Welcome to the Weekly Weather Update – your guide to the world’s oceans and seas. Each week, we highlight key marine weather patterns and analyse unusual or significant weather events. From calm spells under high pressure to tropical cyclones forming in equatorial waters, and from jet streams steering oceanic storms to anomalies in sea-surface temperature that shape global climate patterns. Here’s what this week’s weather has in store.
The weather starts slightly unsettled this week. A high-pressure system lies over Central Europe, occasionally building a ridge towards the North Sea, interspersed with filling troughs coming from the UK. On Wednesday, the winds are generally 20-30 knots around the most of the North Sea with some higher wind in the northwestern areas, around 35 knots. As for the waves, they are expected to be between 1.5-2.5 meters and 2.5-4 meters in the northwest.
A deep low will appear between Iceland and Ireland on Thursday and subsequently track towards the Norwegian Sea while filling. Associated fronts will impact the North Sea mainly on Thursday and Friday, causing a significant deterioration in weather conditions.
A strong south-westerly wind will pick up. Across large parts of the North Sea, winds will increase to 30 knots or sometimes more (Figure 1). Hs will rise to 3–4 m, and in the northern North Sea (due to longer fetch and stronger winds) to 4–5 m Hs. Conditions will be calmer in a narrow coastal strip along the east coast of the UK, as well as in part of the German Bight (Figure 1).
A very severe storm is deepening SE of Greenland on Wednesday and will move across the North Atlantic towards Iceland over the coming days. Atmospheric conditions are perfect for the storm to undergo extreme development in a short period of time.
Specifically, the low-pressure area is situated exactly beneath the left exit region of a very strong jet stream. In this location, air diverges rapidly, creating a deficit of mass at high altitudes. Due to the strong jet stream (180 knots at 200 hPa), this process is occurring quickly. The air deficit aloft is replenished by air rising from lower levels, resulting in the formation of a deep low-pressure system within a short time frame. At the storm's peak, the pressure gradient will be around 20 Pa/km, which is extremely high for a mid-latitude storm; these kinds of values are more commonly seen in hurricanes.
Ultimately, the storm will reach a central pressure of 940 hPa when the system is positioned south of Greenland. Wind gusts of up to 150 km/h are currently forecast around the core of the low. The system will subsequently move towards the sea between Iceland and Ireland, slowly filling as it tracks east.
On the Atlantic Ocean, a significant wave height of no less than 15 m will develop around the low. The theoretical maximum wave height could reach a staggering 27 m. Part of this very high swell will reach the west of Ireland on Wednesday, Thursday, and Friday, where an Hs (significant wave height) of 8–10 m is forecast. The system will fill rapidly from Friday onwards as it moves up into the Norwegian Sea.
The weather starts somewhat unsettled on the North Sea, but particularly on Thursday and Friday, winds will increase significantly (25–40 kts) and Hs will rise to values of 3–5 m across large parts of the North Sea.
However, the most active weather is found over the Atlantic Ocean. A very deep low-pressure system is tracking eastwards there, passing south of Greenland. Particularly along the west coast of Ireland, this low generates very high waves, reaching 8–10 m Hs.
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