Met Office Deep Dive: Warnings still in place as Storm Bram's impacts felt

Author: Met Office

09:02 (UTC) on Wed 10 Dec 2025

Storm Bram has brought a dramatic start to December, with heavy rain, strong winds, and unseasonable warmth.

Storm Bram’s impacts are being felt far and wide. Flights, ferries, and rail services have been cancelled, thousands of homes are without power, and numerous roads are blocked due to flooding and fallen trees.

The combined effects of rain and wind from Storm Bram have brought significant disruption, and many are asking what comes next. In this week’s Deep Dive, we take a closer look at the science behind the storm, the rainfall it has delivered, and what the coming days may hold for the UK’s weather.

Analysing the rainfall: how much and where?

The past 24 hours have seen intense rainfall across parts of the UK. Radar footage shows that after a showery Monday afternoon, the main area of rain associated with Storm Bram moved into the south on Monday evening. The heaviest rain fell across Ireland, western parts of the UK, Wales, and the southwest, continuing into Tuesday morning. In some of the wetter spots of South Wales and Dartmoor, rainfall totals have exceeded 80 millimetres, with one Dartmoor site recording over 100 millimetres.

It’s common to compare these figures with monthly averages, but this can be misleading. For example, Dartmoor is naturally wetter than many other areas, so comparing its rainfall to the average for December doesn’t tell the whole story. A more insightful approach is to look at the percentage of December’s average rainfall that has fallen in just one night. In Dartmoor, 20 to 30 percent of the monthly average fell overnight, while some areas in southeast Wales and central southern England saw 30 to 40 percent. In some places, up to 40 percent of December’s rainfall fell in just a few hours.

Why are some areas more affected than others?

The areas worst affected by flooding and disruption are those that have already seen exceptional rainfall in recent months. These regions are saturated and cannot absorb more water, so even moderate rainfall can quickly lead to flooding. South Wales and Southwest England, for example, have seen their rainfall deficit, built up over a dry spring and summer, completely erased since mid-October. In contrast, East Anglia still has a significant rainfall deficit, despite recent wet weather.

This contrast explains a common question: why are there both rain warnings and hosepipe bans in the UK at the same time? The answer is that rain warnings have mostly been issued for South Wales and Southwest England, while hosepipe bans remain in place in eastern parts of the UK, where the rainfall deficit persists.

The meteorology of Storm Bram: a Shapiro–Keyser low

Storm Bram is a fascinating meteorological feature, classified as a Shapiro–Keyser low. This type of low-pressure system often develops rapidly over the ocean and has a unique structure compared to other lows. In a typical low, the warm front and cold front are connected at a point called the triple point, with a warm sector in between. Eventually, the cold front catches up with the warm front, lifting the warm air above and merging the two fronts.

In a Shapiro–Keyser low, however, the fronts are more fractured. The warm front and cold front are separated, allowing warm air to wrap around the centre of the low, creating a warm core. This structure is important because a warm core leads to more rising air in the centre, adding energy and tightening the pressure gradient. The result is stronger winds circulating around the centre of the low, which can lead to explosive deepening, exactly what we have seen with Storm Bram.

Winds will gradually ease through Wednesday, but blustery conditions will persist in Scotland, northern England, and Northern Ireland. The contrast between north and south will be marked, with clearer skies and lighter winds in the south and southeast.

Unseasonable warmth: what’s behind it?

One striking feature of Storm Bram is the unusually warm air it has brought with it. Measurements from weather balloons launched from Camborne in Cornwall show that the thickness of the atmosphere - between the 1000 and 500 hectopascal pressure levels - is close to values seen during summer heatwaves. This is remarkable for December and highlights the fundamentally warm nature of the air mass, which has travelled from the tropics, North Africa, Iberia, and the warmer Atlantic.

This warmth has helped temperatures climb to near-record levels for December in places like Northern Ireland, where Magilligan recorded 16.3°C, just shy of the December record of 16.7°C. A warmer air mass can also hold more moisture, contributing to the heavy rainfall.

Looking ahead: more rain, but some hope for change

The outlook for the rest of the week remains unsettled. Further spells of rain are expected, with a slow-moving band of rain arriving through Thursday and Friday. The weekend brings another area of low pressure and the potential for widespread heavy rain, especially in western parts of the UK. Computer models differ on the timing and intensity of this rain, but the Met Office model currently suggests the wettest conditions could bring 50 to 100 millimetres to some western hills.

Looking further ahead, the most likely scenario is for continued Atlantic-driven westerly and south-westerly winds, bringing spells of rain, showers, and strong winds. Temperatures are expected to remain above average for the time of year. However, there are subtle hints that the week of Christmas could see a shift towards more settled, or at least less unsettled, weather. There are no signs of any significant cold or snow, but there is a glimmer of hope for something a bit less stormy as the year draws to a close.