Evaluation of the Warn-on-Forecast System with Doppler Lidar and Radiosonde Observations from TORUS2019

Doppler Lidar and mobile radiosonde observations from the Targeted Observations with Radars and UAS of Supercells 2019 (TORUS2019) field project will be compared to the
environmental guidance provided by the NSSL Warn-on-Forecast System (WoFS). The aim of WoF is to provide short-term, storm-scale, probabilistic guidance for severe thunderstorm hazards. As the evolution of convective storms are modulated by the properties of the inflow environment, an accurate prediction of these properties is critical for forecasting the evolution of an individual thunderstorm. However, the scarcity of routine observations of the inflow environment of thunderstorms makes evaluation of the quality of WoFS environmental forecasts difficult. Therefore, this study will assess the accuracy of WoFS predictions of the inflow environment of supercells through comparisons to TORUS2019 Doppler Lidar and radiosonde observations.

Both Doppler Lidar and radiosonde observation systems provide data at a much greater spatio-temporal resolution than WoFS output, so averaging schemes will be applied to ensure that observations have a similar resolution to the model grid (51 vertical levels at 3km horizontal spacing). The accuracy of WoFS predictions of the environmental low-level vertical wind shear is of primary initial interest and will be assessed by comparing observed and forecast hodographs. Statistical analyses will be performed on observed and predicted hodographs to determine the accuracy and character of error(s) in WoFS guidance.

Initial comparisons will focus on observations and predictions of the May 17th 2019 McCook, Nebraska tornadic supercell. TORUS2019 obtained a long-term continuous Doppler Lidar dataset within the inflow of the supercell as well as 8 soundings from varying storm-relative locations. Results will be extended to additional TORUS2019 cases as time allows.