The Influence of Topography on Convective Storm Environments in the Eastern United States as Deduced from the HRRR

Abstract

Abstract Relatively little is known about how topography affects convective storms. The first step toward understanding these effects is to investigate how topography affects storm environments. Unfortunately, the effects of topography on convective environments are not easily observed directly. Instead, it is necessary to resort to using output from the High-Resolution Rapid Refresh (HRRR). The HRRR’s 3-km grid spacing can resolve some of the larger-scale topographic effects. Popular convective storm forecasting parameters obtained from the HRRR are averaged on convective days from February to September 2013–15. It is surmised that most of the day-to-day variability attributable to synoptic- and mesoscale meteorological influences is removed by averaging; the remaining horizontal heterogeneity in parameters related to instability and vertical wind shear is due to the hemispheric-scale meridional temperature and pressure gradient, and likely also topographic influences, especially where recurring longitudinal variations in instability, wind shear, etc. are found. Anomalies are sensitive to the ambient low-level wind direction (i.e., whether winds are locally blowing upslope or downslope), especially for parameters that depend on the low-level vertical shear. The statistical significance of local maxima and minima is demonstrated by comparing the amplitudes of the anomalies to bootstrapped estimates of the standard errors.