202604 - Windstorm Dave

Material from: Linus

1. Overview

On 4-5 April Storm Dave impacted UK, Norway, Denmark and Sweden with severe winds and unseasonal snowfall. The system developed over the eastern North Atlantic and intensified rapidly with central mean sea‑level pressure falling to approximately 970–975 hPa as the cyclone crossed Scotland and entered the North Sea.

Across northern and western parts of the United Kingdom, observed gusts exceeded 30 m/s on many stations, with a maximum measured gust of approximately 42 m/s. The cold air advection on the cyclone’s western and northern flanks resulted in late‑season snowfall over higher terrain, particularly in northern Scotland, where accumulations of 10–30 cm were reported above ~200–300 m elevation.

Over the North Sea, Storm Dave re‑intensified and produced its most severe impacts over southern and western Norway on 5 April. Coastal and exposed inland locations recorded gusts of 40–45 m/s, exceptional for April, accompanied by heavy snowfall (locally 30–50 cm in the mountains). Marine conditions were also extreme, with significant wave heights of 8–10 m. Further east, Denmark and Sweden experienced a weaker but still impactful phase, with severe wind gusts leading to transport disruption, e.g stop in the train service between Gothenburg and Stockholm. Parts of Sweden also experienced atypical early‑April snowfall. The strong winds over Scandinavia lasted for an unusually long period, as seen for Ålborg Airport in Denmark that had wind gusts around 30 m/s for more than 6 hours.

2. Analyses and Observations

2.1 Event Definition

The evaluation will focus on the 10-metre mean wind on 5 April 12UTC in a box 0.5x10.5 degree box centred on Ålborg, Denmark (57.1N, 9.9E). We will also use the 24-hour maximum wind gusts on 5 April for the same box.