Utilizing the Geostationary Lightning Mapper Long-Flash Detection Capability for National Weather Service Decision Support Services

The Geostationary Lightning Mapper (GLM) on the Geostationary Operational Environmental Satellite (GOES)-R series of satellites has a near-infrared optical transient detector that detects brief changes in an optical scene, indicating the presence of lightning. The GLM observes total lightning (i.e., in-cloud, cloud-to-cloud, and cloud-to-ground) activity continuously over its field of view. Since GLM observations are point data, it is necessary to transform the data back to the native spatial footprint for display with GOES-R Advanced Baseline Imager imagery. Visualizing the spatial footprint and extent of lightning with GLM data has advantages, particularly when analyzing long stratiform intra-cloud flashes (i.e., long flashes) that can travel hundreds of miles horizontally. Since cloud-to-ground lightning often occurs along the path of a long flash in either light or no precipitation, they are a significant threat to public safety. Before GOES-16 GLM data it was difficult, if not impossible, for National Weather Service (NWS) forecasters to observe and message the threat of long flash lightning to core partners and the general public in real-time. By integrating GOES-16 GLM data and imagery with WSR-88D radar data and ground based lightning detection network data into the forecaster’s decision support workflow, NWS forecasters can quickly become situationally aware of long flashes. This applied research and presentation will break down a GLM long flash, show how to identify long flashes with GLM data, and illustrate how NWS forecasters can be more confident when messaging the threat of long flashes using examples from the Huntsville, AL and Jacksonville, FL NWS Weather Forecast Offices.