Weather Observation Chart at 0100 GMT on 5 June 1944 (D-Day -1)

This chart shows the weather at 0100 on the morning of the 5th June 1944. It was the information from this chart which allowed forecasters to advise that weather conditions should be acceptable on the 6th and resulted in the allied invasion of occupied Europe being declared 'on'. The isobars and pressure readings on the left of the chart indicate rising pressure and this information was vital to the forecasting.