Rapid-Scan Dual-Polarization Radar Observations of Zdr Column Depth in the Context of Forecaster Conceptual Models

National Weather Service (NWS) forecasters apply scientific conceptual models during their warning decision process to anticipate changes in storm intensity and associated hazards. Dual-polarization radar signatures, such as Z_DRcolumns, may provide forecasters with additional insights into storm intensity and evolution, especially when integrated with existing conceptual models. In addition, as volumetric update times decrease due to new scanning techniques and radar systems (e.g., phased array radars), the depiction of rapidly evolving signatures will likely improve. To examine dual-polarization and single-polarization radar signatures depicted by rapid-scan radar data, a research dual-polarization WSR-88D located in Norman, Oklahoma (KOUN) was used to perform 90° sector scans during multiple severe-weather events. The sector scanning in addition to custom volume coverage patterns allowed for the collection of about 20 rapid-scan (i.e., volume scan update times of less than 2 min) dual-polarization datasets.

The purpose of this study is to use these datasets to analyze Z_DR column depth evolution relative to single-polarization signatures and severe-weather reports across multiple cases and multiple storm modes (e.g., supercells; single cells). To place Z_DR column depth evolution in the context of conceptual models frequently used by NWS forecasters, time series of mesocyclone intensity, upper-level reflectivity core magnitude, and Z_DR column depth evolution were examined to identify any operationally relevant relationships between these signatures. Additionally, Z_DR column depth evolution was compared to the timing of severe-weather reports to identify signature trends that might be observable prior to severe weather occurring at the surface. The lead author will discuss key findings of this ongoing study.