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Alexandra K. Anderson-Frey
,
Yvette P. Richardson
,
Andrew R. Dean
,
Richard L. Thompson
, and
Bryan T. Smith

: The influence of environmental low-level shear and cold pools on tornadogenesis: Insights from idealized simulations . J. Atmos. Sci. , 71 , 243 – 275 , doi: 10.1175/JAS-D-13-0159.1 . 10.1175/JAS-D-13-0159.1 Markowski , P. , J. Straka , and E. Rasmussen , 2003 : Tornadogenesis resulting from the transport of circulation by a downdraft: Idealized numerical simulations . J. Atmos. Sci. , 60 , 795 – 823 , doi: 10.1175/1520-0469(2003)060<0795:TRFTTO>2.0.CO;2 . 10

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Katie A. Wilson
,
Pamela L. Heinselman
, and
Charles M. Kuster

operations, viewing radar-indicated evidence of tornadogenesis in finer temporal detail has resulted in the issuance of earlier warnings by up to 7.5 min, especially during classic supercell events ( Heinselman et al. 2015 ; Wilson et al. 2017 ). In the 2012 PARISE, forecasters achieving above-average tornado warning lead times applied conceptual models that depended on trends only observable in the 1-min PAR updates ( Heinselman et al. 2015 ). P13 emphasized the importance of these trends, reporting

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Paul B. Bogner
,
Gary M. Barnes
, and
James L. Franklin

of the bands CAPEs are likely to be significantly higher; however, these CAPEs are not as high as those soundings made far from any reflectivity features. c. The 1500-m vertical shear Novlan and Gray (1974) identified a threshold vertical shear of the horizontal wind from the surface to 850 mb that was correlated with tornadogenesis in hurricanes. Consequently, a similar shear value was calculated over the first 1500 m of each ODW profile by taking ∂ υ /∂ z from the 10-m estimate to the 1500-m

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Larissa J. Reames

typically have high CAPE. However, many nocturnal environments are characterized by decreased near-surface temperatures and a low-level inversion, leading to less surface-based instability and greater CIN. Logically, these conditions would be expected to inhibit strong tornadogenesis in some cases ( Leslie and Smith 1978 ; Nowotarski et al. 2011 ). Recent research has sought to describe the characteristics of environments in which nocturnal tornadoes form. For example, Davies and Fischer (2009

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Howard B. Bluestein
,
Jeffrey C. Snyder
, and
Jana B. Houser

anticyclonic tornadoes. a. Tornadogenesis and evolution of the parent supercell and other supercells Although there was a brief tornado reported at 2255–2256 UTC ( Fig. 8 ), the most intense and longest lived of all the tornadoes on 31 May 2013 produced by the El Reno supercell (marked with an A in Fig. 12 ) began at 2304 UTC to the west-southwest of our deployment spot; the tornado moved initially to the southeast. The entire genesis phase of this tornado was documented by volume scans ( Table 1 ; Fig

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Bruce D. Lee
and
Catherine A. Finley

1. Introduction a. Motivation The lion’s share of tornado research to date has been understandably focused on the tornadogenesis problem (e.g., Brandes 1978 ; Klemp and Rotunno 1983 ; Wicker and Wilhelmson 1995 ; Davies-Jones and Brooks 1993 ; Markowski and Richardson 2009 , 2014 ; Markowski et al. 2012 ; Coffer and Parker 2017 ). A much smaller subset of studies has focused, at least in part, on tornado maintenance or aspects of tornado evolution after development. The research

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Max D. Ungar
and
Michael C. Coniglio

at every scan below 8000 ft (∼2438 m); and 3) persisted at least two full volume scans. Previous studies have applied similar approaches to identify MVs via WSR-88D data interrogation ( Smith et al. 2015 ; Sessa and Trapp 2020 ). Qualitatively, these criteria follow the findings of Atkins et al. (2004) , which describe tornadic MVs as being “longer-lived and stronger at low levels” and deepening rapidly prior to tornadogenesis. In applying the above criteria, 42 unique MVs ( within 39

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William J. S. Miller
,
Corey K. Potvin
,
Montgomery L. Flora
,
Burkely T. Gallo
,
Louis J. Wicker
,
Thomas A. Jones
,
Patrick S. Skinner
,
Brian C. Matilla
, and
Kent H. Knopfmeier

horizontal grid spacing is far too coarse for resolving tornadoes, Potvin and Flora (2015) showed that idealized Δ x = 3 km simulations could capture low-level mesocyclone tracks reasonably well. Their finding is encouraging, given that (i) mesocyclones are a necessary precursor for tornadogenesis in supercell thunderstorms ( Markowski and Richardson 2010 ); and that (ii) supercells spawn the majority of deadly U.S. tornadoes ( Schoen and Ashley 2011 ). Although only ∼25% of all mesocyclones detected

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Sarah M. Purpura
,
Casey E. Davenport
,
Matthew D. Eastin
,
Katherine E. McKeown
, and
Roger R. Riggin

weather production. For example, flow channeling was indicated as the contributor to localized enhancements in storm-relative helicity (SRH) and instability that were associated with rapidly intensifying supercells and tornadogenesis (e.g., LaPenta et al. 2005 ; Bosart et al. 2006 ; Schneider 2009 ; Tang et al. 2016 ; LeBel et al. 2021 ). Model simulations have further underscored the importance of these terrain-induced environmental variations on supercell evolution. Markowski and Dotzek (2011

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Gregory J. Stumpf
,
Arthur Witt
,
E. DeWayne Mitchell
,
Phillip L. Spencer
,
J. T. Johnson
,
Michael D. Eilts
,
Kevin W. Thomas
, and
Donald W. Burgess

many respects (due to the radar’s sampling characteristics), the integration of information from a variety of other sensors (e.g., near-storm environment, satellites, lightning, etc.) may provide important missing pieces to the puzzle, thereby distinguishing, with more skill, between significant and insignificant vortices (and thus reducing the FAR to a respectable low number). Our understanding of tornadogenesis within thunderstorms is still limited. An extensive tornado field project ( Rasmussen

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