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270 MONTHLY WEATHER REVIEW VOLUME 114Tornadogenesis by Nonprecipitation Induced Wind Shear Lines JAMES W. WILSONNational Center for Atmospheric Research,* Boulder, Colorado 80307(Manuscript received 31 May 1985, in final form 17 September 1985) Five tornadoes occurred within a 40 rain period on 18 May 1984 in eastern Colorado. The evolution of thesetornadoes was documented by
270 MONTHLY WEATHER REVIEW VOLUME 114Tornadogenesis by Nonprecipitation Induced Wind Shear Lines JAMES W. WILSONNational Center for Atmospheric Research,* Boulder, Colorado 80307(Manuscript received 31 May 1985, in final form 17 September 1985) Five tornadoes occurred within a 40 rain period on 18 May 1984 in eastern Colorado. The evolution of thesetornadoes was documented by
1. Introduction One focus of our ongoing research is the relative role of environmental vorticity versus storm-generated vorticity in tornadogenesis and maintenance. In supercell environments, which are characterized by relatively large vertical shear of the horizontal wind, the horizontal vorticity is typically on the order of 10 −2 s −1 in the lower troposphere. In contrast, vorticity can be generated internally within a storm by horizontal buoyancy gradients (i.e., baroclinity). The
1. Introduction One focus of our ongoing research is the relative role of environmental vorticity versus storm-generated vorticity in tornadogenesis and maintenance. In supercell environments, which are characterized by relatively large vertical shear of the horizontal wind, the horizontal vorticity is typically on the order of 10 −2 s −1 in the lower troposphere. In contrast, vorticity can be generated internally within a storm by horizontal buoyancy gradients (i.e., baroclinity). The
supercell simulations and thus assess the merits of various tornado theories. A subsequent paper will report and lightly test a methodology for computing partial vorticities of a parcel along its forward trajectory. The method requires the parcel’s initial vorticity and, along its path, its velocity-gradient matrix and the torques acting on it. This information can be obtained from the output of a simulation. Although still not providing conclusive evidence in favor of a single tornadogenesis theory
supercell simulations and thus assess the merits of various tornado theories. A subsequent paper will report and lightly test a methodology for computing partial vorticities of a parcel along its forward trajectory. The method requires the parcel’s initial vorticity and, along its path, its velocity-gradient matrix and the torques acting on it. This information can be obtained from the output of a simulation. Although still not providing conclusive evidence in favor of a single tornadogenesis theory
1. Introduction The Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al. 1994 ) was conducted during the spring of 1994 and 1995 in the southern Great Plains of the United States. The objectives of this validation experiment were driven by a set of hypotheses (see Rasmussen 1995 ) that concerned (i) the initiation of tornadic storms; (ii) low-level mesocyclogenesis, tornadogenesis, and the role(s) of mesoscale and stormscale boundaries in
1. Introduction The Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al. 1994 ) was conducted during the spring of 1994 and 1995 in the southern Great Plains of the United States. The objectives of this validation experiment were driven by a set of hypotheses (see Rasmussen 1995 ) that concerned (i) the initiation of tornadic storms; (ii) low-level mesocyclogenesis, tornadogenesis, and the role(s) of mesoscale and stormscale boundaries in
MAY 1984 EDWARD A. BRANDES 1033Relationships Between Radar-Derived Thermodynamic Variables and Tornadogenesis EDWARD A. BRANDESNOAA/ERL, National Severe Storms Laboratory, Norman, OK 73069(Manuscript received 23 October 1983, in final form 3 February 1984)ABSTRACT A methodology for obtaining pressure perturbations and buoyancy in
MAY 1984 EDWARD A. BRANDES 1033Relationships Between Radar-Derived Thermodynamic Variables and Tornadogenesis EDWARD A. BRANDESNOAA/ERL, National Severe Storms Laboratory, Norman, OK 73069(Manuscript received 23 October 1983, in final form 3 February 1984)ABSTRACT A methodology for obtaining pressure perturbations and buoyancy in
potential modularing role in tornadogenesis by solenoidal generation of vorticity, in analogy with the extratropicalcyclone, to which the transformed mesocyclone bears a striking resemblance.1. Introduction The Wrnado vortex is one of the atmosphere'smost intense concentrations of vorticity. For atypical violent tornado with a maximum tangentialspeed of 100 m s-~ at a radius of 100 m, the verticalcomponent of vorticity is 2 s-~. The means by whichsuch vorticity is developed within a thunderstormare
