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vortex meets the ground, this region is of particular relevance, typically being the scene of the largest velocities, lowest pressures, sharpest velocity gradients, and greatest damage potential in the entire flow. In concentrating on this part of the flow we knowingly set aside the important question of tornadogenesis on the larger scale, that is, of how the storm-scale flow gives rise to and maintains the swirling, converging plume on the few kilometer scale that makes the occurrence of an intense
vortex meets the ground, this region is of particular relevance, typically being the scene of the largest velocities, lowest pressures, sharpest velocity gradients, and greatest damage potential in the entire flow. In concentrating on this part of the flow we knowingly set aside the important question of tornadogenesis on the larger scale, that is, of how the storm-scale flow gives rise to and maintains the swirling, converging plume on the few kilometer scale that makes the occurrence of an intense
mechanism by which rotation could potentially enhance rain rates. Although the influence of the VPPGF has been investigated in regards to supercells and tornadogenesis, little attention has been devoted to its impact on precipitation processes when supercells or embedded mesovortices are present. On the convective scale, cells that produce the most extreme rain rates have been shown to be associated with a positive potential vorticity (PV) monopole, compared to the expected PV dipole that is seen in
mechanism by which rotation could potentially enhance rain rates. Although the influence of the VPPGF has been investigated in regards to supercells and tornadogenesis, little attention has been devoted to its impact on precipitation processes when supercells or embedded mesovortices are present. On the convective scale, cells that produce the most extreme rain rates have been shown to be associated with a positive potential vorticity (PV) monopole, compared to the expected PV dipole that is seen in
velocities in supercells facilitate production of the largest observed hailstones on Earth (e.g., Wakimoto et al. 2004 ), produce higher cross-tropopause mass transport than ordinary convection ( Mullendore et al. 2005 ) and result in a higher mass detrainment level ( Mullendore et al. 2013 ). Furthermore, supercell updrafts are capable of producing intense low-level vertical accelerations and associated stretching of vertical vorticity, which facilitates tornadogenesis ( Markowski and Richardson 2014
velocities in supercells facilitate production of the largest observed hailstones on Earth (e.g., Wakimoto et al. 2004 ), produce higher cross-tropopause mass transport than ordinary convection ( Mullendore et al. 2005 ) and result in a higher mass detrainment level ( Mullendore et al. 2013 ). Furthermore, supercell updrafts are capable of producing intense low-level vertical accelerations and associated stretching of vertical vorticity, which facilitates tornadogenesis ( Markowski and Richardson 2014
core radii and peak velocities in modeled atmospheric vortices. J. Atmos. Sci., 36, 2413-2424.Brandes, E. A., 1978: Mesocyclone evolution and tornadogenesis: Some observations. Mort. Wea. Rev., 106, 995-10t 1.Church, C. R., and J. T. Snow, 1979: The dynamics of natural tornadoes as inferred from laboratory simulations. J. Rech. At mos., 13, 111-133. , --, G. L. Baker and E. M. Agee, 1979: Characteristics of tornado-like vortices as a function of swirl ratio: a laboratory investigation
core radii and peak velocities in modeled atmospheric vortices. J. Atmos. Sci., 36, 2413-2424.Brandes, E. A., 1978: Mesocyclone evolution and tornadogenesis: Some observations. Mort. Wea. Rev., 106, 995-10t 1.Church, C. R., and J. T. Snow, 1979: The dynamics of natural tornadoes as inferred from laboratory simulations. J. Rech. At mos., 13, 111-133. , --, G. L. Baker and E. M. Agee, 1979: Characteristics of tornado-like vortices as a function of swirl ratio: a laboratory investigation
derivation closely parallelsprevious work on tornadogenesis (Davies-Jones 1982).Then, an equation is obtained that relates the materialderivative of thermal-wind imbalance to a generalizedQ vector Q* and ageostrophic terms, and a PE versionof the omega equation also is found. The generalizedQ vector is the vector mean of the OM and the Sutcliffeet al. forms of the Q vector, with geostrophic velocitygradients replaced by actual ones. In section 4, the quasi-geostrophic Q vector (Q inthe nomenclature
derivation closely parallelsprevious work on tornadogenesis (Davies-Jones 1982).Then, an equation is obtained that relates the materialderivative of thermal-wind imbalance to a generalizedQ vector Q* and ageostrophic terms, and a PE versionof the omega equation also is found. The generalizedQ vector is the vector mean of the OM and the Sutcliffeet al. forms of the Q vector, with geostrophic velocitygradients replaced by actual ones. In section 4, the quasi-geostrophic Q vector (Q inthe nomenclature
