Col Jeremy Green (retired), is a historian and expert on Southwick House, the Allied HQ near Portsmouth, from where Gen “Ike” Eisenhower made the decision to delay by one day. Green said initially there were huge differences between American and British and Norwegian meteorologists. And had Ike, the supreme allied commander, listened to his fellow Americans, D-day could have been a disaster.
“The Americans came here with great enthusiasm based upon an analogue system of taking the weather by a guy called Irving Krick. He basically said if you look at historical weather patterns, and if those conditions are replicated again, the same weather would occur,” said Green. “And the problem for us, the Brits, was he was briefing Eisenhower direct.”
The American military initially refused to talk to the British chief meteorologist, James Stagg, “because he was a civilian”, until Stagg was temporarily made a group captain in the Royal Air Force.
Stagg was receiving information from weather stations including, crucially, Blacksod Lighthouse in County Mayo, on Ireland’s west coast. A huge depression rapidly moving into the Channel did not augur well for 5 June, the original planned day of the Normandy invasion, thought Stagg. Krick thought 5 June was “good to go”.
Ike was living on his nerves, “smoking five packs of cigarettes a day, drinking too much coffee, eating little and sleeping less,” said Green.
With disagreements among the meteorologists, Stagg decided it fell to him to give an “unequivocal and firm opinion on the deterioration of the weather”. He told him 5 June would be overcast, stormy, with winds too strong to land troops, and cloud offering just 500ft-to-zero visibility.
His words were greeted with silence, said Green.
In the end, Eisenhower’s decision rested on Stagg’s opinion that there would be a brief “interlude” on 6 June. Eisenhower made his fateful decision. His diary records that on what should have been invasion day he awoke in the early hours to find “our little camp was shaking and shuddering under a wind of almost hurricane proportions and the accompanying rain seems to be travelling in horizontal streaks”.
Stagg had been right. If the invasion had started that morning, it would have failed.