In a new weekly update for pv magazineSolcast, a DNV company, reports that a persistent high-pressure system over the North Sea in April caused a large excess of solar radiation in western and northern Europe by suppressing clouds and raising the GHI well above average. At the same time, displaced storm tracks reduced insolation in the eastern Mediterranean and parts of eastern Europe, causing shortages in Greece, Turkey and Ukraine, while maintaining a sharp west-east contrast.
Persistent high pressure over the North Sea created one of Europe’s strongest solar anomalies in April in recent years, according to an analysis using the Solcast API. A blocking pattern suppressed cloud formation over much of western and northern Europe, increasing insolation from Iberia to Finland. At the same time, storms moving along the eastern flank of the block reduced insolation over the eastern Mediterranean, including Greece and Turkey, and further northeast of Ukraine.
The dominant feature through April was a persistent high-pressure system anchored over the North Sea, with mean sea level pressure up to 7 hPa above climatic conditions. This circulation pattern kept the lower atmosphere unusually dry and stable, limiting cloud development in France, Germany and the Low Countries. As a result, the GHI across France averaged 13% above the 2007-2025 baseline, 11-14% above average in Germany and Benelux, and 14-16% higher in Sweden and Finland. Iberia also recorded an 8% surplus, while Italy averaged 11% above normal as high areas extended south across the peninsula.
France recorded its fifth sunniest April on record, with a 30% increase in insolation and a 70% rainfall deficit, while locations such as Cannes, Nice and Le Mans reported no rainy days for the entire month. Italy’s surplus marked a sharp reversal from March, when a low associated with Storm Deborah brought persistent cloud and late-season snowfall that suppressed insolation.
The April radiation anomaly was notable because it was caused almost entirely by the cloud. The Clearsky GHI anomalies averaged only +0.9% from the 2007-2025 baseline, indicating that aerosol loads remained close to climatology across Europe. This was in stark contrast to March, when intrusion of Saharan dust reduced clear-sky irradiation, independently of cloud cover across southern Europe. In April, the atmosphere remained relatively optically clean, meaning that the reduction in cloud cover translated directly into a greater amount of solar energy.
While western and northern Europe benefited from clear skies, the same blocking pattern shifted the Atlantic storm tracks to the southeast. Systems that would typically cross central Europe were instead routed into the eastern Mediterranean. Storm Erminio swept across the Ionian Sea in early April, causing flash flooding across Greece before bringing persistent cloud and rain to Turkey. Greece recorded a GHI deficit of 3%, while Turkey and Syria were around 4% below average. Poland and the Balkans remained under the influence of the high-pressure system and recorded a GHI well above average, typically between 9% and 12%. In contrast, Ukraine and Moldova ended up on the edge of the storm track all month – cut off in the last week by Storm Ylvi – and fell about 8% below average despite relatively dry conditions.
This contrast is also evident in GHI profiles on either side of the ridge, with locations below the ridge, such as Lyon, showing consistently elevated and smooth daytime curves, while locations east of the ridge, including Kiev, show suppressed and highly variable profiles indicative of frequent cloud breaks.
Solcast produces these figures by tracking clouds and aerosols worldwide at a resolution of 1-2 km, using proprietary satellite data AI/ML algorithms. This data is used to drive irradiance models, allowing Solcast to calculate high-resolution irradiance, with a typical deviation of less than 2%, as well as cloud tracking predictions. This data is used by more than 350 companies that manage more than 300 GW of solar energy worldwide.
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