Each of these regimes has an associated vortex structure and velocity distribution, which greatly impact the surface wind field. 1997, 2000 Lewellen and Lewellen 2007a, b) models of tornado-like vortices depict a wide range of possible vortical flows. 1979 Church and Snow 1993) and numerical (e.g., Rotunno 1977, 1979, 1984 Lewellen and Sheng 1980 Gall 1983 Walko 1988 Fiedler 1993 Fiedler and Rotunno 1986 Howells et al. Laboratory (e.g., Ward 1972 Davies-Jones 1973, 1976 Church et al. There is significant low-level inflow from 0133:37 to 0134:23 UTC, then weaker inflow through 0140 UTC and the end of the analysis period.Īxisymmetric angular momentum (contours, 10 3 m 2 s −1) and secondary circulation (shading) as a function of radius and height at (a) 0134:23 and (b) 0137:35 UTC. The axisymmetric radial winds as a function of height at a radius of 700 m from 0133:37 to 0140:49 UTC. Also shown are a Rankine, modified Rankine, and Burgers–Rott vortex. Normalized radial profiles of the axisymmetric tangential winds at a height of 40 m AGL from 0133:37 to 0140:49 UTC. The largest axisymmetric tangential velocities occur in the lowest analysis level at 0134:23, 0138:23, 0140:02, and 0140:49 UTC. The vertical black line indicates r = 700 m.Īxisymmetric maximum tangential winds as a function of height from 0135:20 to 0140:49 UTC. During this time, the tornado retains a fully two-celled structure during intensification and demise. The secondary circulation (vectors) and the tangential winds (shading) are shown from 0133:37 to 0140:49 UTC. (b) RMW from raw Doppler data and RMW from GBVTD axisymmetric wind field retrieval.Īxisymmetric tangential winds (shading, m s −1) and radial winds (contours) as a function of time and radius at (a) 40 and (b) 400 m AGL.Īxisymmetric structure (radius–height) of the tornado at each analysis time. (a) Peak Doppler winds and axisymmetric tangential winds. Shown are (left) Doppler velocity and (right) radar reflectivity the location of DOW3 is indicated with an arrow.Įvolution of the Doppler velocity couplet and axisymmetric wind speed couplet. The evolution of the Doppler velocity and received power in the tornado during the GBVTD analysis period.
The green disks indicate the area within the radius of maximum winds as determined from DOW3 data. The track of the Spencer, South Dakota, 1998 tornado as determined from DOW3 data (location of DOW3 marked with black circle). Vertical cross sections are shown in (a)–(d). Idealized vortex structures as a function of swirl ratio.
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