Estimating Downburst-Related Maximum Surface Wind Speeds by Means of Proximity Soundings in New South Wales, Australia

Bart Geerts University of Wyoming, Laramie, Wyoming

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Abstract

A regional climatology of strong wind gusts associated with thunderstorms is presented, and the ability to estimate gust strength from ambient conditions is tested. Strong wind events were selected for 10 stations in New South Wales, Australia, from anemograph records and coincident thunderstorm reports. Most events took place between midafternoon and late evening and during the warmer months of the year, which is broadly consistent with the occurrence of severe thunderstorms in general. One sounding-based index, designed to predict the strength of microbursts, proves to be of limited value in predicting the magnitude of strong convective gusts, even of short-lived gusts. A modified index that combines the microburst index with upper-level wind speed is more useful.

Corresponding author address: Dr. B. Geerts, Dept. of Atmospheric Sciences, University of Wyoming, Laramie, WY 82071.

Email: geerts@uwyo.edu

Abstract

A regional climatology of strong wind gusts associated with thunderstorms is presented, and the ability to estimate gust strength from ambient conditions is tested. Strong wind events were selected for 10 stations in New South Wales, Australia, from anemograph records and coincident thunderstorm reports. Most events took place between midafternoon and late evening and during the warmer months of the year, which is broadly consistent with the occurrence of severe thunderstorms in general. One sounding-based index, designed to predict the strength of microbursts, proves to be of limited value in predicting the magnitude of strong convective gusts, even of short-lived gusts. A modified index that combines the microburst index with upper-level wind speed is more useful.

Corresponding author address: Dr. B. Geerts, Dept. of Atmospheric Sciences, University of Wyoming, Laramie, WY 82071.

Email: geerts@uwyo.edu

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  • Atkins, N., and R. M. Wakimoto, 1991: Wet microburst activity over the southeastern United States: Implications for forecasting. Wea. Forecasting,6, 470–482.

    • Crossref
    • Export Citation
  • Brandes, E. A., 1977: Gust front evolution and tornadogenesis as viewed by Doppler radar. J. Appl. Meteor.,16, 333–338.

    • Crossref
    • Export Citation
  • Brooks, H. E., C. A. Doswell III, and J. B. Cooper, 1994: On the environments of tornadic and nontornadic mesocyclones. Wea. Forecasting,9, 606–618.

    • Crossref
    • Export Citation
  • Bureau of Meteorology, 1989: Plan for upgrading severe thunderstorm warning services. 78 pp. [Available from Bureau of Meteorology, GPO Box 1289k, Melbourne, VIC 3001, Australia.].

  • Carbone, R. E., 1982: A severe frontal rainband. Part 1: Stormwide hydrodynamic structure. J. Atmos. Sci.,39, 258–279.

    • Crossref
    • Export Citation
  • Colquhoun, J. R., 1995: The Sydney supercell thunderstorm? Weather,50, 15–18.

    • Crossref
    • Export Citation
  • ——, D. J. Shepherd, and C. E. Coulman, 1985: The southerly burster of southeastern Australia: An orographically forced cold front. Mon. Wea. Rev.,113, 2090–2107.

    • Crossref
    • Export Citation
  • Easterling, D. R., and P. J. Robinson, 1985: The diurnal variation of thunderstorm activity in the United States. J. Climate Appl. Meteor.,24, 1048–1058.

    • Crossref
    • Export Citation
  • Eilts, M. D., and R. J. Doviak, 1987: Oklahoma downbursts and their asymmetry. J. Climate Appl. Meteor.,26, 69–78.

    • Crossref
    • Export Citation
  • Foster, D. S., 1958: Thunderstorm gusts compared with computed downdraft speeds. Mon. Wea. Rev.,86, 91–94.

    • Crossref
    • Export Citation
  • Fujita, T. T., 1985: The downburst, microburst and macroburst. Satellite and Mesometeorology Research Project Research Paper 210, Dept. of Geophysical Sciences, University of Chicago, 122 pp. [Available from Dept. of Geophysical Sciences, University of Chicago, 5801 South Ellis Ave., Chicago, IL 60637.].

  • ——, 1990: Downbursts—Meteorological features and wind-field characteristics. J. Wind Eng. Ind. Aerodyn.,36, 75–86.

    • Crossref
    • Export Citation
  • Geerts, B., and M. Noke-Raico, 1995: Tornadoes in Australia: Do we really know? Bull. Aust. Meteor. Oceanogr. Soc.,8, 46–51.

  • Griffiths, D. J., J. R. Colquhoun, K. L. Batt, and T. R. Casinader, 1993: Severe thunderstorms in New South Wales: Climatology and means of assessing the impact of climate change. Climatic Change,25, 369–388.

    • Crossref
    • Export Citation
  • Harnack, R. P., D. T. Jensen, and J. R. Cermak, 1997: Investigation of upper-air conditions occurring with warm season severe wind events in Utah. Wea. Forecasting,12, 282–293.

    • Crossref
    • Export Citation
  • Houze, R. A., Jr., 1993: Cloud Dynamics. Academic Press, 570 pp.

  • Johns, R. H., and W. D. Hirt, 1987: Derechos: Widespread convectively induced windstorms. Wea. Forecasting,2, 32–49.

    • Crossref
    • Export Citation
  • ——, and C. A. Doswell III, 1992: Severe local storms forecasting. Wea. Forecasting,7, 588–612.

    • Crossref
    • Export Citation
  • Kessinger, C. J., D. B. Parsons, and J. W. Wilson, 1988: Observations of a storm containing misocyclones, downbursts, and horizontal vortex circulations. Mon. Wea. Rev.,116, 1959–1982.

