The North Atlantic has had some active storms this month, and more are coming. Currently, a large low-pressure area is rotating south of Greenland. With another cold push from the Arctic over the warmer seas late Friday, the pattern will develop a potentially severe windstorm that will blast toward Ireland and Scotland on Sunday. The meteorological services of Ireland and the UK could name it the first Atlantic storm for the season—storm Ashley.
The last significant storm that affected Europe was the ex-hurricane Kirk, which happened about a week ago. Its remnants brought significant winds to Galicia, northwest Spain, and western France as the storm grazed into the European continent.
Recent weather model guidance agrees that a potential severe windstorm will develop on Saturday. Then, it will impact Ireland and Scotland on Sunday as it travels towards northwest Europe during the day. High waves and potentially gale-to-hurricane-force winds are becoming increasingly likely to strike the western coasts of Ireland, Scotland, and the Hebrides.
Atlantic storms are common during late autumn and winter, impacting western Europe. Severe windstorms are less frequent and must be closely monitored due to their potential high impact on populated and coastal areas.
This weekend, a full Moon will also coincide with the upcoming storm Ashley, so coastal flooding caused by a combination of high tide and significant wave heights from the Atlantic system could be higher and more effective than usual.
The current weather picture across the North Atlantic reveals a large frontal system with an impressive core 100 kilometers south of Greenland. Its associated cold front extends towards the southwest, with cold maritime airmass in its wake, dragged from the Labrador Sea and Eastern Canada.
These cold intrusions from the Arctic region onto the much warmer Atlantic often induce additional, sometimes rapidly developing storms that continue their path toward Western Europe.
Deep trough strengthens over the North Atlantic; storm Ashley develops
The dipole weather pattern spread across the Atlantic and Europe will continue into the weekend.
One frontal system has brought destructive flooding to parts of southern France, with a blocking ridge spreading across central and northern Europe.
To the west, an extensive and deep trough is fully developed, fed by continuous intrusions of a cold air mass across the Labrador Sea. At the same time, favorable winds from the south drag warmer and moist air mass towards the north. That’s how the large system has maintained Atlantic storms and frontal systems recently.
The Atlantic sea waters are still much warmer than the average, generally 1-3 °C warmer, even higher in some areas. Sea temperatures have been anomalous continuously for the last year.
With another push of cold air on Saturday, the southern lobe of the trough will intensify and develop a new, potentially intense Atlantic storm. Characterized by a rapid pressure drop and organizing into a deep surface low, it will have conditions to develop into the first significant and named storm of the season – Ashley.
Various weather models agree that storm Ashley’s central pressure will drop into the low 950 mbar early Sunday; some hint at an even lower pressure when the storm develops its peak strength.
With high pressure over continental Europe and a deep low over the Atlantic, a powerful jet stream will occur in between. Strong south-westerlies will spread across western Europe, with stronger winds in the higher elevations.
One good thing about it will be for the eastbound flights coming from the United States to Europe—they will take advantage of these strong upper-level winds, and flight durations will be much shorter than those going the opposite way.
Storm Ashley is expected to occur and get its unique name by Saturday at the latest, as the development will be quite fast and significant.
Powerful windstorms and high waves likely to develop for the western coasts of Ireland and Scotland on Sunday
With a rapidly developing storm under the deep core of the trough aloft, weather models hint that an explosive cyclogenesis will occur on Saturday. This means that the system’s central pressure is forecast to fall from near 980 mbar on Saturday noon to Sunday noon to around 950 mbar.
This is more than 24 mbar in one day, meeting the criteria for explosive cyclogenesis or bombogenesis, as the other known term. When the storm surpasses a pressure drop of 24 mbar within a 24-hour period, the bomb cyclone is born.
As a result, intense windstorms are likely to develop, as suggested by both global and high-resolution weather models. Most of them simulate that peak wind gusts will surpass 150 km/h or 90 mph, likely reaching even higher gusts near the core.
The intensity of the storm depends on its explosive cyclogenesis processes.
Still, there’s good agreement that Storm Ashley will be the first intense Atlantic storm for the season and will blast into Ireland and Scotland on Sunday.
Attached is another peak wind gusts swath chart from the UK Netwether high-resolution weather model, hinting gusts peaking at 160-180 km/h, or 100-110 mph.
There is also a good possibility that the storm could develop a powerful wind maximum, known as the sting jet – in short, potential areas where winds could be particularly intense inside the storm.
Please read about this significant wind phenomenon here. We have prepared an in-depth educational article regarding sting jets: What is a Sting Jet, and why is it important to understand its dangerous impacts?
Another threat of concern is the significant waves normally associated with the most intense North Atlantic storms. Large cyclones with intense wind fields develop large swells and high waves that travel towards the coastal areas and could impact the land with flooding.
This time, the full Moon—which will also be a Supermoon event—will coincide with the impact of storm Ashley on Sunday. This means that high tide will develop with the full Moon and combine with the high swells and waves from the storm Ashley.
High waves will impact western Ireland, Northern Ireland, western Scotland, and Outer Hebrides. The highest waves could reach 10-12 meters high and lead to coastal flooding in the areas affected by the passing storm’s core.
The storm will gradually move northeast on Sunday, most likely traveling across far northwestern Scotland towards the Faroe Islands and Shetlands.
Particularly strong rainfall or excessive rain is unlikely with Ashley; however, about 60-100 mm of rain will be possible across western Scotland over the weekend.
Strong orographic rainfall with sustained southwesterly winds onto the higher terrain will bring high rainfall sums, regardless of the exact track of storm Ashley near Scotland.
Stay alert for rapidly changing weather conditions on Sunday as Ashley travels across the region.