Development of localized damaging wind gusts associated with a frontal wave and mesoscale vortex across south Wales on 18 May 2015

Young, Matthew; Clark, Matthew R.

doi:10.1002/met.1677

Cited by 4 publications

(6 citation statements)

References 23 publications

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“…These represent a descending jet originating from the cloud head behind a bent-back cold front, driven by slantwise CAPE, and possibly evaporation from the cloud head, and distinct from jets associated with the warm and cold conveyor belts; typically sting jets are found in explosively developing cyclones (MartinezAlvarado et al, 2012(MartinezAlvarado et al, , 2014Hart et al, 2017). Volonte et al (2017) use back trajectories to confirm this conceptual picture, while Young and Clark (2018) demonstrate how lesser sting jets may be able to enhance winds in weaker storms. Volonte et al (2017) use a 12 km model grid, demonstrating that very high resolution is not needed for sting jets to be present.…”

Section: Challengesmentioning

confidence: 99%

Current gust forecasting techniques, developments and challenges

Sheridan

2018

Adv. Sci. Res.

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Abstract.Gusts represent the component of wind most likely to be associated with serious hazards and structural damage, representing short-lived extremes within the spectrum of wind variation. Of interest both for short range forecasting and for climatological and risk studies, this is also reflected in the variety of methods used to predict gusts based on various static and dynamical factors of the landscape and atmosphere. The evolution of Numerical Weather Prediction (NWP) models has delivered huge benefits from increasingly accurate forecasts of mean near-surface wind, with which gusts broadly scale. Techniques for forecasting gusts rely on parametrizations based on a physical understanding of boundary layer turbulence, applied to NWP model fields, or statistical models and machine learning approaches trained using observations, each of which brings advantages and disadvantages.Major shifts in the nature of the information available from NWP models are underway with the advent of ever-finer resolution and ensembles increasingly employed at the regional scale. Increases in the resolution of operational NWP models mean that phenomena traditionally posing a challenge for gust forecasting, such as convective cells, sting jets and mountain lee waves may now be at least partially represented in the model fields. This advance brings with it significant new questions and challenges, such as concerning: the ability of traditional gust prediction formulations to continue to perform as phenomena associated with gusty conditions become increasingly resolved; the extent to which differences in the behaviour of turbulence associated with each phenomenon need to be accommodated in future gust prediction methods. A similar challenge emerges from the increasing, but still partial resolution of terrain detail in NWP models; the speed-up of the mean wind over resolved hill tops may be realistic, but may have negative impacts on the performance of gust forecasting using current methods. The transition to probabilistic prediction using ensembles at the regional level means that considerations such as these must also be carried through to the aggregation and post-processing of ensemble members to produce the final forecast. These issues and their implications are discussed.Copyright statement. The works published in this journal are distributed under the Creative Commons Attribution 4.0 License. This license does not affect the Crown copyright work, which is re-usable under the Open Government Licence (OGL). The Creative Commons Attribution 4.0 License and the OGL are interoperable and do not conflict with, reduce or limit each other.

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Section: Challengesmentioning

confidence: 99%

Current gust forecasting techniques, developments and challenges

Sheridan

2018

Adv. Sci. Res.

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“…Such development appears atypical, and the few cases analysed to date all involved unusually small frontal waves with wavelengths on the order of tens of kilometres (e.g. Clark, 2013;Young and Clark, 2018).…”

Section: Conceptual Frameworkmentioning

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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“…Several of the attributes described above resemble miniature versions of features in synoptic-scale cyclones. For example, the wellmarked, curved surface front on the northwest flank of the mesolow and the expanding cloud area associated with the rainfall shield resemble, respectively, the back-bent front and the cloud head in larger cyclonic storms of the Shapiro-Keyser type (Shapiro and Keyser, 1990), as emphasised in the schematic model of Young and Clark (2018) for the case of 18 May 2015 over south Wales (their fig. 13).…”

Section: Radar-observed Storm Structurementioning

confidence: 93%

“…4 of Clark, 2012, and fig. 8 of Young and Clark, 2018). The involvement of an upper‐level PV anomaly suggests that the storms may be considered examples, albeit on an unusually small spatial scale, of the ‘type 2’ cyclonic development of Petterssen and Smebye (1971) (also called ‘multi‐body’ cyclogenesis; Semple, 2003), involving interaction between upper‐level features and a surface front.…”

Section: Synoptic and Mesoscale Settingmentioning

confidence: 96%

Mesoscale cyclonic storms associated with tornadoes and localised wind damage in frontal rainbands

Clark

2023

Weather

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Ten cases are identified of an unusual type of mesoscale windstorm in the United Kingdom between 2006 and 2021. The windstorms, which occurred in association with frontal rainbands, produced wind damage swaths no more than 20–30km wide, but sometimes extending for several hundred kilometres, often with embedded tornadoes. Storm structure and evolution are explored for two cases using radar data, surface observations, a 1.5‐km gridlength model and damage reports obtained from social media platforms and post‐event damage surveys. Findings are summarised in the form of a conceptual model, and some questions are posed for future research.

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Development of localized damaging wind gusts associated with a frontal wave and mesoscale vortex across south Wales on 18 May 2015

Cited by 4 publications

References 23 publications

Current gust forecasting techniques, developments and challenges

Current gust forecasting techniques, developments and challenges

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

Mesoscale cyclonic storms associated with tornadoes and localised wind damage in frontal rainbands

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