Croatian Meteorological and Hydrological Service DHMZ

About computer-based automated forecasts

Weather forecasts can be either subjective or objective. Subjective forecasts are prepared by a meteorologist (forecaster) based on various available observational data, outputs from multiple forecasting models, as well as their own experience. Forecasting models and objective forecasts are developed and produced by meteorologists specializing in numerical weather prediction.

An objective, or computer-based, forecast is the direct output of an atmospheric forecasting model (e.g. ECMWF or ALADIN). The weather symbol is determined from the forecast cloud cover at a given time and the accumulated precipitation in the preceding period up to that time. Air temperature and wind forecasts are taken directly from the model at that time, without adjustments by a forecaster. More about the ALADIN model can be found here, and about ECMWF at www.ecmwf.int.

For these reasons, objective and subjective forecasts may differ significantly. Therefore, direct objective computer-based forecasts should be interpreted as one of the available sources of information and compared with other available objective and subjective forecasts. It should also be kept in mind that forecast reliability decreases as the forecast range increases.