Monday, June 5, had long been planned for launching D-day, the start of the campaign to liberate Nazi-held Western Europe. Yet the fine weather leading up to the greatest invasion the world would ever see was deteriorating rapidly. Would it hold long enough for the bombers, the massed armada, and the soldiers to secure beachheads in Normandy? That was the question, and it was up to Ike’s chief meteorologist, James Martin Stagg, to give him the answer.

On the night of June 4, the weather hung on a knife’s edge. The three weather bureaus advising Stagg—the US Army Air Force, the Royal Navy, and the British Met Office—each provided differing forecasts. Worse, leading meteorologists in the USAAF and Met Office argued stormily. Stagg had only one chance to get it right. Were he wrong, thousands of men would perish, secrecy about when and where the Allies would land would be lost, victory in Europe would be delayed for a year, and the Communists might well take control of the continent.

Table of Contents

Prologue – Whether the Weather:  By late May, 1944, plans for Operation Overlord, the Allied invasion of northwestern France, were complete. Generals and admirals of the Supreme Headquarters Allied Expeditionary Force (SHAEF) had drafted exquisite plans down to which pillbox each platoon would assault. Shortly after midnight on D-day, airborne regiments would drop behind the beaches of Normandy. Heavy bombers would pound enemy emplacements. Landing craft would hover off shore, timed to land soldiers at low tide just as dawn was breaking.  That was the plan, and SHAEF’s commanders, led by General Dwight D. Eisenhower, were as confident of its success as the title of their headquarters suggests. All during May, southern England had enjoyed balmy weather lulling leaders to believe it would continue through D-day. Yet in late May 4,000 miles over Manitoba a dimple formed in the upper atmosphere, the precursor of storms that would douse a forest fire in Maine and throw the schedule for D-day into a cocked hat.  Commanders worried about the weather.  It was the one element of the invasion they could not control.  Since the evolution of meteorology as a science in the mid-1800s, its reputation among the military had been besmirched by suicide, scandal, and errant forecasts. So deeply distrustful of weather predictions were several army and navy commanders, that they took pride in the ability to “weather the weather” whether they liked it or not.

Chapter 1 – The Front:  On a sheet torn from a note pad soon after deciding to launch D-day, the greatest invasion the world would ever see, Ike penciled the words he would read publicly if the landings failed. For two years, the Allies had been pouring men, equipment, and supplies into the United Kingdom.  All was set to go on the night of June 4.  But observers on weather ships and stations in Greenland and Iceland reported that fair weather had turned foul, putting the invasion at risk. It fell to Ike’s weatherman, James Martin Stagg to sort out conflicting forecasts from the U. S. Air Force, Royal Navy, and the civilian British Meteorological Office.  Stagg was not a meteorologist but a world renowned geophysicist. His appointment as SHAEF’s chief weatherman was roundly criticized on all sides.  Operating in cramped quarters with his deputy, Stagg had to get the forecast right.  To err would result in the greatest military debacle in modern history. Had D-day been a failure the fate of the world as we know it could have been very different.  The Russians might well have occupied all of Germany.  French communists would have controlled its National Assembly.  NATO would have been unlikely.  Ike would have been cashiered and never become president opening the door for MacArthur who wanted to use nuclear weapons against China in the Korean War.

Chapter 2 – Polar Extremes: Stagg’s task was to meld forecasts from the US Air Force, the Royal Navy, and the British civilian Meteorological Office up through the ranks of which he had risen over the past 20 years.  Each group of forecasters used different methodology to arrive at their predictions.  Professional jealousies among them were rife, but all were united on one point: Stagg should never have been made Ike’s weatherman.  The job should have gone to a professional meteorologist, meaning one of them.  As they bickered, storms threatening D-day were sweeping across the Atlantic.  When Stagg refused to accept the American view that the weather on the night of June 4 would be suitable for the invasion, Col. Irving P. Krick, its chief advocate who became a meteorologist to make money preparing forecasts for Hollywood studios, attempted to end-run Stagg through generals commanding US Air Forces.  Had Ike listened to his generals instead of Stagg, the invasion would have failed.

Chapter 3 – The Maritimes:  In the northern hemisphere, weather moves from west to east.  Observations that the three weather offices used to make their forecasts came from a few stations on the coast of Greenland where Allied and German weathermen skirmished, on Coast Guard cutters wallowing in heavy Atlantic swells as they steamed in endless circles, at Allied airfields in Iceland, and from recordings made by solo weather reconnaissance flights a thousand miles out to sea.  Gathered under the most difficult conditions and compiled by hand, weather data was always suspect.  In the weather hut at SHAEF’s Advanced Headquarters, as plans for the invasion hang in the balance, two Royal Navy ratings, Jean Farren and Harold Checketts, plot the data on charts Stagg used to make his forecast.  To Ike and his senior commanders, Stagg reports deteriorating weather over the Atlantic.  Ike, having taken Stagg’s measure over the past six months, trusts Stagg and decides to wait to the last possible moment before deciding whether to go or postpone.

