Comparison of Point Precipitation Frequency Analyses of Storm-Typed Maxima and Overall Maxima for a Region in Eastern Tennessee

Abstract

In frequency analysis of point precipitation extremes, one approach that has been suggested is to segregate precipitation data by storm type. Thus, for short-duration (e.g., 2-h) extremes, only observations from convective storms would be considered in the analysis. The supposition informing this choice is that only convective events are capable of generating truly extreme 2-h precipitation depths. In this paper, annual maxima of 2-h point precipitation are evaluated for a region in eastern Tennessee using a storm-type database that identifies convective events. The use of storm typing contrasts with the standard procedure of using data from all storms to develop annual maxima series. This paper presents comparative frequency analyses of convective event and overall annual maxima series. For extremely low-probability events, predicted regional quantiles are slightly lower for convective event maxima than for annual maxima. However, differences between quantiles at individual sites vary widely. The convective event maxima series tend to have lower means, higher coefficients of variation, and slightly lower skewness (with great variability) than annual maxima series. Differences between extreme quantiles for convective event and annual maxima are correlated with differences in skewness. Overall, the differences between the regional results obtained from the convective event and annual maxima used in this study of 2-h precipitation are small, but differences at individual sites vary widely.