Probabilistic forecasting of ceiling and visibility: Blending NWP, LAMP and regression

The physical processes controlling ceiling and visibility (for example, the formation, evolution and motion of low cloud, precipitation, fog and haze) and the diverse seasonal, diurnal and geographic influences that modulate these controls yield a challenging forecast problem that impacts the overall efficiency of the national airspace and the safety of general aviation.

Current and emerging ceiling and visibility (C&V) forecast resources comprise an increasingly diverse and skilled population of probabilistic forecast tools – LAMP, gridded LAMP, SREF, VSREF, MOS, the North American Rapid Refresh Ensemble (NARRE), time-lagged ensembles built out of today's RUC, RR, HRRR and NAM, plus observations-based statistical forecast models. While this diversity is desirable, it raises the question how can the strengths within this population of resources be harnessed and used?

This paper describes the status of current work toward a 1-10 hour C&V forecast guidance product. The product's projected role is to capture and integrate the skill of current forecast capabilities, to deliver probabilistic forecast skill greater than that of its input components, and to evolve over the years as its input forecast components evolve and advance. We outline the key elements of our development approach and lessons learned to date, focusing on

• Development of a logistic regression-based forecast method supplementing forecasts from 1-5 hr;

• Formulation of customized forecast metrics to guide the forecast generation process;

• Automated methods to guide bias removal and advantageous blending among time-lagged model ensembles, LAMP and regression forecasts.

Finally, we summarize an assessment of the skill improvements achieved through our integrated approach.

This research is in response to requirements and funding by the Federal Aviation Administration (FAA). The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA.