December 2017


Period: From December 2017      Issued on 12.12.2017 using data to the end of November 2017

Summary

In south-east England groundwater levels are likely to be below normal, and potentially exceptionally low in places, during December and for the next three months. In south-central and south-eastern parts of the UK river flows are likely to be normal to below normal during December and for the next three months. Elsewhere in the UK river flows and groundwater levels are likely to be normal to above normal in the same period.

Rainfall

For the UK as a whole, rainfall during November was slightly below the long-term average, but as so often there were marked variations. Areas with below average rainfall included central and southern England, and in particular coastal areas of south-east England, and also south Wales, the Pennines, and the catchments of the Forth and Tay in Scotland.

The Met Office 3-month Outlook issued on 24th November indicated that for December, below-average precipitation is slightly more likely than above-average precipitation. For December-January-February as a whole, above-average precipitation is more likely than below-average precipitation.

The probability that UK-average precipitation for December-January-February will fall into the driest of our five categories is between 10% and 15% and the probability that it will fall into the wettest of our five categories is between 30% and 35% (the 1981-2010 probability for each of these categories is 20%). 

River flows

In large areas of south-east England river flows were below normal during November, with  some exceptionally low flows. Elsewhere flows were generally normal to below normal, with only a few rivers in Northern Ireland and northern Scotland recording above average flows.

A marked contrast is likely in river flows for December, and beyond, with northern and western parts of the UK experiencing normal to above normal flows, while elsewhere flows are most likely to be normal to below normal.

Groundwater

Groundwater levels in November remained below normal to notably low across the majority of the southern Chalk aquifer. Elsewhere, groundwater levels were within the normal range, with the exception of south-western Scotland where levels remained above normal.

Although water levels in many aquifers are currently within their seasonal range, and likely to remain normal over one month, there is a notable exception in the Chalk, where Kent, areas north of London and East Anglia will almost inevitably remain below normal, and potentially exceptionally low through December and over the next 3 months, even if rainfall is significantly above normal. 

Further information - December 2017

Comprehensive further information that supports the production of the Hydrological Outlook UK is available here.