Convective Weather Avoidance Modeling for Low Altitude Routes

This document is disseminated under the sponsorship of the Department of Transportation, Federal Aviation Administration, in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. Thunderstorms are a leading cause of delay in the National Airspace System (NAS), and significant research has been conducted to predict the areas pilots will avoid during a storm. An example of such research is the Convective Weather Avoidance Model (CWAM), which provides the likelihood of pilot deviation due to convective weather in a given area. This report extends the scope of CWAM to include low-altitude flights, which typically occur below the tops of convective weather and have slightly different operational constraints. In general, the set of low-altitude flights includes short-hop routes and low-altitude escape routes used to reduce the impact of convective weather in the terminal area. For classification, low-altitude flights are identified as either deviations or non-deviations, and the corresponding weather features are analyzed. Precipitation intensity is observed to be the best predictor of deviation in the low-altitude flight regime, as compared to the difference in altitude between the flight and the echo tops for en route flights. Additionally, the low-altitude CWAM performs better than the departure CWAM currently used in the Route Availability Planning Tool (RAPT) when tested on deterministic weather data.