Thought I would look at a few of the lesser known aspects of the D-Day landings, before, during and after. There are so many aspects of Operation Neptune (the assault phase of Overlord) that are worthy of telling but in this series we look at the weather (before the landings), armoured combat engineering (during the landings) and logistics (after the landings), perhaps lesser known aspects but all absolutely crucial.
The sea journey from the south coast of England to Normandy is not a short one and the weather in the area is unpredictable, even in summer. The inexorable build up to the launch of the invasion led to a single decision and this decision was not about whether there was enough ammunition or enough aircraft, but was the weather suitable for the largest amphibious assault in history.
Adverse weather affected military operations in the 1940’s much more than it does today and the success of operation hinged on the weather. If the weather was too severe, the Higgins boats could not operate and aircraft could not fly, amongst many others.
A number of weather and other conditions had been set before a positive decision to launch could be made including the conditions for the days following the invasion, cloud cover, winds and visibility.
The tides and moon would be suitable between the 5th and the 7th of June so all Eisenhower needed was an accurate weather forecast. Look at any modern weather prediction centre and you will see some of the most sophisticated super computers, satellite imagery and computational software models available in science. Back in 1944 the state of the art was somewhat different, reasonable predictions could still be made however and many of the techniques pioneered in the build up to Neptune are still used today.
At the time there were three forecast centres involved in the business of predicting the weather for D Day, the Met Office, the Naval Meteorological Service and the Weather Service of the United States Army Air Force. The thinking was that three heads were better than one although each had a team of scientists working in parallel.
Different methods were used by these groups, the US team used the traditional methods of map comparison whilst the Met Office team were at the cutting edge using new theories devised by the Norwegian Sverre Petterssen that used high altitude observations from aircraft. The three teams would assemble and thrash out a consensus, this being the advice presented to the the military planners.
Chairing theese meetings and acting as the coordinating forecaster was the famous Group Commander James Stagg, an RAF officer seconded from the Met Office. As with many things to do with D Day this was a delicate balance of opinion, fact and politics. One can imagine the pressure on all sides, it has been reported that the US team called the Met Office team to change their minds and side with them, the US one being incorrect.
The weather in June was unseasonal and on June the third the team met and reached the conclusion by a 2 to 1 majority that the 5th was out. Information received from a Royal Navy ship stationed south of Iceland led the team to conclude that a high pressure ridge was approaching and this would provide a break in the bad weather on the 6th. Eventually Stagg told the the assembled military planners the break in the weather would come and the 6th would provide the opportunity needed. Thousands of men already waiting and being sea sick in boats across the coast of England were extremely glad of the news, the operation was on.
The Germans, without the correct prediction or the means to make one (having lost air and sea superiority) , stood down a number of units, thinking that the weather would be too severe for an invasion. General Erwin Rommel even took the opportunity to sneak home for his wife’s birthday.
The rest is of course history but the success of the entire operation hinged on a weather prediction. If the decision to postpone to the 19th, which was the preferred US option and the consensus on the best available next opportunity, the D Day landings would have been a disaster, a massive storm blew in, the biggest of the twentieth century at that point.
Anyone who remembers the famous South Coast Hurricane will realise the difficulty in predicting the weather, even with the benefit of modern technology. Weather forecasting is a serious business, from whether your local supermarket has enough ice cream to cope with a sudden warm spell or a military operation can proceed.
Truly a fantastic achievement.