Numerical weather prediction

Research on numerical weather prediction is conducted at FMI mainly within the framework of the international ACCORD (A Consortium for Convection-scale Modeming Research and Development) consortium that develops a so-called mesoscale weather forecast model. In addition to the Finnish Meteorological Institute, 25 similar institutes from across Europe and North Africa are participating in the program. Finland's share in development work is 2-3 person-years per year.

Until 2006, the development of a regional weather forecasting system at FMI took place as part of the international HIRLAM (High Resolution Limited Area Model) program, in which the Finnish Meteorological Institute has participated since its inception (1985). The first operational HIRLAM model was introduced in 1990. The HIRLAM model with horizontal resolution of 7.5 km is still run four times a day. However, this model is no longer being developed. The operational runs with the Hirlam RCR system will be discontinued in September 2022.

In 2006 the HIRLAM program partnered with the French-led ALADIN model consortium. The HARMONIE-AROME model, which is the result of this cooperation is capable of 2.5 km horizontal resolution. Thanks to its dense resolution, the model is able to describe e.g. flow structures creating rain showers. Since its emergence, it was for years used alongside HIRLAM.

Starting from 2017, operational weather forecast model calculations at FMI have been performed as part of MetCoOp collaboration with the National Meteorological Institutes of Norway, Sweden and Estonia, using a weather model system called MEPS (Mesoscale Ensemble Prediction System). In this system, the HARMONIE-AROME model is used to produce so-called ensemble forecasts, i.e., multiple forecasts that are produced in parallel from slightly different initial conditions and input. This kind of ensemble forecasting method can assess not only the development of the weather, but also the uncertainty associated with the forecast. Operational forecasts are currently produced every 3 hours and extend to 66 hours. Additionally, an hourly run HARMONIE-AROME-based nowcasting system producing 9 hour forecasts is in use.

The integration area of MEPS HARMONIE-AROME covers Scandinavia, while that of HIRLAM includes Europe, Northern Atlantic, parts of northwest Canada, and Russia approxmately to the Ural mountains.
Integration areas of the two FMI's limited area weather forecast models (inner MEPS/HARMONIE-AROME, outer HIRLAM).

7.3.2022