Sverre Petterssen

Sverre Petterssen (1898–1974) was a Norwegian meteorologist, prominent in the field of weather analysis and forecasting, and an international leader in meteorology.

Early life
Born in Norway into a humble family, he paid for his higher education by working at the telegraph office, and a nursery provided by the armed forces that he joined as a recruit. He studied in Bergen where he met Tor Bergeron during a lecture, and was so impressed by his analysis of a 1922 storm that he joined the Bergen School of Meteorology in 1923.

Career
After school, he remained a weather officer in the Norwegian Air Force until 1939. He went to the US in 1935, lecturing on Norwegian meteorological theories to the US Navy and Caltech. In 1939, he was hired by MIT as head of the meteorology department, and wrote two important books there: Weather analysis and forecasting (1940) and Introduction to Meteorology (1941).

With the invasion of Norway, Petterssen returned to Europe and offered his services in England to the Met Office, on loan from the Norwegian Air Force. During World War II, he served as a weather forecaster for bombing raids and special operations.

He is most remembered for his work in what has been called the most significant weather forecast in history, the D-Day Forecast, where he contributed significantly to the postponement of D-day by one day. Three groups of meteorologists gave advice to General Dwight Eisenhower, and D-Day was originally planned for June 5, 1944. The forecast provided by Sverre Petterssen and the other meteorologists caused Eisenhower to decide at 0430 on 4 June to postpone D-day to June 6. Initially it was proposed to postpone the operation to June 19, but fortunately all three teams predicted a break in the weather on June 6.



On June 19 the worst storm to date in the century struck the English channel. If D-Day had been launched on June 5 as originally planned, the Allied casualties would probably have been much higher, and even higher if launched on June 19. On June 17 all the teams predicted perfect weather conditions for June 19, but D-day was over.