D-Day, How the Weather Helped Shape the Battle of Normandy

Today is the 68th anniversary of the historic battle that helped the United States and its allies secure victory in Europe during the Second World War. In reflecting back on the day, what many people may not realize is that extensive weather forecasting was a major part of  the decision-making process regarding when to land the troops in the days leading up to the June 6th,1944 invasion.

When planning for the invasion, weather forecasters did not have the luxury of computer forecast models like we do today. Meteorologists relied on data from ships at sea to monitor observations, reconnaissance flights, weather balloons and visual observations. Through these methods, meteorologists were able to successfully give the go ahead for the June 6th invasion date. However, June 6th wasn’t the original day officials had marked for the invasion. Originally, the invasion was set to take place June 5th, 1944, but due to a report handed directly to General Eisenhower from his meteorological adviser the landing was rescheduled for the next day. That report included the summary of several factors that needed to come together to make for ideal conditions for the troops coming ashore. The first was that the landing needed to be around the time of a full moon to help illuminate as much of the beach as possible. The second was that it be during a period of high tide so the vehicles could make it inland as far as possible; and the third was the obvious calm weather conditions needed both in a lack of clouds and subdued seas.  Thanks to a re-analysis by the European Centre for Medium Range Weather Forecasts (ECMWF) and data From the US National Weather Service we can see the conditions graphically as they were in early June 1944. Meteorologists were able to successfully predict an occluding area of low pressure and frontal system bringing clouds and high winds to Western Europe and more importantly the English Channel on June 5th, 1944.  

The decision was made to postpone the invasion until the early morning hours of June 6th, and though the conditions weren’t ideal, they were good enough to launch the assault. The alternative would have been to wait until the next month when The moon would once again be full. Here is an analysis of the cloud cover and winds 24 hours later during the early morning hours of June 6th, 1944. With a full moon to illuminate the beach, a high tide and calmer weather conditions the early morning assault began…

Pictures taken of that day confirm that partly cloudy conditions were present.

After the initial invasion, the rest is history! Thank you to all our veterans who are serving and have served. Especially both of my grandparents!

Capt. Donald Block, WWII B-26 Marauder Pilot, Europe                       Capt. William Adams, WWII B-24 Liberator Pilot, Europe

Here is the ECMWF report on the Normandy Invasion http://www.ecmwf.int/research/era/dday/

And here is a link to the US Naval Historical Research Center where my pictures are from   http://www.history.navy.mil/photos/events/wwii-eur/normandy/normandy.htm



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