Seasonal forecasting of river flows in the British Isles using North Atlantic pressure patterns

A potentially useful forecasting relationship is demonstrated between the N orth Atlantic Oscillation index in winter (January-February) and the follow ing summer (July-September) monthly mean flows for selected rivers in the B ritish Isles. The relationship was strongest in August when up to 40% of th e variance in monthly mean flow may be explained. For two rivers in souther n and eastern England, positive phases of the winter North Atlantic Oscilla tion index were found to precede summer flows which were nearly 50% of long -term average. A regression equation which was established to predict Augus t flows in the Great Stour produced a correlation score of 0.6 at a lead ti me of six months. Further research is needed to determine the significance of catchment characteristics and geographic location relative to forecastin g skill.