The Northeast Corridor of the United States is perhaps one of the largest megacities in the world. It has been the focus of continued research on air quality impacts for many decades. As part of its efforts to mitigate against the impact of poor air quality, states that are part of the Northeast Corridor issue air quality forecasts to the public, and in the summertime, the principal pollutant of concern is ozone.

Recently, numerical models have become accurate and fast enough to provide real-time ozone forecast guidance to the operational ozone forecasters in the Northeast Corridor. During 2001-2002, NOAA conducted a two-phase pilot study to evaluate the ability of existing and prototype forecasting methods and models to accurately predict ground-level ozone with a lead time of 24-36hrs. Results demonstrate that the best available system consistently beats persistence and may be as good or better than human forecasters for certain episodes. Thus, this system provides an initial skill benchmark against which future operational systems may be compared.