraska

Corresponding author address: Dr. Adam L. Houston, Department of Geosciences, University of Nebraska at Lincoln, 214 Bessey Hall, Lincoln, NE 68588. Email: ahouston@unl.edu

Abstract

A detailed analysis of the 27 May 1997 central Texas tornadic storm complex is undertaken in an attempt to document the prestorm environment and identify the roles played by preexisting boundaries on storm maintenance/propagation and rotation. Analysis is carried out using a broad suite of synoptic and subsynoptic data but focuses on the level-II and -III Weather Surveillance Radar-1988 Doppler (WSR-88D) data from three Texas radars. The 27 May 1997 event was characterized by a back-building (propagation against the mean flow) storm complex that produced at least 12 tornadoes including the F5 Jarrell, Texas, tornado. Furthermore, five of the eight longest-lived cells during the analysis period are shown to contain midlevel mesocyclones. However, one-dimensional metrics calculated using representative vertical profiles of state variables reveal that, despite the extreme values of CAPE in place (>6500 J kg−1), the (1D) environment associated with this event is best classified as only marginally favorable for supercells and unfavorable for significant, supercellular tornadoes. Furthermore, the observed wind shear values are shown to be more in line with the vertical shear values typically associated with nonsevere back-building storms. Examples of propagation controlled by quasi-continuous maintenance of a single cell as well as successive discrete cell redevelopment are found. In all situations, two preexisting boundaries in place during this event (a cold front and a dryline) are found to have been necessary for the maintenance/propagation of the storm complex. Specifically, it is argued that the “zippering” of the cold front and dryline (the collision of the dryline and cold front that allowed the cold front to overtake the dryline and penetrate into the most unstable air to the east) was essential for the back-building of the storm complex in this event since it resulted in new cell development at points farther south. While midlevel mesocyclones were present in five of the eight longest-lived and well-sampled cells, analysis of the relationship between observed cell motion, expected cell motion, expected supercellular deviation, and boundary motion for the longest-lived and well-sampled cells reveals little evidence that deviate motions generated through supercellular dynamics governed cell motions. Instead, it is shown that boundary motions largely controlled the propagation of individual cells.

* Current affiliation: Department of Geosciences, University of Nebraska at Lincoln, Lincoln, Nebraska

Corresponding author address: Dr. Adam L. Houston, Department of Geosciences, University of Nebraska at Lincoln, 214 Bessey Hall, Lincoln, NE 68588. Email: ahouston@unl.edu

Save
Cover Monthly Weather Review
Monthly Weather Review

  • Barlow, W. , 1983: Analysis of the Grand Island tornadoes of June 3, 1980. Preprints, 13th Conf. on Severe Local Storms, Tulsa, OK, Amer. Meteor. Soc., 277–280.

  • Beebe, R. G. , 1958: Tornado proximity soundings. Bull. Amer. Meteor. Soc., 39 , 195–201.

  • Biggerstaff, M. I. , and Coauthors , 1997: The Texas A&M University convection and lightning experiment—TEXACAL 97. Preprints, 28th Conf. on Radar Meteorology, Austin, TX, Amer. Meteor. Soc., 588–589.

  • 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

  • Bluestein, H. B. , G. T. Marx , and M. H. Jain , 1987: Formation of mesoscale lines of precipitation: Nonsevere squall lines in Oklahoma during the spring. Mon. Wea. Rev., 115 , 2719–2727.

    • Search Google Scholar
    • Export Citation

  • Brooks, H. E. , C. A. Doswell III , and R. B. Wilhelmson , 1994: The role of midtropospheric winds in the evolution and maintenance of low-level mesocyclones. Mon. Wea. Rev., 122 , 126–136.

    • Search Google Scholar
    • Export Citation

  • Brown, J. M. , and K. R. Knupp , 1980: The Iowa cyclonic–anticyclonic tornado pair and its parent thunderstorm. Mon. Wea. Rev., 108 , 1626–1646.

    • Search Google Scholar
    • Export Citation

  • Browning, K. A. , 1977: The Structure and Mechanisms of Hailstorms. Meteor. Monogr., No. 16, Amer. Meteor. Soc., 1–43.

  • 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 , 61–79.

    • Search Google Scholar
    • Export Citation

  • Corfidi, S. F. , 1998: Some thoughts on the role mesoscale features played in the 27 May 1997 central Texas tornado outbreak. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 177–180.

  • Davies-Jones, R. P. , 1984: Streamwise vorticity: The origin of updraft rotation in supercell storms. J. Atmos. Sci., 41 , 2991–3006.

    • Search Google Scholar
    • Export Citation

  • Davies-Jones, R. P. , D. W. Burgess , and M. P. Foster , 1990: Test of helicity as a tornado forecast parameter. Preprints, 16th Conf. on Severe Local Storms, Kananaskis Park, AB, Canada, Amer. Meteor. Soc, 588–592.

  • Fovell, R. G. , and Y. Ogura , 1989: Effect of vertical wind shear on numerically simulated multicell storm structure. J. Atmos. Sci., 46 , 3144–3176.

    • Search Google Scholar
    • Export Citation

  • Hart, J. A. , and W. Korotky , 1991: The SHARP workstation v1.50 users guide. NOAA/National Weather Service, 30 pp. [Available from NWS Eastern Region Headquarters, 630 Johnson Ave., Bohemia, NY 11716.].

