Impact of Phased Array Radar Observations on the Analyses and Forecasts of the 22 May 2011 Ada Supercell Storm

With the advent of emerging Multi-function Phased Array Radar (MPAR) technology, it is now possible to scan the same weather phenomenon using the rapid update capabilities of the system. Yussouf and Stensrud (2010) conducted an Observing System Simulation Experiments (OSSE) and showed that the rapid scanning capability of MPAR yields better analyses and forecasts compared to WSR-88D radars over a short assimilation window. The goal of this study is to extend the findings from Yussouf and Stensrud (2010) to assess the potential of MPAR observations within a realistic mesoscale environment from the 22 May 2011 Ada, Oklahoma tornadic supercell event. A 40-member multiphysics mesoscale ensemble at 12 km horizontal grid spacing on a continental United States domain is initialized from the Short-Range Ensemble Forecasting (SREF) final analysis system at 1500 UTC 21 May 2011 using the Advanced Regional Prediction System (ARPS). Conventional observations are assimilated on the mesoscale domain on an hourly basis for a 9-hour period using the ensemble square-root filter (EnSRF) technique. A 40-member storm-scale ensemble is initialized from the mesoscale ensemble with 2-km horizontal grid spacing centered on the tornadic event at 0000 UTC 22 May 2011. Two sets of data assimilation and forecast experiments are conducted on the storm-scale domain using the four-dimensional asynchronous ensemble square-root filter (4DEnSRF, Wang et al. 2013), a flavor of EnKF technique that benefits most from high-temporal observations. One experiment assimilates the WSR-88D KTLX radar and the other assimilates the MPAR radar observations for a 30-min period. Preliminary results indicate that the MPAR experiment is able to analyze more realistic reflectivity structure and stronger vorticity than that from the KTLX experiments. In addition, the forecast probability of vorticity from the MPAR experiment corresponds better with the observed rotation track. More results and verification will be discussed at the conference. Reference: Yussouf, N., D. J. Stensrud, 2010: Impact of Phased-Array Radar Observations over a Short Assimilation Period: Observing System Simulation Experiments Using an Ensemble Kalman Filter. Monthly Weather Review, 138, 517–538 Wang, S., M. Xue, and J. Min, 2013: A four-dimensional asynchronous ensemble square-root filter (4DEnSRF) and tests with simulated radar data. Quart. J. Roy. Meteor. Soc., 139, 805–819.