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Robert Davies-Jones
and
Paul Markowski

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

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Alexander D. Schenkman
,
Ming Xue
, and
Daniel T. Dawson II

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

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Bruce D. Lee
and
Robert B. Wilhelmson

, 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

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Miriam L. Apsley
,
Kelsey J. Mulder
, and
David M. Schultz

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

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Steven E. Koch
,
Randolph Ware
,
Hongli Jiang
, and
Yuanfu Xie

, 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

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R. Jeffrey Trapp
and
Robert Davies-Jones

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

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Elissa A. Bartos
,
Paul M. Markowski
, and
Yvette P. Richardson

1. Introduction Severe thunderstorms can be hazardous to both life and property because of their tendency to produce damaging winds, hail, and tornadoes. Supercell thunderstorms, in particular, are responsible for the majority of strong tornadoes and large hail ( Smith et al. 2012 ) and, thus, are an important focus of severe storms research. Moreover, tornadogenesis within supercell thunderstorms has been one of the most studied problems in the severe storms community over the past 60

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Brice E. Coffer
,
Matthew D. Parker
,
John M. Peters
, and
Andrew R. Wade

is a poor predictor of supercellular tornadogenesis ( Trapp 1999 ). Although most tornadoes are associated with supercells, perhaps less than 15% of mesocyclones are tornadic ( Trapp et al. 2005 ; Smith et al. 2012 ). The process of supercellular tornadogenesis is often described as having three steps ( Davies-Jones 2015 ). First, an updraft needs to acquire rotation aloft (i.e., the development of a mesocyclone). It is well established that the updrafts of supercells initially acquire their

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John R. Lawson
,
Corey K. Potvin
,
Patrick S. Skinner
, and
Anthony E. Reinhart

predicting the occurrence, timing, and location of supercells, but also an upper bound on already-short practical predictability of associated damaging phenomena such as tornadoes. Storm size is a function of CAPE and 0–6-km shear, among other bulk atmospheric diagnostics ( Lawson 2019 ). A smaller storm will require the NWP model to be run at a smaller Δ x for it to be detected sufficiently, and we might assume a useful forecast of tornadogenesis is more likely when its parent supercell is well

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Wei Huang
and
Ming Xue

. , and M. Xue , 2017 : The role of surface drag in mesocyclone intensification leading to tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 74 , 3055 – 3077 , https://doi.org/10.1175/JAS-D-16-0364.1 . Roberts , B. , M. Xue , A. D. Schenkman , and D. T. Dawson II , 2016 : The role of surface drag in tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 73 , 3371 – 3395 , https://doi.org/10.1175/JAS-D-15-0332.1 . Roberts

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