Editorial Type:
Article
Article Type:
Research Article

The Three-Dimensional Structure and Evolution of a Tornado Boundary Layer

Karen A. Kosiba Center for Severe Weather Research, Boulder, Colorado

Search for other papers by Karen A. Kosiba in
Current site
Google Scholar
PubMed Close
and
Joshua Wurman Center for Severe Weather Research, Boulder, Colorado

Search for other papers by Joshua Wurman in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Dec 2013
DOI:
https://doi.org/10.1175/WAF-D-13-00070.1
Page(s):
1552–1561
Restricted access

Abstract

The finescale three-dimensional structure and evolution of the near-surface boundary layer of a tornado (TBL) is mapped for the first time. The multibeam Rapid-Scan Doppler on Wheels (RSDOW) collected data at several vertical levels, as low as 4, 6, 10, 12, 14, and 17 m above ground level (AGL), contemporaneously at 7-s intervals for several minutes in a tornado near Russell, Kansas, on 25 May 2012. Additionally, a mobile mesonet anemometer measured winds at 3.5 m AGL in the core flow region. The radar, anemometer, and ground-based velocity-track display (GBVTD) analyses reveal the peak wind intensity is very near the surface at ~5 m AGL, about 15% higher than at 10 m AGL and 25% higher than at ~40 m AGL. GBVTD analyses resolve a downdraft within the radius of maximum winds (RMW), which decreased in magnitude when varying estimates for debris centrifuging are included. Much of the inflow (from −1 to −7 m s−1) is at or below 10–14 m AGL, much shallower than reported previously. Surface outflow precedes tornado dissipation. Comparisons between large-eddy simulation (LES) predictions of the corner flow swirl ratio Sc and observed tornado intensity changes are consistent.

Corresponding author address: Dr. Karen A. Kosiba, Center for Severe Weather Research, 1945 Vassar Circle, Boulder, CO 80305. E-mail: kakosiba@cswr.org

Abstract

The finescale three-dimensional structure and evolution of the near-surface boundary layer of a tornado (TBL) is mapped for the first time. The multibeam Rapid-Scan Doppler on Wheels (RSDOW) collected data at several vertical levels, as low as 4, 6, 10, 12, 14, and 17 m above ground level (AGL), contemporaneously at 7-s intervals for several minutes in a tornado near Russell, Kansas, on 25 May 2012. Additionally, a mobile mesonet anemometer measured winds at 3.5 m AGL in the core flow region. The radar, anemometer, and ground-based velocity-track display (GBVTD) analyses reveal the peak wind intensity is very near the surface at ~5 m AGL, about 15% higher than at 10 m AGL and 25% higher than at ~40 m AGL. GBVTD analyses resolve a downdraft within the radius of maximum winds (RMW), which decreased in magnitude when varying estimates for debris centrifuging are included. Much of the inflow (from −1 to −7 m s−1) is at or below 10–14 m AGL, much shallower than reported previously. Surface outflow precedes tornado dissipation. Comparisons between large-eddy simulation (LES) predictions of the corner flow swirl ratio Sc and observed tornado intensity changes are consistent.

Corresponding author address: Dr. Karen A. Kosiba, Center for Severe Weather Research, 1945 Vassar Circle, Boulder, CO 80305. E-mail: kakosiba@cswr.org
Save
Cover Weather and Forecasting
Weather and Forecasting

  • Alexander, C., and Wurman J. , 2005: The 30 May 1998 Spencer, South Dakota, storm. Part I: The structural evolution and environment of the supercell tornadoes. Mon. Wea. Rev., 133, 72–96.

    • Search Google Scholar
    • Export Citation

  • Barnes, S. L., 1964: A technique for maximizing details in numerical weather-map analysis. J. Appl. Meteor.,3, 396–409.

  • Bluestein, H. B., Lee W.-C. , Bell M. , Weiss C. C. , and Pazmany A. L. , 2003: Mobile Doppler radar observations of a tornado in a supercell near Bassett, Nebraska, on 5 June 1999. Part II: Tornado-vortex structure. Mon. Wea. Rev., 131, 2968–2984.

    • Search Google Scholar
    • Export Citation

  • Bluestein, H. B., Weiss C. C. , and Pazmany A. L. , 2004: The vertical structure of a tornado: High-resolution, W-band, Doppler radar observations near Happy, Texas, on 5 May 2002. Mon. Wea. Rev., 132, 2325–2337.

