Today would have been the 70th anniversary of D-Day, if not for an unfavorable weather forecast. In 1994, Lawrence Hogben wrote for the London Review of Books about his experience 50 years prior trying to predict the weather that would determine the date of the attack. He was 28 at the time; after receiving a Distinguished Service Cross for his time in the Royal Navy, he became part of a meteorological committee for advising Dwight Eisenhower. There were three teams of two men: Hogben and Geoffrey Wolfe from the Royal Navy, as well as pairs selected from the United States military and the Met Office. James Stagg, from the British Royal Air Force, was responsible for mediating the three teams and reporting their decisions to Eisenhower.
Hogben's LRB account describes the specific meteorological circumstances the military required for the landing, saying:
That left just four possible days: 5, 6, 19 or 20 June. We worked out the odds on the weather on any one of these four dates conforming to requirements as being 13 to one against. So meteorologically, D-Day was bound to be a gamble against the odds.
But predictions had to be made. Two-day forecasts, understandably, proved to be more reliable than those made five days out, so the ships and troops had to be ready to go on short notice. As the first window in June approached, Eisenhower planned to launch on the June 5, and backed by a favorable forecast from the U.S. military team, "they were for ‘go’ on Monday the 5th; the cautious Met Office were for ‘no go’; so were the pragmatic Royal Navy."
As Sunday the 4th slipped into early Monday morning, Eisenhower and meteorologists watched the weather.
At a hairy 4 a.m. meeting on Sunday morning, faced by a unanimous prediction of strong winds, low clouds and rough seas for the Monday, Ike postponed the operation for 24 hours, only two hours before the main body was due to sail ... The decision had been an emotional drain on all the participants, military and meteorological, and the whole nerve-racking process had now to continue for yet another day.
The postponement proved crucial as a storm swept in. But the 6th, the last option for several weeks, was just a day away, and a decision had to be made. The U.S. military team again voted "go" and the Met Office stuck their guns with "no go." It was Hogben and Wolfe who swapped sides, giving the "go's" the majority and setting the stage for June 6: D-Day.
And we all know now how that turned out: "The gamble that the weather would be both suitable and forecastable had come off." How slim was the margin for one of the most important attacks in history? If they hadn't given a "go" for the 6th, the next option for the Normandy Landing was June 19th. On the 17th, all three teams predicted there would be fine weather that day, only to be what could have been disastrously wrong when a massive storm hit.
Writing in 1994, Hogben considered how much meteorological technology had improved.
For shorter periods, the accuracy of today’s forecasts is most impressive. In 1944 we only just got the most important weather forecast in history right. But we steered the invading army away from a potential disaster at sea and helped to make ultimate victory feasible.