Supercell and Non‐supercell Tornadoes in the United Kingdom and Ireland

Clark, Matthew R.; Smart, David

doi:10.1002/9781118949986.ch3

Cited by 10 publications

(11 citation statements)

References 48 publications

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“…Recent climatologies suggest that the United Kingdom experiences an average of approximately 30 tornadoes per annum (Reynolds, 1999; Kirk, 2007; Mulder and Schultz, 2015), of which 40–50% are associated with precipitation systems exhibiting quasi‐linear morphologies in radar rainfall imagery (Mulder and Schultz, 2015; Clark and Smart, 2016). An important type of quasi‐linear precipitation system is the narrow cold‐frontal rainband (NCFR: Houze et al ., 1976).…”

Section: Introductionmentioning

confidence: 99%

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: Shear‐zone vortex‐genesis in a developing frontal wave

Clark

Parker

Hanley

2021

Quart J Royal Meteoro Soc

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High-resolution model simulations and radar observations are used to investigate the onset of vortex-genesis in a tornadic narrow cold-frontal rain band (NCFR). The timing and location of vortex-genesis was strongly constrained by a developing frontal wave, which tracked northeast across the United Kingdom and Ireland on 17 October 2011. In the simulations, vortices occurred preferentially during the early stages of wave development and just down-front of the wave centre, where large increases in vertical vorticity occurred in concert with decreases in the cross-frontal confluence. Vortex-genesis ceased as the frontal wave matured, due to the onset of frontal fracture. Two distinct scales of vortex-genesis are documented: primary vortex-genesis on the meso-γ-scale, and secondary vortex-genesis on the miso-scale. We show that horizontal shearing instability is the most likely vortex-genesis mechanism, consistent with previous theoretical work on the stability of vertical vortex strips in the presence of horizontal stretching deformation. Secondary vortices occurred along the braid regions between primary vortices where the shear zone became particularly narrow and intense. In the model, these vortices developed extremely rapidly (from small perturbations to maximum vertical vorticity in 5-15 min) and the strongest exhibited near-surface vertical vorticity maxima approaching 10 −1 s −1 .Vortices of both scales were associated with characteristic local perturbations in the NCFR and we show, by comparison with radar reflectivity data, that primary and secondary vortices were likely present in the real NCFR. Tornado reports were associated with small NCFR perturbations like those associated with the secondary vortices in the model simulations. Analysis of the sub-structure of individual simulated vortices suggests that tornado-genesis is most likely within a region of intense near-surface vertical vorticity stretching at the north or northwest flank of the secondary vortices.

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Section: Introductionmentioning

confidence: 99%

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: Shear‐zone vortex‐genesis in a developing frontal wave

Clark

Parker

Hanley

2021

Quart J Royal Meteoro Soc

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“…Mulder and Schultz (2015) found that 42% of tornadoes occurred in storms exhibiting linear morphologies in radar imagery over the period 2004–2012, of which NCFRs are a major subset. Clark and Smart (2016) found that 34.1% of tornadoes over the period 2003–2012 were associated with NCFRs specifically; this percentage increases to 48.8% when the weakest tornadoes (T0 or T1 on the International Tornado Intensity [T] Scale: Meaden, 1976a) are excluded. Furthermore, NCFRs have been responsible for many of the larger outbreaks of tornadoes in the UK (Meaden, 1976b; 1978; 1979; 1983; Elsom, 1983; 1985; Meaden and Rowe, 1985; Turner et al ., 1986; Apsley et al ., 2016).…”

Section: Introductionmentioning

confidence: 99%

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: A generalised measure of tornado risk and identification of synoptic types

Clark

Parker

2020

Quart J Royal Meteoro Soc

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Environments of tornadic and non-tornadic narrow cold-frontal rain bands (NCFRs) are investigated using ERA-Interim reanalyses for a sample of 114 events over the United Kingdom and Ireland (44 tornadic). The results offer a practical tool for prediction of the likelihood of tornadoes in these potentially high-impact events. Of 22 analysed parameters, a bulk measure of shear vorticity, and the front-normal wind component on the cold side of the front, yield the best discrimination between event classes, showing significantly larger values in tornadic events. A generalised measure of tornado probability, p[TN], is obtained using the distribution of points within the two-dimensional parameter space defined by these parameters. Synoptic situations commonly associated with tornadic NCFRs are identified and conceptual models describing the large-scale evolution are developed. Most events are associated with developing secondary cyclones (i.e., frontal waves) along trailing cold fronts (≥54.5%), generally within west to southwesterly large-scale flow. Another significant class of event corresponds to situations where a strong mid-to upper-level jet streak cuts across the front within an amplifying large-scale flow pattern (upstream ridge building and downstream trough extension), generally within northwesterly flow (27.3%). In frontal waves, tornadoes occurred relatively early in the wave's development and just down-front of the wave centre, where rapid increases in p[TN] occurred as the wave amplified. In northwesterly flow cases, tornadoes occurred along a well-defined NCFR bulge close to where the mid-to upper-level jet streak and an associated positive potential-vorticity anomaly intersected the front. Analysis of a high-tornadic subset of tornadic events (NCFRs producing ≥7 tornadoes) revealed an even stronger association with frontal waves (72.2% of cases), suggesting that the highest-impact events are usually associated with secondary cyclogenesis. The possible relevance of identified environmental parameters to This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…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).…”

Section: Previous Hailstorms In Leicestershirementioning

confidence: 99%

Preliminary analysis and perspective of the severe hailstorms on 20 July 2021 – including the Kibworth (Leicestershire) storm

Webb¹

2021

Weather

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Supercell and Non‐supercell Tornadoes in the United Kingdom and Ireland

Cited by 10 publications

References 48 publications

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: Shear‐zone vortex‐genesis in a developing frontal wave

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: Shear‐zone vortex‐genesis in a developing frontal wave

Synoptic‐scale and mesoscale controls for tornadogenesis on cold fronts: A generalised measure of tornado risk and identification of synoptic types

Preliminary analysis and perspective of the severe hailstorms on 20 July 2021 – including the Kibworth (Leicestershire) storm

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