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Severe hailstorms in the United Kingdom and Ireland: a climatological survey with recent and historical case studies
... Geographical surveys of severest hailstorms by UK county area (Webb and Elsom, 2016) indicated that Leicestershire was one of the four counties with the highest frequencies, albeit still well below the incidence of some countries of continental Europe (Webb et al., 2009, section 5). The storm of 28 June 2012 caused far more widespread damage across Leicestershire from a west-southwest to east-northeast tracking supercell (Clark and Smart, 2016) with hailstones 50mm across and with some conglomerate stones measuring 90mm across (see Clark and Webb, 2013;Webb and Elsom, 2016). ...
... Geographical surveys of severest hailstorms by UK county area (Webb and Elsom, 2016) indicated that Leicestershire was one of the four counties with the highest frequencies, albeit still well below the incidence of some countries of continental Europe (Webb et al., 2009, section 5). The storm of 28 June 2012 caused far more widespread damage across Leicestershire from a west-southwest to east-northeast tracking supercell (Clark and Smart, 2016) with hailstones 50mm across and with some conglomerate stones measuring 90mm across (see Clark and Webb, 2013;Webb and Elsom, 2016). This hailswath continued on into Lincolnshire, as did another severe hail squall on 24 July 1994 which severely damaged crops and farm buildings south of Melton Mowbray (Leicestershire). ...
... The exceptional nature of the analyzed event is more evident considering the climatology of the area affected (Webb andElsom, 2015, Baldi et al., 2014), which indicates an expected maximum hail diameter equal to or slightly >2 cm with a frequency of 0.71 events/yr (0.3 event/ yr for hail diameter >2 cm). ...
... Descriptive accounts of floods (as well as short period rainfall) in British Rainfall to 1970 and the Climatological Observer Link (COL) from 1970 were the most widely used sources. Additional information for the most extreme events was found in published books and papers, notably Eden (2008) with respect to weather disasters and Webb and Elsom (2016) for extreme hail events. The flood information for this recent period is still incomplete (compared with the period before 1950) and the chronology therefore requires a facility to enter additional information as it becomes available. ...
The chronology provides a record of flash flood events in Britain based on data collated mainly between 1700 and 2020. The primary purpose of the chronology is to improve the risk assessment of flash floods of given magnitude. It is divided into 18 regions of the country and contains descriptions of nearly 8000 events. It extends a previous chronology covering northern and southwest England which is provided as an online resource in (http://ceg-fepsys.ncl.ac.uk/outputs/). Flash floods have had a variety of previous definitions but are here defined in terms of the speed of onset which can apply to both river floods and surface water floods. The chronology for the first time provides a comprehensive list of surface water floods and their recorded impact on cities, towns and villages. It also draws attention to the prevalence of very rapid rates of rise in river level either as ‘walls of water’, or at a rate likely to endanger life as a result of intense rainfall. Nearly 300 such events have been identified mainly in upland areas of northern England, Wales and Scotland. Practical and theoretical issues with respect to flood risk assessment and warning are discussed. The chronology is available to download and is hosted on https://www.jbatrust.org/how-we-help/publications-resources/rivers-and-coasts/uk-chronology-of-flash-floods-1/
... Later, Webb & Elsom (2016) found that by using decadal totals there was some evidence of a downward trend from a peak in the late 1890's to the early 1900's. ...
Modelling multiple hazard interrelations remains a challenge for practitioners. This article primarily focuses on the interrelations between pairs of hazards. The efficacy of six distinct bivariate extreme models is evaluated through their fitting capabilities to 60 synthetic datasets. The properties of the synthetic datasets (marginal distributions, tail dependence structure) are chosen to match bivariate time series of environmental variables. The six models are copulas (one non-parametric, one semi-parametric, four parametric). We build 60 distinct synthetic datasets based on different parameters of log-normal margins and two different copulas. The systematic framework developed contrasts the model strengths (model flexibility) and weaknesses (poorer fits to the data). We find that no one model fits our synthetic data for all parameters but rather a range of models depending on the characteristics of the data. To highlight the benefits of the systematic modelling framework developed, we consider the following environmental data: (i) daily precipitation and maximum wind gusts for 1971 to 2018 in London, UK, and (ii) daily mean temperature and wildfire numbers for 1980 to 2005 in Porto District, Portugal. In both cases there is good agreement in the estimation of bivariate return periods between models selected from the systematic framework developed in this study. Within this framework, we have explored a way to model multi-hazard events and identify the most efficient models for a given set of synthetic data and hazard sets.
