Novel Extended-Range Storm Impact Outlooks for Finland

Novel six-week climate impact outlooks are developed operationally at the Finnish Meteorological Institute in the CLIPS project (CLImate services supporting Public activities and Safety). Outlook products are aimed to support the Finnish public by increasing the preparedness of upcoming weather type changes. The outlooks are piloted and tested during 2017-2018 with the general public in a living lab, making possible continous evaluation of the skill and usefulness of the products. The outlooks are based on ensemble extended-range forecast data sets produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). Data sets are run twice a week and available up to 46 days ahead. In CLIPS, the products are provided as weekly outlooks for upcoming six weeks and there are four piloting periods divided to summer, autumn, winter and spring seasons. Each period has different variety of outlooks designed for that specific season. In this work, two novel high-impact weather products are described: thunderstorm outlook for summer season and windstorm outlook for autumn and winter seasons. Both being really challenging weather phenomena to predict even some days ahead, simplified methods for developing these weekly outlooks are used. In thunderstorm outlook, weekly climatology is compared to CAPE anomaly forecast and windstorm outlook is a combination of wind speed and pressure fields. Here, we present results of the accuracy and prediction skill of the novel outlooks as well as the feedback and improvement ideas received from the piloting group.