• Barnes, S. L., 1970: Some aspects of a severe, right-moving thunderstorm deduced from mesonetwork rawinsonde observations. J. Atmos. Sci.,27, 634–648.

  • ——, 1973: Mesoscale objective map analysis using weighted time-series observations. NOAA Tech. Memo. ERL NSSL-62, 60 pp. [NTIS COM-73-10781.].

  • Brady, R. H., and E. J. Szoke, 1989: A case study of nonmesocyclone tornado development in northeast Colorado: Similarities to waterspout formation. Mon. Wea. Rev.,117, 843–856.

  • Brandes, E. A., 1978: Mesocyclone evolution and tornadogenesis: Some observations. Mon. Wea. Rev.,106, 995–1011.

  • ——, 1981: Finestructure of the Del City–Edmond tornadic mesocirculation. Mon. Wea. Rev.,109, 635–647.

  • ——, 1984a: Relationships between radar-derived thermodynamic variables and tornadogenesis. Mon. Wea. Rev.,112, 1033–1052.

  • ——, 1984b: Vertical vorticity generation and mesocyclone sustenance in tornadic thunderstorms: The observational evidence. Mon. Wea. Rev.,112, 2253–2269.

  • ——, R. P. Davies-Jones, and B. C. Johnson, 1988: Streamwise vorticity effects on supercell morphology and persistence. J. Atmos. Sci.,45, 947–963.

  • Brewster, K. A., 1984: Kinetic energy evolution in a developing severe thunderstorm. M.S. thesis, School of Meteorology, University of Oklahoma, 171 pp. [Available from School of Meteorology, 100 East Boyd, Norman, Oklahoma, 73019.].

  • Brooks, H. E., C. A. Doswell, 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.

  • Brown, R. A., L. R. Lemon, and D. W. Burgess, 1978: Tornado detection by pulsed Doppler radar. Mon. Wea. Rev.,106, 29–38.

  • Browning, K. A., 1964: Airflow and precipitation trajectories within severe local storms which travel to the right of the winds. J. Atmos. Sci.,21, 634–639.

  • Burgess, D. W., 1982: Lifecycle of the Wichita Falls tornadic storm. Preprints, 12th Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor. Soc., 441–443.

  • Carter, J. K., 1970: The meteorologically instrumented WKY-TV tower facility. NOAA Tech. Memo. ERLTM-NSSL 50, 18 pp. [NTIS COM-71-00108.].

  • Cressman, G. P., 1959: An operational objective analysis system. Mon. Wea. Rev.,87, 367–374.

  • Davies, J. M., and R. H. Johns, 1993: Some wind and instability parameters associated with strong and violent tornadoes. 1. Wind shear and helicity. The Tornado: Its Structure, Dynamics, Prediction and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 573–582.

  • 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.

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

  • Doswell, C. A., III, and D. W. Burgess, 1993: Tornadoes and tornadic storms: A review of conceptual models. The Tornado: Its Structure, Dynamics, Prediction and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 161–172.

  • Dowell, D. C., and H. B. Bluestein, 1996: Dual-Doppler analysis of a tornadic supercell: The Arcadia, OK storm of 17 May 1981. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc., 413–417.

  • ——, ——, and D. P. Jorgensen, 1997: Airborne Doppler radar analysis of supercells during COPS-91. Mon. Wea. Rev.,125, 365–383.

  • Doviak, R. J., P. S. Ray, R. G. Strauch, and L. J. Miller, 1976: Error estimation in wind fields derived from dual-Doppler radar measurement. J. Appl. Meteor.,15, 868–878.

  • Fujita, T. T., G. S. Forbes, and T. A. Umenhofer, 1976: Close-up view of 20 March 1976 tornadoes: Sinking cloud tops to suction vortices. Weatherwise,29, 116–131.

  • Goff, R. C., 1976: Vertical structure of thunderstorm outflows. Mon. Wea. Rev.,104, 1429–1440.

  • Grasso, L. D., and W. R. Cotton, 1995: Numerical simulation of a tornado vortex. J. Atmos. Sci.,52, 1192–1203.

  • Guerrero, H., and W. Read, 1993: Operational use of the WSR-88D during the November 21, 1992 southeast Texas tornado outbreak. Preprints, 17th Conf. on Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc., 399–402.

  • Hane, C. E., and P. S. Ray, 1985: Pressure and buoyancy fields derived from Doppler radar in a tornadic thunderstorm. J. Atmos. Sci.,42, 18–35.

