Sting jet
[2][3][4] Sting jets are short-lived, lasting on the order of hours,[5] and the area subjected to their strong winds is typically no wider than 100 km (62 mi), making their effects highly localised.
Sting jets were first formally identified in 2004 by Keith Browning at the University of Reading in an analysis of the great storm of 1987, though forecasters have known of their effects since at least the late 1960s.
[6] The sting jet emerges from within the end of an extratropical cyclone's cloud head – a hook-shaped region of cloudiness near the centre of low pressure – and accelerates as it descends to the surface.
[7] They are characterised in part by their mid-tropospheric origin and the acceleration of descending air, and are distinct from the low-tropospheric airstreams accompanying the cold and warm conveyor belts of extratropical cyclones.
[8][9] Sting jets constitute one possible mechanism through which high winds can be produced in extratropical cyclones without being directly caused by atmospheric convection.
[3] The sting jet originates equatorward of the cyclone centre at the end of the back-bent front and near the tip of the cloud head following the frontal fracture stage of the Shapiro–Keyser model.
[25] Meteorologist Keith Browning at the University of Reading formally identified sting jets in a paper published in 2004 analysing the intense winds associated with the Great Storm of October 1987.
[26] His coinage of "sting jet" paid homage to the pioneering work of Norwegian meteorologists in the mid-20th century who likened the area of strong winds at the end of back-bent occlusions in storms affecting Norway to the "poisonous tail" of a scorpion.
[28] However, conclusive identification of sting jets requires confirmation of the presence of a descending airstream,[2] and detection can be difficult with routine meteorological observations.
[30][31] Research into sting jets outside of the northern Atlantic has been limited,[31] with case studies primarily focusing on European windstorms affecting the British Isles.
[33] The first aerial in situ observations of a sting jet were taken in Cyclone Friedhelm in 2011 as part of the Diabatic Influences on Mesoscale Structures in Extratropical Storms (DIAMET) field campaign.
[34] The appearance of banded structures in the cloud head associated with sloped circulations with alternating regions of ascending and descending air – possibly indicative of the release of conditional symmetric instability (CSI) – may also play a direct role in sting jet development, with air sinking in one of the cloud head downdraughts.
[1] The sting jet's rate of descent depends on the instability of the troposphere,[40] which in turn may be influenced by the local behaviour of water vapour, such as through evaporative cooling or the release of CSI.
[47] However, the boundary layer stability may be sufficiently high in some cases to prevent the descending sting jet from reaching the surface.
Longer range forecasts of sting jets rely on gauging whether or not the broader environmental conditions favour the development of a Shapiro–Keyser cyclone.
[50] The horizontal spacing of model grid cells must be smaller than about 10–15 km (6.2–9.3 mi) to depict sting jets, and finer resolutions are needed to resolve localised details.