    • Search Google Scholar
    • Export Citation

  • Church, C. R., Snow J. T. , Baker G. L. , and Agee E. M. , 1979: Characteristics of tornado-like vortices as a function of swirl ratio: A laboratory investigation. J. Atmos. Sci., 36, 1755–1776.

    • Search Google Scholar
    • Export Citation

  • Davenport, A. G., Grimond C. S. B. , Oke T. R. , and Wieringa J. , 2000: Estimating the roughness of cities and sheltered country. Preprints, 12th Conf. on Applied Climatology, Asheville, NC, Amer. Meteor. Soc., 96–99.

  • Davies-Jones, R. P., Trapp R. J. , and Bluestein H. B. , 2001: Tornadoes and tornadic storms. Severe Convective Storms, Meteor. Monogr., No. 50, Amer. Meteor. Soc., 167–221.

  • Dowell, D. C., Alexander C. R. , Wurman J. M. , and Wicker L. J. , 2005: Centrifuging of hydrometeors and debris in tornadoes: Radar-reflectivity patterns and wind-measurement errors. Mon. Wea. Rev., 123, 1501–1524.

    • Search Google Scholar
    • Export Citation

  • Edwards, R., LaDue J. G. , Ferree J. T. , Scharfenberg K. , Maier C. , and Coulbourne W. L. , 2013: Tornado intensity estimation: Past, present, and future. Bull. Amer. Meteor. Soc., 94, 641–653.

    • Search Google Scholar
    • Export Citation

  • Hoecker, W. H., 1960: Wind speed and air flow patterns in the Dallas tornado of April 2, 1957. Mon. Wea. Rev.,88, 167–180.

  • Kessler, E., 1986: Thunderstorm Morphology and Dynamics. Vol. 2, Thunderstorms: A Social, Scientific, and Technological Documentary, University of Oklahoma Press, 432 pp.

  • Koch, S. E., desJardins M. , and Kocin P. J. , 1983: An interactive Barnes objective map analysis scheme for use with satellite and conventional data. J. Climate Appl. Meteor.,22, 1487–1503.

  • Kosiba, K. A., and Wurman J. , 2010: The three-dimensional axisymmetric wind field structure of the Spencer, South Dakota, 1998, tornado. J. Atmos. Sci., 67, 3074–3083.

    • Search Google Scholar
    • Export Citation

  • Kosiba, K. A., Trapp R. J. , and Wurman J. , 2008: An analysis of the axisymmetric three-dimensional low-level wind field in a tornado using mobile radar observations. Geophys. Res. Lett., 35, L05805, doi:10.1029/2007GL031851.

    • Search Google Scholar
    • Export Citation

  • Kosiba, K. A., Wurman J. , Markowski P. , Richardson Y. , Robinson P. , and Marquis J. , 2013: Genesis of the Goshen County, Wyoming, tornado on 5 June 2009 during VORTEX2. Mon. Wea. Rev., 141, 1157–1181.

    • Search Google Scholar
    • Export Citation

  • Lee, W.-C., and Wurman J. , 2005: Diagnosed three-dimensional axisymmetric structure of the Mulhall tornado on 3 May 1999. J. Atmos. Sci., 62, 2373–2393.

    • Search Google Scholar
    • Export Citation

  • Lee, W.-C., Jou B. J.-D. , Chang P.-L. , and Deng S.-M. , 1999: Tropical cyclone kinematic structure retrieved from single-Doppler radar observations. Part I: Doppler velocity patterns and the GBVTD technique. Mon. Wea. Rev.,127, 2419–2439.

  • Lewellen, D. C., and Lewellen W. S. , 2007: Near-surface intensification of tornado vortices. J. Atmos. Sci., 64, 2176–2194.

  • Lewellen, D. C., Lewellen W. S. , and Xia J. , 2000: The influence of a local swirl ratio on tornado intensification near the surface. J. Atmos. Sci., 57, 527–544.

    • Search Google Scholar
    • Export Citation

  • Lewellen, D. C., Gong B. , and Lewellen W. S. , 2008: Effects of finescale debris on near-surface tornado dynamics. J. Atmos. Sci., 65, 3247–3262.

    • Search Google Scholar
    • Export Citation

  • Lewellen, W. S., 1976: Assessment of knowledge and implications for man. Proc. Symp. on Tornadoes, Lubbock, TX, Texas Tech University, 107–143.