  • Johnson, K. W., P. S. Ray, B. C. Johnson, and R. P. Davies-Jones, 1987: Observations related to the rotational dynamics of the 20 May 1977 tornadic storms. Mon. Wea. Rev.,115, 2463–2478.

  • Klemp, J. B., and R. B. Wilhelmson, 1978: Simulations of right- and left-moving storms produced through storm splitting. J. Atmos. Sci.,35, 1097–1110.

  • ——, and R. Rotunno, 1983: A study of the tornadic region within a supercell thunderstorm. J. Atmos. Sci.,40, 359–377.

  • Leise, J. A., 1981: A multidimensional scale-telescoped filter and data extension package. NOAA Tech. Memo. ERL WPL-82, 18 pp. [NTIS PB82-164104.].

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

  • Lewellen, W. S., 1993: Tornado vortex theory. The Tornado: Its Structure, Dynamics, Prediction and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 19–39.

  • Magsig, M. A., and D. W. Burgess, 1996: A vorticity and divergence analysis relating to tornadogenesis as seen by a WSR-88D radar. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc., 418–422.

  • O’Brien, J., 1970: Alternative solutions to the classical vertical velocity problem. J. Appl. Meteor.,9, 197–203.

  • Rasmussen, E. N., and J. M. Straka, 1996: Mobile mesonet observations of tornadoes during VORTEX-95. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc., 1–5.

  • ——, ——, R. Davies-Jones, C. A. Doswell III, F. H. Carr, M. D. Eilts, and D. R. MacGorman, 1994: Verification of the origins of rotation in tornadoes experiment: VORTEX. Bull. Amer. Meteor. Soc.,75, 995–1006.

  • Ray, P. S., C. L. Ziegler, W. Bumgarner, and R. J. Serafin, 1980: Single- and multiple-Doppler radar observations of tornadic storms. Mon. Wea. Rev.,108, 1607–1625.

  • ——, B. C. Johnson, K. W. Johnson, J. S. Bradberry, J. J. Stephens, K. K. Wagner, R. B. Wilhelmson, and J. B. Klemp, 1981: The morphology of several tornadic storms on 20 May 1977. J. Atmos. Sci.,38, 1643–1663.

  • Rotunno, R., and J. Klemp, 1985: On the rotation and propagation of simulated supercell thunderstorms. J. Atmos. Sci.,42, 271–292.

  • Taylor, W. L., Ed., 1982: 1981 spring program summary. NOAA Tech. Memo. ERL NSSL-93, 97 pp. [NTIS PB82-244757.].

  • Trapp, R. J., and B. H. Fiedler, 1995: Tornado-like vortexgenesis in a simplified numerical model. J. Atmos. Sci.,52, 3757–3778.

  • ——, and E. D. Mitchell, 1995: Characteristics of tornadic vortex signatures detected by WSR-88D radars. Preprints, 27th Conf. on Radar Meteorology, Vail, CO, Amer. Meteor. Soc., 211–212.

  • Wakimoto, R. M., and J. W. Wilson, 1989: Non-supercell tornadoes. Mon. Wea. Rev.,117, 1113–1140.

  • ——, W. C. Lee, H. B. Bluestein, C. H. Liu, and P. H. Hildebrand, 1996: ELDORA observations during VORTEX 95. Bull. Amer. Meteor. Soc.,77, 1465–1481.

  • 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.

  • Ward, N. B., 1972: The exploration of certain features of tornado dynamics using a laboratory model. J. Atmos. Sci.,29, 1194–1204.

  • 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, 2479–2498.

  • Wicker, L. J., 1996: The role of near surface wind shear on low-level mesocyclone generation and tornadoes. Preprints, 18th Conf. on Severe Local Storms, San Francisco, CA, Amer. Meteor. Soc., 115–119.

  • ——, and R. B. Wilhelmson, 1995: Simulation and analysis of tornado development and decay within a three-dimensional supercell thunderstorm. J. Atmos. Sci.,52, 2675–2703.

  • Wilson, J. W., 1986: Tornadogenesis by nonprecipitation-induced wind shear lines. Mon. Wea. Rev.,114, 270–284.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 128 67 4
PDF Downloads 107 50 3

The Arcadia, Oklahoma, Storm of 17 May 1981: Analysis of a Supercell during Tornadogenesis

View More View Less
  • 1 School of Meteorology, University of Oklahoma, Norman, Oklahoma
Restricted access

Abstract

On 17 May 1981, an extensive dataset was collected for a supercell thunderstorm that produced an F2 tornado near Arcadia in central Oklahoma. Coordinated dual-Doppler scans of the storm by 10-cm research radars were collected at approximately 5-min intervals from 30 min before the tornado touched down until 15 min after the tornado had dissipated. The Arcadia storm was also well sampled by a 444-m-tall instrumented tower. The low-level inflow, updraft, mesocyclone, and rear precipitation core of the supercell all passed across the tower.

