An Observational Study of Atmospheric Bore Formation from Colliding Density Currents

David E. Kingsmill Desert Research Institute, Reno, Nevada

Search for other papers by David E. Kingsmill in
Current site
Google Scholar
PubMed
Close
and
N. Andrew Crook National Center for Atmospheric Research,* Boulder, Colorado

Search for other papers by N. Andrew Crook in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Observations from east-central Florida during the Convection and Precipitation/Electrification (CaPE) experiment are used to investigate the factors that influence atmospheric bore formation from colliding density currents. Ten cases involving the collision of a gust front with a sea-breeze front are analyzed with Doppler radar and sounding and surface mesonet data. The gust fronts in these collisions were generally deeper, denser, and faster propagating than their sea-breeze-front counterparts. Seven of the 10 cases produced dual boundaries that moved away from each other in a relative sense after the collision. Post-collision boundaries moving in the same direction and oriented similarly to the pre-collision gust front occurred in all 10 cases. They transported mass in the manner of a density current in six cases, while the others behaved more like bores or bore–density current hybrids, as they were characterized by little or no mass transport. Similarity of gust-front and sea-breeze-front propagation speed prior to the collision was the best indicator of bore character in post-collision boundaries induced by gust fronts. Sea-breeze-front-induced post-collision boundaries occurred in the seven cases in which the pre-collision sea-breeze front was nonstationary. These post-collision boundaries exhibited no purely mass transport behavior and were all categorized as bores or bore/density current hybrids. The potential ability to predict dual zones of convergence emanating from boundary collisions as demonstrated in this study may be of value to convective nowcasting in Florida and perhaps other locales, as 70% of the observed post-collision boundaries initiated new convection or enhanced existing convection.

Corresponding author address: David E. Kingsmill, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512. Email: davidk@dri.edu

Abstract

Observations from east-central Florida during the Convection and Precipitation/Electrification (CaPE) experiment are used to investigate the factors that influence atmospheric bore formation from colliding density currents. Ten cases involving the collision of a gust front with a sea-breeze front are analyzed with Doppler radar and sounding and surface mesonet data. The gust fronts in these collisions were generally deeper, denser, and faster propagating than their sea-breeze-front counterparts. Seven of the 10 cases produced dual boundaries that moved away from each other in a relative sense after the collision. Post-collision boundaries moving in the same direction and oriented similarly to the pre-collision gust front occurred in all 10 cases. They transported mass in the manner of a density current in six cases, while the others behaved more like bores or bore–density current hybrids, as they were characterized by little or no mass transport. Similarity of gust-front and sea-breeze-front propagation speed prior to the collision was the best indicator of bore character in post-collision boundaries induced by gust fronts. Sea-breeze-front-induced post-collision boundaries occurred in the seven cases in which the pre-collision sea-breeze front was nonstationary. These post-collision boundaries exhibited no purely mass transport behavior and were all categorized as bores or bore/density current hybrids. The potential ability to predict dual zones of convergence emanating from boundary collisions as demonstrated in this study may be of value to convective nowcasting in Florida and perhaps other locales, as 70% of the observed post-collision boundaries initiated new convection or enhanced existing convection.

Corresponding author address: David E. Kingsmill, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512. Email: davidk@dri.edu

Save
  • Atkins, N. A., and R. M. Wakimoto, 1997: Influence of the synoptic-scale flow on sea breezes observed during CaPE. Mon. Wea. Rev., 125 , 21122130.

    • Search Google Scholar
    • Export Citation
  • Atkins, N. A., R. M. Wakimoto, and T. M. Weckwerth, 1995: Observations of the sea-breeze front during CaPE. Part II: Dual-Doppler and aircraft analysis. Mon. Wea. Rev., 123 , 944969.

    • Search Google Scholar
    • Export Citation
  • Benjamin, T. B., 1968: Gravity currents and related phenomena. J. Fluid Mech., 31 , 209248.

  • Blanchard, D. O., and R. E. Lopez, 1985: Spatial patterns of convection in south Florida. Mon. Wea. Rev., 113 , 12821299.

  • Boyd, J. G., 1965: Observations of two intersecting radar fine lines. Mon. Wea. Rev., 93 , 188.

  • Braun, S. A., R. A. Houze Jr., and B. F. Smull, 1997: Airborne dual-Doppler observations of an intense frontal system approaching the Pacific Northwest coast. Mon. Wea. Rev., 125 , 31313156.

    • Search Google Scholar
    • Export Citation
  • Brock, F. V., G. H. Saum, and S. R. Semmer, 1986: Portable Automated Mesonet II. J. Atmos. Oceanic Technol., 3 , 573582.

  • Byers, H. R., and R. R. Braham Jr., 1949: The Thunderstorm. U.S. Government Printing Office, 287 pp.

