On sure uncommon events, strange folks within the midst of a mean day have modified historical past.

In 1947, Muhammad edh-Dhib, a younger Bedouin shepherd in search of a sheep gone astray, found a hidden cave that contained the Lifeless Sea Scrolls, the earliest identified model of many of the Hebrew Bible. Making his rounds one night time in 1972, Frank Wills, a Washington, D.C., safety guard, seen a bit of tape holding a lock open in a constructing the place he labored — and because of this he uncovered the Watergate break-in, finally resulting in the resignation of President Richard M. Nixon.

However neither of them formed as many lives as instantly as Maureen Flavin, a postal clerk on a distant stretch of the northwest Irish coast who, in 1944, on her twenty first birthday, helped decide the end result of the Second World Battle.

She died on Dec. 17 in a nursing residence in Belmullet, Eire, close to the put up workplace the place she used to work, her grandson Fergus Sweeney stated. She was 100.

The occasions that led Ms. Flavin to her unforeseeable second of worldwide consequence started in 1942 when she noticed an advert for a job within the put up workplace of the coastal village of Blacksod Level.

She received the job and discovered that the distant put up workplace additionally served as a climate station. Her duties included recording and transmitting climate knowledge. She did that work diligently, although she didn’t even know the place her climate studies had been going.

In reality, they had been a part of the Allied battle effort.

Eire was impartial in World Battle II however quietly helped the Allies in a number of methods, together with by sharing climate knowledge with Britain. Eire’s place on Europe’s northwestern edge gave it an early sense of climate heading towards the continent. Blacksod Level was simply concerning the westernmost level of the coast.

Climate forecasting turned out to be a vital a part of the Allies’ most well-known gambit of the battle — D-Day, the invasion geared toward gaining a foothold on the European mainland.

It took two years of meticulous planning. The American basic Dwight D. Eisenhower, who led the assault, determined to ship greater than 160,000 troops, almost 12,000 plane and almost 7,000 sea vessels to invade a 50-mile stretch of seashore alongside the Normandy area of the French coast.

The Allies settled on June 5, 1944, which promised a full moon, aiding visibility, and low tides, granting simpler entry to the seashore.

A profitable invasion would additionally rely upon clear skies for the Allies’ aerial assault and calm seas for his or her touchdown. And the comparatively primitive expertise of the day — no satellites, no laptop fashions — meant that the Allies would solely have a couple of days’ warning concerning the climate.

By 1944, Ms. Flavin’s work orders had elevated from on excessive: She and her colleagues now despatched in climate studies not each six hours, however each hour of the day.

“You’d solely have one completed when it was time to do one other,” she recalled in a documentary made by RTÉ, Eire’s public broadcaster, in 2019.

On her birthday, June 3, she had a late-night shift: 12 a.m. to 4 a.m. Checking her barometer, she registered a speedy drop in strain indicating a probability of approaching rain or stormy climate.

The report went from Dublin to Dunstable, the city that housed England’s meteorological headquarters.

Ms. Flavin then obtained an uncommon collection of calls about her work. A girl with an English accent requested her, “Please verify. Please repeat!”

She requested the postmistress’s son and Blacksod’s lighthouse keeper, Ted Sweeney, if she was making a mistake.

“We checked and rechecked, and the figures had been the identical each instances so we had been comfortable sufficient,” she later instructed Eire’s Eye journal.

The identical day, Normal Eisenhower and his advisers had been assembly at their base in England. James Stagg, a British navy meteorologist, reported based mostly on Ms. Flavin’s readings that unhealthy climate was anticipated. He suggested Normal Eisenhower to postpone the invasion by a day.

The final agreed. June 5 noticed tough seas, excessive winds and thick cloud cowl. Some commentators — together with John Ross, the writer of “Forecast for D-Day: And the Weatherman behind Ike’s Biggest Gamble” (2014) — have argued that the invasion may nicely have failed if it had occurred that day.

Suspending the invasion past the sixth offered different points. The tides and moon wouldn’t have been favorable once more for a number of weeks, when the Germans anticipated an assault. The component of shock would have been misplaced. Mr. Ross instructed USA Right this moment that victory in Europe might need been delayed a 12 months.

But Ms. Flavin’s studies indicated not solely that June 5 can be disastrous, but additionally that the climate on June 6 can be simply adequate. Normal Eisenhower ordered an invasion during which he proclaimed, “We’ll settle for nothing lower than full victory.”

By midday on the sixth, the skies cleared. The Allies endured 1000’s of casualties, however they gained a European beachhead.

“We owe loads to Maureen of the west of Eire, us who invaded France on D-Day,” Joe Cattini, a British D-Day veteran, stated within the RTÉ documentary, “as a result of if it hadn’t been for her studying of the climate we’d have perished within the storms.”

Maureen Flavin was born on June 3, 1923, within the southwestern village of Knockanure, Eire, the place she grew up. Her mother and father, Michael and Mary (Mullvihill) Flavin, ran a basic retailer.

She married Mr. Sweeney, the lighthouse keeper, in 1946. When his mom, the postmistress, died, Ms. Sweeney succeeded her within the job.

She first heard concerning the significance of her climate forecast in 1956, when officers mentioned it after shifting the native climate station from Blacksod Level to a close-by city. It gained wider publicity throughout D-Day’s fiftieth anniversary, when the meteorologist Brendan McWilliams wrote concerning the episode in The Irish Instances.

Mr. Sweeney died in 2001. Along with Fergus Sweeney, Ms. Sweeney is survived by three sons, Ted, Gerry and Vincent, all of whom have labored within the Irish lighthouse service; a daughter, Emer Schlueter; 12 different grandchildren; 20 great-grandchildren; and two great-great-grandchildren.

In interviews, Ms. Sweeney marveled on the distinction between the immense forces in want of a climate forecast and the little world of the Blacksod Level put up workplace.

“There they had been with 1000’s of plane they usually couldn’t tolerate low cloud,” she stated on Irish public radio in 2006. “We’re delighted we put them on the precise street. We ultimately had the ultimate say.”