Air quality forecast (AQF) system has been established at NOAA/NCEP in 2003 as a collaborative effort of NOAA and EPA. The system is based on NCEP’s Eta mesoscale meteorological model and EPA’s CMAQ air quality model. The purpose of the system is to provide national guidance for ozone, particulate matter and other pollutants with sufficient accuracy for people to take actions to limit the harmful effects of poor air quality. As a first stage of the project, ozone concentrations are predicted on real-time basis since summer 2003. Based on initial series of experiments, the updated version of the AQF system is set for operational status by end of summer 2004.

Surface layer ozone concentrations from AIRNOW measurements and from CMAQ forecasts were incorporated into NCEP’s Forecast Verification System (FVS). CMAQ predicted concentrations are interpolated to the observation points. Average statistics (e.g. bias, root mean square error, correlation etc) are computed for North East Coast, South East Coast, Mid-West, Gulf of Mexico and several other areas. Statistics for critical thresholds for ozone concentration are also computed. Differences in the model performance between AQF versions for Summer 2003 and Summer 2004 are examined. Skill of ozone predictions in different regions, dependence on synoptic regime and the importance of vertical structure of meteorological variables (temperature profile, PBL height) will be presented.