Use of High-Resolution Lightning Potential Forecasts for Vermont Utility Applications

Operators of high voltage transmission lines consider lightning to be the most frequent cause of outages and interruptions. Today, close to one-third of all power outages are lightning-related which costs the nation roughly $1 billion annually. More specifically, power system faults caused by lightning can cost large commercial customers millions of dollars due to losses in production. The increasing trend of severe weather phenomena over the past few years has put electric utilities under high risk. In light of potential impacts, improving our ability to understand and forecast the potential for lightning is critical not just to ensure a reliable electric grid, but to our very ability to maintain a safe and functioning society.

Vermont’s complex terrain and vast local variability coupled with large gaps in observational data pose many challenges from a weather forecasting perspective. In a collaborative effort to increase the resiliency of Vermont’s electrical grid, Vermont Electric Power Company (VELCO) and statewide partners developed the Vermont Weather Analytics Center (VWAC) to increase grid reliability, lower weather event-related operational costs, and optimize the utilization of renewable generation resources. 

The weather prediction component is powered by IBM’s Deep Thunder, an advanced NWP model that is based, in part, on a configuration of the Advanced Research core of the Weather Research and Forecasting (WRF-ARW) model.  Deep Thunder runs two 72-hour forecasts daily at 1 km horizontal resolution and outputs variables at 10 minute intervals. Vertical resolution is also high with 51 vertical levels in order to account for characteristics of the wind turbines. Deep Thunder uses RAP for background fields and NAM for lateral boundary conditions, as well as complex physics configurations to account for highly rural and urban environments.  Deep Thunder’s lightning output utilizes the Lightning Potential Index or LPI (Lynn & Lair, 2010) which represents the potential for charge generation and separation that produces lightning strikes within convective thunderstorms. The LPI is mathematically defined as the volume integral of the total mass flux of ice and liquid water within the charging zone of a developing thundercloud. Similar to the CAPE instability parameter, the LPI is measured in units of J/kg.

The presentation will first provide background information on how lightning impacts the transmission system. Synoptic and mesoscale forecasting challenges within Vermont will then be discussed followed by an overview of the VWAC project. Numerous case studies will then be presented comparing LPI forecasts to the observed Cloud-to-Ground (CG) lightning strikes during the event (via the NLDN). Finally, potential future work and applications of the operational weather model will be discussed, including outage/impact prediction, road weather forecasting, recreational forecasting, and climate change.