Using the 21 June 2008 California Lightning Outbreak to Improve Dry Lightning Forecast Procedures

Abstract

An anomalous lightning event occurred on 20?21 June 2008 in central and northern California. Most of the thunderstorms produced frequent lightning with little precipitation, resulting in over 1500 new fires. Many of these fires became large, and massive firefighting efforts continued through August in order to contain all the fires. This event was not well forecast, with only isolated lightning strikes expected. Several computer model forecast parameters pointed toward the impending lightning outbreak, including satellite and lightning observations, as well as model data from 19 June. An existing procedure to forecast dry thunderstorms showed the strong possibility of a thunderstorm outbreak over California. This procedure proved to be helpful, but has been modified to better handle moisture advection and low-level forcing, which provides a more comprehensive framework for forecasting potential dry thunderstorm outbreaks.