Flavors of Atmospheric Rivers making landfall in Northern California

Understanding the role of climate variability in modulating the behavior of landfalling Atmospheric Rivers (ARs) is important for seasonal and subseasonal predictability. We examine ARs hitting the Northern California coast over a 65-year period using observations of synoptic-scale circulation, high-resolution precipitation, and a long-term AR detection catalog to quantify distinct flavors of ARs making landfall at a single location. We demonstrate how dramatically different atmospheric states evolve into a landfalling AR along distinct pathways that are modulated by interannual and subseasonal modes of large-scale climate variability. Different configurations of climate variability modes are shown to produce ARs having different characteristics in terms of integrated vapor transport, wind fields, and landfall orientation. Analysis of extreme precipitation patterns in a topographic setting reveals hydrometeorological differences resulting from these different flavors of Atmospheric Rivers. We also examine the prevalence and conditional probability of AR occurrence during different phases of common teleconnection indices and find that some modes offer a potentially useful degree of predictability. Other modes are less influential in determining if an AR will occur, but remain influential in determining the flavor of an AR.