Vertical Wind Shear Associated with Left-Moving Supercells

Matthew J. Bunkers NOAA/NWS Weather Forecast Office, Rapid City, South Dakota

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Abstract

Vertical wind shear parameters are presented for 60 left-moving supercells across the United States, 53 of which produced severe hail (≥1.9 cm). Hodographs corresponding to environments of left-moving supercells have a tendency to be more linear than those of their right-moving supercell counterparts. When curvature is present in the hodographs of the left-moving supercells, it is typically confined to the lowest 0.5–1 km. Values of 0–6-km wind shear for left-moving supercells—both bulk and cumulative—are within the ranges commonly found in right-moving supercell environments, but the shear values do occur toward the lower end of the spectrum. Conversely, the absolute values of storm-relative helicity (SRH) for left-moving supercells are much smaller, on average, than what occur for right-moving supercells (although SRH values for many right-moving supercells also fall well below general guidelines for mesocyclone development). A significant fraction of the 0–3-km SRH (25%) and 0–1-km SRH (65%) for left-moving supercells is positive, owing to the shallow clockwise curvature of the hodographs. However, nearly all of the 1–3-km SRH for left-moving supercells is negative, with absolute values comparable in magnitude to those for right-moving supercells. A limited climatological analysis of vertical wind shear associated with convective environments across parts of the central United States suggests that clockwise curvature of the low-level shear vector is most common in the central/southern plains, partially explaining the preeminence of right-moving supercells in that area. In contrast, hodographs are more linear over the northern high plains, suggesting left-moving supercells may be relatively more common there. It would be beneficial to implement operational radar algorithms that can detect mesoanticyclones across the United States.

Corresponding author address: Matthew J. Bunkers, NOAA/NWS Weather Forecast Office, 300 E. Signal Dr., Rapid City, SD 57701-3800. Email: matthew.bunkers@noaa.gov

Abstract

Vertical wind shear parameters are presented for 60 left-moving supercells across the United States, 53 of which produced severe hail (≥1.9 cm). Hodographs corresponding to environments of left-moving supercells have a tendency to be more linear than those of their right-moving supercell counterparts. When curvature is present in the hodographs of the left-moving supercells, it is typically confined to the lowest 0.5–1 km. Values of 0–6-km wind shear for left-moving supercells—both bulk and cumulative—are within the ranges commonly found in right-moving supercell environments, but the shear values do occur toward the lower end of the spectrum. Conversely, the absolute values of storm-relative helicity (SRH) for left-moving supercells are much smaller, on average, than what occur for right-moving supercells (although SRH values for many right-moving supercells also fall well below general guidelines for mesocyclone development). A significant fraction of the 0–3-km SRH (25%) and 0–1-km SRH (65%) for left-moving supercells is positive, owing to the shallow clockwise curvature of the hodographs. However, nearly all of the 1–3-km SRH for left-moving supercells is negative, with absolute values comparable in magnitude to those for right-moving supercells. A limited climatological analysis of vertical wind shear associated with convective environments across parts of the central United States suggests that clockwise curvature of the low-level shear vector is most common in the central/southern plains, partially explaining the preeminence of right-moving supercells in that area. In contrast, hodographs are more linear over the northern high plains, suggesting left-moving supercells may be relatively more common there. It would be beneficial to implement operational radar algorithms that can detect mesoanticyclones across the United States.

Corresponding author address: Matthew J. Bunkers, NOAA/NWS Weather Forecast Office, 300 E. Signal Dr., Rapid City, SD 57701-3800. Email: matthew.bunkers@noaa.gov

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  • Achtemeier, G. L., 1969: Some observations of splitting thunderstorms over Iowa on August 25–26, 1965. Preprints, Sixth Conf. on Severe Local Storms, Chicago, IL, Amer. Meteor. Soc., 89–94.

    • Search Google Scholar
    • Export Citation
  • Andra, D. L. Jr,, 1993: Observations of an anticyclonically rotating severe storm. Preprints, 17th Conf. on Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc., 186–190.

    • Search Google Scholar
    • Export Citation
  • Bluestein, H. B., and Weisman M. L. , 2000: The interaction of numerically simulated supercells initiated along lines. Mon. Wea. Rev., 128 , 31283149.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brown, R. A., 1993: A compositing approach for preserving significant features in atmospheric profiles. Mon. Wea. Rev., 121 , 874880.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brown, R. A., and Meitín R. J. , 1994: Evolution and morphology of two splitting thunderstorms with dominant left-moving members. Mon. Wea. Rev., 122 , 20522067.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bunkers, M. J., Klimowski B. A. , Zeitler J. W. , Thompson R. L. , and Weisman M. L. , 2000: Predicting supercell motion using a new hodograph technique. Wea. Forecasting, 15 , 6179.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Burgess, D. W., and Curran E. B. , 1985: The relationship of storm type to environment in Oklahoma on 26 April 1984. Preprints, 14th Conf. on Severe Local Storms, Indianapolis, IN, Amer. Meteor. Soc., 208–211.

