The Huntsville office has a long history of using total lightning information from the North Alabama Lightning Mapping Array (NALMA) for warning decision-making. Since 2003, WFO Huntsville has been ingesting and receiving a source density product from NASA SPoRT. However, recently, we decided to begin migrating to Flash Extent Density (FED) data; this is more consistent with the Geostationary Lightning Mapper, more consistent with recent operational research, and easier to convey and understand. Typically we are trying to apply the “two-sigma” lightning jump algorithm suggested by Schultz et al. (2009, 2012).
On June 8, a weak front moved across the Huntsville forecast area, initiating development of strong to severe thunderstorms. An 1800 UTC sounding from Redstone Arsenal indicated a relatively high threat for wet microbursts.
One of the storms moved across extreme southern Jackson and northern DeKalb Counties in northeast Alabama. I was viewing the NALMA FED data and watched as the storm went from less than 10 flashes, to 40 flashes, in three “scans” (from 2214 to 2218 UTC). (Interestingly, despite using SAILS with the KHTX radar, AWIPS-2 matched all three lightning images to a single 0.5-degree radar scan.)
Since we cannot get the formal lightning jump algorithm into AWIPS-2 at this time, forecasters need to do some quick mental math to decide if jumps such as these constitute a real jump. I was certain this did (and later Excel work verified this) so I issued a severe thunderstorm warning, despite the storm being very close to the Georgia state border.
This storm produced structural damage in the Cartersville community near the state line shortly after the warning was issued, tearing the roof off of an apartment complex and downing trees and powerlines. There was not much lead time (there rarely is with these kinds of storms) but this reinforces our past experience with total lightning–and reinforces that lightning may be especially useful during a challenging warm season warning environment.