To the west of Ireland, an Atlantic depression is losing pressure at such a speed that it is entering the so-called explosive cyclogenesis. At 6pm today, 29 September 2026, the Met Office is forecasting a low of around 964 hPa near Rockall. The effects are much less abstract: strong winds, heavy seas and rain between Ireland and the UK, before the system turns back towards Iceland.
IPMA, the Portuguese meteorological service, also reports an explosive cyclogenesis to the west of Ireland today. It is the phenomenon that in headlines is often called “bomb cyclone” or bombogenesis: according to the Met Office, we conventionally speak of explosive development when the central pressure of a depression in mid-latitudes drops by approximately 24 hPa in 24 hours. The name is spectacular, the meteorological dynamics are very precise.
Ireland gets wind and rain first
The worsening has already entered the Irish bulletins. Met Éireann has issued yellow warnings for strong and gusty winds in several western and southern counties and heavy rain across Cork, Kerry and Waterford.
Possible effects include difficulty in moving, falling branches and trees, localized flooding and problems along the coasts, where wind, waves and high tides can add up. The sea, for its part, will do little to go unnoticed: in Met Éireann’s marine forecasts, winds up to force 8 and locally force 9 appear, with significant swell.
The front will move rapidly across Ireland during the afternoon and evening. Here the transition should be relatively quick; further north, however, the depression will continue to deepen.
Large waves and gusts in the United Kingdom, especially in the west
Between the evening of Tuesday and Wednesday the front will also reach the United Kingdom. The Met Office forecasts around 10 millimeters of rain in many areas, with accumulations that may locally exceed 40 millimeters in the most exposed western areas.
The wind could exceed 50 miles per hour, around 80 km/h, especially on the north-west coasts. Large waves are also expected along western shorelines, just as astronomical tides are high.
These numbers are already concrete enough without the need to reach 150 km/h above the British rooftops. Gusts above that threshold appear in the simulations especially near the heart of the depression, in the middle of the Atlantic.
The British maritime bulletin itself shows how wide the circulation of the system is: storm warnings affect a band that includes Rockall, Hebrides, Bailey, Fair Isle, Faroe and the south-eastern Icelandic sector.
And the 12 meter waves?
Weather models push swell up to values of the order of 10-12 meters in the Atlantic west of Ireland and Scotland, along with gusts above 150 km/h near the core of the depression.
Here, however, we must keep number and place together. These are mainly conditions expected offshore in the areas closest to the center of the gyre. The operational bulletins for the coasts currently speak of very strong wind, storms and large waves, with values lower than the maximums that appear on the modeling maps. The difference seems small only on paper. Between 80 and 150 km/h another wind practically passes through.
Then the system goes back towards Iceland
Between Wednesday and Thursday the depression will continue northwards and it will be mainly the southern and eastern regions of Iceland that will receive large amounts of moisture. The Icelandic Meteorological Office forecasts easterly and south-easterly winds of between 10 and 18 meters per second and considerable to heavy rainfall in the south and south-west. The rainiest part of the system is expected to move toward the Southeast and East Fjords on Wednesday; on Thursday, south-eastern winds could reach 15-23 meters per second.
Towards Iceland the system will also drag a long band of very humid air, a configuration that can take on the characteristics of what in meteorology is called an atmospheric river.
Some simulations estimate local accumulations in the order of 250-300 millimeters on the southern Icelandic mountains. The national weather service, however, currently speaks of “considerable” or “strong” precipitation without confirming those quantities. The 250-300 millimeters therefore remain a projection of the models, not an accumulation already written on the Icelandic rain gauges.
The depression will however be very deep and will involve a huge swath of the North Atlantic for several days. Ireland, the United Kingdom and then Iceland will feel the most direct effects. The 150 km/h wind and 12 meter waves belong, for now, to the most exposed ocean areas and the most intense projections.
