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Weather Forecasts & D-Day

June 6, 2017

By Paul Homewood



If you think it’s wet and windy today, just give a thought to the soldiers, sailors and airmen 73 years ago, who were fighting for their lives on D-Day.

I guess that pretty much all of us are aware of the role that weather played back in June 1944, but it is still worth reading this analysis from the History Channel:


Years of detailed planning went into the D-Day invasion on June 6, 1944, but success hinged on one element that no military commander could control—the weather. In the days leading up to the invasion, Allied meteorologists delivered the most important weather forecast in history. If they got it wrong the Allies might have lost tens of thousands of men and World War II might have been lost forever.

In contrast to the bright morning about to dawn over Portsmouth, England, on June 4, 1944, gloom settled over the Allied commanders gathered inside Southwick House at 4:15 a.m. Years of preparation had been invested in the invasion of Normandy, but now, just hours before the launch of D-Day operations, came the voice of Group Captain James Stagg urging a last-minute delay. As Operation Overlord’s chief meteorological officer, the lanky Brit was hardly a battlefield commander, but the ultimate fate of D-Day now rested in his decision-making.


1944, aquatic landing craft, germans, normandy, battle at normandy, world war II, d-day, allied troopsAllied troops packed tightly into an aquatic landing craft wait for their turn to face the Germans at Normandy.Corbis


The disappointed commanders knew that the list of potential invasion dates were only a precious few because of the need for a full moon to illuminate obstacles and landing places for gliders and for a low tide at dawn to expose the elaborate underwater defenses installed by the Germans. June 5, chosen by Allied Supreme Commander Dwight Eisenhower to be D-Day, was the first date in a narrow three-day window with the necessary astronomical conditions. The massive Normandy landings, however, also required optimal weather conditions. High winds and rough seas could capsize landing craft and sabotage the amphibious assault; wet weather could bog down the army and thick cloud cover could obscure the necessary air support.

The critical, but unenviable task of predicting the English Channel’s notoriously fickle weather fell to a team of forecasters from the Royal Navy, British Meteorological Office and U.S. Strategic and Tactical Air Force, and as D-Day approached, storm clouds brewed inside the meteorological office. Observations from Newfoundland taken on May 29 reported changing conditions that might arrive by the proposed invasion date. Based on their knowledge of English Channel weather and observations, the British forecasters predicted the stormy weather would indeed arrive on June 5. The American meteorologists, relying on a differing forecasting method based on historic weather maps, instead believed that a wedge of high pressure would deflect the advancing storm front and provide clear, sunny skies over the English Channel.


Group Captain James StaggGroup Captain James Stagg


In the early hours of June 4, Stagg believed foul weather was only hours away. He sided with his fellow British colleagues and recommended a postponement. Knowing that the weather held the potential to be an even fiercer foe than the Nazis, a reluctant Eisenhower agreed in the early hours of June 4 to delay D-Day by 24 hours.

On the other side of the English Channel, German forecasters also predicted the stormy conditions that indeed rolled in as Stagg and his fellow Brits had feared. The Luftwaffe’s chief meteorologist, however, went further in reporting that rough seas and gale-force winds were unlikely to weaken until mid-June. Armed with that forecast, Nazi commanders thought it impossible that an Allied invasion was imminent, and many left their coastal defenses to participate in nearby war games. German Field Marshal Erwin Rommel even returned home to personally present a pair of Parisian shoes to his wife as a birthday present.

German Luftwaffe meteorologists, however, relied on less sophisticated data and models than their Allied counterparts, says John Ross, author of “The Forecast for D-Day: And the Weatherman behind Ike’s Greatest Gamble.” “The Allies had a much more robust network of weather stations in Canada, Greenland and Iceland; of weather ships and weather flights over the North Atlantic and observations by secret agreement from weather stations in the neutral Republic of Ireland,” he says. Those weather stations, in particular one at a post office at Blacksod Point in the far west of Ireland, proved crucial in detecting the arrival of a lull in the storms that Stagg and his colleagues believed would allow for an invasion on June 6. As rain and high winds lashed Portsmouth on the night of June 4, Stagg informed Eisenhower of the forecast for a temporary break. With the next available date for an invasion nearly two weeks away, the Allies risked losing the element of surprise if they waited. In spite of the pelting rain and howling winds outside, Eisenhower placed his faith in his forecasters and gave the go-ahead for D-Day.


Allied Supreme Commander Dwight Eisenhower speaking with troops before the invasion of Normandy.Allied Supreme Commander Dwight Eisenhower speaking with troops before the invasion of Normandy.


