NASA Data Supports Lightning Safety

June 21-27, 2009 is Lightning Safety week with the National Weather Service. One of the products that SPoRT provides to support lightning safety this week, and every other week of the year comes from the North Alabama Lightning Mapping Array (NALMA). This network can observe intra-cloud flashes of lightning, which often precede the first cloud-to-ground strikes in a thunderstorm. This helps the forecasters of the National Weather Service provide additional lead-time to organizations (from airports to large outdoor festivities) that the lightning threat is imminent. A good example of this was captured on May 31, 2004. The first image shows the image of cloud-to-ground lightning activity as a strong line of thunderstorms approached northwest Alabama and the Muscle Shoals airport. Notice how in the circled regions there are no cloud-to-ground strikes observed, but the NALMA already shows intra-cloud activity (Figure 1). At this point the Huntsville, Alabama NWS issued an update to the Muscle Shoals airport indicating that cloud-to-ground lightning activity was imminent. Figure 2 shows that 5 minutes later, cloud-to-ground strikes were observed, exactly in the locations where the NALMA observations showed the storms to already be electrically active. The end result was a successful forecast by the forecasters ensuring all airport personnel were safely indoors long before the first cloud-to-ground strike occurred.

Figure 1: The left half of this image shows the locations of cloud-to-ground lightning strikes observed by the National Lightning Detection Network at 0409 UTC. Notice that in the circled regions, there are no cloud-to-ground strikes observed. However, on the right is a plot of the North Alabama Lightning Mapping Array (NALMA) observations of total lightning for the same time. Notice that the NALMA is observing intra-cloud flashes, indicating that the storms are already electrically active and could produce a cloud-to-ground strike at any moment.

Figure 2: This is the same area as Figure 1, but taken 5 minutes later at 0414 UTC. Notice how the circled regions where only the NALMA showed lightning activity now show cloud-to-ground strikes on the left. The NALMA data provided forecasters a 5 minute lead time to the initiation of cloud-to-ground activity.

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