On 4 June 1944, the lighthouse keeper at Blacksod Bay on the far northwest of County Mayo relayed his usual weather observations to Dublin and on to London. On receiving the report from Blacksod, the Allied commanders decided to postpone for a day Operation Overlord that was to launch the invasion of German-occupied western Europe: a wise move since the Force 7 winds and heavy rain experienced in the Channel the next day could have seriously compromised the success of the operation. Sitting astride the main storm tracks, Ireland has always provided an early warning system, particularly for Britain, of forthcoming extreme events originating over the Atlantic, as well as a shield which lessens their severity.