Sadeennusteet

Sadeennusteet, or rain forecasts, are predictions of precipitation for a future time period. They are a central product of meteorological services and are used by individuals, businesses, and transportation sectors to plan activities and operations.

Production and data sources: In Finland, the Finnish Meteorological Institute (FMI) is the main producer of official sadeennusteet, while other national and international agencies contribute through shared forecast models. Modern forecasts combine numerical weather prediction models with radar and satellite observations, as well as data from weather stations. Nowcasting uses high-resolution radar data to predict rain for the next few hours, while longer-term forecasts rely on ensemble model runs to estimate probabilities and a range of possible outcomes. Forecasts are routinely updated and disseminated via official websites, mobile apps, and media outlets.

Content and interpretation: A sadeennuste typically includes the probability of precipitation, expected rainfall amounts (measured in millimeters) for a forecast period, and sometimes the anticipated precipitation type (rain, snow, sleet) and its intensity. Forecast horizons commonly span nowcasting (0–6 hours), short-term (6–24 hours), and extended outlooks (1–5 days). Ensemble forecasts help convey uncertainty by showing a range of possible outcomes rather than a single value.

Limitations: Forecast accuracy declines with longer lead times and in locally complex conditions such as varied terrain or urban areas. Uncertainties arise from model resolution, data gaps, or rapid atmospheric changes, and users are often advised to consult multiple sources for decision-making.