An average of about 10 tornadoes occur in Ireland each year, according to Met Éireann.
Usually referred to as “mini-tornadoes” to distinguish them from the larger ones recorded in the US and other countries, these infrequent weather events can nonetheless pose risks for people and property.
“Tornadoes are rare but not uncommon in Ireland. They aren’t on the scale you see in the US but even a small tornado can cause damage,” according to meteorologist Aoife Kealy of Met Éireann.
US tornadoes usually occur in the mid-west or south, mainly in spring and early summer. Bangladesh has a history of devastating tornadoes; the deadliest of these killed an estimated 1,300 people in 1989. In Europe, about 200-300 tornadoes a year are reported.
What is believed to be Ireland’s first documented tornado occurred near Kilbeggan, Co Westmeath, on April 30th, 1054 and is documented in the Annals of the Four Masters.
In 1967, a tornado in Killeagh, Co Cork, carved a swathe of havoc 100m (328ft) wide along a five-mile track. Ricks of hay were lifted into the air and scattered over a wide area, slates were ripped from houses and trees in its path were felled or stripped of foliage.
A similar event occurred in Ballyhaunis, Co Mayo, in November 1977, when a swirling funnel, 10m (32ft) in diameter caused damage. Another tornado in Youghal, Co Cork, in 1995 briefly lifted caravans in a park before depositing them across the road.
Traditionally, supercells – a type of thunderstorm with a deep rotating updraft – are necessary to spawn the strongest tornadoes. Supercells are extremely rare in Ireland and thus landspouts (weak tornadoes not associated with a supercell) are more common. Landspouts are often generated along squall lines or associated with briefly energetic cumulus clouds. Funnel clouds also form in Ireland – those that do not come into contact with the ground or other surface are most common.
Summertime is marginally more conducive to the formation of tornadoes, but in Ireland the risk, though low, spans the year. Most tornadoes here are weak and brief and many occur without being noticed.
Some scientists are looking at the possibility that thunderstorms with conditions favourable for tornado events and warmer, unstable weather attributed to climate change may be linked.