Search Results

You are looking at 51 - 60 of 914 items for :

  • Tornadogenesis x
  • Refine by Access: All Content x
Clear All
Shawn S. Murdzek
,
Paul M. Markowski
, and
Yvette P. Richardson

1. Introduction Tornado research has focused primarily on tornadogenesis within supercell thunderstorms owing to the fact that supercells produce a disproportionate number of significant tornadoes. 1 Tornadogenesis within supercells can be conceptualized as a three-step process (e.g., Davies-Jones 2015 ). First, midlevel rotation develops from the tilting of environmental horizontal vorticity ( Rotunno 1981 ). Second, vertical vorticity develops close to the surface (the tornado “seed,” e

Full access
Michael M. French
and
Darrel M. Kingfield

1. Introduction Operational forecasters face a number of challenges in attempts to skillfully “nowcast” (i.e., 0–1-h forecasts) the tornado life cycle. Here, we break up the life cycle simply into tornadogenesis, tornado intensification, and tornado dissipation. Difficulty in understanding and prediction in any of these stages derives from the small spatiotemporal scales over which relevant processes are thought to occur, which makes them difficult to observe. Most research efforts have focused

Full access
Roger M. Wakimoto
,
Hanne V. Murphy
, and
Huaqing Cai

produced datasets that are able to resolve supercell structure in greater detail than was previously possible and also has raised a number of new questions concerning the processes that lead to tornadogenesis (e.g., Wakimoto et al. 1998 ; Trapp 1999 ; Wakimoto and Cai 2000 ; Dowell and Bluestein 2002a , b ). Wakimoto and Liu (1998) and Trapp (1999) examined the Garden City, Kansas, mesocyclone during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al

Full access
J. M. Wilczak
,
D. E. Wolfe
,
R. J. Zamora
,
B. Stankov
, and
T. W. Christian

VOLUME 120 MONTHLY WEATHER REVIEW APRIL 1992Observations of a Colorado Tornado. Part I: Mesoscale Environment and Tornadogenesis J. M. WILCZAK,* T. W. CHRISTIAN,t D. E. WOLFE,* R. J. ZAMORA,* AND B. STANKOV* *NOAA/ERL/Wave Propagation Laboratory, Boulder, Colorado~'Cooperative Institute for Research in the Environmental Sciences (CIRES), University of Colorado/NOAA, Boulder, Colorado

Full access
David C. Dowell
and
Howard B. Bluestein

. Tornadogenesis relies on horizontal convergence within the boundary layer to amplify vertical vorticity to magnitudes characteristic of tornadoes ( Ward 1972 ; Lewellen 1993 ). In some cases, thunderstorms concentrate vertical vorticity already present in the storm environment ( Wilson 1986 ; Brady and Szoke 1989 ; Wakimoto and Wilson 1989 ). In contrast, supercell thunderstorms appear to act upon low-level vertical vorticity produced by the storm itself ( Barnes 1970 ; Brandes 1984b ; Rotunno and Klemp

Full access
Lawrence B. Dunn
and
Steven V. Vasiloff

. As noted by Dunn (1990) the addition of Doppler radar to an NWS office makes it possible to observe the development of both supercell ( Browning 1964 ; Lemon and Doswell 1979 ; Klemp et al. 1981 ; Klemp and Rotunno 1983 ; Davies-Jones 1986 ) and nonsupercell ( Wakimoto and Wilson 1989 ; Brady and Szoke 1989 ; Collins et al. 2000 ) tornadoes in real-time operations. Tornadogenesis has received considerable interest from the research community for many years and although much has been

Full access
Felicia Guarriello
,
Christopher J. Nowotarski
, and
Craig C. Epifanio

low-level shear, LCL, and supercell tornadogenesis are not fully understood, some straightforward hypotheses have been proposed. In terms of shear, stronger low-level shear is often associated with larger storm-relative helicity, implying greater potential for updraft rotation through the tilting and stretching of environmental streamwise vorticity within the supercell updraft, which is responsible for the generation of the midlevel mesocyclone ( Davies-Jones 1984 ). In turn, as rotation aloft

Full access
Robert Davies-Jones
and
Paul M. Markowski

the positive ω 0 × N ⋅ d x . c. Vortex formation in axisymmetric flow In axisymmetric simulations of tornadogenesis (e.g., Markowski et al. 2003 ; Davies-Jones 2008 ), L ( t ) would be a horizontal circle of variable radius σ ( t ) centered on the axis. In this section, M represents angular momentum. The circulation Γ is related to M by Γ ≡ 2 πM . In cylindrical coordinates ( r , ϕ , z ) with corresponding wind components ( u r , M / r , w ), imposing axisymmetry on (7) yields

Full access
Bruce D. Lee
,
Catherine A. Finley
, and
Christopher D. Karstens

. 1997 ; Bluestein and Pazmany 2000 ; Bluestein and Wakimoto 2003 ), a considerable number of high-resolution kinematic datasets have been obtained from tornadic supercells. Given the difficulty involved in positioning near-surface observing systems, far fewer datasets, either mobile mesonet ( Straka et al. 1996 ) or StickNet ( Weiss and Schroeder 2008 ), exist to describe proximate tornado or tornadogenesis region thermodynamic and kinematic characteristics. Only a few mesonet studies provide a

Full access
Paul Markowski
,
Yvette Richardson
, and
George Bryan

other wind-shift lines within the storm and occasionally migrate toward the low-level mesocyclone center, subsequently being absorbed into the broader circulation ( Dowell et al. 2002 ; Finley et al. 2002 ; Bluestein et al. 2003 ; Lee et al. 2012 ; Richardson et al. 2012 ; Snyder et al. 2013 ). It is unclear whether the vortices play a role in tornadogenesis or tornado maintenance, which are topics beyond the scope of this paper. Given their regular spacing, it seems likely that these vortices

Full access