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Sho Yokota
,
Hiroshi Niino
,
Hiromu Seko
,
Masaru Kunii
, and
Hiroshi Yamauchi

LMCs ( Markowski et al. 2002 , 2003 , 2008 ; Straka et al. 2007 ). Because this horizontal vorticity and convective updraft are intensified by environmental low-level vertical shear and water vapor, respectively, the preexisting low-level environment is especially important for tornadogenesis ( Thompson et al. 2003 ; Craven and Brooks 2004 ; Markowski and Richardson 2014 ; Parker and Dahl 2015 ). Even in the presence of MMCs and LMCs, however, tornadoes are not necessarily generated. Trapp

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Jannick Fischer
and
Johannes M. L. Dahl

proposed by Davies-Jones (1982) , although speculations about the role of downdrafts in tornadogenesis date back even further (e.g., Ludlam 1963 ). Davies-Jones argued that in an environment with large horizontal vorticity but devoid of vertical vorticity, an updraft alone cannot achieve large vertical vorticity at the surface via vortex-line reorientation. The reason is that as the horizontal vorticity is reoriented into the vertical within the updraft gradient, parcels are rising away from the

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Robert Davies-Jones

1. Introduction The rain curtain associated with the hook-shaped appendage to a supercell’s radar echo is usually regarded as a passive indicator of a possible tornado. Close-range airborne and mobile radar observations made during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al. 1994 ) in 1994–95 and in subsequent follow-up experiments have revealed the presence of a hook echo prior to tornadogenesis in every case. Development of the hook is

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Tao Tao
and
Tetsuro Tamura

1. Introduction To understand the mechanism of supercell tornadogenesis, identifying the responsible vorticity sources is a vitally important issue. Despite several decades of study on this issue, a complete understanding remains ambiguous. Previous studies included field observations and idealized numerical simulations. It was suggested that the baroclinic effects are prominent in generating the vorticity of tornadoes (e.g., Davies-Jones and Brooks 1993 ; Adlerman et al. 1999 ; Straka et al

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Eigo Tochimoto
and
Hiroshi Niino

radar near the damage paths of the corresponding tornadoes ( Fig. 1a ). Since the radar was not in full operational mode, and had performed only three scans at the lower elevation angles around the time of the tornadogenesis, they were unable to clarify the detailed relationship between the mesovortices and tornadogenesis. A maximum surface wind of 35 m s −1 ( Fig. 1b ) with rapid change in wind direction from east to west was observed by an anemometer located at the southern end of the runway at

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Brett Roberts
and
Ming Xue

1. Introduction Supercells are characterized by a persistent mesocyclone ( Lemon and Doswell 1979 ), and the midlevel [3–6 km above ground level (AGL)] mesocyclone is understood to result mainly from tilting of vorticity associated with the vertical shear of environmental wind ( Davies-Jones 1984 ). While all supercells feature midlevel rotation, some also develop mesocyclones below 2 km AGL, and this development can be important for tornadogenesis. Markowski et al. (1998) investigated the

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Yoshi K. Sasaki

applicable to tornadic phenomena and is made applicable to solve mysteries of tornadogenesis. Furthermore, the balance is a newly found one, because it is different from the other known balance conditions, such as hydrostatic, (quasi-) geostrophic, cyclostrophic, Boussinesq, and anelastic balance. The variational formalism is similar to the one observed by Euler in 1736 and referred to as the Euler equation ( Oden and Reddy 1976 ; Lanczos 1970 ) and later as the Gateaux derivative ( Gateaux 1913 ) in

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Paul M. Markowski

1. Introduction a. A brief summary of our current understanding of tornadogenesis in supercell storms Tornado formation in supercell thunderstorms is among the most intensely studied problems in mesoscale meteorology, 1 as evidenced by the numerous reviews that have been written on the subject ( Ludlam 1963 ; Rotunno 1993 ; Davies-Jones and Brooks 1993 ; Davies-Jones et al. 2001 ; Markowski and Richardson 2009 , 2014a ; Davies-Jones 2015 ). More studies have been devoted to

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Qin Jiang
and
Daniel T. Dawson II

; Wicker and Wilhelmson 1993 ; Lewellen and Lewellen 2007a , b ; Davies-Jones 2015 ). A growing body of literature has indicated that the near-ground horizontal vorticity generated by surface drag may play an important role in tornadogenesis if it can be tilted into the vertical and sufficiently concentrated ( Schenkman et al. 2014 ; Markowski 2016 ; Roberts et al. 2016 ; Roberts and Xue 2017 ; Roberts et al. 2020 ; Fischer and Dahl 2022 ). Other studies have shown that surface drag may have

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Takumi Honda
and
Tetsuya Kawano

tornadogenesis. For example, Wicker and Wilhelmson (1995) conducted an idealized numerical simulation and showed that a rear-flank downdraft (RFD) plays a role in tornadogenesis. The importance of such downdraft and related baroclinic vorticity generation has been indicated by theoretical ( Davies-Jones and Brooks 1993 ), observational ( Straka et al. 2007 ; Markowski et al. 2008 , 2012a , b ), and recent numerical ( Dahl et al. 2014 ) investigations. The baroclinically generated horizontal vorticity and

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