Three weather centrals – the US Strategic and Tactical Air Force (USSTAF), Met Office (roughly the equivalent of the US civilian weather bureau), and the Royal Navy – provided predictions for D-day. It was Stagg’s task to meld them into a single forecast to which all agreed. Lead briefers from each met with Stagg and his deputy, Yates, on secure telephone conference calls an hour or two before Stagg was to brief Ike and his commanders. The calls were as stormy as the weather proved to be.
USSTAF, located at 8th Air Force Headquarters at Bushy Park, was dominated by Irving Krick, former chair of the meteorology department at Caltech, who believed that weather could be forecast weeks in advance, that weather patterns repeated themselves, and that historic weather maps held the key to predicting the next day’s weather.
The Met’s Central Forecasting Office, located at Dunstable north of London near the code-breaking center at Bletchley Park, was led by Sverre Petterssen, a Norwegian who’d studied weather front theory under atmospheric physicists of the famed Bergen school and who’d chaired the meteorology department at MIT. Petterssen and Krick were bitter rivals and argued endlessly. Petterssen’s colleague was C.K.M. Douglas, who intuited the theory of cold fronts as a pilot during WWI, whose knowledge of weather history over the Channel was encyclopedic, but whose presentations were often difficult to follow.
The Royal Navy’s forecasters were sequestered deep underground in the Citadel in London. Its principal briefers, Instructor Lt. Commander Geoffrey Wolfe and Instructor Lt. Lawrence Hogben, bore stellar academic credentials and experience at sea. Their analyses shaded the forecast either toward USSTAF’s or Met Office’s view. Joining them were two American Air Force lieutenants both geologists, Charles Bates and John Crowell, whose duty it was to forecast wave heights on the invasion beaches. If they were wrong, thousands would drown.
Stagg and Yates convened their conference calls from half a Nissen hut next to Southwick Manor, Ike’s advanced headquarters. Often they had to run from their phones to make the Supreme Commander’s meetings.