Search Results

You are looking at 1 - 10 of 968 items for :

  • Tornadogenesis x
  • Refine by Access: All Content x
Clear All
Jason Naylor and Matthew S. Gilmore

the environment (also known as barotropic vorticity), or transport of vertical vorticity to the surface. More than one of these processes contributes to the rotation within the low-level mesocyclone ( Klemp and Rotunno 1983 ; Davies-Jones and Brooks 1993 ; A99 ; Markowski et al. 2008 ); however, the relative importance of these processes to tornadogenesis appears to vary among cases. First, modeling studies by Davies-Jones and Brooks (1993) and Grasso and Cotton (1995) found that the

Full access
David G. Lerach and William R. Cotton

diameter of rain and hail distributions (all else being equal) reduced the net surface area of the hydrometeors, thereby reducing evaporative cooling and melting rates. This produced weaker low-level downdrafts and weaker, shallower cold pools. While the precise mechanisms of supercell tornadogenesis are still up for debate, studies have suggested that tornadoes are often linked to the rear flank downdraft (RFD), which can transport vertical vorticity to the surface, baroclinically generate horizontal

Full access
Kristofer S. Tuftedal, Michael M. French, Darrel M. Kingfield, and Jeffrey C. Snyder

1. Introduction Despite major advances in our understanding of supercell tornadoes over the past two decades, skillful, short-term (0–1 h) forecasting (i.e., “nowcasting”) of tornadogenesis remains elusive owing to a lack of understanding of the complicated processes involved and a dearth of observations at the spatiotemporal scales commensurate with the process. Work to distinguish differences between tornadic and nontornadic supercells are ongoing using both observations and numerical

Restricted access
Paul M. Markowski, Timothy P. Hatlee, and Yvette P. Richardson

reflectivity isopleth observed by DOW7 also is overlaid at 0108, 0116, 0124, and 0132 UTC (blue contours). The locations of the photographs that appear in Figs. 11a–c are indicated by the green, black, and purple camera icons, respectively (the photograph time are indicated beside the icons). Following a brief explanation of the available data and the analysis methods in section 2 , a detailed description of the chain of events that led to tornadogenesis are presented in sections 3 and 4 . The

Full access
Joshua Wurman, Yvette Richardson, Curtis Alexander, Stephen Weygandt, and Peng Fei Zhang

1. Introduction Tornadic storms, and tornadogenesis in supercellular storms have been observed visually, with surface observations, and with radars for decades (e.g., Stout and Huff 1953 ; Ludlam 1963 ; Fujita 1975 ; Ray et al. 1975 , 1981 ; Brandes 1977 , 1978 , 1981 , 1984a ; Fujita and Wakimoto 1982 ; Brandes et al. 1988 ; Dowell and Bluestein 1997 , 2002a , b ; Wakimoto and Liu 1998 ; Trapp 1999 ; Trapp et al. 1999 ; Wakimoto and Cai 2000 ; Bluestein

Full access
Wataru Mashiko, Hiroshi Niino, and Teruyuki Kato

1. Introduction Significant progress has been made in our understanding of supercell storms through Doppler radar measurements and three-dimensional numerical simulations. However, our knowledge of the dynamics of tornadogenesis in supercell storms is still limited because of difficulties in collecting detailed observational data with good spatial and temporal resolutions and in numerically simulating a tornado that is more than two orders of magnitude smaller than a supercell storm. The

Full access
Alexander D. Schenkman, Ming Xue, and Alan Shapiro

is the frictional generation of near-surface horizontal vorticity associated with the intensification of the inflow into the Minco mesovortex. This flow profile takes about 10 min to develop after the genesis of the Minco mesovortex. We speculate that weaker, shorter-lived mesovortices may dissipate before a rotor circulation develops, which could preclude tornadogenesis. The important role of surface drag and the rotor circulation raises a number of questions that will be the focus of future

Full access
Dongmin Kim, Sang-Ki Lee, and Hosmay Lopez

1. Introduction The National Oceanic and Atmospheric Administration’s Storm Prediction Center (NOAA SPC) provides a 1–8-day lead-time severe weather forecast, including tornado watches. This severe weather forecast is based on synoptic-scale atmospheric instability [e.g., convective available potential energy (CAPE) and low-level wind shear (LLWS)] from numerical weather forecast models and observations. To extend the current forecast lead time for tornadogenesis to subseasonal time scales (i

Free access
Jannick Fischer and Johannes M. L. Dahl

proposed by Davies-Jones (1982) , although speculations about the role of downdrafts in tornadogenesis date back even further (e.g., Ludlam 1963 ). Davies-Jones argued that in an environment with large horizontal vorticity but devoid of vertical vorticity, an updraft alone cannot achieve large vertical vorticity at the surface via vortex-line reorientation. The reason is that as the horizontal vorticity is reoriented into the vertical within the updraft gradient, parcels are rising away from the

Restricted access
Robert Davies-Jones

1. Introduction The rain curtain associated with the hook-shaped appendage to a supercell’s radar echo is usually regarded as a passive indicator of a possible tornado. Close-range airborne and mobile radar observations made during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX; Rasmussen et al. 1994 ) in 1994–95 and in subsequent follow-up experiments have revealed the presence of a hook echo prior to tornadogenesis in every case. Development of the hook is

Full access