Weathermen of D-Day - The Most Important Forecast in History

Added: 2026-05-30

[00:00:08]A quick word on this week's sponsor, the hotly anticipated Second World War film, Pressure.

[00:00:14]Set in the tense final days before D-Day, Pressure follows Allied commanders as they wrestle with one of the most consequential decisions of the Second World War. Brendan Fraser stars as General Dwight D. Eisenhower. Damen Lewis plays General Montgomery and Andrew Scott plays meteorologist James Stag, the man tasked with predicting if the weather will doom the invasion before it begins. Pressure releases in theaters on Friday the 29th of May. The Western Allies invaded Normandy on the 6th of June 1944. With the success of Operation Overlord far from a given, the landing craft and duplex drive swimming tanks were tossed around by rough seas, sinking many before they reached the shore. Overcast skies limited close air support and hampered the pre-invasion aerial bombardment.

[00:01:03]Yet, despite these difficulties, the Allies managed to establish a fern beach head by the end of D-Day.

[00:01:11]But why did they choose to land in less than ideal conditions which contributed to high casualties, especially on Omaha Beach?

[00:01:19]In this video, we will examine the crucial decisions that were made prior to the invasion and explain why the 6th of June and not any other date will go down in history.

[00:01:32]Planning for Operation Overlord began after the Casablanca Conference in January of 1943.

[00:01:39]Beginning in March, Lieutenant General Frederick Morgan of the British Army was assigned as Chief of Staff, Supreme Allied Commander with the expectation that the operation would commence on the 1st of May, 1944.

[00:01:54]Morgan's initial plan formed the basis for the eventual invasion.

[00:01:58]It identified Normandy as the primary landing point, calling for a massive deception operation and advocated for the use of artificial harbors along with airborne landings.

[00:02:10]However, Supreme Allied Commander Dwight Eisenhower and General Bernard McGomery, commander-in-chief of Allied ground forces, believed not enough men were committed to the initial assault.

[00:02:22]Cenamed Operation Neptune. Morgan's plan called for only three seaborn divisions with two airborne divisions to make the attack.

[00:02:32]Eisenhower and Montgomery revised the plan to involve five seaborn divisions and three airborne divisions in order to ensure proper weight of numbers and firepower.

[00:02:43]This would also allow the divisions earmarked for the assault to get in extra training.

[00:02:50]However, the decision forced the delay of Overlord by a month in order to requisition more landing craft.

[00:02:57]This would not have been a problem except May of 1944 had been a month of perfect weather conditions. Early June would not be the same.

[00:03:09]The date for the invasion was set for the 5th of June 1944.

[00:03:14]With everything in place to launch Operation Neptune, the only variable left was the weather. General Morgan and the rest of the Allied planners had set strict conditions on which days the invasion could be launched.

[00:03:29]A full moon to allow for illumination at night for aircraft, especially the vital airborne landings. This would also provide the highest and lowest possible tides.

[00:03:40]Low winds and calm seas to make it easier for the landing craft and DD tanks to wade ashore.

[00:03:47]Clear skies devoid of cloud cover to allow allied aircraft to provide support to the landings.

[00:03:55]17 hours of daylight to allow as many troops to come ashore during the day.

[00:04:00]an inshore wind to blow smoke away from the areas targeted by the pre-invasion naval and aerial bombardment.

[00:04:09]The man responsible for determining whether these conditions could be met was group Captain James Stag of the Royal Air Force, General Eisenhower's chief meteorological officer.

[00:04:21]The Supreme Allied Commander described Stag as a daer, but Canny Scott, who fully understood the responsibilities he had been given.

[00:04:30]Stag was not a meteorologist by trade, nor a soldier. He had originally worked as a geoysicist before the war and was given the title group captain in the RAF's volunteer reserve to lend him the necessary military authority.

[00:04:45]from his post at Sodic House, which served as Supreme Headquarters Allied Expeditionary Force. Stag spent months pouring over meteorological data sent to him from various weather posts across the Atlantic Ocean.

[00:04:59]On the 1st of June 1944, general embarcation for the invasion began with men and material being loaded onto transport while Royal Navy and US Navy warships prepared to sorty from Scappa Flow in the Orgny Islands.

