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—a scenario that is conducive for tornadogenesis. Baroclinically generated vorticity dominates simulated vorticity budgets once cold pools become suitably established (e.g., Dahl et al. 2014 ; Dahl 2015 ; Markowski 2016 ), although frictionally generated vorticity can be the main vorticity source for near-surface parcels when surface drag is included in simulations ( Schenkman et al. 2014 ; Roberts et al. 2016 ). Observational studies in the Great Plains of the United States have also explored the
—a scenario that is conducive for tornadogenesis. Baroclinically generated vorticity dominates simulated vorticity budgets once cold pools become suitably established (e.g., Dahl et al. 2014 ; Dahl 2015 ; Markowski 2016 ), although frictionally generated vorticity can be the main vorticity source for near-surface parcels when surface drag is included in simulations ( Schenkman et al. 2014 ; Roberts et al. 2016 ). Observational studies in the Great Plains of the United States have also explored the
centered on understanding the processes that govern supercell maturation and subsequent tornadogenesis. The process of supercell mesocyclonic tornadogenesis can be characterized by three steps (e.g., Davies-Jones 2015 ): 1) the formation of a midlevel [e.g., ≈3–7 km above ground level (AGL)] mesocyclone, 2) the generation of vertical vorticity ( ζ ) near the surface, and 3) the formation of a tornado via the contraction (convergence and stretching) of the resultant near-surface ζ . It has long been
centered on understanding the processes that govern supercell maturation and subsequent tornadogenesis. The process of supercell mesocyclonic tornadogenesis can be characterized by three steps (e.g., Davies-Jones 2015 ): 1) the formation of a midlevel [e.g., ≈3–7 km above ground level (AGL)] mesocyclone, 2) the generation of vertical vorticity ( ζ ) near the surface, and 3) the formation of a tornado via the contraction (convergence and stretching) of the resultant near-surface ζ . It has long been
1. Introduction Supercell mesocyclonic tornadogenesis has been described as a three-step process ( Davies-Jones and Brooks 1993 ; Davies-Jones 2015 ). First, a thunderstorm acquires rotation through tilting of environmental horizontal vorticity into the vertical. Second, generation of horizontal vorticity and tilting via a downdraft produces vertical vorticity at the surface. Finally, a tornadic circulation spins up at the ground as vertical vorticity is converged and stretched into a deep
1. Introduction Supercell mesocyclonic tornadogenesis has been described as a three-step process ( Davies-Jones and Brooks 1993 ; Davies-Jones 2015 ). First, a thunderstorm acquires rotation through tilting of environmental horizontal vorticity into the vertical. Second, generation of horizontal vorticity and tilting via a downdraft produces vertical vorticity at the surface. Finally, a tornadic circulation spins up at the ground as vertical vorticity is converged and stretched into a deep
, while Part III reports on model parameter studies investigating the role of convective available potential energy (CAPE) and ambient vertical and horizontal shear in the evolution of landspouts. Until this past decade most attention in tornado research has been placed on understanding supercell tornadogenesis due to the severity of this type of tornado. NSTs have attracted more recent attention as they affect geographical areas of increasing population density such as the High Plains just east of
, while Part III reports on model parameter studies investigating the role of convective available potential energy (CAPE) and ambient vertical and horizontal shear in the evolution of landspouts. Until this past decade most attention in tornado research has been placed on understanding supercell tornadogenesis due to the severity of this type of tornado. NSTs have attracted more recent attention as they affect geographical areas of increasing population density such as the High Plains just east of
Polarimetric Radar Signatures of a Rare Tornado Event over South Koreaal. 2006 ; Byko et al. 2009 ). The DRC typically occurs prior to the development of the hook echo. The DRC signatures can be used to detect tornadogenesis. DRCs may or may not be associated with tornadic storms. Rasmussen et al. (2006) performed the preliminary study on DRCs in which they described the characteristics of DRC in convective storms. They also discussed the frequency of occurrence of DRCs prior to tornadic supercell storms. Subsequently, Kennedy et al. (2007) presented a
al. 2006 ; Byko et al. 2009 ). The DRC typically occurs prior to the development of the hook echo. The DRC signatures can be used to detect tornadogenesis. DRCs may or may not be associated with tornadic storms. Rasmussen et al. (2006) performed the preliminary study on DRCs in which they described the characteristics of DRC in convective storms. They also discussed the frequency of occurrence of DRCs prior to tornadic supercell storms. Subsequently, Kennedy et al. (2007) presented a
