A prototype real-time sting jet precursor tool for forecasters

刺痛喷流是一种下行气流，可能会在秋季和冬季的暴风雨中导致破坏性的地面风和阵风。英国影响最大的喷气式飞机风暴包括大风暴(1987)，以及最近的圣犹大日(2013)和乔治娜(2018)风暴。项目组开发了一种基于对流不稳定的STING急流前兆，以在由于空间分辨率不足而无法代表STING急流的数据集中识别这些风暴。这些数据集包括再分析和全球集合天气预报模式输出。气候学分析表明，在所有北大西洋风暴中，约有30%存在这种前兆，对于爆炸性发展的风暴，这一比例增加到约40%。一项类似的分析适用于21世纪末使用最极端(RCP8.5)气候强迫情景的气候模型输出，发现具有前兆的爆炸性发展风暴增加了60%。此外，即使在重新分析中，带有前兆的风暴也是英国风暴相关强风的主要原因。在现实中，这些风将因刺痛急流的实际发生而增强。使用前兆及早发现风暴可以提前发出风力风险增强的预警，从而改善国家恶劣天气预警，从而改善气候适应能力。该项目的目的是开发一个供气象局预报员使用的原型实时前兆工具。现有的前兆诊断代码将被调整为对业务全球集合预报输出进行常规工作，以告知预报员未来7天内影响英国和欧洲的风暴是否具有前兆。我们将与预报员合作，开发合适的图形输出，并在2019年秋冬两季试用原型工具。如果原型工具成功，英国气象局预计将在他们的模型系统中实施它，以便所有他们的预测系统都可以使用STING-JET前兆诊断。

Sting jets are descending airstreams that can lead to damaging surface winds and gusts in autumn and winter storms. UK impacting sting-jet storms include the Great Storm (1987) and the more recent St Jude's day (2013) and Georgina (2018) windstorms. A convective-instability-based precursor to sting jets has been developed by the project team to identify these storms in datasets unable to represent sting jets due to insufficient spatial resolution. These datasets include reanalyses and global ensemble weather forecast model output. Climatological analysis has shown that this precursor is present in about 30% of all North Atlantic storms, increasing to about 40% for explosively-developing storms. A similar analysis applied to end of 21st century climate-model output using the most extreme (RCP8.5) climate forcing scenario found a 60% increase in explosively-developing storms with the precursor. Furthermore, even in reanalyses, storms with the precursor are the dominant cause of storm-related strong UK winds. In reality these winds will be enhanced by the actual occurrence of sting jets. Early detection of storms with the precursor could give advanced warning of enhanced wind risk and so improve national severe weather warnings and thus climate resilience. The project aim is to develop a prototype real-time precursor tool for use by Met Office forecasters. The existing precursor diagnostic code will be adapted to work routinely on operational global ensemble forecast output to inform forecasters whether or not storms impacting the UK and Europe up to seven days in the future have the precursor. We will work with forecasters to develop suitable graphical outputs and trial the prototype tool during autumn and winter 2019. If the prototype tool is successful then the Met Office anticipate implementing it within their model system such that the sting-jet precursor diagnostic would be available to all their prediction systems.