Impact of WSR-88D Intra-volume Low-level Scans on Tornado Warning Performance Parsed by Storm Type

The National Weather Service (NWS) Radar Operations Center (ROC) continues to develop new Volume Coverage Pattern (VCP) options for the operational Weather Surveillance Radar 1988-Doppler (WSR-88D) network to better meet the needs of forecasters and forecast models. The supplemental adaptive intra-volume low-level scan (SAILS) VCP option was introduced in 2014, followed by the multiple elevation scan option for SAILS (MESO-SAILS). In order to quantify the impact of these new VCP options on NWS severe weather warning performance, Cho et al. (2022) analyzed historical statistical relationships between (MESO-)SAILS usage and warning performance. Results yielded statistically meaningful improvement in severe thunderstorm, flash flood, and tornado warning performance with (MESO-)SAILS usage.

In this follow-on study, statistical relationships between (MESO-)SAILS and tornado warning performance are parsed by storm type. This effort was motivated by questions like whether the overall statistical results might have been biased by lower (MESO)-SAILS usage for storm types that tend to have lower tornado warning performance, and whether most of the apparent (MESO)-SAILS benefit is concentrated in just a few storm types. The results show that SAILS usage is associated with statistically meaningful improvement in detection probability for the majority of storm categories, and that progressively higher MESO-SAILS tiers (more frequent base scan updates) are associated with higher detection probability in a smaller subset of storm types. As with the previous overall tornado warning results, statistically meaningful impact of (MESO)-SAILS usage on lead time was generally not observed among the different storm types.

Reference:

Cho, J. Y. N., J. M. Kurdzo, B. J. Bennett, M. E. Weber, J. W. Dellicarpini, A. Loconto, and H. Frank, 2022: Impact of WSR-88D intra-volume low-level scans on severe weather warning performance. Wea. Forecasting, 37, 1169-1189, https://doi.org/10.1175/WAF-D-21-0152.1.

DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited. This material is based upon work supported by the National Oceanic and Atmospheric Administration under Air Force Contract No. FA8702-15-D-0001. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration.