AN ASSESSMENT OF THUNDERSTORM PROBABILITY FORECASTING SKILL

An analysis of the 11-year (1983-1993) skill of subjective 24-h thunde rstorm probability forecasts made by staff and students at the State U niversity of New York at Albany is presented. Skill is measured relati ve to the long-term National Weather Service climatology of thunder he ard at 10 U.S. cities using the well-known Brier verification score. T he 11-year average skill was 21.8% (standard deviation of 3.9%), and t he annual increase in skill was a disappointing 0.1%. The sample corre lation coefficient between the frequency of thunder events and the yea r-to-year variability of forecast skill was 0.53 for all cities combin ed.