Flood frequency analyses and probable maximum flood (PMF) studies are integral aspects of hydrologic design requirements and provide for the establishment of policies and risk assessments to both people and property. Precipitation frequency analysis and probable maximum precipitation (PMP) estimation are often included in flood frequency and PMF computations, respectively. Both approaches, probabilistic and deterministic, have limitations that would benefit from further research. For example, both approaches often fail to account for nonstationary conditions and spatial and multivariate effects. The impact of nonstationarity on hydrometeorological extremes is difficult to quantify yet important to understand because these changes may have significant implications for risk analyses and new infrastructure design as well as operations and management of existing infrastructure. For PMP estimates, basin-specific studies or general reports (such as the NOAA Hydrometeorological Report series) have been completed for decades, yet there remains a significant amount of misunderstanding and confusion within the water resources community as to development of these estimates as well as the limitations of the usage. The need for a detailed understanding of the physical processes of the atmosphere is great, as precipitation values from either precipitation frequency analyses or PMP estimates provide the basis for almost all flood hazard studies. Values that are too high can cause an overestimate of flooding and result in costly and unnecessary modifications to dam or levee structures. Underestimates of precipitation, conversely, could generate a higher risk of hydrologic failure, which could be devastating to communities near any faulty projects. Ultimately, these precipitation estimates and flood analyses must be communicated to policy makers at all levels of the government, as well as any at-risk populations. Including estimates of uncertainty in frequency analyses and PMP may increase the usefulness of such studies to decision-makers. This session covers a vital subject that demonstrates the critical link between meteorologists and engineers, as well as the general public, with regard to the impacts and risks in the weather and water enterprise. This session is expected to focus on new and emerging methods for probabilistic and PMP analyses and the estimation of hydrometeorological extremes. Subjects within this topic can include frequency analyses, uncertainty quantification, analysis of extreme storm events, case studies addressing climate and land-use changes, and communication of flood risk to the public.

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