Operational Use, Analysis, and Applications of Geostationary Lightning Mapper Data in the Hazardous Weather Testbed

The Geostationary Lightning Mapper (GLM) was introduced to National Weather Service (NWS) forecasters and broadcast meteorologists as part of the 2018 Hazardous Weather Testbed (HWT) and GOES-R Proving Ground Spring Experiment. Throughout the month of May, the forecasters evaluated the GLM products in the context of live severe and hazardous weather issuing regional discussion, special weather statements, and warnings; forecasters provided feedback through surveys, live blogs, and lightning scientists. The 2018 products were developed based upon forecaster feedback from the 2017 HWT and Operations Proving Ground evaluations and through previous research focused on visualizing the spatial and temporal applications of total lightning data.

Initial products in 2018 included (all at 1-min with 1-min updates): Flash Extent Density, Event Density, Group Extent Density, Average Flash Size, Average Group Size, Total Optical Energy, Flash Centroid Density and Group Centroid Density. Immediate feedback early in the experiment resulted in the creation of 5-min and 2-min summary products (with 1-min updates) to help forecasters better visualize lightning trends over time. Forecasters highly utilized the 5-min Flash Extent Density (with one-min updates) as the primary GLM product. For deeper storm interrogation, storm-electrification understanding, and spatial coverage prediction forecasters also gravitated to the Average Flash Size and Total Optical Energy products at 5 min totals (with one minute updates). Other products such as the Flash Centroid Density will likely see use in data fusion applications that incorporate flash rates and for data assimilation efforts into convective allowing models such as the High-Resolution Rapid Refresh (HRRR).

Based on feedback and survey results from 2018, we have three recommendations regarding operational implementation of the GLM data:

1. Flash Extent Density, Average Flash Size, and Total Optical Energy products (5 min and 1 min products both with 1 min update) are a minimal baseline for operational display of the GLM data within NWS. The products mutually reinforce one another, promoting forecaster confidence and clear thinking about storm processes.
2. Due to the inherent use of the data within rapidly changing environments, the latency of the product needs to be consistently no more than 1-2 min maximum.
3. Increased training opportunities need to be provided to forecasters at the time of the operational implementation beyond previous required training modules and quick guides. These training modules should be developed with a regional and applied focus, allowing forecasters to participate in active and practical training options in context of other data and within real weather events. In addition to storm-growth and severe-storm-interrogation, training should address likely GLM uses such as Decision-Support Services and lightning safety, fire weather, aviation warnings and use over radar-sparse regions.