GLM Extent Density of Lightning is the number of lightning flashes that occur within a grid cell over a given period of time. FED was the first GLM product routinely available to weather service forecasters. The FED product is the best single metric to convey both the quantity and extent of lightning activity. It is useful for both storm trending applications and to depict geographic coverage.

In this visualization, GLM is superimposed on a GeoColor background image.

GLM data is produced between 54°N and 54°S.

• For more details, see the Geostationary Lightning Mapper Quick Guide, (PDF, 1.98 MB)