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The contemporaneous pointwise product of convective available potential energy (CAPE) and precipitation is shown to be a good proxy for lightning. In particular, the CAPExP proxy for lightning faithfully replicates seasonal maps of lightning over the contiguous United States, as well as the shape, amplitude, and timing of the diurnal cycle in lightning. Globally, CAPExP correctly predicts the distribution of flash rate densities over land, but it does not predict the pronounced land-ocean contrast in flash rate density; some factor other than CAPE or P is responsible for that land-ocean contrast.

Plain Language Summary Forecasting lightning is a challenge because weather and climate models do not resolve the processes that lead to the electrification of clouds. Instead, simple models must be used to predict lightning based on the available data. One model that has been proposed is the product of convective available potential energy, which is a measure of potential storm energy, times the precipitation rate. It is shown here that convective available potential energy times the precipitation rate explains the distribution and timing of lightning over land but does not explain the large land-ocean contrast in lightning flash rates.