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Johannes M. L. Dahl
,
Matthew D. Parker
, and
Louis J. Wicker

1. Introduction The origin of vertical vorticity in tornadoes is one of the most critical questions about tornadogenesis. A widely used approach to address this problem, both in models and dual-Doppler analyses, is the backward integration of trajectories initialized within the near-surface vortex. Based on these trajectories, vorticity or circulation budgets following individual parcels may be computed. However, these budgets—and the inferred sources of vorticity—critically depend on the

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Christopher C. Weiss
,
David C. Dowell
,
John L. Schroeder
,
Patrick S. Skinner
,
Anthony E. Reinhart
,
Paul M. Markowski
, and
Yvette P. Richardson

simple climate data and daily measurements of ablation . Ann. Glaciol. , 50 , 9 – 15 , doi: 10.3189/172756409787769726 . Brandes , E. A. , 1978 : Mesocyclone evolution and tornadogenesis: Some observations . Mon. Wea. Rev. , 106 , 995 – 1011 , doi: 10.1175/1520-0493(1978)106<0995:MEATSO>2.0.CO;2 . Dahl , J. M. L. , M. D. Parker , and L. J. Wicker , 2014 : Imported and storm-generated near-ground vertical vorticity in a simulated supercell . J. Atmos. Sci. , 71 , 3027 – 3051 , doi

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Synoptic-Scale Environments and Precipitation Morphologies of Tornado Outbreaks from Quasi-Linear Convective Systems in the United Kingdom

Ty J. Buckingham
and
David M. Schultz

, type 1). Conversely, type 2 tornado reports tended to occur less than 1 h after the development of cores ( Fig. 22 , type 2). Thus, type 1 events took longer to reach tornadogenesis than type 2 events. Fig . 22. Timelines of each QLCS tornado outbreak event, indicating the time periods of the QLCS (black bar), precipitation cores that develop within the QLCS (orange bar) and tornado reports associated with each event (gray bar). However, both the type 2 case of 29 May 2015 and the unassigned case

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Nicholas A. Goldacker
and
Matthew D. Parker

; Markowski et al. 2008 , 2012 ; Schenkman et al. 2014 ; Dahl 2015 ; Parker and Dahl 2015 ; Markowski 2016 ; Roberts et al. 2016 ; Roberts and Xue 2017 ; Roberts et al. 2020 ). However, Coffer and Parker (2017) showed that both nontornadic and tornadic supercells generate ample pretornadic ζ sfc . The step that “makes or breaks” the mechanism of tornadogenesis is likely step 3: the ability for ζ sfc to be contracted into a tornado. Step 3 is most strongly favored when overlying rotation

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Paul M. Markowski

was concluded that the volatility associated with downdraft position and strength, which affect the baroclinic vorticity generation within the storm, may explain the failure of many supercells to produce tornadoes in seemingly favorable environments. Yokota et al. (2018) investigated the dynamics of tornadogenesis (50-m horizontal grid spacing) in a 33-member ensemble of supercell simulations for a case that occurred in a landfalling tropical cyclone in Japan. The initial conditions and

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Christian H. Boyer
and
Johannes M. L. Dahl

tornadogenesis. Intense Atmospheric Vortices , L. Bengtsson and J. Lighthill, Eds., Springer, 175–189 . Davies-Jones , R. , 2000 : A Lagrangian model for baroclinic genesis of mesoscale vortices. Part I: Theory . J. Atmos. Sci. , 57 , 715 – 736 , https://doi.org/10.1175/1520-0469(2000)057<0715:ALMFBG>2.0.CO;2 . Davies-Jones , R. , 2017 : Roles of streamwise and transverse partial-vorticity components in steady inviscid isentropic supercell-like flows . J. Atmos. Sci. , 74 , 3021 – 3041 , https

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Michael M. French
,
Donald W. Burgess
,
Edward R. Mansell
, and
Louis J. Wicker

characteristics of the environment within the hook echo. In turn, many past studies have discussed the important influence that the thermodynamic attributes of supercell RFDs may have on supercell evolution, including, but not limited to, tornadogenesis (e.g., Markowski et al. 2002 ; Grzych et al. 2007 ) and tornado maintenance (e.g., Marquis et al. 2012 ). Information about PSDs has been obtained from convective storms mainly through two different methods: direct PSD data from disdrometers and estimated

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Roger M. Wakimoto
,
Nolan T. Atkins
, and
Joshua Wurman

1. Introduction A major milestone was reached in the operational detection of severe weather when the hook echo was first observed by radar and shown to be associated with tornadogenesis ( Stout and Huff 1953 ; Forbes 1981 ). Subsequent studies examining radial velocities based on Doppler radars measurements were able to resolve the mesocyclone and the tornadic-vortex signature (TVS), which can be associated with the parent circulation of the tornado and the tornado, respectively (e.g., Brown

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Roger M. Wakimoto
,
Nolan T. Atkins
,
Kelly M. Butler
,
Howard B. Bluestein
,
Kyle Thiem
,
Jeffrey C. Snyder
,
Jana Houser
,
Karen Kosiba
, and
Joshua Wurman

taken at the same location as the radar deployment site. Elevation- and azimuth-angle grids were created using photogrammetric techniques and superimposed on each image. These grids correspond to the radar scanning angles since the photographer and radar were collocated. A description of the photogrammetry analysis used in the current study has been presented in Wakimoto et al. (2015) . a. Tornadogenesis and the tornadic debris signature The approximate time of tornadogenesis (2303:14 UTC) is shown

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Johannes M. L. Dahl
,
Matthew D. Parker
, and
Louis J. Wicker

. Discussion An interesting question is how the above analysis relates to tornadogenesis. As discussed in section 3b , we have rather limited faith in the treatment of near-ground trajectories once they descend below the bottom scalar model level, so we cannot describe vortex genesis faithfully. However, when animated, the vertical vorticity field at the lowest scalar model level clearly shows how the rivers and lobes of positive ζ move downstream and feed into the developing vortex (see also Fig. 5

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