[00:05:15]Throughout April and May, Eisenhower had been continually testing Stag and his weather team by demanding 3-day forecasts which were then checked against reality.

[00:05:26]So far, Stag and his team had passed these tests, but on the eve of D-Day, he began to receive conflicting data.

[00:05:35]Deep depressions had been detected forming in the North Atlantic, which would indicate rough seas, but the different American and British meteorological departments disagreed on what this meant for the invasion.

[00:05:48]On the afternoon of the 1st of June, Stag informed Major General Harold Bull, Eisenhower's assistant chief of staff, that the situation is difficult and complex.

[00:06:00]With everyone in southern England on edge, Bull lost his temper. For heaven's sake, Snack, get it sorted out by tomorrow morning before you come to the Supreme Commander Conference. General Eisenhower is a very worried man.

[00:06:16]The decision on whether to proceed with the invasion rested solely upon Eisenhower's shoulders.

[00:06:23]The Supreme Commander had three basic options. Launch the operation, launch after a 24-hour provisional postponement, or cancel and await developments after 2 weeks.

[00:06:35]The 24-hour postponement was considered by many to be the riskiest option.

[00:06:40]As this decision would need to be taken at the last minute, this meant that the ships already headed for Normandy would have to return to port.

[00:06:49]The warships leaving Scapper Flow would have to do the same. But this could only be done once without needing to refuel.

[00:06:56]Above all else, the chances of the invasion fleet being spotted by enemy reconnaissance aircraft or patrol ships would increase exponentially.

[00:07:06]Eisenhower himself worried about his men. He was concerned that a postponement would cause the soldiers in the first waves to be stuck aboard the cramped transport ships for too long. He did not want them to lose their fighting edge.

[00:07:22]At the morning conference at 10:00 a.m.

[00:07:23]on the 2nd of June, Stag was forced to report that he did not have any new developments on the weather, much to the despair of Eisenhower and his staff.

[00:07:34]The decision to postpone or cancel the invasion had to be made by the following evening. or it would be too late to recall the ships already on route to Normandy.

[00:07:44]The invasion would have to go ahead regardless of the conditions.

[00:07:49]Stag once again canvased his staff and once again found a deadlocked consensus.

[00:07:55]The British meteorological teams were nervous about the prospect of storms while the Americans were optimistic that the operation could proceed.

[00:08:04]The chief meteorological officer later remembered, "Had it not been fraught with such potential tragedy, the whole business was ridiculous.

[00:08:13]In less than half an hour, I was expected to present to General Eisenhower an agreed forecast for the next 5 days, which covered the time of launching the greatest military operation ever mounted.

[00:08:25]No two of the expert participants in the discussion could agree on the likely weather, even for the next 24 hours.

[00:08:33]At the 9:30 p.m. evening conference on the 2nd of June, Eisenhower began the proceedings with, "Well, Stag, what have you got for us this time?"

[00:08:43]Trusting his gut, Stag responded.

[00:08:46]The whole situation from the British Isles to Newfoundland has been transformed in recent days and is now potentially full of menace.

[00:08:55]He described a bleak picture of the weather for the 4th and 5th of June.

[00:09:00]The officers present could not believe this forecast, some glancing out the window at the picture perfect summer day.

[00:09:08]When asked by Eisenhower if the situation would improve on the 6th or 7th of June, Stag responded plainly. If I answered that, sir, I would be guessing, not behaving as your meteorological adviser.

[00:09:22]The Supreme Allied Commander adjourned the conference without making a decision, waiting until the following day for more data.

[00:09:33]Stag's intuition proved to be correct.

[00:09:36]On the morning of the 3rd of June, barometers began to fall across the North Atlantic while the weather post in Ireland reported gale force winds and low cloud cover. Armed with this knowledge, he recommended Eisenhower postpone the invasion.

[00:09:52]With a heavy heart, the order went out for a provisional postponement.

[00:09:58]The warships and convoys were turned around while destroyers went out to retrieve any landing craft without radios and shepherd them back support.

[00:10:08]Operation Neptune rested on a knife's edge. If the weather did not improve in the next 48 hours, the invasion would have to be pushed back by 2 weeks when tidal conditions would be right again.

