June 6, 1944 was the historic Allied invasion of Normandy commonly known as D-Day that turned the tide of World War II. What many may not know is a meteorologist played one of the most important roles in the entire attack in what some have dubbed "the most important weather forecast in history."
This is one of my favorite pieces of weather history, but I'm no historian. Click the links on the right from History.com and Weather.com for a full story on this fascinating string of events. Here's the summarized version...
The invasion demanded perfect weather for success. Waves needed to be low for a smooth coastal landing and for boats to be able to see German underwater traps. The skies needed to have clear visibility for bombing and paratroop drops. Beaches needed to be dry so soldiers could run easily rather than get bogged down in soggy sand.
Most importantly, they needed a full moon for gliders to land the night before. The full moon provided a light source at night, and they only had a three day window for that, but they also needed clear skies. Because of the need for a full moon, the options for an invasion date were very few, and if the meteorological conditions weren't good enough for this June window, they would have needed to wait weeks before they could try again.
The original date for the invasion was going to be June 5, but Allied meteorologists led by Group Captain James Stagg strongly advised a last minute postponement. A storm was rolling through that day and conditions were not good.
It was, however, looking good that June 6 would have a clear window of opportunity. Stagg advised Allied Supreme Commander Dwight Eisenhower to launch the attack which was successful and changed the future of the war in Europe. German meteorologists had a more stormy (and incorrect) forecast for June 6 that led Nazi military to think an invasion very unlikely for most of that month, so the Germans were unprepared for an assault.
After the war, Sir James Stagg was knighted and commended on many levels inside and outside of the British military.
There's so much more to this tale. Click the links and learn more about this incredible time in weather history. To this day, military meteorologists play a pivotal role in all branches of the armed forces.