Mathematical properties of the three‐parameter log normal probability distribution are detailed. Two methods for estimation of the third parameteraare compared. The estimator ofausing sample mean, median, and standard deviation is found to be more variable and have larger bias for distributions of interest in operational hydrology than the estimator using sample mean, standard deviation, and skew. Graphical solutions for the third parameteraare presented; a single feasible value ofais shown to result when the skew estimator is used; two feasible solutions result when the median estimator is used. The smaller of the two solutions is shown to correspond to skews of less than 5.87 and hence is the desired solution in most hydrologic application
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