potential modularing role in tornadogenesis by solenoidal generation of vorticity, in analogy with the extratropicalcyclone, to which the transformed mesocyclone bears a striking resemblance.1. Introduction The Wrnado vortex is one of the atmosphere'smost intense concentrations of vorticity. For atypical violent tornado with a maximum tangentialspeed of 100 m s-~ at a radius of 100 m, the verticalcomponent of vorticity is 2 s-~. The means by whichsuch vorticity is developed within a thunderstormare
southwest from the storm and often marked by young developing cells, indicates the leading edge of RFD-associated outflow. Brandes (1981) examined supercell structural evolution through the tornado life cycle. His Fig. 10 (shown here as Fig. 1d ) shows a region of dry upper-level air intruding on the southwest side of the storm at the pretornado time, under which a rear-flank downdraft develops near the time of tornadogenesis. The swirling component of the low-level flow is at maximum during the
southwest from the storm and often marked by young developing cells, indicates the leading edge of RFD-associated outflow. Brandes (1981) examined supercell structural evolution through the tornado life cycle. His Fig. 10 (shown here as Fig. 1d ) shows a region of dry upper-level air intruding on the southwest side of the storm at the pretornado time, under which a rear-flank downdraft develops near the time of tornadogenesis. The swirling component of the low-level flow is at maximum during the
Massachusetts 95-GHz (W-band) mobile Doppler radar collected high-resolution radar reflectivity and velocity data from several seconds after tornadogenesis until the end of the life of a tornado that occurred near the town of Stockton in northwest Kansas (hereafter “the Stockton tornado,” see Fig. 1 ). The Stockton tornado occurred in an isolated thunderstorm that developed over Rooks County, Kansas, at around 1920 CDT. Surface outflow from nearby thunderstorms generated easterly surface flow of 9 m s
Massachusetts 95-GHz (W-band) mobile Doppler radar collected high-resolution radar reflectivity and velocity data from several seconds after tornadogenesis until the end of the life of a tornado that occurred near the town of Stockton in northwest Kansas (hereafter “the Stockton tornado,” see Fig. 1 ). The Stockton tornado occurred in an isolated thunderstorm that developed over Rooks County, Kansas, at around 1920 CDT. Surface outflow from nearby thunderstorms generated easterly surface flow of 9 m s
1. Introduction In meteorology, the laws governing mass, energy, momentum, angular momentum, and entropy, should be sacrosanct. In supercell simulations, invented forces should be tolerated only to the extent that they do not fundamentally alter the results. The latest supercell simulations with surface drag have such high resolution that they reproduce strong to violent tornadoes. These simulations seek to understand tornadogenesis. Use of a fictitious force that generates spurious horizontal
1. Introduction In meteorology, the laws governing mass, energy, momentum, angular momentum, and entropy, should be sacrosanct. In supercell simulations, invented forces should be tolerated only to the extent that they do not fundamentally alter the results. The latest supercell simulations with surface drag have such high resolution that they reproduce strong to violent tornadoes. These simulations seek to understand tornadogenesis. Use of a fictitious force that generates spurious horizontal
and Parker 2019 ; Flournoy and Coniglio 2019 ; Boyer and Dahl 2020 ; Marion and Trapp 2021 ) suggests that QLCS tornadogenesis can be characterized in two general ways, based on what appear to be the dominant processes. The first encompasses the sequence of processes involving mesocyclonic rotation thought to lead to tornadoes in most supercells (e.g., Davies-Jones et al. 2001 ), and accordingly, this is classified herein as pre-tornadic mesocyclone dominant (PMD). In generally reverse
and Parker 2019 ; Flournoy and Coniglio 2019 ; Boyer and Dahl 2020 ; Marion and Trapp 2021 ) suggests that QLCS tornadogenesis can be characterized in two general ways, based on what appear to be the dominant processes. The first encompasses the sequence of processes involving mesocyclonic rotation thought to lead to tornadoes in most supercells (e.g., Davies-Jones et al. 2001 ), and accordingly, this is classified herein as pre-tornadic mesocyclone dominant (PMD). In generally reverse
