Examining 8-km total lightning over Huntsville

NWS and Environment Canada forecasters monitoring the 8-km total lightning flash extent density product in warning operations over the Huntsville, AL CWA.
Tonight's IOP focuses on severe weather warning over the Huntsville, AL WFO CWA. Huntsville was chosen because of the availability of total lightning data from the Northern Alabama Lightning Mapping Array (NALMA). This provides us the unique opportunity to examine the 8-km pseudo-GLM total lightning flash extent density product in real-time warning operations. Forecasters have noticed a few interesting features of the data, including it's ability to pick up on trailing stratiform lightning over more intense convective storms. The raised the fact that this would be very useful for aviation type forecasts and warnings, as well as lightning warnings for the general public who may think that they are out of danger from lightning after the main convective region passed. They also noticed that the product located areas of more intense updrafts within line segments that are otherwise indistinguishable on radar reflectivity. These more active regions were found to highlight regions where small intense circulations were seen within the lines, which may lead to short tornadic threats. Forecasters were also able to compare the pseudo-GLM data to NLDN via the situational awareness screens on the back wall of the HWT. It was noticed that, particularly in the trailing stratiform regions, that the 8-km total flashes extent densities showed much more information on the total lightning occurring along the line of convection. Total flash rates were available in Google Earth. As expected, lightning jumps were seen with rapidly increasing radar reflectivity. However, the unavailability of these data within the local AWIPS system hindered the forecasters ability to use it effectively, but they expressed lots of interest in seeing this in the future.

8-km total lightning flash extent density product within HWT AWIPS system overlaid on radar at 2338 UTC on 20 May 2010.
The data are being provided with AWIPS as a smoothed grid so that forecasters are able to overlay the data on radar or satellite imagery. The smoothing has somewhat masked the fact that the data are on an 8x8 km grid, but it does seem to show details that are being used to detect more active regions nonetheless. The data are also provided as a running 2-min average, which may be different that what the GLM will provide. However, this may turn out to be a useful way to process the data once the GLM is launched in order to reduce the amount of data being transferred into every AWIPS system.

8-km total lightning flash extent density trends provided on Google Earth within the HWT on 20 May 2010.