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field) environmental lower-tropospheric vertical wind shear and the probability of significant tornadoes ( Doswell and Evans 2003 ; Markowski et al. 2003b ; Rasmussen 2003 ; Thompson et al. 2003 ; Craven et al. 2004 ). It has been unclear how the environmental vertical wind profile within the storm’s inflow sector relates to the production of surface vertical vorticity within a storm’s outflow air, which has been demonstrated to precede tornadogenesis. It is possible that the aforementioned
field) environmental lower-tropospheric vertical wind shear and the probability of significant tornadoes ( Doswell and Evans 2003 ; Markowski et al. 2003b ; Rasmussen 2003 ; Thompson et al. 2003 ; Craven et al. 2004 ). It has been unclear how the environmental vertical wind profile within the storm’s inflow sector relates to the production of surface vertical vorticity within a storm’s outflow air, which has been demonstrated to precede tornadogenesis. It is possible that the aforementioned
predicting the occurrence, timing, and location of supercells, but also an upper bound on already-short practical predictability of associated damaging phenomena such as tornadoes. Storm size is a function of CAPE and 0–6-km shear, among other bulk atmospheric diagnostics ( Lawson 2019 ). A smaller storm will require the NWP model to be run at a smaller Δ x for it to be detected sufficiently, and we might assume a useful forecast of tornadogenesis is more likely when its parent supercell is well
predicting the occurrence, timing, and location of supercells, but also an upper bound on already-short practical predictability of associated damaging phenomena such as tornadoes. Storm size is a function of CAPE and 0–6-km shear, among other bulk atmospheric diagnostics ( Lawson 2019 ). A smaller storm will require the NWP model to be run at a smaller Δ x for it to be detected sufficiently, and we might assume a useful forecast of tornadogenesis is more likely when its parent supercell is well
. , and M. Xue , 2017 : The role of surface drag in mesocyclone intensification leading to tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 74 , 3055 – 3077 , https://doi.org/10.1175/JAS-D-16-0364.1 . Roberts , B. , M. Xue , A. D. Schenkman , and D. T. Dawson II , 2016 : The role of surface drag in tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 73 , 3371 – 3395 , https://doi.org/10.1175/JAS-D-15-0332.1 . Roberts
. , and M. Xue , 2017 : The role of surface drag in mesocyclone intensification leading to tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 74 , 3055 – 3077 , https://doi.org/10.1175/JAS-D-16-0364.1 . Roberts , B. , M. Xue , A. D. Schenkman , and D. T. Dawson II , 2016 : The role of surface drag in tornadogenesis within an idealized supercell simulation . J. Atmos. Sci. , 73 , 3371 – 3395 , https://doi.org/10.1175/JAS-D-15-0332.1 . Roberts
rain curtain in a supercell instigate tornadogenesis barotropically? J. Atmos. Sci. , 65 , 2469 – 2497 , doi: 10.1175/2007JAS2516.1 . 10.1175/2007JAS2516.1 Davies-Jones , R. , 2015 : A review of supercell and tornado dynamics . Atmos. Res. , 158–159 , 274 – 291 , doi: 10.1016/j.atmosres.2014.04.007 . 10.1016/j.atmosres.2014.04.007 Davies-Jones , R. , and H. E. Brooks , 1993 : Mesocyclogenesis from a theoretical perspective. The Tornado: Its Structure, Dynamics, Prediction, and
rain curtain in a supercell instigate tornadogenesis barotropically? J. Atmos. Sci. , 65 , 2469 – 2497 , doi: 10.1175/2007JAS2516.1 . 10.1175/2007JAS2516.1 Davies-Jones , R. , 2015 : A review of supercell and tornado dynamics . Atmos. Res. , 158–159 , 274 – 291 , doi: 10.1016/j.atmosres.2014.04.007 . 10.1016/j.atmosres.2014.04.007 Davies-Jones , R. , and H. E. Brooks , 1993 : Mesocyclogenesis from a theoretical perspective. The Tornado: Its Structure, Dynamics, Prediction, and
