January was occasionally unsettled but was predominantly dry, exceptionally so in some areas. While there were mild spells, and the mean UK temperature for January was near-average, the month had a distinctly wintry character. The impact of the ‘sudden stratospheric warming’ that occurred in late December began to be felt, with northwesterly airflows bringing very cold weather and some disruptive snowfall. With frontal systems making little impression except in the north of Scotland, river flows generally declined steeply and January mean flows were depressed across the country, exceptionally so in some catchments. With recharge slowed or arrested across most aquifers, below normal and notably low groundwater levels were also widespread. At the national scale, reservoir stocks were moderately below average (4% below for England and Wales) but were appreciably below average in some northern impoundments (e.g. Kielder, Derwent Valley) and at Grafham and Ardingly in the English Lowlands. While the wetter December yielded some modest replenishment in the south, rainfall has been below average for much of the period from late spring 2018. The window for groundwater recharge and reservoir replenishment has narrowed further – late winter/early spring rainfall will be influential for the water resources outlook for summer 2019. February started with some very wet weather, and the latest outlooks marginally favour wetter-than-average conditions for the next three months, but with significant uncertainties.
The full Hydrological Summary can be found here.