True Positive Convective Storms Without Lightning in ThunderCast

The Thunderstorm Nowcasting Tool (ThunderCast) is a 24-hour, year-round model for predicting the location of convection that is likely to initiate or remain a thunderstorm in the next 0-60 minutes in the continental United States (CONUS). ThunderCast utilizes a U-Net convolutional neural network for semantic segmentation trained with four inputs and one target dataset. The inputs are satellite bands from the Geostationary Operational Environmental Satellite (GOES-16) Advanced Baseline Imager (ABI) in the visible, shortwave infrared, and longwave infrared spectrum, and the targets are Multi-Radar Multi-Sensor (MRMS) radar reflectivity greater than or equal to 30 dBZ at the -10°C isotherm in the atmosphere. Under a variety of geographic and meteorological conditions, ThunderCast effectively nowcasts the location of newly initiated and ongoing active convection within the next 60 minutes in the CONUS. However, there are true positive cases (predictions are present and radar observations are consistent with the model’s target) where the convection does not produce lightning. Such cases could contribute to a decrease in the model’s usefulness to forecasters. To avoid predictions of non-electric convective storms, a robust understanding of the convection is sought by determining the frequency, location, and environmental conditions for each true positive case without lightning.