November 2015


Period: From November 2015      Issued on 10.11.2015 using data to the end of October 2015

Summary

Normal river flows and groundwater levels are likely for the next one to three months across the UK. This is despite the generally dry August to October period which led to depressed October river flows across the north and west, and below normal groundwater levels in some areas. The outlook tends towards normal (with above normal flows and levels possible in some areas) due to the driving meteorological forecasts, which suggest the next three months are more likely to be wetter than average. However, there is high uncertainty in the outlook, with a wide range of possible outcomes in the forecasts. 

Rainfall

For both November and November-December-January, above-average precipitation is considered more probable than below-average. The probability that UK-average precipitation for November-December-January will fall into the driest of five equal categories is between 10% and 15% and the probability that it will fall into the wettest of the five categories is between 25% and 30% (the 1981-2010 probability for each of these categories is 20%).

River flows

October saw a contrast between southern and eastern England, where flows were largely in the normal range, and northern and western areas where flows were mostly notably or exceptionally low, with some record October minima in northern Scotland. However, both the one month and the three month outlooks suggest normal flows are likely to predominate, although confidence is low, with different forecasting methods yielding contrasting outcomes. Forecasts based on historic observations suggest a continuation of normal to below normal flows, while predictions based on meteorological forecasts favour normal flows over the next three months, with a slightly increased likelihood of above normal flows in some regions (i.e. southwest England, southeast England, Yorkshire and southwest Scotland), reflecting the pronounced shift towards above average conditions in the precipitation forecasts. 

Groundwater

In the Chalk, levels in October were mostly normal or below. Notably low levels persisted in north-east England, while southern England saw a mixed pattern with some notably low levels in more central areas contrasting with above normal levels in parts of the far south. Levels in other aquifers were also mostly normal or below. The one month outlook indicates a similar pattern. For the three month outlook, below-normal levels are far less prevalent, with normal levels predominant across all aquifers and above normal levels possible in some localised areas. The shift towards normal levels again reflects the precipitation forecasts but, as with river flows, projections are highly uncertain. Groundwater projections are particularly uncertain at this transitional time of year; late autumn and early winter rainfall will be highly influential on the longer-term outlook. 

Further information - November 2015

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