This report documents the results of a study requested by the Strategic Air Command Deputy Chief of Staff for Operations (SAC/DO) to update previous contrail forecasting research done by Herbert Appleman for HQ Air Weather Service in 1953. Advancements in aircraft power plants, especially the development of bypass turbofan engines, made the new study necessary. This attempt to update and improve current contrail forecasting methods was performed by the SAC Directorate of Weather (SAC/DOW). It describes the development of new contrail forecast algorithms for several types of engines used in high-flying aircraft. It also provides contrail forecasting rules that correlate synoptic- scale upward vertical motion with contrail formation. The results indicate significant improvement in contrail forecasting accuracy over the Appleman technique now in use at the Air Force Global Weather Central. Weather, Climatology, Clouds, Cirrus, Clouds, Forecasting, Algorithms, Condensations trails, Contrails, Exhaust trails, Vapor trails.

Accurate forecasts of contrail occurrence are essential to military aircrews. Although classical forecast methods have been reasonably successful predicting contrails, there is need for improvement at low ambient relative humidity. This thesis examines the performance of the Hanson method, which was developed to provide better contrail forecasts under drier atmospheric conditions. As a secondary objective, the forecast methods of Schumann and Hanson are compared to the algorithm currently in use by the Air Force Global Weather Central. Data used to validate the algorithms were collected at Wright- Patterson AFB, OH and Edwards AFB, CA. Theoretical contrail forecasts were made for each observation, using the flight level pressure, ambient temperature, and relative humidity. Comparisons were then made between the forecast and actual observation of contrail conditions. Forecast and occurrence data were then statistically analyzed to gauge each method's performance. All methods detected roughly 75 percent of observed contrails under moist atmospheric conditions. However, the Hanson method's performance decreased when drier atmospheric observations were tested. Schumann's method performed as well as the AFGWC algorithm under all atmospheric conditions. Based on this research the Hanson method is not recommended for operational use.

The principles of contrail formation and dissipation are reviewed. Methods are described for predicting the occurrence of contrails and for estimating their persistence in a form suitable for weather station use. Contrail 'climatology' for long-range forecasts is discussed as are factors that affect the visual detection of contrails. (Author).