What are medium-range weather forecasts?

Short-range forecasts

Forecasting the weather for tomorrow and up to the next few days is a task for the national meteorological services. Will outdoor work be possible on the building site, or should under-cover work be planned? Will there be ice or snow on the roads tomorrow? What about the day after?

Medium-range forecasts

A ship leaves Tokyo to sail to San Francisco. Its trip will take ten days. What route should it follow to complete the trip in the shortest time, with maximum saving of fuel, avoiding strong head winds, and heavy seas which could damage the cargo? Its owners have a ship-routeing contract with a European Meteorological Service.

Météo France wants to help Electricité de France to plan exchange of electric power with neighbouring countries for the coming week.

A particularly high tide is expected next week. Low air pressure, especially if accompanied by on-shore winds, could cause severe flooding. What is the expected weather? Are special precautions required?

Making useful weather forecasts for a week or so ahead requires the most sophisticated numerical models, the most complete database of weather observations, and the most powerful computers. Complex scientific and technical problems must be solved. Recognising the economic and social benefits to be derived from more accurate medium-range forecasts, the European States agreed to combine their scientific and technical resources in this aspect of weather forecasting to establish the European Centre for Medium-Range Weather Forecasts (ECMWF).

ECMWF provides its numerical products to the meteorological offices of the Member States via a dedicated telecommunications network. The Member States use these products to prepare medium-range forecasts for end users.

A selection of the most useful products of the Centre's forecasting system is made available to all countries of the world via the Global Telecommunications System, operated by the World Meteorological Organisation.