Abstract. Estimating risks generated by multi-hazard scenarios remains a challenge for practitioners. Here we evaluate the efficacy of bivariate extreme modelling approaches by fitting six distinct stochastic models to synthetic datasets. The properties of the synthetic datasets (marginal distributions, tail dependence structure) are chosen to match bivariate time series of environmental variables. The six models are copulas (one non-parametric, one semi-parametric, four parametric). We build 60 distinct synthetic datasets based on different parameters of log-normal margins and two different copulas. We contrast the model strengths (model flexibility) and weaknesses (poorer fits to the data). We find that no one model fits our synthetic data for all parameters, but rather a range of models are more appropriate To highlight the benefits of the systematic modelling framework developed, we consider the following environmental data: (i) daily precipitation and maximum wind gust in London, UK; (ii) daily mean temperature and wildfire number in Porto district, Portugal. In both cases there is good agreement in the estimation of bivariate return periods between models selected from the systematic framework developed in this study. Within this framework, we have explored a way to model multi-hazard events and identify the most efficient models for a given set of synthetic data and hazard sets.
Globally and yearly, individual hazards and hazard interrelations have the potential to result in socio-economic losses. Here, in this critical review, we use grey- and peer-review literature to identify and compare current research available for the quantification of hazard interrelations, focussing on 14 different natural hazards. We first provide a historical context for quantitative single hazard and multi-hazard assessment. We then construct a literature database with 146 references related to multi-hazard interrelations. We use our literature database to identify trends for hazard interrelation and multi-hazard and from these group hazard interrelations into five types: triggering, change condition, compound, independence and mutually exclusive. Our critical review identifies 19 different modelling methods to quantify natural hazard interrelationships which we cluster into three broad modelling approaches: stochastic, empirical, and mechanistic. We then synthesize results of our classification of quantification methods for hazard interrelationships and using two matrices illustrate this in practice for 24 different interrelations between 14 natural hazards, one for cascading hazards (temporal order in the multi-hazard event) and one for compound hazards (two or more hazards acting together). Finally, we provide examples of applications for each the three quantitative modelling approaches defined. We believe that this review will lead to a better understanding of quantification methodologies for hazard interrelations between different sub-disciplines that focus on natural hazards, thus aiding cross-disciplinary approaches for better understanding potential risk related to multi-hazard events.
At the time of a severe hailstorm on 5 June 1983, a quantity of coke and clinker, with small amounts of coal and gravel, ranging in size from dust and grit to pieces weighing up to 18 to 50 grammes fell coated in ice along with golfball-sized hail. This was witnessed, independently, by several dozens of people in Wareham, Poole and Bournemouth in the county of Dorset. The paper summarises the quantitative evidence and concludes that not far to the west of Wareham the contents of a heap of coke together with some furnace waste, standing possibly in the grounds of a factory or industrial plant, were levitated by tornadic-type winds to atmospheric-icing levels. In extreme east Bournemouth near Hengistbury Head, a rain of sand with hail occurred and much further east at Brighton (Sussex) a crab fell with the big hailstones. These other events, too, would seemingly be attributed to the effects of whirling rising winds. -Author
Hailstorms developed rapidly along the south coast of England during the late morning of 5 June 1983. They occurred on the cold side of a narrow baroclinic zone and just ahead of a rather shallow middle-level trough. Although these synoptic features were moving eastwards, satellite and radar indicates that all the storms originated close to the south coast of Devon over a period of three hours, suggesting that some form of localized forcing was occurring in this region.-Author
During a very thundery 36 hour period, two severe thunderstorm events on 17 May 1997 deposited hailstones 40 mm diameter or more in Oxfordshire, Buckinghamshire and Bedfordshire.
Following a brief incursion of very warm air into SE England on 15 July 2007, a severe thunderstorm system, with a locally destructive hailstorm and squall, affected East Sussex, Kent and adjacent coastal areas.
Statistics of thunderstorm days and days with hail and ice of different types for climatological stations in the United Kingdom are presented. Means for the ten climatological districts and lists of days and months with most activity are given. -Author
The results of this analysis clearly suggest that the Thames Valley, including London, the East Midlands, and southern parts of East Anglia are the areas most at risk. Although many falls of "large hail' are very localised, the most destructive hailstorms (TORRO severity H6 or more) are usually associated with a long storm track, occasionally hundreds of kilometers long and many kilometres wide. An extreme example of such an event was the historic storm of 22 September 1935, which is described in some detail. On that occasion large hail fell along an apparently unbroken swath, about 330km long and up to 16km in width, extending from the Bristol Channel to the Norfolk coast. -from Authors