The impact of WSR-88D Super-Resolution data in low-level mesocyclone evaluation

In 2008 the resolution of all WSR-88D base products was upgraded, this base data is now routinely used by National Weather Service forecasters in their warning decision making process. We examined the difference in user-defined storm-scale vortex strength at the 0.5 degree elevation between the upgraded resolution and a recombined resolution designed to represent the original “legacy” resolution in 1606 individual volume scans. Each volume scan was determined to be either tornadic or non-tornadic, using a temporal window and Storm Data to establish differences between tornadic and non-tornadic mesocyclones. An analysis of tornado discrimination performance was then created by incrementing a threshold of rotational velocities and performing dichotomous tests depending on whether or not a tornado occurred in association with the mesocyclone within a temporal window surrounding tornado occurrence. We find that a majority of storm-scale vortices, as measured by rotational velocity, are stronger in the upgraded resolution and are also stronger at far distances from the radar. However, the ability of super-resolution velocity data to discriminate tornadic vs. nontornadic mesocyclones shows very small, to almost no difference to that of the recombined velocity data. This later result may be a testimony to the robustness of the recombination algorithm to preserve the strength of mesocyclones.