A Lightning Climatology for the Northern California Region

A climatology of lightning occurrences for the northern portion of California has been developed by the National Weather Service Forecast Office in Eureka, California. The study comprises 23 years of lightning data obtained by the National Lightning Detection Network. Though upgrades in the NLDN network make quantitative yearly comparisons problematic, analysis of the areal distribution of lightning remains consistent over the dataset. As such, high-resolution lightning density maps have been produced to emphasize the influence of terrain and meso-meteorological conditions on lightning occurrence. The occurrence of lightning is examined by the month of year and hour of day. By linking the occurrence of lightning to the vertical wind profile at the nearest proximal sounding, density maps are created to demonstrate the prime locations for lightning strikes under several prevalent storm motion regimes. From a geographic perspective, lightning occurrence over the near-coast zone of California is primarily influenced by early summer low pressure systems and troughs coming onshore. This is in contrast to the peak in lightning activity inland, over the northern Sierra Nevada Mountains, which occurs under later summer monsoonal regimes. Some basic thermodynamic analysis is performed to see what sounding parameters might best be utilized to evaluate lightning potential, but a lack of cases and continuity in the dataset makes it difficult to glean reliable results. Special emphasis throughout this climatology is paid to impacts upon the fire weather community. Further study intends to examine meteorological patterns that not only contribute to extensive lighting outbreaks, but lightning events where large numbers of high-impact fires are started... A set of cases that is not necessarily mutually inclusive.