How the Met Office decides when to name a storm
Why UK and Irish storms get names, who chooses them, the threshold a storm has to reach and why some letters of the alphabet are always skipped.
Storm names have become a fixture of British and Irish autumns and winters. They are chosen and applied under a system run jointly by three national weather services, and a storm only gets a name if it is expected to have a significant impact.
Who names the storms
The UK's Met Office and Met Éireann in Ireland began naming storms together in 2015. The Dutch national weather service, KNMI, later joined, and the three now share one list. Together they form what is known as the western group, one of several groups of European forecasters that each name storms affecting their own region.
The aim is public safety. A single, memorable name makes it easier for broadcasters, councils, emergency services and the public to talk about the same weather system, and it helps warnings cut through.
When a storm gets a name
A storm is named when it is forecast to bring medium or high impacts to the UK, Ireland or the Netherlands. In practice, that means it is likely to lead to amber or red weather warnings from at least one of the three services.
Wind is the main factor, but the decision also takes account of rain and snow. A deep area of low pressure can bring heavy rain that floods homes and roads without the wind ever being exceptional, and it may still be named because of the impact.
Forecasters consider the impact of the weather, not just how strong it is. The same wind speed can cause far more disruption in October, when trees are still in leaf, or in a densely populated area, than it would on a remote coast in midwinter.
Naming is not automatic. Many windy spells pass with only yellow warnings and no name at all.
How the names are chosen
The list for each season runs from September to the following August and is usually published in early September. Names alternate between male and female and run in alphabetical order. Members of the public can suggest names, and the three services each contribute to the list, so it tends to mix English, Irish and Dutch names.
The letters Q, U, X, Y and Z are not used, in line with the convention followed by the US National Hurricane Center for Atlantic storms. That keeps the naming system consistent across the ocean.
Most seasons do not come close to reaching the end of the list.
Not every named storm affecting Britain comes from the western group's list. If a storm has already been named by another European group, such as the one covering Spain, Portugal, France and Belgium, it keeps that name when it reaches the UK.
The same applies to the remnants of Atlantic hurricanes. When a former hurricane crosses the ocean and affects the UK or Ireland, it is referred to by its existing name with "Ex-" in front, rather than being given a new one.
What a name means for you
A name is a signal to pay attention, not a separate type of warning. The detail is in the warnings themselves. Yellow, amber and red warnings each describe the likely impact and the areas affected, and they are updated as forecasts firm up.
Practical steps when a named storm is forecast include securing bins, garden furniture and trampolines, checking travel updates before setting out and avoiding coastal paths and sea fronts during high winds. Flood warnings in England are issued separately by the Environment Agency, and in Scotland, Wales and Northern Ireland by their own agencies, so check those alongside the Met Office forecast.
