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Douglas Schneider
and
Scott Sharp

tornadic environments was 10°F (5.6 K). In a tropical cyclone environment, the boundary layer relative humidity is typically high, and thus the LCL height and surface dewpoint depressions are typically low. These conditions, along with strong low-level wind shear and sufficient buoyancy, will create an environment favorable for tornadogenesis. It is uncertain whether the critical values of LCL height and surface dewpoint depression in the Great Plains studies by Rasmussen and Blanchard (1998) and

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Shawn S. Murdzek
,
Paul M. Markowski
,
Yvette P. Richardson
, and
Robin L. Tanamachi

tornado-warned areas and about three-fourths of tornado warnings were never associated with a tornado ( Anderson-Frey et al. 2016 ). One way to improve the probability of detection for tornadoes and reduce the number of false alarms is to better understand the conditions and processes that result in tornadogenesis or tornadogenesis failure. a. Tornadogenesis within supercells Owing to the disproportionate number of significant tornadoes 1 produced by supercells compared to other storm modes

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Lance F. Bosart
,
Anton Seimon
,
Kenneth D. LaPenta
, and
Michael J. Dickinson

disrupt low-level flows and preclude tornadogenesis in instances that might otherwise yield tornadoes over flat terrain and/or whether significant mountain tornadoes are relatively underreported because fewer people live in the mountains, damage surveys are more difficult to conduct, and fewer structures can be damaged. Although generally not explicitly stated in studies on tornado climatology, anecdotal evidence is that rough terrain is viewed as an inhibitor of tornado occurrence in mountain

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Alexander D. Schenkman
,
Ming Xue
, and
Ming Hu

increased rotation in the mesocyclone led to upward pressure gradient forces that were responsible for generating a strong low-level updraft. In turn, this low-level updraft tilted baroclinically generated horizontal vorticity into the vertical and then stretched it leading to tornadogenesis. WW95 was unable to explain the development of rotation next to the surface and they did not discuss the cause of the midlevel mesocyclone intensification responsible for low-level updraft intensification. Most of

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Karen Kosiba
,
Joshua Wurman
,
Yvette Richardson
,
Paul Markowski
,
Paul Robinson
, and
James Marquis

Rotunno 1983 ; Rotunno and Klemp 1985 ( RK85 ); Wicker and Wilhelmson 1995 ( WW95 ); Adlerman et al. 1999 ; Markowski et al. 2003 ], and theoretical studies (e.g., Davies-Jones and Brooks 1993 ; Davies-Jones et al. 2001 ) of tornadic and nontornadic supercells have advanced our knowledge of the processes necessary for tornadogenesis. But, the manner by which the finescale details of these processes and their interconnectivity instigate tornadogenesis is not well understood (see review papers

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Wataru Mashiko

1. Introduction Important unresolved issues pertaining to supercell tornadogenesis include its triggering factor and vorticity sources. Although the development of a low-level mesocyclone in a supercell often precedes tornadogenesis, the existence of the low-level mesocyclone is not a sufficient condition for tornadogenesis (e.g., Burgess et al. 1993 ; Trapp 1999 ; Trapp et al. 2005 ; Markowski et al. 2011 ). To address these issues, extensive field observations have been conducted over the

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Jana Lesak Houser
,
Howard B. Bluestein
,
Kyle Thiem
,
Jeffrey Snyder
,
Dylan Reif
, and
Zachary Wienhoff

1. Introduction Tornadogenesis and, particularly, the manner by which tornado-strength rotation makes contact with the ground have long been a topic of deep interest to the meteorological community. Several early idealized numerical simulations and observational studies initially suggested that the evolution of strong vertical vorticity associated with tornado formation occurred in a rather slow [time scales O (∼5–10) min ( Mitchell et al. 1998 ; Trapp 1999 )], top-down manner by which

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Howard B. Bluestein
,
Christopher C. Weiss
, and
Andrew L. Pazmany

1. Introduction Our knowledge of the dynamics of tornadogenesis in supercells is limited to a large extent by our restricted ability to observe tornadogenesis near the ground. Much of what we have learned in the last 25 years is based on Doppler radar measurements that have enabled us to visualize the wind field near tornadoes, but on spatial scales that do not explicitly resolve the tornado very well or at all. For example, early fixed-site dual-Doppler studies of tornadic storms described the

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Amanda Markert
,
Robert Griffin
,
Kevin Knupp
,
Andrew Molthan
, and
Tim Coleman

topography and vegetation, posing questions on how the lowest several hundred meters of the atmosphere, that is, the surface layer to lower boundary layer are influenced by horizontal gradients in the land surface roughness and how the tornadogenesis process may be affected. Figure 1. Tornado-track density for all EF0–EF5 tornadoes that occurred across counties intersecting the ARMOR coverage area from 1950 to 2014. This map reveals two areas with high frequencies of tornado occurrences for a given area

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Brice E. Coffer
,
Matthew D. Parker
,
Johannes M. L. Dahl
,
Louis J. Wicker
, and
Adam J. Clark

1. Introduction Despite increased understanding of how environmental profiles of temperature, humidity, and winds affect the tornadic potential of convective storms, much is still unknown about what ultimately differentiates between seemingly similar nontornadic and tornadic supercells. Observations and simulations of nontornadic supercells show remarkable similarity to their tornadic counterparts, with operationally unobservable differences ultimately leading to tornadogenesis failure. While

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