 In 1973 the European Centre for Medium-Range Weather Forecasts (ECMWF) was formed, and Wiin-Nielsen was appointed as its first director in January 1974.In 1979, the 8th World Meteorological Congress appointed him to be the United Nations' World Meteorological Organization's third Secretary-General, so he left ECMWF at the end of that year.He served from 1 January 1980 to 31 December 1983.