Tornado Thermodynamics Observations and the Boundary-layer Evolution and Structure of Tornadoes (BEST) Study

Our knowledge of tornadogenesis, evolution, and structure has advanced substantially with the increase in computing resources and the availability of fine temporal- and spatial- scale observations.  Even so, many questions/hypotheses remain observationally unconfirmed/untested.  These include: the role of secondary rear-flank downdraft surges in the tornado genesis/maintenance process, the mechanisms of the generation of horizontal vorticity (ωh) and its transformation into tornado-strength near-surface vertical vorticity (ζ), how the evolution of the low-level mesocyclone relates to tornadogenesis, evolution and dissipation, the variability of tornado wind speeds with height and time, and how tornado intensity, propagation speed and structure, including variations in wind with height and time, affect human-impacting damage.  The degree to which the answers to these questions vary depending on the strength, size, structure, and persistence/duration of tornadoes is unknown.  

Answering these critical questions relating to the evolution of ζ, the role of downdrafts, updrafts, and baroclinic zones depends on the diagnosis of kinematically important quantities involving vector wind fields such as Div(V), vertical velocity (w), ωh and ζ, and tilting/stretching of ωh and ζ.  In tandem with DOW radar deployments, surface weather stations (Pods) have been utilized in many DOW tornado missions for well over a decade, obtaining not only surface wind data, but surface thermodynamic data, as well.  These integrated observations have been collected over a wide range of tornado structures and at various times in tornado evolution.  Results will be presented from analyses of multiple cases with both low-level DOW radar and surface thermodynamic data.  Preliminary observations suggest that there is a distinct and localized change in the near-field thermodynamics during tornado evolution over short time and spatial scales, which suggest changes in storm processes.     

Plans for the proposed 2023-2024 BEST (Boundary-layer Evolution and Structure of Tornadoes) project, focusing on characterizing the thermodynamic and kinematic structure of tornadoes below 100 m AGL, especially below 50 m AGL, using proximate DOW radars, PODNet, and Driftersondes from the University of Illinois Flexible Array of Radars and Mesonets (FARM) will be presented.