Exploring the boundary of skilful seasonal forecasts for extreme storms over the North-Atlantic (EX-Storms)

西北大西洋强烈的天气尺度风暴事件正在影响英国和中欧西部冬季（DJF）。在2021/22年度的最后一个季度，损失金额约为36.1亿欧元。这些破坏性的罕见事件与北大西洋气候系统中强风暴气旋的发展有关。该项目将探索机会，在11月冬季风暴季节之前提供技术和有用的冬季风暴季节预测。因此，它将探索和了解我们预测它是否会是一个活跃季节（严重事件的数量）的能力，我们是否可以在发布预测时对预测有信心，以及这种信心的原因是什么。对即将到来的冬季风暴季节预测的可用性取决于a)我们对导致风暴变化的因素的理解，以及b)我们对下一季节的预测如何依赖于这些因素的理解。该项目将探讨一个潜在的关键因素及其在导致损失和损害的严重事件的预测技能中的作用。操纵北大西洋和欧洲气候条件的一个关键因素是大气条件（尤其是其斜压性）受到海面温度异常模式的影响。所谓的（在秋季/冬季）重新出现的温度异常（从夏季开始）将提供一种从夏末/初秋到冬季（通过气候系统缓慢变化的组成部分）记忆传输的潜在机制，并最终导致极端风暴活动。季节性预报套件的最新发展已经存在，用于预测这些海洋再次出现的事件，本项目将探索它们在现实中控制风暴季节变化方面的作用，并量化它们在获得模式领域预测技能方面的潜在作用。《前风暴》将采用一种新颖的方法（UNSEEN，即由申请人首创），利用来自百年季节和十年后播（多成员集合）的未实现但物理上一致的事件来探索影响冬季风暴活动水平的物理途径。这是第一次，前风暴将探索我们目前的能力在多大程度上允许对即将到来的严重风暴风险进行季前观察。

Severe synoptic-scale windstorm events in the Northwest Atlantic are affecting the UK and western Central Europe in winter (DJF). Damages in the magnitude of ca. EUR 3,610 million were recorded for the last season in 2021/22. Those damaging, rare events are linked to the development of strong storm cyclones in the climate system of the North-Atlantic. This project will explore the opportunity to provide skilful and useful predictions of the winter storm season ahead of the season in November. Thus, it will explore and understand our ability to predict whether it will be e.g., an active season (number of severe events) or not, whether we can have confidence in the forecast at the time of it being issued and what the reasons for this confidence would be. Usability of predictions of the upcoming winter storm season depends a) on our understanding of the factors leading to the variability of storms, and b) on our understanding how a forecast for the next season will depend on these factors. This project will explore one potential critical factor and its role for the forecast skill of severe events leading to loss and damage. One crucial factor of steering the climatic conditions in the North-Atlantic and Europe is the forcing of the atmospheric conditions (and here especially its baroclinicity) from anomalous sea-surface temperature patterns. So called re-emerging (in autumn/winter) temperature anomalies (from summer) would provide a potential mechanism for memory transport (via slow-varying components of the climate system) from late summer/early autumn to winter and finally resulting in extreme storm activity. Recent developments in seasonal forecast suites to forecast those oceanic re-emerging events are existing and this project will explore their role in steering variability of the storm season in reality as well as to quantify their potential role in gaining forecast skill in the model domain. EX-Storms will apply a novel approach (UNSEEN, i.a. pioneered by the applicant) to use non-realised but physically consistent events from century long seasonal and decadal hindcast (multi-member ensembles) to explore this physical pathway influencing the winter storm activity level. For the first time, EX-Storms will explore how far our current abilities allow for a pre-season view on the upcoming risk of severe storms.