    • Search Google Scholar
    • Export Citation
  • Burgess, D. W., and Lemon L. R. , 1991: Characteristics of mesocyclones detected during a NEXRAD test. Preprints, 25th Int. Conf. on Radar Meteorology, Paris, France, Amer. Meteor. Soc., 39–42.

    • Search Google Scholar
    • Export Citation
  • Charba, J., and Sasaki Y. , 1971: Structure and movement of the severe thunderstorms of 3 April 1964 as revealed from radar and surface mesonetwork data analysis. J. Meteor. Soc. Japan, 49 , 191214.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Concannon, P. R., Brooks H. E. , and Doswell III C. A. , 2000: Climatological risk of strong and violent tornadoes in the United States. Preprints, Second Conf. on Environmental Applications, Long Beach, CA, Amer. Meteor. Soc., 212–219.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R. P., 1986: Tornado dynamics. Thunderstorm Morphology and Dynamics, E. Kessler, Ed., University of Oklahoma Press, 197–236.

    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R. P., Burgess D. W. , and Foster M. P. , 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.

    • Search Google Scholar
    • Export Citation
  • Dickins, J., 1994: South Australian supercells—A composite hodograph. Preprints, Fourth Severe Thunderstorm Conf., Mount Macedon, Victoria, Australia, Bureau of Meteorology, 1–9.

    • Search Google Scholar
    • Export Citation
  • Doswell, C. A. I. I. I,, and Rasmussen E. N. , 1994: The effect of neglecting the virtual temperature correction on CAPE calculations. Wea. Forecasting, 9 , 625629.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Droegemeier, K. K., Lazarus S. M. , and Davies-Jones R. , 1993: The influence of helicity on numerically simulated convective storms. Mon. Wea. Rev., 121 , 20052029.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Edwards, R., and Thompson R. L. , 2000: RUC-2 supercell proximity soundings. Part II: An independent assessment of supercell forecast parameters. Preprints, 20th Conf. on Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 435–438.

    • Search Google Scholar
    • Export Citation
  • Fankhauser, J. C., 1971: Thunderstorm–environment interactions determined from aircraft and radar observations. Mon. Wea. Rev., 99 , 171192.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grasso, L. D., 2000: The dissipation of a left-moving cell in a severe storm environment. Mon. Wea. Rev., 128 , 27972815.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grasso, L. D., and Hilgendorf E. R. , 2001: Observations of a severe left-moving thunderstorm. Wea. Forecasting, 16 , 500511.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hamill, T. M., and Church A. T. , 2000: Conditional probabilities of significant tornadoes from RUC-2 forecasts. Wea. Forecasting, 15 , 461475.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hart, J. A., and Janish P. R. , 1999: SeverePlot: Historical Severe Weather Report Database. Version 2.0. Storm Prediction Center, Norman, OK. [Available online at www.spc.noaa.gov/software/svrplot2/index.html.].

    • Search Google Scholar
    • Export Citation
  • Houze, R. A. Jr,, Schmid W. , Fovell R. G. , and Schiesser H-H. , 1993: Hailstorms in Switzerland: Left movers, right movers, and false hooks. Mon. Wea. Rev., 121 , 33453370.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kleyla, R. P., 1993: A radar and synoptic scale analysis of a splitting thunderstorm over north-central Texas on November 10, 1992. Preprints, 17th Conf. on Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc., 211–214.

    • Search Google Scholar
    • Export Citation
  • Knupp, K. R., and Cotton W. R. , 1982: An intense, quasi-steady thunderstorm over mountainous terrain. Part II: Doppler radar observations of the storm morphological structure. J. Atmos. Sci., 39 , 343358.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Maddox, R. A., 1976: An evaluation of tornado proximity wind and stability data. Mon. Wea. Rev., 104 , 133142.

  • Markowski, P. M., Straka J. M. , and Rasmussen E. N. , 1998a: The sensitivity of storm-relative helicity to small hodograph changes and resolution. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 363–366.

    • Search Google Scholar
    • Export Citation
  • Markowski, P. M., and Blanchard D. O. , 1998b: Variability of storm-relative helicity during VORTEX. Mon. Wea. Rev., 126 , 29592971.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Matthews, G. N., and Turnage T. J. , 2000: An example of a left-split supercell producing 5-inch hail: The Big Spring, Texas storm of 10 May 1996. Preprints, 20th Conf. on Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 526–529.

    • Search Google Scholar
    • Export Citation
  • McCann, D. W., 1983: Synoptic patterns associated with splitting thunderstorms. Preprints, 13th Conf. on Severe Local Storms, Tulsa, OK, Amer. Meteor. Soc., J1–J4.

    • Search Google Scholar
    • Export Citation
  • Milton, J. S., and Arnold J. C. , 1990: Introduction to Probability and Statistics: Principles and Applications for Engineering and the Computing Sciences. McGraw-Hill, 700 pp.

    • Search Google Scholar
    • Export Citation
  • Mitchell, M. J., Arritt R. W. , and Labas K. , 1995: A climatology of the warm season Great Plains low-level jet using wind profiler observations. Wea. Forecasting, 10 , 576591.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Monteverdi, J. P., Blier W. , Stumpf G. , Pi W. , and Anderson K. , 2001: First WSR-88D documentation of an anticyclonic supercell with anticyclonic tornadoes: The Sunnyvale–Los Altos, California, tornadoes of 4 May 1998. Mon. Wea. Rev., 129 , 28052814.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nielsen-Gammon, J. W., and Read W. L. , 1995: Detection and interpretation of left-moving severe thunderstorms using the WSR-88D: A case study. Wea. Forecasting, 10 , 127140.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Phillips, G., 1994: Observation of a left-moving severe thunderstorm. NOAA/NWS CR WSR-88D Operational Note 94-06, 5 pp. [Available from NWS Central Region, 601 E. 12th St., Rm. 1836, Kansas City, MO 64106-2897.].

    • Search Google Scholar
    • Export Citation
  • Rasmussen, E. N., and Wilhelmson R. B. , 1983: Relationships between storm characteristics and 1200 GMT hodographs, low-level shear, and stability. Preprints, 13th Conf. on Severe Local Storms, Tulsa, OK, Amer. Meteor. Soc., J5–J8.

    • Search Google Scholar
    • Export Citation
  • Rasmussen, E. N., and Blanchard D. O. , 1998: A baseline climatology of sounding-derived supercell and tornado forecast parameters. Wea. Forecasting, 13 , 11481164.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rasmussen, E. N., and Straka J. M. , 1998: Variations in supercell morphology. Part I: Observations of the role of upper-level storm-relative flow. Mon. Wea. Rev., 126 , 24062421.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Scarlett, J. R., 1998: A severe splitting storm in the upper Yellowstone valley. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 530–531.

    • Search Google Scholar
    • Export Citation
  • Stensrud, D. J., Cortinas Jr. J. V. , and Brooks H. E. , 1997: Discriminating between tornadic and nontornadic thunderstorms using mesoscale model output. Wea. Forecasting, 12 , 613632.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stuart, N. A., 1997: The Wakefield, Virginia WSR-88D depiction of the 6 September 1994 split cell thunderstorm over southern Virginia. Natl. Wea. Dig., 21 ((2),) 1830.

    • Search Google Scholar
    • Export Citation
  • Thompson, R. L., and Edwards R. , 2000: A comparison of Rapid Update Cycle 2 (RUC-2) model soundings with observed soundings in supercell environments. Preprints, 20th Conf. on Severe Local Storms, Orlando, FL, Amer. Meteor. Soc., 551–554.

    • Search Google Scholar
    • Export Citation
  • UCAR, 1996: A Convective Storm Matrix: Buoyancy/Shear Dependencies. University Corporation for Atmospheric Research–Cooperative Program for Operational Meteorology, Education, and Training CD-ROM. Version 1.1. [Available from COMET, P.O. Box 3000, Boulder, CO 80307-3000.].

    • Search Google Scholar
    • Export Citation
  • Weaver, J. F., Dostalek J. F. , and Phillips L. , 2001: Left-moving thunderstorms in a high plains, weakly sheared environment. Preprints, 18th Conf. on Weather Analysis and Forecasting, Fort Lauderdale, FL, Amer. Meteor. Soc., 208–213.

    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., and Klemp J. B. , 1986: Characteristics of isolated convective storms. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 331–358.

    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., and Rotunno R. , 2000: The use of vertical wind shear versus helicity in interpreting supercell dynamics. J. Atmos. Sci., 57 , 14521472.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wilhelmson, R. B., and Klemp J. B. , 1981: A three-dimensional numerical simulation of splitting severe storms on 3 April 1964. J. Atmos. Sci., 38 , 15811600.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wilks, D. S., 1995: Statistical Methods in the Atmospheric Sciences. Academic Press, 467 pp.

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