2017–18 UK and Ireland windstorm season

Aileen
Aileen located over the North Sea on 13 September 2017
Area affected	Northwestern Europe
Date of impact	12–13 September 2017
Maximum wind gust	134 km/h
Lowest pressure	990 hPa
Fatalities	0
Power outages	69,000
Damage	Unconfirmed

Ophelia
Ex-Hurricane Ophelia moving over Ireland on 16 October
Area affected	Portugal, Spain, France, Ireland, United Kingdom, Faroe Islands, Norway, Sweden, Finland, Russia
Date of impact	16–17 October 2017.
Maximum wind gust	191 km/h
Lowest pressure	959 hPa or 962.2 hPa (onshore).
Fatalities	3 direct, 51 indirect
Power outages	360,000
Damage	€60m

Brian
Brian located over the eastern Atlantic on 20 October
Date of impact	21 October 2017
Maximum wind gust	137 km/h
Lowest pressure	956 hPa
Fatalities	3
Power outages	Unknown
Damage	Unconfirmed

Caroline
Caroline approaching the British Isles on 5 December
Area affected	Ireland, Scotland, Faroe Islands, Norway.
Date of impact	7 December 2017
Maximum wind gust	93 miles per hour (150 km/h) Fair Isle, Shetland.
Lowest pressure	~959 hPa
Fatalities	1
Damage	Unconfirmed

.

The 2017–18 UK and Ireland windstorm season is the third and current instance of the United Kingdom's Met Office and Ireland's Met Éireann naming high impact extratropical cyclones. The first system, Storm Aileen, formed on 12 September. The season also featured Ex-Hurricane Ophelia, the extratropical remnants of Atlantic hurricane Ophelia. Storm Brian struck Ireland less than a week later, resulting in three fatalities.

The season succeeded the 2016–17 UK and Ireland windstorm season.

In 2015, the Met Office and Met Éireann announced a pilot project to name storm warnings as part of the Name our Storms project for wind storms and asked the public for suggestions. The meteorological offices produced a full list of names for 2015–16 and 2016–17, common to both the UK and Ireland. A new list of names was released on 6 September 2017 for the 2017–18 season. Names in the UK will be based on the National Severe Weather Warning Service, when a storm is assessed to have the potential for an Amber 'be prepared' or Red 'take action (danger to life)' warning.

The following were selected as storm names:

The Met Office's and Met Éireann's announcement of the season's names also noted that Fionn is to be pronounced 'Fyunn', Niall is to be pronounced 'Nye-ul' and Tali is to be pronounced 'Tarly'. In addition to the names on the list, when Ophelia, named Ophelia by the NHC, transitioned from tropical to extratropical and was expected to hit Ireland and the UK as a hurricane-strength windstorm, the Met Office and Met Éireann allowed it to retain its NHC-designated name instead of naming it Brian. (Only Aileen had previously occurred in the season.)

A storm will be named when it is deemed able to have a "substantial" impact on the UK or Ireland. They will be taken from the list, in alphabetical order, alternating between male and female names – the same naming convention that is used by the United States for tropical cyclones. In the case of storms resulting from ex-tropical storms and hurricanes, the original name allocated by the US National Hurricane Center will be used, an example of which during this season is Ophelia. Met Éireann name any storm which triggers a status Orange or Red weather warning for wind. The basis for such, as outlined on their weather warning service, are mean wind speeds in excess of 40 mph (65 km/h) or gusts over 68 mph (110 km/h). Similarly, the Met Office name storms that have the potential to cause medium (Amber) or high (Red) impacts to the UK. It describes the wind strength relative to observations such as "falling trees or tiles, other items like garden furniture being blown around and even a number of properties left without electrical power."