Sting jets in extratropical cyclones: a review

This paper reviews the current state of knowledge of sting jets in extratropical cyclones. Sting jets were formally identified in 2004 by the pioneering work of Keith Browning. Reviewing this and subsequent studies, we define the sting jet as a coherent air flow that descends from mid-levels inside the cloud head into the frontal-fracture region of a Shapiro-Keyser cyclone over a period of a few hours leading to a distinct region of near-surface stronger winds. It therefore lies above the cold conveyor belt during some stage its life, but, at least in some cases, descends to reach the top of boundary layer ahead of the cold conveyor belt. It is not attributed to a specific mechanism in this definition. We conclude that it is likely that a continuum of sting jet descent and speed-up mechanisms exists. At one extreme is balanced descent partly associated with frontolysis in the frontal-fracture region. More horizontally small-scale and stronger frontolytic descent may occur associated with weak stability to slantwise convective downdraughts. Instability to slantwise convective downdraughts may occur in some systems, leading to multiple slantwise convective downdraughts associated with the release of conditional symmetric instability and even, possibly, symmetric instability. The global climatology of sting jets and the interaction between the atmospheric boundary layer and sting jets are revealed as specific areas where more research is needed. Finally, we describe eight myths and misunderstandings that exist in the current literature with the aim of guiding future research into the sting jet phenomenon.