Chapter 4 – Unknown Allies: During the war, important weather data is being gathered by all sides. After the war begins, Germans continue to use international protocols for transmitting encoded weather information. Recognizing the pattern of the data, British code breakers at Bletchley Hall suspect it is related to the weather, which is confirmed when the Royal Navy captured its first Enigma machine from a German weather ship thus breaking the much vaunted code.  US Air Force Col. Donald Yates, Stagg’s deputy, establishes weather stations in Russia.   Though officially neutral, Ireland signs a secret treaty with England to provide weather data. Two postal clerks - Ted Sweeny and Maureen Flavin  record weather observations critical for D-day decisions on Blacksod Point on the far west coast of County Mayo, a remote but critical outpost, where they fall in love.

Chapter 5 – High Pressure: To ease the strain when off watch, Royal Navy ratings Farren and Checketts read Chinese poetry to each other. They too fall in love.  Stagg is plagued by anxiety as well and takes lonely walks around Southwick estate debating pros and cons of styles of US Air Force, Royal Navy, and Met Office forecasting centers.  Americans are sanguine that, based on their belief in the predictive power of 50 years of daily weather maps, a ridge of high pressure will protect Normandy from the rapidly advancing storm fronts. The Royal Navy and Met Office adamantly disagree and the weather conference call at 0300 on 4 June is extremely rancorous, with much argument and some personal invective.   Stagg has one hour to forge consensus among them on the forecast to present to Ike and his commanders.

Chapter 6 – Postpone: At 0415 on 4 June, Stagg and Yates present a dreary forecast of wind, cloud, and seas well above the limits set for invasion.  Ike queries his commanders:  Montgomery, in charge of all ground forces is ready to go regardless of the weather.  Adm. Ramsay, naval supreme commander, believes he can put men ashore.  Air forces commander Leigh-Mallory opposes the launch because cloud and wind could make air operations – where Allies reigned supreme – all but impossible.  But the ultimate fate of the invasion rests with one man: Ike decides to tentatively postpone for 24 hours.  Invasion fleet is halted but battered by rough seas. Germans, seeing the approach of the same cold front, let down their guard.  Rommel returns to Germany for wife’s birthday and a meeting w/Hitler to plead for permission to deploy Panzers in the event of an Allied landing.  Most German commanders opt to attend war games, one steals away to Paris for a weekend tryst with his paramour.  Stagg and Yates return to their tent as dawn, lovely and serene, is breaking.

Chapter 7 – Glimmer in the West:  The two weathermen awake to a beautiful dawn on the morning of June 4 and feel nauseated that their forecast was wrong.  But by breakfast time, clouds begin to fill the sky and thicken during the day.  Jousting for which weather central deserves credit for the postponement all but derails the early afternoon weather conference call.  Three hours later, when the conference call reconvenes, observations from Blacksod Point and other weather stations in Ireland convey that a strong front is passing and that the weather will improve the next day.  At 9:30 p.m., Ike holds firm to his decision to postpone until the next commanders meeting at 4:15 a.m. on June 5.  Stagg leaves the commanders with the feeling that the forecast will be better tomorrow morning. All commanders eagerly hope so.  If not, troop transports that left their harbors when the invasion was scheduled for the night of 4 June, will run out of oil and have to return to port with the fleet snarled in unimaginable confusion.  The next time tide conditions allow for a launch is in mid-June.  But, but a two-week delay ups the odds that the Germans will discover that Normandy is the Allies’ target.

Chapter 8 – Go!:  At 4:15  a.m. on 5 June, high winds and heavy rain pummels Southwick House, yet Stagg’s briefing to the supreme commanders confirms a 36-hour window of milder weather, still not ideal, for night of 5/6 June.  Ike says go.  Though German meteorologists too see the break in weather, but the German commanders’ preconceived idea that the invasion could only come at high tide lulls them into false security.  Surprise is complete, though weather hinders the invasion to be sure.  Soldiers reeling from seasickness and reeking of vomit prefer landing in the teeth of enemy fire to one more moment on their landing craft.  Bombers miss their targets.  Wind scatters the airborne assault.  Waves sink amphibious tanks.  Still D-day succeeds.

Chapter 9 – Gale of the Century: The fallback dates for D-day were 17 – 19 June. Though the Allies could have landed forces on the 17th and 18th, a ferocious gale blew across the Bay of the Seine and onto Normandy on 19 and 20 June.  Had Ike decided not to invade on 5/6 June and delayed for two weeks, the critical post-landing buildup of men, heavy weapons, and supplies to secure the beachhead would have been totally disrupted with the prospect that Rommel would drive the invaders back into the sea.

Epilogue – The Hero and the Goat:   After the war, Stagg becomes Principal Deputy Director of the Met Office and, later, president of the Royal Meteorological Society. Stagg is named a Companion in the Most Honourable Order of the Bath. He wins international renown for his work in geophysics.  Krick returns to chair the meteorology department at CalTech, which fires him for misuse of university property to further his private business interests.  He founds a private weather forecasting firm, which is sued when contracts it has secured to make rain over desert communities fail.  For unprofessional practices, he is expelled from the American Meteorological Society.