Blending of Model Data, Observations and Weather Camera Imagery in the Development of a Ceiling and Visibility Analysis Product for Alaska

Low cloud ceilings and poor visibility claim the lives of more general aviation (GA) pilots and passengers than any other cause of weather-related GA accidents. A key element of the strategy to boost GA safety relative to these hazards is to improve real-time access to representative analyses of current ceiling and visibility (C&V) conditions.

This paper outlines the initial development of an automated C&V analysis product for Alaska. The product utilizes RAP model data enhanced through blending with current surface observations, C&V information derived from automated weather cameras, and (starting in FY 15) satellite observations. A key challenge in this work has been the development of a method to extract viable C&V information from the network of automated FAA weather cameras in use in Alaska, each providing six images per hour. The method in place uses if-then rules applied to image properties to discriminate between two sky cover conditions (full to broken vs scattered to clear). If-then rules are further used in conjunction with image landmarks to identify instances of terrain obscuration and to estimate C&V values blended into the product.

The product is first targeted toward operational evaluation and use by the staff of the NWS Alaska Aviation Weather Unit (AAWU) beginning in the fall of 2014. In fully proven and mature form its production would include inputs and controls by AAWU forecasters and direct availability to the public. Experience gained with this Alaska product suggests that the use of model data could significantly benefit the first-generation automated C&V analysis product now in operation for the CONUS and available at http://www.aviationweather.gov/cva.