  • Carbone, R. E., 1982: A severe frontal rainband. Part I: Stormwide hydrodynamic structure. J. Atmos. Sci., 39 , 258279.

  • Carbone, R. E., J. W. Conway, N. A. Crook, and M. W. Moncrieff, 1990: The generation and propagation of a nocturnal squall line. Part I: Observations and implications for mesoscale predictability. Mon. Wea. Rev., 118 , 2649.

    • Search Google Scholar
    • Export Citation
  • Charba, J., 1974: Application of gravity current model to analysis of squall-line gust front. Mon. Wea. Rev., 102 , 140156.

  • Christie, D. R., K. J. Muirhead, and A. L. Hales, 1978: On solitary waves in the atmosphere. J. Atmos. Sci., 35 , 805825.

  • Clarke, R. H., 1983: Internal atmospheric bores in northern Australia. Aust. Meteor. Mag., 31 , 147160.

  • Clarke, R. H., 1984: Colliding sea-breezes and the creation of internal atmospheric bore waves: Two-dimensional numerical studies. Aust. Meteor. Mag., 32 , 207226.

    • Search Google Scholar
    • Export Citation
  • Crook, N. A., 1988: Trapping of low-level internal gravity waves. J. Atmos. Sci., 45 , 15331541.

  • Crook, N. A., and M. J. Miller, 1985: A numerical and analytical study of atmospheric undular bores. Quart. J. Roy. Meteor. Soc., 111 , 225242.

    • Search Google Scholar
    • Export Citation
  • Doviak, R. J., and R. Ge, 1984: An atmospheric solitary gust observed with a Doppler radar, a tall tower and surface network. J. Atmos. Sci., 41 , 25592573.

    • Search Google Scholar
    • Export Citation
  • Fankhauser, J. C., N. A. Crook, J. Tuttle, L. J. Miller, and C. G. Wade, 1995: Initiation of deep convection along boundary layer convergence lines in a semitropical environment. Mon. Wea. Rev., 123 , 291313.

    • Search Google Scholar
    • Export Citation
  • Fulton, R., D. S. Zrnic, and R. J. Doviak, 1990: Initiation of a solitary wave family in the demise of a nocturnal thunderstorm density current. J. Atmos. Sci., 47 , 319337.

    • Search Google Scholar
    • Export Citation
  • Haase, S. P., and R. K. Smith, 1984: Morning glory wave clouds in Oklahoma: A case study. Mon. Wea. Rev., 112 , 20782089.

  • Haase, S. P., and R. K. Smith, 1989: The numerical simulation of atmospheric gravity currents. Part II: Environments with stable layers. Geophys. Astrophys. Fluid Dyn., 46 , 3551.

    • Search Google Scholar
    • Export Citation
  • Hane, C. E., H. B. Bluestein, T. M. Crawford, M. E. Baldwin, and R. M. Rabin, 1997: Severe thunderstorm development in relation to along-dryline variability: A case study. Mon. Wea. Rev., 125 , 231251.

    • Search Google Scholar
    • Export Citation
  • Intrieri, J. M., A. J. Bedard, and R. M. Hardesty, 1990: Details of colliding thunderstorm outflows as observed by Doppler lidar. J. Atmos. Sci., 47 , 10811098.

    • Search Google Scholar
    • Export Citation
  • Kingsmill, D. E., 1995: Convection initiation associated with a sea-breeze front, a gust front, and their collision. Mon. Wea. Rev., 123 , 29132933.

    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., R. Rotunno, and W. C. Skamarock, 1997: On the propagation of internal bores. J. Fluid Mech., 331 , 81106.

  • Koch, S. E., P. B. Dorian, R. Ferrare, S. H. Melfi, W. C. Skillman, and D. Whiteman, 1991: Structure of an internal bore and dissipating gravity current as revealed by Raman lidar. Mon. Wea. Rev., 119 , 857887.

    • Search Google Scholar
    • Export Citation
  • Laird, N. F., D. A. R. Kristovich, R. M. Rauber, H. T. Ochs III, and L. J. Miller, 1995: The Cape Canaveral sea and river breezes: Kinematic structure and convective initiation. Mon. Wea. Rev., 123 , 29422956.

    • Search Google Scholar
    • Export Citation
  • Lauritsen, D. K., Z. Malekmadani, C. Morel, and R. McBeth, 1987: The Cross-chain Loran Atmospheric Sounding System (CLASS). Extended Abstracts, Sixth Symp. on Meteorological Observations and Instrumentation, New Orleans, LA, Amer. Meteor. Soc., 340–343.

    • Search Google Scholar
    • Export Citation
  • Mahoney, W. P., 1988: Gust front characteristics and the kinematics associated with interacting thunderstorm outflows. Mon. Wea. Rev., 116 , 14741491.

