Removing acoustic-mode pressure oscillations from storm-scale EnKF analyses

When an ensemble Kalman filter (EnKF) and compressible model are used to assimilate storm-scale radar data, dynamically unbalanced analysis increments can incite high-amplitude acoustic waves and attendant pressure oscillations that preclude investigation of pressure-gradient-driven processes. Fortunately, thermodynamic retrieval techniques traditionally applied to dual-Doppler wind analyses can be modified to diagnose the balanced (uncontaminated) portion of EnKF pressure posteriors, thereby eliminating the fast-mode oscillations. The efficacy of this approach is demonstrated using a high-resolution supercell simulation as well as simulated and real EnKF supercell analyses.