Numerical simulation of a cyclic tornadic thunderstorm augmented by EnKF assimilation of mobile Doppler radar data

Volumetric Doppler reflectivity and velocity data were collected in the 4 May 2007 Greensburg, Kansas cyclic tornadic thunderstorm by both the National Weather Service WSR-88D network and a mobile, X-band Doppler radar (UMass X-Pol). Experiments in which these data were assimilated into the Weather Research and Forecasting (WRF) numerical weather prediction model, using the ensemble adjustment Kalman filter (EAKF) technique, are described. Via qualitative examination of the resulting ensemble of flow fields, it is shown that the near-surface circulation is better resolved when UMass X-Pol velocity data are assimilated rather than withheld. It is also shown that minor improvement in observation-space diagnostics results when UMass X-Pol data are assimilated, particularly at low elevations (i.e., < 1 km) where WSR-88D data are relatively sparse.