The weather during the initial hours of D-Day was still not ideal. Thick clouds resulted in Allied bombs and paratroopers landing miles off target. Rough seas caused landing craft to capsize and mortar shells to land off the mark. By noon, however, the weather had cleared and Stagg’s forecast had been validated. The Germans had been caught by surprise, and the tide of World War II began to turn.

Weeks later, Stagg sent Eisenhower a memo noting that had D-Day been pushed to later in June, the Allies would have encountered the worst weather in the English Channel in two decades. “I thank the Gods of War we went when we did,” Eisenhower scribbled on the report. He could also have been thankful for Stagg overruling the advice of the American meteorologists who wanted to go on June 5 as planned, which Ross says would have been a disaster. “The weather over Normandy contained too much cloud cover for Ike’s greatest strategic asset, the Allied air forces, to effectively protect the landings from German armor, artillery and infantry reserves. Winds were too strong for the deployment of paratroopers to secure bridges and crossroads inland from the beaches thus preventing German reinforcement of coastal positions. Waves were too high for landing craft to put soldiers and supplies ashore. The key element of surprise—location and time—would have been lost, and the conquest of western Europe could well have taken another year.”

I read somewhere that when people have nothing tangible to worry about, they become afraid of imaginary things.

For the snowflake generation, read climate change.

  1. Joe Public permalink
    June 6, 2017 11:45 am

    An amazing story & responsibility. Thanks for sharing.

  2. AlecM permalink
    June 6, 2017 12:00 pm

    Today is cold and wet because the temperature of the North Atlantic is low, a bit like 1944.

    It is low for two reasons: firstly low solar input energy; secondly because CO2 effects although real are almost exactly offset by the water cycle.

    The background to this is the Mie analysis by van der Hulst in 1967 and James Hansen in 1969. The sign of the 2nd AIE is the reverse of the IPCC’c claim (Van der Hulst is dead).

    The lesson is never accept any scientific claim without a century of experimental evidence.

    • June 6, 2017 3:03 pm

      AlecM writes: “———because CO2 effects although real are almost exactly offset by the water cycle.” Well said. This is worth expanding.

      The water/Hydro cycle is in essence a Rankine Cycle, operating at very low pressures due to Dalton’s Law of partial pressures.
      Briefly: 1) The boiler operates at the earth’s surface at roughly 0.1781 Lbs/sq.ins.
      2) Work is done against gravity as the water rises, being lighter than dry air in the gaseous form. (the piston, as it were) -(check the atomic weights)
      3) Excess energy is dissipated to the atmosphere during and post the point where condensation occurs ( the condenser phase).
      4) On returning to earth as rain, snow or ice, gravity provides the feed pump energy to increase the pressure and additional feed heating is absorbed from the atmosphere. Hence arriving back in the boiler as above.
      The thermodynamics of this is well known.

      Every kilogram of water evaporated, equivalent to 1 sq.m at 1 cm thick, dissipates through this process some 680 Watthrs per sq.m some of which reaching the top of the Troposphere, cutting straight through CO2.
      The energy here is so markedly greater than the purported energy associated with CO2 that one can but wonder upon the current obsession with CAGW.
      Water has provided this thermostat for millions of years. I suspect this will continue however much we argue.

      In trite terms one could say that just like you and I, the earth sweats to keep cool.

      • AlecM permalink
        June 6, 2017 4:42 pm

        Good explanation by a US trained engineer (I suspect!).

      • Jack Broughton permalink
        June 7, 2017 10:46 am

        Hate to be pedantic over relatively unimportant numbers, as the theme is right, but 1 kg water is a layer 1mm thick over 1 m2 surface (density of water 1000kg/m3). Thus, as most of the solar input is absorbed within this distance, is even more exciting than 1 cm.

  3. David Richardson permalink
    June 6, 2017 12:18 pm

    Thanks for the reminder of those events Paul. Days when computer models were a little while away and real knowledge and a feel for the weather were needed.

    I recommend “Forecast for Overlord” written by James Stagg himself (available on Amazon – other booksellers are available) to anyone with an interest in the “D” day forecasting. Events are well described in the History Channel piece, but the book is fascinating both meteorologically and politically.

    In my early days in the Meteorological Office (1960’s) there were still forecasters around who had immense experience and feel in the days with no computer model support. I went on to be a forecaster, but I don’t think I ever had anything close to the ability that these much respected guys had.

    As they say – 1944 18 to 20 year olds stormed the beaches of Normandy, now 18 to 20 year olds need a safe space to shield them from any opposing opinion.

