The October 2017 North Bay Fires: Applying New Observational and Prediction Tools to Smoke and Air Quality Forecasting

On October 8 and 9, 2017, numerous wildfires started and spread rapidly in the North Bay region of the San Francisco Bay Area. The combination of very strong winds, low relative humidity, and dry fuels resulted in extreme fire behavior. Over the following ten days, the fires burned over 200,000 acres, destroyed nearly 9,000 structures, and caused 44 deaths. Smoke from the fires caused severe air quality issues in the densely-populated Bay Area. Concentrations of fine particles (PM_2.5) in the smoke plumes were the highest measured since regular monitoring for PM_2.5 began in the Bay Area in 1999.

The complexity and magnitude of this air pollution event presented several challenges for the Bay Area Air Quality Management District (Air District), the agency responsible for monitoring, forecasting, and regulating air quality in the Bay Area. To augment the Air District’s existing PM_2.5 monitoring network and provide additional air quality information for communities nearest the fires, mobile incident-response monitors were deployed in key locations downwind of the fires. New observational tools, such as GOES-16 visible imagery and infrared hotspot detection, were instrumental in tracking the narrow but dense smoke plumes and the development of new fires. NOAA’s experimental HRRR (High-Resolution Rapid Refresh) Smoke model was utilized to help predict shifts in wind direction and subsequently, in the smoke plumes, as these shifts resulted in high spatial and temporal variability in air quality conditions. Predictions of PM_2.5 concentrations from the HRRR-Smoke model were later compared to surface PM_2.5 observations to assess model performance during this extreme event. This presentation will focus on the use of these relatively new, high-resolution data sets, as they aided Air District forecasters in providing accurate and timely air quality information to the public and for decision makers at area schools, governments, and other concerned organizations.