[00:10:20]Morale and secrecy were in jeopardy after so much careful planning.

[00:10:28]Stag awoke on the morning of the 4th of June to another beautiful day with no wind.

[00:10:34]The horrified chief meteorological officer wondered if he had forecast wrong and could not face his fellow officers at breakfast.

[00:10:43]However, he felt some measure of relief when the predicted storm rolled in later in the afternoon. battering Sodic House with rain and high winds.

[00:10:55]Despite the suddenly wretched weather, Stag soon received welcome news. At the 9:30 p.m. conference, he faced the Allied leadership as a new man.

[00:11:05]Gentlemen, since I presented the forecast last evening, some rapid and unexpected developments have occurred over the North Atlantic.

[00:11:14]There would be a gap in the bad weather beginning on the evening of the 5th of June, lasting for up to 36 hours.

[00:11:22]Stag cautioned Eisenhower that the weather would not be ideal, but it would be good enough for an amphibious landing.

[00:11:29]A spirited discussion followed.

[00:11:32]Admiral Bertrand Ramsey, the commander of the naval component of Operation Neptune, made it clear that they had to decide in the next 30 minutes if the invasion would go ahead or else his warships would have to be recalled again.

[00:11:46]Air Chief Marshall Safford Lee Mallalerie, the air commanderin-chief, expressed concern that the bombers would have bad visibility and proposed cancellation.

[00:11:55]Finally, Eisenhower turned to Montgomery and asked, "Do you see any reason why we should not go on Tuesday?"

[00:12:04]Montgomery responded immediately, "No, I would say go."

[00:12:10]Eisenhower pondered for a second before saying, "I'm quite positive we must give the order. I don't like it, but there it is. I don't see how we can possibly do anything else."

[00:12:23]He ended the conference and ordered Stack to report to leadership again at 4:15 a.m. the next morning to confirm the weather.

[00:12:32]The chief meteorologist returned early on the morning of the 5th of June with a confident report. The weather forecasts had held and his recommendation stood.

[00:12:43]With wind and rain continuing to batter Southern House, Eisenhower once again pulled his staff. Montgomery was impatient to get on with it while Ramsay deferred to Lee Mallalerie.

[00:12:56]The air chief was still uneasy but finally said he was willing to proceed.

[00:13:01]The Supreme Commander smiled and confirmed his decision. Okay, let's go.

[00:13:07]The room erupted into cheering and the aids at hand quickly dashed out of Sodic House to relay the orders.

[00:13:16]A relieved Stag returned to his bedroom to grab some muchneeded sleep.

[00:13:22]Months prior, General Morgan had teased him by saying, "Good luck, Stag. May all your depressions be nice little ones, but remember, we'll string you up from the nearest lamp post if you don't read the omens right."

[00:13:36]The weather held true, and Operation Neptune went ahead as planned.

[00:13:41]As predicted by the meteorological team, the conditions were not ideal, but were good enough for the invasion of France to be a success.

[00:13:50]Stag and his staff were proven right in more ways than one.

[00:13:55]Had Eisenhower canceled the landings and gone ahead 2 weeks later between the 18th to the 22nd of June, they would have run into the worst storm in 40 years along the Normandy coast.

[00:14:07]The surge and wind was so powerful that it destroyed one of the two artificial harbors supporting the invasion.

[00:14:15]One member of Stag's staff, New Zealander, Lieutenant Commander Lawrence Hogben, later recalled, "On the 17th of June, all six of us produced a forecast for the 19th for almost perfect conditions, but the invasion would have been a complete catastrophe.

[00:14:32]As fate would have it, the 6th of June 1944 proved to be the only possible day in June that D-Day could have been carried out successfully.

[00:14:45]Thanks again to this week's sponsor, the hotly anticipated Second World War film Pressure in theaters Friday, 29th of May. Also, be sure to head over to our brand new podcast, The War Office, available on Spotify, Apple, or wherever you get your podcasts. Thanks again to our amazing patrons whose support enables us to make these videos. If you'd like to support us to keep making these videos, please join our Patreon at patreon.com/theoperations room and get access to exclusive benefits such as early access to videos add and sponsor free. We'd love to have you as part of our community and really appreciate your support.