Fluid Dynamics. Cambridge University Press, 615 pp . Benjamin , T. B. , 1968 : Gravity currents and related phenomena . J. Fluid Mech. , 31 , 209 – 248 . Bryan , G. H. , and J. M. Fritsch , 2002 : A benchmark simulation for moist nonhydrostatic numerical models . Mon. Wea. Rev. , 130 , 2917 – 2928 . Davies-Jones , R. P. , 1982a : A new look at the vorticity equation with application to tornadogenesis. Preprints, 12th Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor
Fluid Dynamics. Cambridge University Press, 615 pp . Benjamin , T. B. , 1968 : Gravity currents and related phenomena . J. Fluid Mech. , 31 , 209 – 248 . Bryan , G. H. , and J. M. Fritsch , 2002 : A benchmark simulation for moist nonhydrostatic numerical models . Mon. Wea. Rev. , 130 , 2917 – 2928 . Davies-Jones , R. P. , 1982a : A new look at the vorticity equation with application to tornadogenesis. Preprints, 12th Conf. on Severe Local Storms, San Antonio, TX, Amer. Meteor
1. Introduction The successful tornadogenesis paradigm must explain why tornadic vortex signatures (TVSs) and embryonic tornadoes are sometimes, but not always, observed aloft prior to tornadogenesis. A TVS is a large value (typically >1 × 10 −2 s −1 ) of azimuthal shear between two adjacent sampling volumes in a Doppler-radar radial-velocity field and usually forms within (but not necessarily in the center of) a mesocyclone (e.g., Brown et al. 1978 ). It is presumed that a TVS is a degraded
1. Introduction The successful tornadogenesis paradigm must explain why tornadic vortex signatures (TVSs) and embryonic tornadoes are sometimes, but not always, observed aloft prior to tornadogenesis. A TVS is a large value (typically >1 × 10 −2 s −1 ) of azimuthal shear between two adjacent sampling volumes in a Doppler-radar radial-velocity field and usually forms within (but not necessarily in the center of) a mesocyclone (e.g., Brown et al. 1978 ). It is presumed that a TVS is a degraded
supercell they studied. However, data presented in Finley et al. (2010) and Lee et al. (2012) suggest the thermodynamic properties of internal outflow surges may vary dramatically within a single storm. They analyzed mobile mesonet data from a strongly tornadic supercell and found four internal outflow surges all with different thermodynamic properties during a single low-level mesocyclone occlusion cycle. Warm surges were generally present during times of tornadogenesis and intensification, whereas
supercell they studied. However, data presented in Finley et al. (2010) and Lee et al. (2012) suggest the thermodynamic properties of internal outflow surges may vary dramatically within a single storm. They analyzed mobile mesonet data from a strongly tornadic supercell and found four internal outflow surges all with different thermodynamic properties during a single low-level mesocyclone occlusion cycle. Warm surges were generally present during times of tornadogenesis and intensification, whereas
tool. Indeed, Atkins et al. (2004) showed that tornadoes were more likely to form from parent misovortices along the convective line that had greater rotation rates, implying that the strongest vortices may favor tornadogenesis. Before discussing how tornadoes form along linear convective storms, we need to distinguish between the parent circulations that precede the tornadoes and the tornadoes themselves. One of the characteristics often observed in narrow cold-frontal rainbands is the presence
tool. Indeed, Atkins et al. (2004) showed that tornadoes were more likely to form from parent misovortices along the convective line that had greater rotation rates, implying that the strongest vortices may favor tornadogenesis. Before discussing how tornadoes form along linear convective storms, we need to distinguish between the parent circulations that precede the tornadoes and the tornadoes themselves. One of the characteristics often observed in narrow cold-frontal rainbands is the presence
, arc-shaped ribbon of anomalously high equivalent potential temperature ( θ e > 336 K) directed right at the southeast corner of the Windsor CI region at the time of tornadogenesis ( Fig. 7f ). Also note the intensification of the dryline as southerly winds crossed the Palmer Lake Divide and flowed downslope to create drier conditions just to the south of Denver, in association with increased vertical mixing that arose with the late-morning sensible heating. The Windsor supercell storm formed in
, arc-shaped ribbon of anomalously high equivalent potential temperature ( θ e > 336 K) directed right at the southeast corner of the Windsor CI region at the time of tornadogenesis ( Fig. 7f ). Also note the intensification of the dryline as southerly winds crossed the Palmer Lake Divide and flowed downslope to create drier conditions just to the south of Denver, in association with increased vertical mixing that arose with the late-morning sensible heating. The Windsor supercell storm formed in
