The local airspace surrounding San Francisco International Airport (SFO) is prone to regular occurrences of low cloud ceiling conditions from May through October due to the intrusion of marine stratus along the Pacific coast. The low cloud conditions prohibit dual-parallel approaches of aircraft to the airport's closely spaced parallel runways, effectively cutting the arrival capacity in half. The behavior of marine stratus evolves on a daily cycle, filling the San Francisco Bay region overnight, and dissipating during the morning. Often the low ceiling conditions persist throughout the morning hours and interfere with the high rate of air traffic scheduled into SFO from mid-morning to early afternoon. The result is a substantial number of delayed flights into the airport, contributing to SFO's dubious distinction as one of the highest delay airports in the United States.

An automated system for acquiring data and providing cloud forecast guidance was demonstrated operationally during the summer of 2001. The system was sponsored by the Federal Aviation Administration, and was developed by MIT Lincoln Laboratory in collaboration with San Jose State University, the University of Quebec at Montreal, Penn State University, and the Central Weather Service Unit (CWSU) at Oakland Center. Realtime data were processed to support a display of weather graphics, and to provide input to a suite of four independent cloud forecast models developed specifically for the marine stratus application. The forecast models were run repeatedly each morning to provide updates during the evolution of cloud dissipation in the Bay area. As part of each update cycle, output from the models were combined to provide a single unified Consensus Forecast product. The automated forecasts were utilized in realtime by meteorologists at the CWSU at Oakland Center, the National Weather Service (NWS) in Monterey, and the Weather Center at United Airlines. The weather information was well received by forecasters. Sensor data not previously available to forecasters had an immediate impact, while the model guidance products were gradually incorporated into the operational forecast as they gained acceptance throughout the 5-month demonstration period.

A summary of the system demonstration is presented. Included is an overview of the realtime system, a high level description of the four forecast models, and the methodology for combining the component forecasts models into a unified consensus forecast. Operational performance of the system and its utility to forecasters is also discussed.

*This work was sponsored by the Federal Aviation Administration under Air Force Contract No. F19628-00-C-0002. The views expressed are those of the authors and do not reflect the official policy or position of the U.S. Government. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the US Government.