Fr Kevin Hegarty
Seventy-five years ago next week the weather forecast from Blacksod, the most westerly point of Mayo, determined the timetable for the D-Day invasion of Normandy. Initially planned for June 5, 1944, D-Day was postponed for a day because of the information that came from Blacksod.
Called officially ‘Operation overlord’ D-Day had been organised under the leadership of General Dwight Eisenhower, who later served two terms as US president.
‘Operation Overlord’ envisaged the landing of 175,000 troops on French soil, accompanied by 5,000 ships and 11,000 aircraft. Its purpose was to end the German occupation of France as a prelude to the eventual defeat of Adolf Hitler.
The D-Day plan depended on favourable weather conditions. Rough seas could delay the landing of ships carrying troops. Low cloud and poor visibility presented another threat since the landings depended on the Allied air forces being able to knock out German coastal batteries and defensive positions.
Captain James Stagg had the responsibility of providing accurate weather information to Eisenhower and his fellow generals. He was the leading metereologist in Britain. He shared the task with an American, Colonel Donald Norton Yates, with whom he had an uneasy relationship.
Since April of that year, Stagg had been providing three-day weather forecasts on the Mondays. These were checked against reality later in the week.
In drawing up his forecasts, he was hampered by a lack of information. As most of the Northern Hemisphere was at war, he had to rely on forecasts from Britain, Spain, Portugal, Ireland, Iceland and Greenland. According to Brendan McWilliams in his ‘Weather Eye’ column in The Irish Times, ‘most of mainland Europe and the Atlantic Ocean, comprised one vast meteorological blank’.
During the month of May 1944 England experienced a heatwave. By the beginning of June there were indications that the weather was about to change as some deep depressions were forming over the North Atlantic. Stagg and Yates disagreed about the relevance of the new data for the impending French invasion. When Stagg told Eisenhower’s assistant Major General Harold Bull of the difference of opinion, Bull exploded, “For heaven’s sake, Stagg, get it sorted out by tomorrow morning before you came to the Supreme Commanders Conference. General Eisenhower is a very worried man.”
On Friday, June 27, Stagg and Yates met with Eisenhower and his team to give their forecast for June 5. Stagg later wrote of his feelings about that meeting: “Had it not been fraught with such potential tragedy, the whole business was ridiculous. In less that half an hour I was expected to present to General Eisenhower an agreed forecast for the next five days which covered the time of launching of the greatest military operation ever mounted; no two of the expert participants in the discussion could agree on the likely weather for the next 24 hours.”
The meeting ended by postponing a decision on whether or not the invasion would take place on June 5.
Meanwhile, utterly unaware of the nervous discussion in Portsmouth, in the quiet seaside village of Blacksod, Ted Sweeney, the local lighthouse keeper, sent his weather report to the Dublin Met Office, as was his daily practice. His report included the information that the barometer was falling rapidly and that heavy rain and strong winds were to be expected. Though Ireland was neutral in World War II, the Dublin Met Office continued to share information with its British counterparts.
When Stagg heard the news from Blacksod and had it confirmed by phone, he had the definitive meteorological information that he had been looking for. It was the final piece of the weather jigsaw. If the invasion went ahead on June 5 a cold front was likely to be over the battle area bring rain and wind. Armed with this information he convinced Eisenhower to postpone the plan. Conditions improved quickly allowing the invasion to proceed the next day, June 6. It proved successful and was the beginning of the end of the war.