A comparison of the instrumented tower measurements with a dual-Doppler synthesis reveals that the latter qualitatively resolved the low-level flow. However, the magnitudes of the low-level horizontal winds and updraft speed were underestimated. In addition, the vertical shear of the horizontal wind in the lowest kilometer was unresolved in the Doppler winds.

In the storm environment, horizontal vorticity was strong (∼1.5 × 10−2 s−1) and approximately streamwise over the depth of the instrumented tower. Just upstream (northeast) of the updraft, the magnitude of horizontal vorticity was nearly twice this value and had likely been enhanced by baroclinic generation of horizontal vorticity and/or stretching of horizontal vorticity. Tilting of the resulting horizontal vorticity into the vertical produced the pretornadic low-level mesocyclone. Low-level mesocyclone inflow was primarily from the east, but during the tornadic stage, parcels approaching from the north and west were also drawn into the circulation.

The tornado formed southeast of the mesocyclone center and near the tip of the reflectivity hook echo while low-level mesocyclone vorticity was increasing. Tornadogenesis occurred near the nose of the rear downdraft within a region of horizontal shear between southeasterly inflow into the storm and westerly outflow from the rear downdraft. Pressure retrievals suggest the rear downdraft south of the mesocyclone center was associated with a downward-directed perturbation pressure gradient force. The tornado and the parent storm dissipated as outflow surged eastward ahead of the updraft.

This case study is the first to include a comparison of independent measurements of the wind field in and near the low-level mesocyclone of a supercell. The wind analysis is also complemented by the instrumented tower thermodynamic measurements.

Corresponding author address: David C. Dowell, School of Meteorology, University of Oklahoma, 100 East Boyd, Room 1310, Norman, OK 73019-0628.

Email: ddowell@ou.edu

Abstract

On 17 May 1981, an extensive dataset was collected for a supercell thunderstorm that produced an F2 tornado near Arcadia in central Oklahoma. Coordinated dual-Doppler scans of the storm by 10-cm research radars were collected at approximately 5-min intervals from 30 min before the tornado touched down until 15 min after the tornado had dissipated. The Arcadia storm was also well sampled by a 444-m-tall instrumented tower. The low-level inflow, updraft, mesocyclone, and rear precipitation core of the supercell all passed across the tower.

A comparison of the instrumented tower measurements with a dual-Doppler synthesis reveals that the latter qualitatively resolved the low-level flow. However, the magnitudes of the low-level horizontal winds and updraft speed were underestimated. In addition, the vertical shear of the horizontal wind in the lowest kilometer was unresolved in the Doppler winds.

In the storm environment, horizontal vorticity was strong (∼1.5 × 10−2 s−1) and approximately streamwise over the depth of the instrumented tower. Just upstream (northeast) of the updraft, the magnitude of horizontal vorticity was nearly twice this value and had likely been enhanced by baroclinic generation of horizontal vorticity and/or stretching of horizontal vorticity. Tilting of the resulting horizontal vorticity into the vertical produced the pretornadic low-level mesocyclone. Low-level mesocyclone inflow was primarily from the east, but during the tornadic stage, parcels approaching from the north and west were also drawn into the circulation.

The tornado formed southeast of the mesocyclone center and near the tip of the reflectivity hook echo while low-level mesocyclone vorticity was increasing. Tornadogenesis occurred near the nose of the rear downdraft within a region of horizontal shear between southeasterly inflow into the storm and westerly outflow from the rear downdraft. Pressure retrievals suggest the rear downdraft south of the mesocyclone center was associated with a downward-directed perturbation pressure gradient force. The tornado and the parent storm dissipated as outflow surged eastward ahead of the updraft.

This case study is the first to include a comparison of independent measurements of the wind field in and near the low-level mesocyclone of a supercell. The wind analysis is also complemented by the instrumented tower thermodynamic measurements.

Corresponding author address: David C. Dowell, School of Meteorology, University of Oklahoma, 100 East Boyd, Room 1310, Norman, OK 73019-0628.

Email: ddowell@ou.edu

Save