MOISTURE EFFECTS ON SOARING THERMAL FORECASTS

Abstract

Sailplane pilots preparing for recreational or local weekend soaring as well as for cross-country flying need or want to know trigger temperature and time of occurrence, height of thermals and thermal strength. The contest pilot has this information fumished by a formally trained meteorologist after an exhaustive examination of meteorological data not available to the recreational soaring pilot. My 1991 paper, "Do-It-Yourself Soaring Thermal Forecasting" presented a simple, easy to use method, including a single page reproducible forecasting form, enabling the enthusiast to reach a "go" ot "no-go" decision in less than 10 minutes before driving to the gliderport. The system has proven correct 97% of the time in the southwestem United States as well as Istanbul, Turkey as reported at the XXII OSTIV Congress, Broiling, Sweden in 1993, Aslan, et al, (1993). This paper records further findings since the publication of my original paper. Of particular interest are the discoveries and quantification of the effect of moisture on both thermal altitudes and trigger temperatures. The result is an improved forecast form including cloudbase forecasting. This updated method is based on analysis of recorded forecasts and flight results of 480 of my flights over an eleven-year period.