Mesoscale influences of land use, topography, antecedent rainfall, and atmospheric conditions on summertime convective storm initiation under weak synoptic scale forcing

Abstract

Abstract Throughout the summer months in the Southeast United States, the initiation of isolated convection can occur abundantly during the daytime with weak synoptic support (e.g., weak wind shear). Centered around this premise, a dual-summer, limited area case study of CI events concerning both geographical and meteorological features was conducted. The goal of this study was to help explain SEUS summertime CI in weak synoptic environments, which can enhance CI predictability . Results show that spatial CI non-randomness event patterns arise, with greater CI event density appearing over high elevation by midday. Later in the day, overall CI event counts subside with other mechanisms/factors emerging (e.g., urban heat island). Antecedent rainfall, instability, and moisture features are also higher on average where CI occurred. In a random forest feature importance analysis, elevation was the most important variable in dictating CI events in the early to mid-afternoon while antecedent rainfall and wind direction consistently rank highest in permutation importance. The results cumulatively allude to, albeit in a muted, non-significant statistical signal, and a degree of spatial clustering of CI event occurrences cross the study domain as a function of daytime heating and contributions of features to enhancing CI probabilities (e.g., differential heating, mesoscale thermal circulations).