simulation. Thus our results do not address the question of tornadogenesis but deal with the question of how the details of the low-level, tornado flow depend upon larger-scale features in the thunderstorm represented by the boundary conditions on our domain. Different thunderstorms undoubtedly exhibit a wide variety of detailed velocity distributions on an inner domain boundary corresponding to the edges of our computational domain. In this paper, we restrict our attention to one possible set of
simulation. Thus our results do not address the question of tornadogenesis but deal with the question of how the details of the low-level, tornado flow depend upon larger-scale features in the thunderstorm represented by the boundary conditions on our domain. Different thunderstorms undoubtedly exhibit a wide variety of detailed velocity distributions on an inner domain boundary corresponding to the edges of our computational domain. In this paper, we restrict our attention to one possible set of
: TITAN: Thunderstorm Identification, Tracking Analysis and Nowcasting—A radar-based methodology. J. Atmos. Oceanic Technol. , 10 , 785 – 797 . Dowell , D. C. , and H. B. Bluestein , 1997 : The Arcadia, Oklahoma, storm of 17 May 1981: Analysis of a supercell during tornadogenesis. Mon. Wea. Rev. , 125 , 2562 – 2582 . Dowell , D. C. , and H. B. Bluestein , 2002 : The 8 June 1995 McLean, Texas, Storm. Part I: Observations of cyclic tornadogenesis. Mon. Wea. Rev. , 130 , 2626
: TITAN: Thunderstorm Identification, Tracking Analysis and Nowcasting—A radar-based methodology. J. Atmos. Oceanic Technol. , 10 , 785 – 797 . Dowell , D. C. , and H. B. Bluestein , 1997 : The Arcadia, Oklahoma, storm of 17 May 1981: Analysis of a supercell during tornadogenesis. Mon. Wea. Rev. , 125 , 2562 – 2582 . Dowell , D. C. , and H. B. Bluestein , 2002 : The 8 June 1995 McLean, Texas, Storm. Part I: Observations of cyclic tornadogenesis. Mon. Wea. Rev. , 130 , 2626
.1 until the vertical grid spacing reached 2000 m, above which it was kept constant. The model top extended beyond 23 km above ground level (AGL), and there were nine model levels within the first kilometer AGL. These grid spacings are sufficient to resolve storm-scale features and processes, but are insufficient to simulate tornadogenesis. The long time step was 5 s. The basic radiative condition was applied at the lateral boundaries ( Klemp and Wilhelmson 1978a ), a Rayleigh friction layer was
.1 until the vertical grid spacing reached 2000 m, above which it was kept constant. The model top extended beyond 23 km above ground level (AGL), and there were nine model levels within the first kilometer AGL. These grid spacings are sufficient to resolve storm-scale features and processes, but are insufficient to simulate tornadogenesis. The long time step was 5 s. The basic radiative condition was applied at the lateral boundaries ( Klemp and Wilhelmson 1978a ), a Rayleigh friction layer was
updraftalong the trailing gust front and the vault updraft. Between the two updraft cores is a downdraft. The downdraft is first apparent at 2230. It increases in size andmagnitude throughout the lifetime of the vortex. Noprecipitation is associated with the downdraft. Therefore it must be a dynamically driven downdraft, withprecipitation loading and diabatic cooling effects absent. This is a very significant finding which is particularly applicable to issues in tornadogenesis.8. Discussion This study
updraftalong the trailing gust front and the vault updraft. Between the two updraft cores is a downdraft. The downdraft is first apparent at 2230. It increases in size andmagnitude throughout the lifetime of the vortex. Noprecipitation is associated with the downdraft. Therefore it must be a dynamically driven downdraft, withprecipitation loading and diabatic cooling effects absent. This is a very significant finding which is particularly applicable to issues in tornadogenesis.8. Discussion This study
, whereas in a tornado the rotation has a somewhat uncertain origin ( Rotunno 1984 ; Rotunno and Klemp 1985 ): it is thought to be linked to the preexistence of a downdraft that, together with precipitation introduced as in Markowski et al. (2003) , transports angular momentum to the ground where the circulation is then closed [see Wicker and Wilhelmson (1995) , and references therein]. More recent studies of tornadogenesis have included the effects of moisture and buoyancy, together with
, whereas in a tornado the rotation has a somewhat uncertain origin ( Rotunno 1984 ; Rotunno and Klemp 1985 ): it is thought to be linked to the preexistence of a downdraft that, together with precipitation introduced as in Markowski et al. (2003) , transports angular momentum to the ground where the circulation is then closed [see Wicker and Wilhelmson (1995) , and references therein]. More recent studies of tornadogenesis have included the effects of moisture and buoyancy, together with
