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Infrequent lightning flashes occurring outside of surface precipitation pose challenges to Impact-Based Decision Support Services (IDSS) for outdoor activities. This paper examines the remote sensing observations from an event on 20 August 2019 where multiple cloud-to-ground flashes occurred over 10 km outside surface precipitation (lowest radar tilt reflectivity, 10 dBZ and no evidence of surface precipitation) in a trailing stratiform region of a mesoscale convective system. The goal is to demonstrate the fusion of radar with multiple lightning observations and a lightning risk model to demonstrate how reflectivity and differential reflectivity combined provided the best indicator for the potential of lightning where all of the other lightning safety methods failed. A total of 13 lightning flashes were observed by the Geostationary Lightning Mapper (GLM) within the trailing stratiform region between 2100 and 2300UTC. The average size of the 13 lightning flashes was 3184 km², with an average total optical energy of 7734 fJ. A total of 75 NLDN flash locations were coincident with the 13GLMflashes, resulting in an average of 5.8 NLDN flashes [in-cloud (IC) and cloud-to-ground (CG)] per GLM flash. In total, five of the GLM flashes contained at least one positive cloud-to-ground flash (1CG) flash identified by the NLDN, with peak amplitudes ranging between 66 and 136 kA. All eight CG flashes identified by the NLDN were located more than 10 km outside surface precipitation. The only indication of the potential of these infrequently large flashes was the presence of depolarization streaks in differential reflectivity (ZDR) and enhanced reflectivity near the melting layer. [ABSTRACT FROM AUTHOR]

The two most distinct inner‐core lightning outbreaks in Hurricane Dorian (2019) are analyzed using the Geostationary Lightning Mapper (GLM). The first outbreak occurred during Dorian's intensification, including a rapid intensification (RI), and the second occurred during weakening. During RI, inner‐core lightning flash density increased as flashes concentrated inside of the radius of maximum wind (RMW). As weakening commenced, numerous flashes still occurred within the RMW, with a flash rate more than three times that during RI–a signal typically associated with strengthening. These flashes, however, were much smaller and less energetic than those during intensification. Evidence is presented that barotropic mixing and secondary eyewall formation increased the number of small, low‐energy lightning flashes in the inner core while simultaneously weakening the storm. The results suggest that flash area and energy from GLM could help distinguish between lightning outbreaks that correspond to intensification and those that correspond to weakening. Plain Language Summary: Lightning can be a useful tool for forecasting hurricane intensity. Usually an increase in lightning within the storm means that it is likely to intensify. But sometimes even weakening hurricanes have large lightning outbreaks, so forecasters must carefully look at other data to see what a lightning outbreak really means for a hurricane's intensity. The Geostationary Lightning Mapper (GLM) is a new tool that provides a lot more information about lightning in hurricanes than was previously available. GLM is able to continuously detect the size and energy of lightning flashes, even over the open oceans. Here we show that the lightning flashes in Hurricane Dorian (2019) were larger and more energetic when the storm was intensifying than when it was weakening. We also argue that changes in the location of lightning flashes could help to identify processes that affect a storm's intensity. This information provides clues into how storm structure changes at peak intensity and can potentially help forecasters interpret whether a lightning outbreak signifies storm intensification or weakening. Key Points: Lightning flashes during Dorian's rapid intensification were larger and more energetic than those during moderate intensificationAs Dorian weakened, lightning flashes were more numerous, but were smaller and less energetic than during intensificationGLM observations reveal processes that affect hurricane intensity, including barotropic mixing and secondary eyewall formation [ABSTRACT FROM AUTHOR]