How an Irish weather station decided D-Day

Approaching the Normandy beaches: On D-Day the weather made a crucial difference. Image: By Herman V Wall, via Wikimedia Commons

Climate change and fickle elements can save nations or sink them. Irish weather was crucial to the Allies in June 1944.

COUNTY MAYO, IRELAND, 24 August, 2021 − Any military analyst worth his or her stripes will be aware of the challenges to operations caused by climate change and differing weather patterns. The Irish weather held the balance in 1944 as the Allies prepared to attack the Nazi forces in northern France.

How would heavy military equipment cope now in Arctic conditions as the permafrost melts and the ice cover becomes ever thinner? Will naval bases be threatened by rising sea levels? Will drought and environmental devastation be the catalyst for more conflicts round the world, and where will they occur? Ireland’s World War II experience could be salutary.

Brendan McWilliams, who died in 2007, was a prominent Irish meteorologist who, for several years, wrote a daily column for the Irish Times.

Among his many erudite observations, he analysed what impact the weather and climate had had on various key historical military events.

On 18 June 1815 the Emperor Napoleon was planning his attack on the Anglo-Dutch forces led by the Duke of Wellington near the small town of Waterloo, south of Brussels in Belgium.

Surprise lost

“Napoleon was the master of the quick manoeuvre”, said McWilliams. “His success as a general rested largely on his being able to deal a crushing blow to the weakest spot when it was least expected.

“He would use his artillery as one might aim a pistol, continually searching for the point where maximum advantage might be gained, and reacting to the ebb and flow of fortune at different places on the battlefield.

“For these tactics dry ground and a firm footing were essential; both were denied to him at Waterloo.”

McWilliams says that the day before the battle a small but very active depression caused very heavy falls of rain in the environs of Waterloo, turning fields into quagmires.

Napoleon had planned his attack for early morning on the 15th but had to postpone it till noon, in the hope that the ground would dry out. In the event, Napoleon’s troops became bogged down and could not sustain their advance; the delay in the attack allowed time for reinforcements to arrive.

“Rain and Force 7 winds affected the English Channel around the time for which the invasion had been originally planned”

Wellington won the battle and the tide of history, courtesy the weather, was radically changed.

On another June day nearly 130 years later, during World War II, Allied forces under the command of US General Dwight Eisenhower were about to launch Operation Overlord – the Normandy landings and the ground attack on German forces in mainland Europe.

Light winds, good visibility and calm seas were essential if the attack was to be a success; military planners selected 5 June as the best day for the invasion to go ahead.

At that time, McWilliams points out, accurate weather forecasting was still in its infancy.

On 3 June reports started coming in from a weather station at Blacksod Point in County Mayo in the west of Ireland of the approach of an active – and totally unexpected – cold front.

Postponement lifted

The small weather station was manned by the Sweeney family, who also ran the local post office. Though Ireland was neutral in the war, weather reports sent to Dublin were passed on to London.

It was obvious, says McWilliams, that the cold front would be over the invasion area by 5 June, bringing rain and strong winds, and likely to severely hamper the operations of Allied forces. The military command decided to postpone the invasion for a day.

“Sure enough, rain and Force 7 winds affected the English Channel around the time for which the invasion had been originally planned”, says McWilliams.

“By 6 June, however, the depression had lost much of its intensity, the cold front had passed the battle area, and the weather was sufficiently good not to interfere with operations.”

And the rest, due to the weather and the observations of the Sweeney family, is history. − Climate News Network