  • Hemler, R. S. , F. B. Lipps , and B. B. Ross , 1991: A simulation of a squall line using a nonhydrostatic cloud model with 5-km horizontal grid. Mon. Wea. Rev., 119 , 3012–3033.

    • Search Google Scholar
    • Export Citation

  • Houston, A. L. , and R. B. Wilhelmson , 2007: Observational analysis of the 27 May 1997 Central Texas tornadic event. Part II: Tornadoes. Mon. Wea. Rev., 135 , 727–735.

    • Search Google Scholar
    • Export Citation

  • Klemp, J. B. , R. B. Wilhelmson , and P. S. Ray , 1981: Observed and numerically simulated structure of a mature supercell thunderstorm. J. Atmos. Sci., 38 , 1558–1580.

    • Search Google Scholar
    • Export Citation

  • Korotky, W. , R. W. Przybylinski , and J. A. Hart , 1993: The Plainfield, Illinois tornado of August 28, 1990: The evolution of synoptic and mesoscale environments. The Tornado: Its Structure, Dynamics, Prediction, and Hazards, C. R. Church, Ed., Vol. 79, Amer. Geophys. Union, 611–624.

    • Search Google Scholar
    • Export Citation

  • Lemon, L. R. , and C. A. Doswell III , 1979: Severe thunderstorm evolution and mesocyclone structure as related to tornadogenesis. Mon. Wea. Rev., 107 , 1184–1197.

    • Search Google Scholar
    • Export Citation

  • Magsig, M. A. , D. W. Burgess , and R. R. Lee , 1998a: Multiple boundary evolution and tornadogenesis associated with the Jarrell, Texas events. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 186–189.

  • Magsig, M. A. , J. G. LaDue , D. W. Burgess , and R. R. Lee , 1998b: A radar and satellite analysis of tornadic storm updraft evolution on 27 May 1997. Preprints, 16th Conf. on Weather Analysis and Forecasting, Phoenix, AZ, Amer. Meteor. Soc., 320–322.

  • NCDC , 1997: Storm Data. Vol. 39, No. 5, 229 pp.

  • Newton, C. W. , 1963: Dynamics of severe convective storms. Severe Local Storms, Meteor. Monogr., No. 27, Amer. Meteor. Soc., 33–58.

  • NOAA , 1998: The central Texas tornadoes of May 27, 1997. Service Assessment, 99 pp. [Available from National Weather Service, 1325 East–West Highway, Silver Spring, MD 20910-3283.].

  • NSSL , 2000: WATADS (WSR-88D Algorithm Testing and Display System) 2000: Reference guide for version 10.2. NSSL, 200 pp. [Available from Storm Scale Applications Division, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK 73069.].

  • Rasmussen, E. N. , 2003: Refined supercell and tornado forecast parameters. Wea. Forecasting, 18 , 530–535.

  • Rasmussen, E. N. , and D. O. Blanchard , 1998: A baseline climatology of sounding-derived supercell and tornado forecast parameters. Wea. Forecasting, 13 , 1148–1164.

    • Search Google Scholar
    • Export Citation

  • Ross, B. B. , 1987: The role of low-level convergence and latent heating in a simulation of observed squall line formation. Mon. Wea. Rev., 115 , 2298–2321.

    • Search Google Scholar
    • Export Citation

  • Rotunno, R. , and J. B. Klemp , 1982: The influence of the shear-induced pressure gradient on thunderstorm motion. Mon. Wea. Rev., 110 , 136–151.

    • 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 , 271–292.

    • Search Google Scholar
    • Export Citation

  • Sanders, F. , 2005: Real front or baroclinic trough? Wea. Forecasting, 20 , 647–651.

  • Segal, M. , and R. W. Arritt , 1992: Nonclassical mesoscale circulations caused by surface sensible heat-flux gradients. Bull. Amer. Meteor. Soc., 73 , 1593–1604.

    • 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 , 1243–1261.

    • Search Google Scholar
    • Export Citation

  • Wade, C. G. , and G. B. Foote , 1982: The 22 July 1976 case study: Low-level airflow and mesoscale influences. Hailstorms of the Central High Plains, C. A. Knight and P. Squires, Eds., Vol. 2, Colorado Associated University Press, 115–130.

    • Search Google Scholar
    • Export Citation

  • Weaver, J. F. , 1979: Storm motion as related to boundary-layer convergence. Mon. Wea. Rev., 107 , 612–619.

  • Weaver, J. F. , and S. P. Nelson , 1982: Multiscale aspects of thunderstorm gust fronts and their effects on subsequent storm development. Mon. Wea. Rev., 110 , 707–718.

    • Search Google Scholar
    • Export Citation

  • Weaver, J. F. , W. Purdom , and E. J. Szoke , 1994: Some mesoscale aspects of the 6 June 1990 Limon, Colorado, tornado case. Wea. Forecasting, 9 , 45–61.

    • Search Google Scholar
    • Export Citation

  • Weisman, M. L. , M. S. Gilmore , and L. J. Wicker , 1998: The impact of convective storms on their local environment: What is an appropriate ambient sounding? Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 238–241.

  • Wilson, J. W. , and W. E. Schreiber , 1986: Initiation of convective storms at radar-observed boundary-layer convergence lines. Mon. Wea. Rev., 114 , 2516–2536.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 1196 494 19
PDF Downloads 890 376 15