Winter road maintenance services have a tough job. It’s all about balancing safety, without letting costs spiral. Treating roads too late can lead to accidents and traffic jams, but unnecessary treatments mean high costs and avoidable environmental damage.
Treating roads naturally depends on weather conditions — and the accuracy of weather information services. Reliable weather data helps support treatment decisions, with greater insight on when and where to deploy treatments during the winter months.
Reflecting on winter 2019/20 in Europe, the European end-of-season report reveals most of the continent saw an outstanding mild winter from November to March. Colder conditions than average were only reported in northern and western Europe in November and then in parts of the British Isles and the Iberian Peninsula in March.
Averaged across the region, 95% of DTN road frost forecasts were correct during the road winter season 2019/2020. Accurate weather information services are even more critical in mild seasons when it is challenging to make confident decisions on when to treat roads—impacting safety, resources and costs.
Outstanding Mild Winter Across Europe
November was warmer than the 1981-2010 average over central and eastern Europe, while colder than average over western Europe and Scandinavia. Edinburgh, for example, reported two days with snowfall and 12 days with frost that month. The east and southeast of the continent have been milder than average.
December was unusually mild throughout Europe. The temperature was 3.2C above the long-term mean value, which made it the warmest December month on record in Europe. This trend continued in January, which was the warmest on record with 3.1C above average. In particular, Scandinavia saw much warmer temperatures than usual for the season. Some areas were 6C above the average temperature. In early January, temperatures in Sunndalsora, Norway, reached 19C, making it the warmest January day in Norway since measurements started.
February was warmer than average throughout the European continent. In Berlin, Germany, it was the first winter month since measurements started without any freezing temperatures. March, in many parts of Europe, showed further above-average temperatures but to a lesser extent than the months before.
Record Wet February in Central and Northern Parts of Europe
February saw extraordinary precipitation levels. A series of low-pressure systems rushing through northern Europe brought record-breaking precipitation to parts of the continent and the British Isles. The United Kingdom saw the wettest February on record, compared to the 1981-2010 period. Recorded rainfall was 237% above the average precipitation, which led to widespread and long-lasting flooding.
How DTN Forecasts Performed During the European Winter
On average, DTN forecasts for road surface temperatures within the next night deviated less than 0.9C from the observed lows. On nights with temperatures in the critical range for winter services, 95.4% of the forecasts proved correct.
Weather forecasts for winter road clearance services require a careful balance between the possible forecast scenarios in uncertain weather conditions with the possibility of short-term clear spells. Only 7% of the forecasts proved to be false alarms, and in only 7% of the cases were frost events detected too late. These results demonstrate the quality and accuracy of the DTN road weather forecasting system and our considerable meteorological expertise.
Impact of Mild Weather on Winter Road Services
In many regions of Europe, winter 2019/20 was mild and extraordinarily dry. Therefore, the roads did not need treating as often as usual. However, this is not the new standard. As soon as precipitation is involved, milder weather usually causes more work than extreme cold and dry situations.
It is expected that in some regions the number of winter maintenance-related events will decrease in the long term. However, winters in the UK and Europe show significant natural variability. Even with an overall rising temperature trend, climate projections indicate this variability will continue. Changes between mild and more severe winter seasons are anticipated.
Managing marginal conditions, when temperatures are around the freezing point, will continue to be a challenge — even as the temperature increases globally. When the number of nights with values close to freezing point increase with rising temperatures, reliable weather forecasts are more important. This scenario also applies to possible changes in the type of precipitation, as studies indicate the frequency of freezing rain events may increase with rising temperature levels. These events, along with the challenge of marginal and volatile weather conditions require accurate weather data and forecasts for confidence in making the right road maintenance decisions.