What is UNSEEN?

The UNprecedented Simulated Extreme ENsemble (UNSEEN, Thompson et al., 2017) approach is an increasingly popular method that exploits seasonal prediction systems to assess and anticipate climate extremes beyond the observed record. The approach uses pooled forecasts as plausible alternate realities. Instead of the ‘single realization’ of reality, pooled forecasts can be exploited to better assess the likelihood of infrequent events, which only have a limited chance of occurring in observed records. This method has for example been used to improve design levels of storm-surges in the river Rhine and to anticipate and understand heatwaves in China.

Recently, we applied this method to SEAS5 for the first time, with promising results for extreme precipitation over Norway and Svalbard (submitted to *NPJ Climate and Atmospheric Science*). SEAS5 is a good dataset for the UNSEEN approach because it is freely available and has a high resolution and a large ensemble compared to global climate models. To make this approach more accessible, we develop an open, reproducible and transferable workflow for the UNSEEN method using the open access SEAS5 dataset on the CDS.