The extreme event solutions business unit of Verisk estimates industry insured losses due to wind from Winter Storm Ciarán will range between EUR 800 mn and EUR 1.3 bn, the majority of which are expected in France.
Storm Ciarán, following close on the heels of Storm Babet just two weeks ago, has been driven by a powerful jet stream from the Atlantic, unleashing heavy rain and furious winds that have already caused heavy flooding in Northern Ireland and parts of Britain, according to Forbes.
Tornados happen mostly in North America, although a very small number are reported each year in the U.K. The Met Office has confirmed that a tornado hit Jersey on November 1.
Ciarán has also set a record, delivering the lowest mean sea level pressure recorded in England and Wales in November. A low pressure system has lower pressure at its centre than the areas around it and tends to create unsettled weather with clouds and precipitation.
Severe convective storms are among the most common, most damaging natural catastrophes in the United States. The result of warm, moist air rising from the earth, they manifest in various ways, depending on atmospheric conditions – from drenching thunderstorms with lightning, to tornadoes, hail, or destructive straight-line winds.
The U.S. is experiencing its costliest year ever in 2023 for severe convective storms, with insured losses from these events exceeding $50 bn through the October
Recent years have seen an increase in organized lines of thunderstorms with widespread damaging winds, known as derechos.
The 2023 weather and climate disasters causing at least $1 billion in damage, both insured and uninsured, are chronicled by the federal government and featured in a chart Triple-I (Severe Thunderstorms the Main Driver for Insured NatCat losses).
Meteorological Background of Ciaran
Ciarán began as a shallow low that developed over the Ohio Valley, U.S., on Sunday 29 October, associated with very strong temperature gradients in the region (see Worldwide Severe Convective Storms: Listing of Global Events & Economic Loss)
The storm explosively deepened by 34 mb in 24 hours over warm sea surface temperatures, classifying Ciarán as a bomb cyclone.
The low-pressure center of Ciarán arrived in south-western parts of England overnight into Thursday 2 November at 952 mb, the lowest pressure ever recorded in England and Wales in November.
However, high-exposure regions in the area were spared the worst impacts from the storm. Rainfall totals in north-western Europe were less remarkable, but following a period of sustained wet weather, there was some further flooding in parts of southern England.
The long trailing cold front from Ciarán spawned another shallow low over the Alps, causing significant flooding in southern parts of Europe, most notably the Tuscany region of Italy, far away from the center of the storm.
This flooding, along with the impacts in France and elsewhere from windstorm Domingos over the past weekend, may contribute losses to this event, which, depending on hours clauses, could be considered a single loss occurrence along with Ciarán’s wind impacts.
Hazard and Damage Observations
Ciarán’s impacts were most pronounced in northwest France and the Channel Islands. In France, the worst damage was in the northwest, in Brest. Similar impacts were observed in the Channel Islands.
Jersey in particular was very hard hit, with some of the more extreme roof and structural damage there likely caused by a strong tornado that was spawned by the storm.
Jersey also saw golf ball-sized hail which contributed to both roof and automobile damage. The large amount of tree-related damage from this storm was exacerbated by the fact that most trees in the region still have leaves on them and the ground was quite saturated, making it more likely for trees to become uprooted or fall over.
Verisk’s modeled insured loss estimates include insured physical damage from wind to property (residential, commercial, industrial, agricultural, and motor, including structures and their contents, as well as business interruption and additional living expenses (for the UK only).
How much this is down to climate change?
British weather is internationally known as bad and now it seems it’s going to get worse. The big question is how much this is down to climate change.
According to the latest State of the U.K. Climate report, the U.K. has become wetter over the last few decades, although the extent varies from year to year. Overall, the years 2011-2020 were 9% wetter than 1961-1990.
Although rainfall patterns in the U.K. vary, the country is expected to experience wetter winters and drier summers. Summer rain will likely be more intense. For example, rainfall from an event that typically occurs once every two years in summer is expected to increase by around 25%.
The consequences for infrastructure, transport and the wider economy are significant. More frequent and severe surface water flooding is expected, particularly in urban areas. And as global temperatures rise, the number of extreme rainfall days is expected to increase. The link with climate change is becoming increasingly apparent.Edited by Oleg Parashchak