  • Lewellen, W. S., 1993: Tornado vortex theory. The Tornado: Its Structure, Dynamics, Prediction and Hazards, Geophys. Monogr., Vol. 79, Amer. Geophys. Union, 19–39.

  • Lewellen, W. S., Lewellen D. C. , and Sykes R. I. , 1997: Large-eddy simulation of a tornado's interaction with the surface. J. Atmos. Sci., 54, 581–605.

    • Search Google Scholar
    • Export Citation

  • Nolan, D. S., 2013: On the use of Doppler radar–derived wind fields to diagnose the secondary circulations of tornadoes. J. Atmos. Sci., 70, 1160–1171.

    • Search Google Scholar
    • Export Citation

  • Snow, J. T., 1982: A review of recent advances in tornado vortex dynamics. Rev. Geophys. Space Phys., 20, 953–964.

  • Tanamachi, R. L., Bluestein H. B. , Lee W.-C. , Bell M. , and Pazmany A. , 2007: Ground-based velocity display (GBVTD) analysis of W-band Doppler radar data in a tornado near Stockton, Kansas, on 15 May 1999. Mon. Wea. Rev., 135, 783–800.

    • Search Google Scholar
    • Export Citation

  • Wakimoto, R. M., Stauffer P. , Lee W.-C. , Atkins N. T. , and Wurman J. , 2012: Finescale structure of the LaGrange, Wyoming, tornado during VORTEX2: GBVTD and photogrammetric analyses. Mon. Wea. Rev., 140, 2939–2958.

    • Search Google Scholar
    • Export Citation

  • Wurman, J., 1998: Preliminary results and report of the ROTATE-98 tornado experiment. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 120–123.

  • Wurman, J., 2001: The DOW mobile multiple Doppler network. Preprints, 30th Int. Conf. on Radar Meteorology, Munich, Germany, Amer. Meteor. Soc., 95–97.

  • Wurman, J., 2008: Preliminary results and report of the ROTATE-2008 radar/in-situ/mobile mesonet experiment. Proc. 24th Conf. on Severe Local Storms, Savannah, GA, Amer. Meteor. Soc., 5.4. [Available online at https://ams.confex.com/ams/24SLS/webprogram/Paper142200.html.]

  • Wurman, J., and Gill S. , 2000: Finescale radar observations of the Dimmitt, Texas, tornado. Mon. Wea. Rev., 128, 2135–2164.

  • Wurman, J., and Randall M. , 2001: An inexpensive, mobile, rapid-scan radar. Preprints, 30th Conf. on Radar Meteorology, Munich, Germany, Amer. Meteor. Soc., P3.4. [Available online at https://ams.confex.com/ams/pdfpapers/21577.pdf.]

  • Wurman, J., and Kosiba K. , 2013: Finescale radar observations of tornado and mesocyclone structures. Wea. Forecasting, 28, 1157–1174.

  • Wurman, J., Straka J. , and Rasmussen E. , 1996: Fine-scale Doppler radar observation of tornadoes. Science, 272, 1774–1777.

  • Wurman, J., Straka J. , Rasmussen E. , Randall M. , and Zahrai A. , 1997: Design and deployment of a portable, pencil-beam, pulsed, 3-cm Doppler radar. J. Atmos. Oceanic Technol., 14, 1502–1512.

    • Search Google Scholar
    • Export Citation

  • Wurman, J., Alexander C. , Robinson P. , and Richardson Y. , 2007a: Low-level winds in tornadoes and potential catastrophic tornado impacts in urban areas. Bull. Amer. Meteor. Soc., 88, 31–46.

    • Search Google Scholar
    • Export Citation

  • Wurman, J., Richardson Y. , Alexander C. , Weygandt S. , and Zhang P. F. , 2007b: Dual-Doppler analysis of winds and vorticity budget terms near a tornado. Mon. Wea. Rev., 135, 2392–2405.

    • Search Google Scholar
    • Export Citation

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

    • Search Google Scholar
    • Export Citation

  • Wurman, J., Kosiba K. , and Robinson P. , 2013a: In situ, Doppler radar, and video observations of the interior structure of a tornado and the wind–damage relationship. Bull. Amer. Meteor. Soc., 94, 835–846.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 3135 1235 107
PDF Downloads 1379 313 18