  4. Dung permalink
    June 6, 2017 12:29 pm

    I blame Corbyn ^.^

    • AlecM permalink
      June 6, 2017 1:02 pm

      Don’t blame him; blame the Bliar who, acting for the Bilderbergers, only recruited thickos like Cobryn.

  5. June 6, 2017 1:10 pm

    I was only 5 at the time but from a coal mining family and community that suffered little in terms of loved ones lost.

    A long time before ‘Saving Private Ryan’ I was in awe and full of gratitude to individuals prepared to leave loved ones and safety behind them and travel thousands of miles to put themselves in the fighting line to save Europe from the horrors of Nazism.

    ‘Saving Private Ryan’ brought home the realism of what it must have been like more than I ever could have imagined.

  6. June 6, 2017 1:28 pm

    Well they had computers – slide rules, models ie formulae and unbiased political input.

  7. BLACK PEARL permalink
    June 6, 2017 2:36 pm

    Nice piece Paul

  8. June 6, 2017 2:46 pm

    “I guess that pretty much all of us are aware of the role that weather paid back in June 1944,”

    “…the role weather played…”

  9. Steve permalink
    June 6, 2017 3:56 pm

    Enjoyed reading that, thanks.

  10. June 6, 2017 5:01 pm

    Reply to AlecM: No. Trained by the Royal Navy in the days of slide rules and log tables! Still have my steam tables to consult; but sometimes get screwed up converting from Lbs, BTUs etc.

  11. Gamecock permalink
    June 6, 2017 7:21 pm

    ‘If they got it wrong the Allies might have lost tens of thousands of men and World War II might have been lost forever.’

    Melodramatic. The Soviets were driving west at speed. WWII would have been won regardless.

    But WWIII would have followed as we tried to get the Soviets out of France.

    • nigel permalink
      June 7, 2017 8:04 am

      Of course “what-ifs” are just a game. But…

      We do know that the Germans grossly overestimated the ability of the Western Allies to launch simultaneous amphibious attacks, and kept much of their forces in unnecessary and ill-placed reserve positions.

      If Overlord had failed, the Germans would have had sufficient forces to switch to the East to stop the Russians, who were beginning to run out of cannon fodder themselves. The V-Weapons would have pounded a demoralized United Kingdom. The Yanks would have gone home.

      Peace treaties would have broken out all over the world. Hitler, Roosevelt,Stalin, Churchill were all dying anyway.

      Then America and Germany would complete development of atomic weapons at the same time…

      • nigel permalink
        June 7, 2017 8:09 am

        Some vague animal answering to my name might be around today, as I was conceived (what a mistaka to maka) on a pre-invasion leave.

  12. June 6, 2017 7:47 pm

    So basically nothing has changed in 73 years. 😉

    We have a local Meteorologist (not a weatherman – he does it for a living advising private businesses) who is very down on the American model, but very high on the European model when forecasting storms. He still swears by the European model and claims an 80% accuracy 72 hours out. ANd he does better than any local weatherman AND the NWS out of Wakefield (just a stones throw from this area).

  13. June 6, 2017 9:03 pm

    Reblogged this on WeatherAction News and commented:
    Great post for a windy June day

  14. tom0mason permalink
    June 6, 2017 9:14 pm

    Of course for the true believers 1944 CO2 levels worldwide were so much lower than now, and the storms were not driven by manmade climate change thus they must have been milder. Of course today’s snowflakes would believe such nonsense.

    Storms these days are so much more —
    More expected, more reported, more fabricated alarming, more widely communicated, more visual, and more devastating as we now expect ‘someone was to blame’ for any subsequent damage.

    • Ken permalink
      June 7, 2017 4:17 am

      Errm 1944 CO2 levels were NOT much lower than now. The famous chart that uses Mauna Loa data only begins in mid 1950’s. So it appears some cherry picking was done to make the data look more extreme because there is data showing CO2 levels higher in 1820 and 1940 that are higher as they are now.

      180 years of data:

  15. Derek Buxton permalink
    June 7, 2017 10:19 am

    I would have expected higher levels of CO2 in 1940, and yes, I was at school then. But there was a war on, bombs, guns all going off, aircraft all over the shop from all sides, then the steel works were working flat out to produce the munitions. It left our steel industry and the railways overworked to the point of destruction. Then we paid our enemies to rebuild!!!!!!.

  16. Ben Vorlich permalink
    June 8, 2017 11:29 am

    The Mulberry Harbour at Omaha beach was severely damaged by a storm at the end of June 1944, so much so that it was abandoned. Stormy month June 1944.

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