    • Search Google Scholar
    • Export Citation
  • Mueller, C. K., and R. E. Carbone, 1987: Dynamics of a thunderstorm outflow. J. Atmos. Sci., 44 , 18791898.

  • Noonan, J. A., and R. K. Smith, 1986: Sea-breeze circulations over Cape York Peninsula and the generation of Gulf of Carpentaria cloud line disturbances. J. Atmos. Sci., 43 , 16791693.

    • Search Google Scholar
    • Export Citation
  • Noonan, J. A., and R. K. Smith, 1987: The generation of North Australian cloud lines and the morning glory. Aust. Meteor. Mag., 35 , 3145.

    • Search Google Scholar
    • Export Citation
  • Purdom, J. F. W., 1976: Some uses of high-resolution GOES imagery in the mesoscale forecasting of convection and its behavior. Mon. Wea. Rev., 104 , 14741483.

    • Search Google Scholar
    • Export Citation
  • Ralph, F. M., P. J. Neiman, and T. L. Keller, 1999: Deep-tropospheric gravity waves created by leeside cold fronts. J. Atmos. Sci., 56 , 29863009.

    • Search Google Scholar
    • Export Citation
  • Rider, G. C., and J. E. Simpson, 1968: Two crossing fronts on radar. Meteor. Mag., 97 , 2430.

  • Rottman, J. W., and J. E. Simpson, 1989: The formation of internal bores in the atmosphere: A laboratory model. Quart. J. Roy. Meteor. Soc., 115 , 941963.

    • Search Google Scholar
    • Export Citation
  • Rottman, J. W., J. E. Simpson, J. C. R. Hunt, and R. E. Britter, 1985: Unsteady gravity current flows over obstacles: Some observations and analysis related to the phase II trials. J. Hazard. Mater., 11 , 325340.

    • Search Google Scholar
    • Export Citation
  • Schaefer, J. T., 1986: The dryline. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 549–572.

  • Shreffler, J. H., and F. S. Binkowski, 1981: Observations of pressure jump lines in the Midwest, 10–12 August 1976. Mon. Wea. Rev., 109 , 17131725.

    • Search Google Scholar
    • Export Citation
  • Simpson, J. E., 1997: Gravity Currents: In the Environment and the Laboratory. 2d ed. Cambridge University Press, 244 pp.

  • Simpson, J. E., and R. E. Britter, 1980: A laboratory model of an atmospheric mesofront. Quart. J. Roy. Meteor. Soc., 106 , 485500.

  • Smith, R. K., 1986: Evening glory wave-cloud lines in northwestern Australia. Aust. Meteor. Mag., 34 , 2733.

  • Smith, R. K., 1988: Traveling waves and bores in the lower atmosphere: The “morning glory” and related phenomena. Earth-Sci. Rev., 25 , 267290.

    • Search Google Scholar
    • Export Citation
  • Turnbull, D., J. McCarthy, J. Evans, and D. Zrnic, 1989: The FAA Terminal Doppler Weather Radar (TDWR) program. Preprints, Third Int. Conf. on Aviation Weather Systems, Anaheim, CA, Amer. Meteor. Soc., 414–419.

    • Search Google Scholar
    • Export Citation
  • Wakimoto, R. M., 1982: The life cycle of thunderstorm gust fronts as viewed with Doppler radar and rawinsonde data. Mon. Wea. Rev., 110 , 10601082.

    • Search Google Scholar
    • Export Citation
  • Wakimoto, R. M., and J. K. Lew, 1993: Observations of a Florida waterspout during CaPE. Wea. Forecasting, 8 , 412423.

  • Wakimoto, R. M., and D. E. Kingsmill, 1995: Structure of an atmospheric undular bore generated from colliding boundaries during CaPE. Mon. Wea. Rev., 123 , 13741393.

    • Search Google Scholar
    • 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 , 21692187.

    • Search Google Scholar
    • Export Citation
  • Wilson, J. W., and W. E. Schreiber, 1986: Initiation of convective storms at radar-observed boundary layer convergence lines. Mon. Wea. Rev., 114 , 25162536.

    • Search Google Scholar
    • Export Citation
  • Wilson, J. W., and C. K. Mueller, 1993: Nowcasts of thunderstorm initiation and evolution. Wea. Forecasting, 8 , 113131.

  • Wilson, J. W., and D. L. Megenhardt, 1997: Thunderstorm initiation, organization, and lifetime associated with Florida boundary layer convergence lines. Mon. Wea. Rev., 125 , 15071525.

    • Search Google Scholar
    • Export Citation
  • Yuter, S. E., and R. A. Houze Jr., 1995: Three-dimensional kinematic and microphysical evolution of Florida cumulonimbus. Part I: Spatial distribution of updrafts, downdrafts, and precipitation. Mon. Wea. Rev., 123 , 19211940.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 297 69 8
PDF Downloads 232 51 2