algorithm based on multiscale wavelet analysis of radial velocity data. Finally, neural network methods have been developed that show skill in identifying precursor circulations for tornadogenesis ( Marzban and Stumpf 1996 ). This approach also allows the level of confidence in the predicted outcome (tornado or no tornado) to be computed. In this study, radial wind observations from two or more close-proximity Doppler radars with overlapping domains are fit to an analytical low-order model of a vortex
algorithm based on multiscale wavelet analysis of radial velocity data. Finally, neural network methods have been developed that show skill in identifying precursor circulations for tornadogenesis ( Marzban and Stumpf 1996 ). This approach also allows the level of confidence in the predicted outcome (tornado or no tornado) to be computed. In this study, radial wind observations from two or more close-proximity Doppler radars with overlapping domains are fit to an analytical low-order model of a vortex
A Variational Method for Filling in Missing Data in Doppler Velocity Fields-in fields utilizing a histogram and a linear regression model. Figure 9 presents KOUN WSR-88D scans of ground-relative base Doppler velocity ( V r ), base reflectivity ( Z ) of and base spectrum width ( σ υ ) of the violent El Reno tornado as collected with superresolution (0.5° azimuthal interval and 250-m range increment) at the 0.97° launch angle at 2311:04 UTC 31 May 2013. Tornadogenesis, tornado evolution, photogrammetric and polarimetric analyses, and aerial damage survey in the El Reno tornadic
-in fields utilizing a histogram and a linear regression model. Figure 9 presents KOUN WSR-88D scans of ground-relative base Doppler velocity ( V r ), base reflectivity ( Z ) of and base spectrum width ( σ υ ) of the violent El Reno tornado as collected with superresolution (0.5° azimuthal interval and 250-m range increment) at the 0.97° launch angle at 2311:04 UTC 31 May 2013. Tornadogenesis, tornado evolution, photogrammetric and polarimetric analyses, and aerial damage survey in the El Reno tornadic
/NCAR 40-Year Reanalysis Project . Bull. Amer. Meteor. Soc. , 77 , 437 – 471 , doi: 10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2 . Klemp , J. B. , 1987 : Dynamics of tornadic thunderstorms . Annu. Rev. Fluid Mech. , 19 , 369 – 402 , doi: 10.1146/annurev.fl.19.010187.002101 . Lemon , L. R. , and C. A. Doswell III , 1979 : Severe thunderstorm evolution and mesocyclone structure as related to tornadogenesis . Mon. Wea. Rev. , 107 , 1184 – 1197 , doi: 10
/NCAR 40-Year Reanalysis Project . Bull. Amer. Meteor. Soc. , 77 , 437 – 471 , doi: 10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2 . Klemp , J. B. , 1987 : Dynamics of tornadic thunderstorms . Annu. Rev. Fluid Mech. , 19 , 369 – 402 , doi: 10.1146/annurev.fl.19.010187.002101 . Lemon , L. R. , and C. A. Doswell III , 1979 : Severe thunderstorm evolution and mesocyclone structure as related to tornadogenesis . Mon. Wea. Rev. , 107 , 1184 – 1197 , doi: 10
Chernokulsky , A. V. , M. V. Kurgansky , and I. I. Mokhov , 2017 : Analysis of changes in tornadogenesis conditions over Northern Eurasia based on a simple index of atmospheric convective instability . Dokl. Earth Sci. , 477 , 1504 – 1509 , https://doi.org/10.1134/S1028334X17120236 . 10.1134/S1028334X17120236 Chernokulsky , A. V. , F. A. Kozlov , O. G. Zolina , O. N. Bulygina , and V. A. Semenov , 2018 : Climatology of precipitation of different genesis in Northern Eurasia
Chernokulsky , A. V. , M. V. Kurgansky , and I. I. Mokhov , 2017 : Analysis of changes in tornadogenesis conditions over Northern Eurasia based on a simple index of atmospheric convective instability . Dokl. Earth Sci. , 477 , 1504 – 1509 , https://doi.org/10.1134/S1028334X17120236 . 10.1134/S1028334X17120236 Chernokulsky , A. V. , F. A. Kozlov , O. G. Zolina , O. N. Bulygina , and V. A. Semenov , 2018 : Climatology of precipitation of different genesis in Northern Eurasia
Abstract
