## 1 Introduction
### Impact of Climate Change on Wind  
The world has warmed over the last 50 years, mainly due to anthropogenic activities. The rising temperatures and the associated threats, particularly the frequency and intensity of extreme events, are the most concerning ones [13; 14]. Europe has experienced several extreme events since the start of the 21 st century, including the floods of 2002, 2013, 2021 and 2024 [15].  
Among these extreme events, extreme winds caused one of the largest economic damages to Europe. According to MunichRe (international insurance group), natural disasters caused losses of USD 320 bn in 2024. Extreme meteorological events, including winds, were responsible for 93% of overall losses and 97% of insured losses [16]. Other sectors also rely on knowledge of extreme winds like infrastructure construction, afforestation, wind power, etc. [13]. Due to the growing demand of these sectors, assessments of the frequency and intensity of extreme wind events are very important, particularly in the future under climate change. The common notion is that wind-speed alterations under climate change might be generally insignificant.  
Many broad-scale assessments (e.g., IPCC AR5, IPCC 2021) report low to medium confidence that average near-surface wind speeds will undergo large or consistent trends in mid-latitude regions. Several modeling studies suggest that any future changes in typical or seasonal-mean wind speeds could be small compared to temperature or precipitation changes [17].  
However, storm-related extremes can still strengthen, regardless of modest mean-wind shifts. For instance, extratropical cyclone intensification or poleward storm-track shifts [18] may cause more frequent and stronger peak wind episodes. A shift was found that increases both the intensity and frequency of high-impact windstorms in northern and central Europe, particularly under higher warming (SSP5-8.5) [19]. Thus, from an impact/risk viewpoint, extreme-wind events potentially become more damaging, even if long-term averages remain relatively stable [18].  
The Second Assessment of Climate Change for the Baltic Sea Basin (BACC II) confirms that observed average wind speeds across the Baltic region display multi-decadal fluctuations rather than robust linear trends [20]. In future projections, the ensemble of earlier RCM (Regional Climate Model) runs indicates fairly small changes in mean wind speeds [17; 21; 22]. Yet BACC II also stresses that extreme wind speeds or storm episodes may well intensify, especially north of 55\({}^{\circ}\) N. While the overall significance of these changes varies across model ensembles, they do not always align with insignificant mean-wind shifts.  
Figure 2: Location of Nowakowo and Elblag gauging stations (blue triangles, based on [12]).  
BACC II also highlights that even small wind changes can have greater coastal impact under rising sea levels. Projected sea-level increases in the Baltic Sea (e.g., around 0.3-0.8 m by late century) amplify storm-surge risks [23]. Consequently, marginal changes in average wind speeds can still become crucial if storm surges strike at higher baselines. Similarly, [PERSON] and [PERSON] [13], using 12 km Euro-CORDEX data, found that wind changes remained fairly modest, but local extremes could become slightly more frequent, especially in coastal/ mountainous areas. For example, an event historically expected once every 30 years might recur every 20-25 years by 2070-2100.  
Consequently, focusing solely on insignificant average-wind changes misses the more critical possibility that storms (and thus peak wind speeds) may become stronger or more frequent. Therefore, adaptation planning around ports, offshore wind infrastructure, and flood defenses in the southern Baltic region must not disregard extreme-wind scenarios. Considering this, this study was conducted to model the wind surges in the Vistula Lagoon using the HEC-RAS model.