In 1924 Stagg became an assistant in the
British Meteorological Office and he was appointed superintendent of
Kew Observatory in 1939. In the winter of 1932/33 he led the British Polar Expedition of Arctic Canada. In the
1937 Coronation Honours, he was appointed
Officer of the Order of the British Empire (OBE) for his work as a senior technical officer with the
Air Ministry's Meteorological Office. Stagg was appointed the Chief Meteorological Officer,
SHAEF for
Operation Overlord. On 6 November 1943, he was granted an emergency commission with the rank of
group captain in the
Royal Air Force Volunteer Reserve; this lent him the necessary authority in a military milieu unused to outsiders. Stagg worked with three forecasting teams from the
Royal Navy,
Met Office and the
USAAF. The detail of the D-Day forecasts is in the accounts published by participants, including Stagg himself.
D-Day weather map showing
weather fronts on 5 June 1944 Planners of the
Normandy landings in June 1944 allowed for the tides, the time of day, and the phase of the moon – these conditions would be satisfactory on only a few days in each month. A full moon was desirable, as it would provide illumination for aircraft pilots and have the
highest tides. The landings would be shortly before dawn, mid-way between low and high tide, with the tide coming in. This would improve the visibility of obstacles on the beach, while minimising the amount of time the men would be exposed in the open. Eisenhower had tentatively selected 5 June as the date for the assault. However, at 13:00 on 3 June, 21-year-old
Maureen Flavin Sweeney was first to forecast a severe storm approaching Europe from over the Atlantic Ocean. Despite the official neutrality of Ireland during World War Two, information gathered by the Irish Meteorological Service was shared with the Allies. Mrs Sweeney received a phone call from Stagg's office asking for the readings to be checked again. The tests were re-run and her results confirmed. Stagg met Eisenhower on the evening of 4 June. Using Sweeney's forecast data, he and his meteorological team predicted that the weather would improve enough for the invasion to proceed on 6 June. The next available dates with the required tidal conditions (but without the desirable full moon) would be two weeks later, from 18 to 20 June. Postponement of the invasion would have required recalling men and ships already in position to cross the Channel, and would have increased the chance that the invasion plans would be detected. After much discussion with the other senior commanders, Eisenhower decided that the invasion should go ahead on the 6th. A major storm battered the Normandy coast from 19 to 22 June, which would have made the beach landings impossible. Allied control of the Atlantic gave Allied meteorologists an advantage in the
North Atlantic weather war for storm prediction. As the
Luftwaffe meteorological centre in Paris was predicting two weeks of stormy weather, many Wehrmacht commanders left their posts to attend
war games in
Rennes, and men in many units were given leave. German Commander Field Marshal
Erwin Rommel returned to Germany for his wife's birthday and to meet with Hitler to try to obtain more
Panzers. For his invaluable services over the D-Day period, Stagg was appointed an Officer of the US
Legion of Merit in October 1945. ==Later life==