Surface boundaries in supercells have been suspected of being important in the arrangement and concentration of vorticity for the development and intensification of tornadoes, but there has been little attention given to the effects of the underlying surface roughness on their behavior. This study investigates the impact of surface drag on the structure and evolution of these boundaries, their associated distribution of near-surface vorticity, and tornadogenesis and maintenance. Comparisons between idealized simulations without and with drag introduced in the mature stage of the storm prior to tornadogenesis reveal that the inclusion of surface drag substantially alters the low-level structure, particularly with respect to the number, location, and intensity of surface convergence boundaries. Substantial drag-generated horizontal vorticity induces rotor structures near the surface associated with the convergence boundaries in both the forward and rear flanks of the storm. Stretching of horizontal vorticity and subsequent tilting into the vertical along the convergence boundaries lead to elongated positive vertical vorticity sheets on the ascending branch of the rotors and the opposite on the descending branch. The larger near-surface pressure deficit associated with the faster development of the near-surface cyclone when drag is active creates a downward dynamic vertical pressure gradient force that suppresses vertical growth, leading to a weaker and wider tornado detached from the surrounding convergence boundaries. A conceptual model of the low-level structure of the tornadic supercell is presented that focuses on the contribution of surface drag, with the aim of adding more insight and complexity to previous conceptual models.
Abstract
Surface boundaries in supercells have been suspected of being important in the arrangement and concentration of vorticity for the development and intensification of tornadoes, but there has been little attention given to the effects of the underlying surface roughness on their behavior. This study investigates the impact of surface drag on the structure and evolution of these boundaries, their associated distribution of near-surface vorticity, and tornadogenesis and maintenance. Comparisons between idealized simulations without and with drag introduced in the mature stage of the storm prior to tornadogenesis reveal that the inclusion of surface drag substantially alters the low-level structure, particularly with respect to the number, location, and intensity of surface convergence boundaries. Substantial drag-generated horizontal vorticity induces rotor structures near the surface associated with the convergence boundaries in both the forward and rear flanks of the storm. Stretching of horizontal vorticity and subsequent tilting into the vertical along the convergence boundaries lead to elongated positive vertical vorticity sheets on the ascending branch of the rotors and the opposite on the descending branch. The larger near-surface pressure deficit associated with the faster development of the near-surface cyclone when drag is active creates a downward dynamic vertical pressure gradient force that suppresses vertical growth, leading to a weaker and wider tornado detached from the surrounding convergence boundaries. A conceptual model of the low-level structure of the tornadic supercell is presented that focuses on the contribution of surface drag, with the aim of adding more insight and complexity to previous conceptual models.
rotation near the ground ( Ludlam 1963 ; Fujita 1975 ; Burgess et al. 1977 ; Barnes 1978 ; Lemon and Doswell 1979 ), their precise role in the tornadogenesis process remains unclear. A lengthy review of observational, numerical modeling, and theoretical findings pertinent to hook echoes and RFDs recently has been completed by Markowski (2002) . In a companion paper by Markowski et al. (2002) , it was observed that the air parcels at the surface within the RFDs of tornadic supercells tend to be
rotation near the ground ( Ludlam 1963 ; Fujita 1975 ; Burgess et al. 1977 ; Barnes 1978 ; Lemon and Doswell 1979 ), their precise role in the tornadogenesis process remains unclear. A lengthy review of observational, numerical modeling, and theoretical findings pertinent to hook echoes and RFDs recently has been completed by Markowski (2002) . In a companion paper by Markowski et al. (2002) , it was observed that the air parcels at the surface within the RFDs of tornadic supercells tend to be
