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Edward A. Brandes

JuLY 1978 E D W A R D A. B R A N D E S 995Mesocyclone Evolution and Tornadogenesis: Some Observations EDWARD A. BRANDESNational Severe Storms Laboratory, NOAA, Norman, OK 73069(Manuscript received 15 September 1977, in final form 3 April 1978) ABSTRACT Updraft mesocyclones in tornado-producing thunderstorms form along convergent and cyclonicallysheared boundaries that

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Catherine A. Finley
,
W. R. Cotton
, and
R. A. Pielke Sr.

tornadogenesis following the interaction between a supercell and other convection have been documented by Wolf (1998) , Sabones et al. (1996) , Goodman and Knupp (1993) , and Bullas and Wallace (1988) . The connection between cell merger and tornadogenesis in this case will be discussed further in Part II. As quickly as the convection intensified near the updraft merger point, it weakened, and by 0021 UTC updrafts in the region were 14–18 m s −1 at z = 6.1 km. All during this time period, S1 (which

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Bruce D. Lee
and
Robert B. Wilhelmson

1. Introduction In Part I of this series of articles on the simulation of nonsupercell tornadogenesis (NSTG), misocyclone initiation and evolution were investigated along outflow boundaries possessing significant across-front horizontal shear with a dry, nonhydrostatic, three-dimensional numerical model ( Lee and Wilhelmson 1997, hereafter LW97) . Misocyclone circulations, which by definition ( Fujita 1981 ) have diameters less than 4 km, are the parent circulations of nonsupercell tornadoes

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Jessica M. McDonald
and
Christopher C. Weiss

—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

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Mankin Mak

addresses nonsupercell tornadogenesis. Closest to it is a suggestion for dust devil formation by Barcilon and Drazin (1972) in terms of Kelvin–Helmholtz and Rayleigh–Taylor instability, but a dust devil is distinctly much smaller, shallower, and weaker than a NST. While an intense localized surface heating must be a crucial factor for dust devil, it is not the case for NST. There is a numerical simulation study of NST with some success ( Lee and Wilhelmson 1997 , LW97 hereafter). They used a high

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Nicholas A. Goldacker
and
Matthew D. Parker

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

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Brice E. Coffer
and
Matthew D. Parker

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

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Bruce D. Lee
and
Robert B. Wilhelmson

1. Introduction Most attention in tornado research has been placed on understanding supercell tornadogenesis due to the severity of this type of tornado; however, in the past decade, nonsupercell tornadoes (NSTs) have attracted increasing attention as they affect geographical areas of expanding population such as the High Plains just east of the Front Range and the Florida peninsula. For instance, near and just east of the Denver to Ft. Collins corridor, NSTs account for a large majority of the

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

1. Introduction Despite a growing body of literature describing observations of tornadogenesis and dissipation ( Roberts and Wilson 1995 ; Wakimoto and Atkins 1996 ; Dowell and Bluestein 1997 , 2002b ; Wakimoto and Liu 1998 ; Dunn and Vasiloff 2001 ; Ziegler et al. 2001 ; Bluestein and Wakimoto 2003 ; Bluestein et al. 2003 ; Wakimoto et al. 2004 ; Van Den Broeke et al. 2008 ; Wurman et al. 2007 , 2010 ; Markowski and Richardson 2009 ; Palmer et al. 2011 ; Marquis et al. 2012

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S. Lim
,
S. Allabakash
,
B. Jang
, and
V. Chandrasekar

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

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