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D-Day: Saved By A Weather Forecast
June 5, 2022 at 11:25 AM EDT
By WeatherBug Meteorologist, Alyssa Robinette
On this day in 1944, the famous D-Day invasion took place, and weather played a big part in the day and outcome.
More than 160,000 Allied troops landed along a 50-mile stretch of heavily armored French coastline on June 6, 1944, to fight Nazi Germany on the beaches of Normandy, France. More than 5,000 ships and 13,000 aircraft supported what became known as the D-Day invasion. At the end of the day, the Allies gained traction in Continental Europe, but more than 9,000 Allied soldiers were killed or wounded. While the cost in lives on D-Day was high, their sacrifice allowed other Allied soldiers to start the slow, hard trudge across Europe and eventually defeat Adolf Hitler’s troops. Planning for the operation began in 1943, but the success of the mission was ultimately dependent on an unknown variable: the weather.
When picking a date to invade, it was crucial to have a full moon and a low tide at dawn. The full moon would help illuminate obstacles and landing places for gliders, while a low tide would expose the elaborate underwater defenses installed by the Germans. This created a narrow three-day window in the beginning of June, or else they would have to wait until the middle of June. The first date chosen by Allied Supreme Commander Dwight Eisenhower was June 5th.
However, the massive Normandy landings also required optimal weather conditions as rough seas and high winds could capsize landing craft and sabotage the water assault. Wet weather could also bog down the army and thick cloud cover could obscure the necessary air support.
The critical task of predicting the weather for the English Channel fell to a team of forecasters from the Royal Navy, British Meteorological Office and the U.S. Strategic and Tactical Air Force. Observations from Newfoundland taken on May 29th reported changing weather that may arrive by the proposed invasion date. The British forecasters predicted the stormy weather would indeed arrive on June 5th based on the observations and their knowledge of the English Channel weather. Relaying on a different forecasting method based on historic weather maps, the American meteorologists believed that a ridge of high pressure would deflect the advancing storm front and provide clear, sunny skies.
It was ultimately up to Group Captain James Stagg, the Operation Overlord’s chief meteorological officer, on which forecast was most likely. He believed that cloudy, rainy weather was only a few hours away on June 4th, and decided to follow his fellow British colleagues’ predictions and recommend a postponement. Knowing the weather could make or break the operation, a reluctant Eisenhower agreed to delay D-Day by 24 hours.
German forecasters had also predicted the stormy conditions that Stagg and his fellow Brits had. However, the German’s chief meteorologist predicted that rough seas and strong winds were unlikely to weaken until mid-June. Armed with that forecast, Nazi commanders believed that it was impossible that an Allied invasion was imminent, and many left their coastal defenses to participate in nearby war games.
Meteorologists for Germany relied on less sophisticated data and forecast models than their Allied counterparts. The Allies had a more robust network of weather stations in Canada, Greenland and Iceland, with weather ships and weather flights over the North Atlantic and observations by secret agreement from weather stations in Ireland. As a result, this allowed the Allies to detect the arrival of a lull in the storms that would allow for the invasion on June 6th. Eisenhower placed his faith in his forecasters and gave the go-ahead for D-Day on June 6th.
During the initial hours of D-Day, the weather was still not ideal. Thick clouds caused Allies bombs and paratroopers to land miles off target. Rough seas caused landing craft to capsize and mortar shells to land off mark. However, the weather cleared by midday, validating Stagg and the British’s forecast. The Germans had been caught by surprise, and the tide of World War II began to turn.
Weeks later, both Stagg and Eisenhower admitted that it was a good thing that they pushed back the invasion a day. The weather over Normandy on June 5th contained too much cloud cover, winds were too strong, and waves were too high. If they were to have gone on June 5th, they would have lost the element of surprise and potentially the invasion itself.
