Regional weather and climates of the British Isles – Part 6: Ireland

Abstract

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. Ireland possesses a rich and varied climate mosaic, a product of its distinctive topography and geography, which interact with airstreams to produce a complex spatial arrangement of climates not often appreciated beyond its shores. In Victorian times the geomorphology of Ireland was taught by an analogy to an apple pie – the hard crusty bits around the edges enclosing a soft centre. This geological legacy of hard Caledonian and Armorican rocks around the perimeter and soft Carboniferous limestones in the centre creates an unusual topographic arrangement (Figure 1). In the west, with only a few breaks in the mountainous edge at Sligo Bay, Galway Bay and the Shannon Estuary that allow easier access for maritime air masses, there are some surprisingly sheltered pockets. The south and north coasts also have their mountain bulwarks in the Cork–Kerry and Donegal mountains and some protection is even afforded to the east coast by the Antrim Plateau and the Wicklow Mountains. A coast-versus-interior geography is, therefore, the chief characteristic of the Irish climate, so that the climate of the Central Plain has more in common with lowland England than with its Celtic neighbours of Wales and Scotland. The legacy of past weather observations