    • Crossref
    • Export Citation
  • Koch, S. E., A. Aksakal, and J. T. McQueen, 1997: The influence of mesoscale humidity and evapotranspiration fields on a model forecast of a cold frontal squall line. Mon. Wea. Rev.,125, 58–83.

    • Crossref
    • Export Citation
  • Kraus, H., C. M. Ewenz, M. Kremer, and J. M. Hacker, 2000: The multi-scale structure of the Australian cool changes. Meteor. Atmos. Phys.,73, 157–175.

    • Crossref
    • Export Citation
  • Laudet, T., P. King, and J. R. Colquhoun, 1994: A preliminary climatology of lightning in NSW. Preprints, Fourth Severe Thunderstorm Conf., Mt. Macedon, Australia, Bureau of Meteorology, 71–102. [Available from Bureau of Meteorology, GPO Box 1289K, Melbourne, VIC 3001, Australia.].

  • Matthews, C., and B. Geerts, 1995: Characteristic thunderstorm distribution in the Sydney area. Aust. Meteor. Mag.,44, 127–138.

  • McCann, D. W., 1994: WINDEX—A new index for forecasting microburst potential. Wea. Forecasting,9, 532–541.

    • Crossref
    • Export Citation
  • McCarthy, J., J. W. Wilson, and T. T. Fujita, 1982: The Joint Airport Weather Studies Project. Bull. Amer. Meteor. Soc.,63, 15–22.

    • Crossref
    • Export Citation
  • Mills, G. A., and J. R. Colquhoun, 1998: Objective prediction of severe thunderstorm environments: Preliminary results linking a decision tree with an operational regional NWP model. Wea. Forecasting,13, 1078–1092.

    • Crossref
    • Export Citation
  • Orf, L. G., and J. R. Anderson, 1999: A numerical study of traveling microbursts. Mon. Wea. Rev.,127, 1244–1258.

    • Crossref
    • Export Citation
  • Pino, J. P., and J. T. Moore, 1989: An interactive method for estimating hailstone size and convectively-driven wind gusts from forecast soundings. Preprints, 12th Conf. on Weather Analysis and Forecasting, Seattle, WA, Amer. Meteor. Soc., 103–106.

  • Proctor, F. H., 1989: Numerical simulations of an isolated microburst. Part II: Sensitivity experiments. J. Atmos. Sci.,46, 2143–2165.

  • ——, and R. L. Bowles, 1992: Three-dimensional simulation of the Denver 11 July 1988 microburst-producing storm. Meteor. Atmos. Phys.,49, 107–124.

    • Crossref
    • Export Citation
  • Przybylinski, R. W., 1995: The bow echo: Observations, numerical simulations, and severe weather detection methods. Wea. Forecasting,10, 203–218.

  • Roux, F., V. Marecal, and D. Hauser, 1993: The 12/13 January 1988 narrow cold-frontal rainband observed during MFDP/FRONTS 87. Part I: Kinematics and thermodynamics. J. Atmos. Sci.,50, 951–974.

    • Crossref
    • Export Citation
  • Schmidt, J. M., and W. R. Cotton, 1989: A high plains squall line associated with severe surface winds. J. Atmos. Sci.,46, 281–302.

    • Crossref
    • Export Citation
  • Speer, M., and B. Geerts, 1994: A synoptic-meso-α scale climatology of flash floods in the Sydney metropolitan area. Aust. Meteor. Mag.,43, 87–103.

  • Srivastava, R. C., 1985: A simple model of evaporatively driven downdraft: Application to a microburst downdraft. J. Atmos. Sci.,42, 1004–1023.

    • Crossref
    • Export Citation
  • ——, 1987: A model of intense downdrafts driven by the melting and evaporation of precipitation. J. Atmos. Sci.,44, 1752–1773.

    • Crossref
    • Export Citation
  • Vescio, M. D., and R. H. Johnson, 1992: The surface-wind response to transient mesoscale pressure fields associated with squall lines. Mon. Wea. Rev.,120, 1837–1850.

    • Crossref
    • Export Citation
  • Wakimoto, R. M., 1985: Forecasting dry microburst activity over the high plains. Mon. Wea. Rev.,113, 1131–1143.

    • Crossref
    • Export Citation
  • ——, and V. N. Bringi, 1988: Dual-polarization observations of microbursts associated with intense convection: The 20 July storm during the MIST project. Mon. Wea. Rev.,116, 1521–1539.

    • Crossref
    • Export Citation
  • Weckwerth, T. M., and R. M. Wakimoto, 1992: The initiation and organization of convective cells atop a cold-air outflow boundary. Mon. Wea. Rev.,120, 2169–2187.

    • Crossref
    • Export Citation
  • ——, J. W. Wilson, and R. M. Wakimoto, 1996: Thermodynamic variability within the convective boundary layer due to horizontal convective rolls. Mon. Wea. Rev.,124, 769–784.

    • Crossref
    • Export Citation
  • Weisman, M. L., 1992: The role of convectively generated rear-inflow jets in the evolution of long-lived mesoconvective systems. J. Atmos. Sci.,49, 1826–1847.

    • Crossref
    • Export Citation
  • ——, 1993: The genesis of severe, long-lived bow echoes. J. Atmos. Sci.,50, 645–670.

    • Crossref
    • Export Citation
  • Wolfson, M. M., 1990: Understanding and predicting microbursts. Preprints, 15th Conf. on Severe Local Storms, Kananaskis Park, AB, Canada, Amer. Meteor. Soc., 340–351.

  • Zhang, G. J., and H. R. Cho, 1991: Parameterization of the vertical transport of momentum by cumulus clouds. Part I: Theory. J. Atmos. Sci.,48, 1483–1492.

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