Sverre Petterssen, the Bergen School, and the Forecasts for D-Day

Abstract

The beginning of the end of World War Two in Europe depended on what were arguably the three most critical forecasts in history -- two successful ones by the Allies and one failure by the Germans. On the Allied side, six meteorologists working in three different teams were responsible for the D-Day forecasts. The American team used an analogue method that compared the current weather with past conditions. Their forecast was overly optimistic and would have resulted in disaster on June 5, 1944. The British Admiralty and the British Meteorological Office urged delay. They were aided by the brilliant Norwegian theoretician Sverre Petterssen (1898-1974), a giant in the field of weather analysis and forecasting and an international leader in meteorology during the mid-twentieth century. In the wee hours of June 5, beneath the storm-drenched skies of England, the Allied forecasters advised General Eisenhower that a very short break in the weather would allow the invasion to proceed. On Tuesday, June 6, 1944, under barely tolerable conditions, the largest amphibious landing force ever assembled landed on the beaches of Normandy. Ironically the German meteorologists, aware of new storms moving in from the North Atlantic, had decided that the weather would be much too bad to permit an invasion attempt. The Germans were caught completely off guard. Their high command had relaxed and many officers were on leave; their airplanes were grounded; their naval vessels absent. This paper focuses on Petterssen’s early career and contributions to the war effort, highlighting his role as the only Norwegian-trained meteorologist involved in the contentious forecasts for D-Day.