Source: Army.mil, History.com, Wikipedia
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Image: Into the Jaws of Death. (Chief Photographer's Mate (CPHOM) Robert F. Sargent, U.S. Coast Guard, The Coast Guard at Normandy)
More than 160,000 Allied troops landed along a 50-mile stretch of heavily armored French coastline on June 6, 1944, to fight Nazi Germany on the beaches of Normandy, France. More than 5,000 ships and 13,000 aircraft supported what became known as the D-Day invasion. At the end of the day, the Allies gained traction in Continental Europe, but more than 9,000 Allied soldiers were killed or wounded. While the cost in lives on D-Day was high, their sacrifice allowed other Allied soldiers to start the slow, hard trudge across Europe and eventually defeat Adolf Hitler’s troops. Planning for the operation began in 1943, but the success of the mission was ultimately dependent on an unknown variable: the weather.
When picking a date to invade, it was crucial to have a full moon and a low tide at dawn. The full moon would help illuminate obstacles and landing places for gliders, while a low tide would expose the elaborate underwater defenses installed by the Germans. This created a narrow three-day window in the beginning of June, or else they would have to wait until the middle of June. The first date chosen by Allied Supreme Commander Dwight Eisenhower was June 5th.
However, the massive Normandy landings also required optimal weather conditions as rough seas and high winds could capsize landing craft and sabotage the water assault. Wet weather could also bog down the army and thick cloud cover could obscure the necessary air support.
The critical task of predicting the weather for the English Channel fell to a team of forecasters from the Royal Navy, British Meteorological Office and the U.S. Strategic and Tactical Air Force. Observations from Newfoundland taken on May 29th reported changing weather that may arrive by the proposed invasion date. The British forecasters predicted the stormy weather would indeed arrive on June 5th based on the observations and their knowledge of the English Channel weather. Relaying on a different forecasting method based on historic weather maps, the American meteorologists believed that a ridge of high pressure would deflect the advancing storm front and provide clear, sunny skies.
It was ultimately up to Group Captain James Stagg, the Operation Overlord’s chief meteorological officer, on which forecast was most likely. He believed that cloudy, rainy weather was only a few hours away on June 4th, and decided to follow his fellow British colleagues’ predictions and recommend a postponement. Knowing the weather could make or break the operation, a reluctant Eisenhower agreed to delay D-Day by 24 hours.
German forecasters had also predicted the stormy conditions that Stagg and his fellow Brits had. However, the German’s chief meteorologist predicted that rough seas and strong winds were unlikely to weaken until mid-June. Armed with that forecast, Nazi commanders believed that it was impossible that an Allied invasion was imminent, and many left their coastal defenses to participate in nearby war games.
Meteorologists for Germany relied on less sophisticated data and forecast models than their Allied counterparts. The Allies had a more robust network of weather stations in Canada, Greenland and Iceland, with weather ships and weather flights over the North Atlantic and observations by secret agreement from weather stations in Ireland. As a result, this allowed the Allies to detect the arrival of a lull in the storms that would allow for the invasion on June 6th. Eisenhower placed his faith in his forecasters and gave the go-ahead for D-Day on June 6th.
During the initial hours of D-Day, the weather was still not ideal. Thick clouds caused Allies bombs and paratroopers to land miles off target. Rough seas caused landing craft to capsize and mortar shells to land off mark. However, the weather cleared by midday, validating Stagg and the British’s forecast. The Germans had been caught by surprise, and the tide of World War II began to turn.
Weeks later, both Stagg and Eisenhower admitted that it was a good thing that they pushed back the invasion a day. The weather over Normandy on June 5th contained too much cloud cover, winds were too strong, and waves were too high. If they were to have gone on June 5th, they would have lost the element of surprise and potentially the invasion itself.
Source: Army.mil, History.com, Wikipedia
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Image: Into the Jaws of Death. (Chief Photographer's Mate (CPHOM) Robert F. Sargent, U.S. Coast Guard, The Coast Guard at Normandy)