The complex phenomenology controlling ceiling and visibility effects (e.g., the formation and evolution of fog, low cloud, and precipitation; haze and aerosol effects; and others) and the diverse seasonal and geographic influences that modulate these controls across the continental U.S. yield an extremely difficult analysis and forecast problem. This same phenomenology deals serious negative impacts on the safety of aviation operations. Recent development of an exploratory ceiling and visibility forecast system for the continental U.S. has utilized an expert system methodology to merge numerical and observational inputs in the synthesis of ceiling and visibility forecasts out to six hours. Its products (posted at www.rap.ucar.edu/projects/cvis/index.html) have yielded encouraging early results and useful insight into needs for future research. This paper outlines the ongoing research and development necessary to evolve this forecast approach to next-generation capability and, ultimately, to operational readiness for the contiguous U.S. and Alaska.

Key elements of the research and development work outlined here include (i) the conduct of field studies to improve the understanding of physical processes and regional ceiling and visibility phenomenology; (ii) improvement in the numerical modeling of physical processes critical to the occurrence of fog, low/mid-level cloud, and precipitation, including the use of a very high resolution column model to enhance detailed representation of boundary layer processes; (iii) research on the diagnostic and predictive value of operational observations from satellite, radar, surface, and aircraft; (iv) development of climatological and observations-based statistical forecast methodologies; (v) further development of expert system methods for forecast synthesis; and (vi) systematic analysis and verification of the performance value of forecast methodology components and their integrated results.

The work is carried out by a newly-established National Ceiling and Visibility product development team as part of the FAA’s Aviation Weather Research Program.