Objective identification and tracking of merging and splitting storms in the 24 May 2011 Oklahoma tornadic supercell outbreak

A number of recent studies have examined the role of storm mergers and splits on tornado formation and demise. We seek an objective method to detect and characterize storm mergers and splits using rapidly updated radar observations. A comprehensive data set was collected in the 24 May 2011 western Oklahoma tornadic supercell outbreak by the National Weather Radar Testbed Phased Array Radar (NWRT PAR). We assimilated these data into NCOMMAS, and generated analyses of the storms with 250 m horizontal grid spacing and 1 min temporal resolution. In the analyzed fields, we objectively identified reflectivity objects (“storms”), vertical velocity objects (“updrafts” and “downdrafts”), and vorticity objects (“vortices”) using the enhanced watershed algorithm, then associated these objects across time using a tracking algorithm. The resulting automatically generated catalog of objects for this case will be used to characterize storm splits and mergers and their association with vorticity changes in each analyzed storm.