The Definition of GOES Infrared Lightning Initiation Interest Fields

Within cumulus cloud fields that develop in conditionally unstable air masses, only a fraction of the cumuli may eventually develop into deep convection. Identifying which of these convective clouds is most likely to generate lightningoften startswith littlemore than a qualitative visual satelliteanalysis. The goal ofthis study is to identify the observed satellite infrared (IR) signatures associated with growing cumulus clouds prior to the first lightning strike, or lightning initiation (LI). This study quantifies the behavior of 10 Geostationary Operational Environmental Satellite-12 (GOES-12) IR fields of interest in the 1 h in advance of LI. A total of 172 lightning-producing storms, which occurred during the 2009 convective season, are manually tracked and studied over four regions: northern Alabama, central Oklahoma, the Kennedy Space Center, and Washington, D.C. Four-dimensional and cloud-to-ground lightning array data provide a total cloud lightning picture(in-cloud,cloud-to-cloud,cloud-to-air,andcloud-to-ground)andthus preciseLI pointsforeachstorm in both time and space. Statistical significance tests are conducted on observed trends for each of the 10 LI fields to determine the unique information eachfield provides in terms of behaviorprior to LI. Eight out of 10 LI fields exhibited useful information at least 15 min in advance of LI, with 35 min being the average. Statisticaltests on theseeightfields arecomparedforseparatelargegeographical areas.MedianIR temperatures and 3.9-mm reflectance values are then determined for all 172 events as an outcome, which may be valuable when implementing a LI prediction algorithm into real-time satellite-based systems.