Impacts of Targeted PAR Radial Velocity Observations on Idealized Supercell Low-Level Rotation Forecasts

The potential future installation of a phased-array radar (PAR) network will provide more frequent updates compared to the current WSR-88D network with capabilities of case-specific adaptive scanning. Many factors will affect adaptive scanning strategies including very short-term convective-scale model forecasts. An ensemble-based targeted observation algorithm is applied to an Observing System Simulation Experiment (OSSE) where the impacts of synthetic idealized supercell radial velocity observations are estimated before the observations are “collected” and assimilated. This method is able to sufficiently predict how PAR observation sets will impact the accuracy of a low-level rotation forecast metric (0-1 km updraft helicity), a surrogate for tornado prediction. In some scenarios, a subset of a full-volume scan assimilation produces better forecasts than all observations within the full volume. The targeted observation algorithm is able to reasonably predict this advantage before the observation time. Knowing the impacts adaptive scanning may have on short-term forecasts will influence scanning strategy decision-making. Broader implications of these results will be discussed.