Potential impacts of Tropical Storm Delta in the Canary Islands under warmer ocean conditions

This work analyzes Tropical Storm Delta (2005), its extratropical transition and its associated impacts, had it developed over ocean temperatures 2 ºC higher than those given, characteristics of a warmer future climate. The focus will be on the impacts of the cyclone on the Canary Islands (Spain) and how they would change in this scenario due to the influence of warmer sea surface temperatures (SSTs). To this end, two simulations performed with the high-resolution HARMONIE-AROME model are considered: a control simulation based on initial and boundary conditions from the ERA5 reanalysis, and a warm simulation where a disturbance of +2 ºC is added to the SSTs. The economic impact is studied employing data from the Spanish Insurance Compensation Consortium and following their official criterion to consider regions at risk due to atypical cyclonic storms. The results show that Delta becomes a deeper and more intense cyclone in the warmer scenario, reaching hurricane status. Consequently, its extratropical transition becomes a much more severe phenomenon, with a significantly greater impact on the Canary Islands. This occurs in the type of precipitation, coastal impacts, and especially strong wind gusts, which cause a 29% increase in the potential economic losses due to Delta. These results are particularly relevant, since they quantify the increase in economic damage caused by a tropical cyclone due to the oceanic warming projected in future scenarios.