Winter 2017/18 Netherlands End-of-Season Report
Similar to the previous four years, for The Netherlands, the winter of 2017-2018 as a whole went quite smoothly. However, the differences between the individual months were large. One of the top ten warmest months of January ever in De Bilt, was followed by the coldest February since 1996.
Quick start to the winter
On the night of November 6th/7th the temperature declined to below freezing on a large scale, for the first time in the season. Later in November there was a light frost a few times during the night.
Mixed feelings about December
The first days of December brought considerably colder weather. On December 1st, the temperature in Gilze-Rijen fell to -5.6 °C in the evening. The next day, the eastern regions experienced the first icy day in many places (maximum temperature below 0 °C), due to persistent fog. Then, after a milder intermezzo, colder air began to flow again on the 7th December leading to significant snowfall on December 10th and 11th, in almost the whole of the Netherlands. The biggest amount, more than 30 cm of snow, was reported locally on the Veluwe. Eventually, the mild air won the battle and the remainder of December was mostly non-wintry and changeable weather. On New Year's Eve the temperature reached 14.5 °C in Arcen!
In January temperatures remained above zero most of the time. The national lowest January temperature was -3.1 °C, in Nieuw-Beerta in Groningen on January 8th. The most significant weather events that month were two very severe storms on the 3rd and 18th of January. The second one was the most severe since January 1990. At sea, an hourly average wind force 11 Beaufort was reported, and also deep inland, local force 9 Beaufort was reached. In addition, wind gusts up to 124 km/h were observed in Enschede and 143 km/h in Hook of Holland. Apart from the storms, really spring-like weather which came on January 24th is worth mentioning, with maximum temperatures up to 14.7 °C in Woensdrecht.
Freezing in February
The weather pattern changed in February. Frequent easterly winds allowed colder and drier air to enter the country. That gave the sun a lot more room, leading to frequent frost in the nights. During the last days of February and the beginning of March it was icy cold. Due to strong easterly winds extremely cold air from Siberia was transported and the temperature remained negative for five days in a row, at some locations. It was extremely cold, especially on the last day of February. During the day the maximum temperature in Enschede was only -6.0 °C. The lowest winter temperature was measured in Woensdrecht, on February 28th (-10.5). At the same time, there was a wind force 5 to 8 beaufort lowering the perceived temperature down below -15 °C. On top of that, at the end of February snow showers spread over the German Bight into the Wadden Sea region, resulting in more than 10 cm of snow locally.
Figure 1. Percentage of correct road frost forecasts by MeteoGroup during the 2017/18 season in the Netherlands. Between 80 and 100 nights during the season have been critical for road frost (including bridges), and on average 97% of them have been forecasted correctly. The average false alarm ratio was less than 2%.
From cold to warm and back again
March started in quite a winterly way, with icy days and a cold east wind. Ice-skating was possible in many places, even in Amsterdam. On March 3rd mild air from the south attacked the cold air mass, resulting in more than 5 cm of snow on the frontal zone in some places in the south. The mild air eventually conquered the entire country. From one day to the next the cold was gone. On March 10th it was even 16.7 °C in Ell. However, the winter cold came back. As a result of an icy easterly wind, it remained freezing in many places during the day on March 17th. March was again a clearly cold month and was even colder than December and January.
February saved the sunny image of the winter
Despite a very dark December and January, the winter appeared to be sunnier than average, thanks to a record-breaking February. On average over the country, the sun shone 48 hours more than usual during the three winter months. In February, the number of hours with sun (162 hours on average for the country) was about twice as much as in December (32 hours) and January (50 hours). Also, in March sunny weather was more frequent than the long-term average.
December was particularly wet with 112 mm precipitation on average over the country. January was also slightly wetter than normal with 89 mm, but February was considerably drier, by 23 mm on average.