On the potential use of weather types to describe the interannual variability of annual maximum discharge across the conterminous United States

Weather types or weather regimes represent the dominant modes of large-scale atmospheric circulation patterns and have been used to understand and explain the physical mechanisms of different weather events. While there have been many studies that analyse the changes in extreme climate events through the lenses of weather typing, there is a lack of studies that attribute changes in flood extremes to changes in weather regimes. Here we examine the potential applicability of weather types as predictors of flood extremes. For 4535 streamgages across the conterminous United States, we employ a statistical attribution approach to model the seasonal and annual maximum discharge, utilizing five weather types with distinct synoptic features. Although there are regional patterns in the relationship between weather types and the major climate drivers of flooding, our results show that the frequency of weather types does not provide enough information to model the interannual variability in the magnitude of flood peaks across the conterminous United States. We investigate the potential applicability of weather type frequencies as predictors for modelling peak discharge across the conterminous United States. Although there is a statistical relationship between weather type frequencies and precipitation and temperature, our results show that the frequencies of weather types have limited skill as predictors for the modelling of the interannual variability of seasonal and annual maximum streamflow.image