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Max L. Dupilka
and
Gerhard W. Reuter

vector magnitude did not. These and other studies (e.g., Kerr and Darkow 1996 ; Rasmussen and Blanchard 1998 ; Monteverdi et al. 2003 ) emphasize the important point that severe thunderstorm and tornadoes occur within a broad range of shear and CAPE environments. It is extremely important to keep in mind that it is likely the interaction of a number of physical processes that leads to tornadogenesis, and these processes may (or may not) be well represented by particular environmental parameters or

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

of the environmental parameters associated with an environment conducive to tornadogenesis. We know that the combination of 0–6-km vector shear magnitude (SHR6, the magnitude of the vector difference in winds between the surface and 6-km height) and mixed-layer convective available potential energy (MLCAPE) provides a good first estimate of supercell potential ( Brooks et al. 2003 ), with at least marginal CAPE necessary to fuel the updraft and SHR6 essential for developing the midlevel rotation

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Matthew J. Onderlinde
and
Henry E. Fuelberg

tornadogenesis (e.g., McCaul 1987 ; Spratt et al. 1997 ; Suzuki et al. 2000 ; McCaul et al. 2004 ; Edwards 2008 ). However, these TC-related supercells often are shallower and smaller than their midlatitude counterparts ( McCaul and Weisman 1996 ). These differences must be considered when forecasting TC-related tornadoes. The magnitude of instability (e.g., CAPE) appears to be less important in TC-related tornadoes than in midlatitude scenarios. Indeed CAPE typically is observed to be considerably

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

and tornadogenesis downstream of prominent terrain features are often attributed to leeside vortex stretching ( Keighton et al. 2004 ; Lyza and Knupp 2014 ), but not all supercells experience leeside intensification ( Prociv 2012 ). Numerical simulations of supercells interacting with complex terrain have indicated that terrain slope, peak altitude, and orientation relative to the low-level environmental flow can modulate storm intensity by altering the instability and vertical shear in the

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Robert J. Trapp
,
Sarah A. Tessendorf
,
Elaine Savageau Godfrey
, and
Harold E. Brooks

radar scans collected by the Jackson, Mississippi (KJAN), Weather Surveillance Radar-1988 Doppler (WSR-88D; see Trapp et al. 1999 ). Hence, as in the other cases of QLCS tornadoes preliminarily investigated by Trapp et al. (1999) , traditional radar-based indicators of impending tornadogenesis likely offered little operational tornado-warning guidance for this event. And since this example (which is one of several) of QLCS tornado occurrence happened during the overnight hours, guidance from storm

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David L. Andra Jr.
,
Elizabeth M. Quoetone
, and
William F. Bunting

anticipate intelligently storm evolution and threat and therefore the range of potential outcomes necessary to determine warning content. For example, a tornado is more likely to occur with a classic supercell than a bowing squall line, where damaging wind is often the primary threat. Consider the case of the collapsing supercell: the disappearance of the reflectivity hook and lowering of the storm top could suggest a weakening storm, or, in the eyes of an expert, it might signal tornadogenesis ( Lemon

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Timothy A. Coleman
and
P. Grady Dixon

versus tornado count–tornado days As illustrated by Dixon and Mercer (2012) , large differences in spatial patterns can occur if one uses point analysis [i.e., the point of tornadogenesis; e.g., Brooks et al. (2003) ] instead of pathlength analysis (e.g., Dixon et al. 2011 ). Given that the pathlength of a tornado is much more proportional to the area it affects, its destructive capability, and its overall impact on the risk of a tornado striking an area within its radius of influence in the KDE

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E. De Wayne Mitchell
,
Steven V. Vasiloff
,
Gregory J. Stumpf
,
Arthur Witt
,
Michael D. Eilts
,
J. T. Johnson
, and
Kevin W. Thomas

strong azimuthal velocity gradient was observed coincident with the developing hook echo. Later, the first pulsed Doppler radar observation of a tornado was made during the Brookline, Massachusetts, tornado on 9 April 1972 ( Kraus 1973 ). Interestingly, no hook echo was observed at the time of the tornado; however, a hook echo was observed prior to tornadogenesis. In 1973, the National Severe Storms Laboratory’s 10-cm pulsed Doppler radar scanned through a tornadic thunderstorm near Union City

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Richard L. Thompson

discriminating between tornadic and nontornadic thunderstorm environments ( Weisman and Klemp 1982 ; Stensrud et al. 1997, hereafter SCB97 ). In the BRN denominator, as calculated by SCB97, U avg is defined as the magnitude of the difference between the 0–6-km density-weighted mean wind and the density-weighted mean wind in the lowest 0.5 km: BRN shear = 0.5( u avg ) 2 . Numerical simulations of supercells have begun to elucidate processes relevant to supercell tornadogenesis, and the

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Philip N. Schumacher
and
Joshua M. Boustead

below 3 km after 0030 UTC 25 June, during which time 32 tornadoes occurred. In addition, tornadoes in this region showed a general increase in damage rating with time, with the most damaging tornadoes occurring after 0100 UTC 25 June. Supercells also developed along the cold front in sector 3 and also were responsible for tornadoes. This would be the source region for a quasi-linear convective system (QLCS) that later produced tornadoes in sector 2. Fig . 1. Sectors for mode of tornadogenesis with

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