Abstract. There are distinctive methodological and conceptual challenges in rare and severe event (RSE) forecast-verification, that is, in the assessment of the quality of forecasts involving natural hazards such as avalanches or tornadoes. While some of these challenges have been discussed since the inception of the discipline in the 1880s, there is no consensus about how to assess RSE forecasts. This article offers a comprehensive and critical overview of the many different measures used to capture the quality of an RSE forecast and argues that there is only one proper skill score for RSE forecast-verification. We do so by first focusing on the relationship between accuracy and skill and show why skill is more important than accuracy in the case of RSE forecast-verification. Subsequently, we motivate three adequacy constraints for a proper measure of skill in RSE forecasting. We argue that the Peirce Skill Score is the only score that meets all three adequacy constraints. We then show how our theoretical investigation has important practical implications for avalanche forecasting by discussing a recent study in avalanche forecast-verification using the nearest neighbour method. Lastly, we raise what we call the “scope challenge" that affects all forms of RSE forecasting and highlight how and why the proper skill measure is important not only for local binary RSE forecasts but also for the assessment of different diagnostic tests widely used in avalanche risk management and related operations. Finally, our discussion is also of relevance to the thriving research project of designing methods to assess the quality of regional multi-categorical avalanche forecasts.

中文翻译：

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罕见和严重事件预测验证中的方法和概念挑战

摘要。在罕见和严重事件 (RSE) 预测验证中存在独特的方法和概念挑战，即质量评估涉及雪崩或龙卷风等自然灾害的预报。虽然自 1880 年代该学科成立以来就已经讨论了其中一些挑战，但对于如何评估 RSE 预测尚未达成共识。本文对用于捕捉 RSE 预测质量的许多不同措施进行了全面而重要的概述，并认为 RSE 预测验证只有一个适当的技能分数。为此，我们首先关注准确性和技能之间的关系，并说明为什么在 RSE 预测验证的情况下，技能比准确性更重要。随后，我们激发了三个充分性约束以获得适当的RSE 预测技能的衡量标准。我们认为 Peirce Skill Score 是唯一满足所有三个充分性约束的分数。然后，我们通过讨论最近使用最近邻法进行雪崩预测验证的研究，展示了我们的理论研究如何对雪崩预测具有重要的实际意义。最后，我们提出了我们所说的影响所有形式的 RSE 预测的“范围挑战”，并强调了适当的技能测量如何以及为什么不仅对本地二元 RSE 预测很重要，而且对评估广泛用于雪崩的不同诊断测试也很重要风险管理和相关操作。最后，我们的讨论也与设计方法来评估区域多类别雪崩预测质量的蓬勃发展的研究项目有关。