The Great Storm of 1987

A sting jet is a meteorological phenomenon which has been postulated to cause some of the most damaging winds in extratropical cyclones, developing according to the Shapiro-Keyser model (though perhaps not exclusively)[1] of oceanic cyclones.

Concept

Conceptual model for a European Windstorm and the associated strong wind 'footprints'. Note that storm track, footprint locations and footprint sizes vary by case, and that all footprints are not always present.[2]
Conceptual model for a European Windstorm and the associated strong wind 'footprints'. Note that storm track, footprint locations and footprint sizes vary by case, and that all footprints are not always present.[2]

Following reanalysis of the UK Great Storm of 1987, led by Professor Keith Browning at the University of Reading, researchers identified a mesoscale flow where the most damaging winds were shown to be emanating from the evaporating tip of the hooked cloud head on the southern flank of the cyclone. This cloud, hooked like a scorpion's tail, gives the wind region its name the "sting jet".[3]

It is thought that a zone of strong winds, originating from within the mid-tropospheric cloud head of an explosively deepening depression, are enhanced further as the "jet" descends, drying out and evaporating a clear path through snow and ice particles. The evaporative cooling leading to the air within the jet becoming denser, leading to an acceleration of the downward flow towards the tip of the cloud head when it begins to hook around the cyclone centre. Windspeeds in excess of 80 kn (150 km/h) can be associated with the sting jet.[4]

Sting jets are generally about 10 to 20 kilometres wide. A narrow area of land may be hit by very intense winds of 85 knots (157 km/h) or more, but 50 km away there may be the wind speeds associated with a normal storm, of about 50–60 knots (93–111 km/h), making the damage from a sting jet very localised.[5]

Sting jets have been reproduced in high-resolution runs with the mesoscale version of the Unified Model of weather prediction. The sting jet is distinct from the usual strong-wind region associated with the warm conveyor belt and main cold front. There are indications that conditional symmetric instability also plays a role in its formation but the importance of these processes remains to be quantified.[6][7]

One North Atlantic storm, Cyclone Tilo (November 6–11, 2007) was analysed and found not to display a sting jet, despite generating strong surface winds and displaying a fractured cold front.[7] [8]

Globally

The sting jet mechanism has been considered less significant in Pacific Northwest windstorms which occur over the Pacific Ocean (which impact the Northwestern United States and British Columbia).[9] Evidence of mesoscale high wind areas has not been noted in most large windstorms occurring there, along with cloud geometry associated with the phenomena being absent in satellite imagery of major Pacific Northwest storms.[9] Although a case study of a sting jet in the region has been produced.[10] High resolution computer models of the phenomena have also shown realistically strong winds without the need for sting jet dynamics.[9]

List of sting jet cyclones

For a list of sting jet cyclones and proposed occurrences, see List of sting jet cyclones.

Sting jets can be spotted on satellite images as they develop, due to the end of the cold conveyor being marked by a scorpion-like hook-shaped cloud with a point at the end.[5] About a dozen confirmed sting jets have been identified since the Great Storm of 1987 which led to their discovery. See the associated list.

Further reading

References

  1. ^ Schultz, David M.; Browning, Keith A. (March 2017). "What is a sting jet?". Weather. 72 (3): 63–66. Bibcode:2017Wthr...72...63S. doi:10.1002/wea.2795.
  2. ^ Hewson, Tim D.; Neu, URS (2015-01-01). "Cyclones, windstorms and the IMILAST project". Tellus A. 67 (1): 27128. Bibcode:2015TellA..6727128H. doi:10.3402/tellusa.v67.27128.
  3. ^ Browning, Keith; Peter Clark; Tim Hewson; Robert Muir-Wood (2003). "Damaging winds from European cyclones". The Royal Society. Retrieved 27 March 2013.
  4. ^ Meteorological glossary Booty.org, retrieved 2007-17-10
  5. ^ a b Slawson, Nicola (18 February 2022). "What is a 'sting jet'? Scientists warn of repeat of 1987 phenomenon". The Guardian.
  6. ^ Cyclonic storms Archived 2003-12-14 at archive.today UWERN newsletter, retrieved 2007-17-10
  7. ^ a b Gray, S. L.; Martínez-Alvarado, O.; Baker, L. H.; Clark, P. A. (2011). "Conditional symmetric instability in sting-jet storms". Quarterly Journal of the Royal Meteorological Society. 137 (659): 1482–1500. Bibcode:2011QJRMS.137.1482G. doi:10.1002/qj.859.
  8. ^ Slawson, Nicola (2022-02-18). "What is a 'sting jet'? Scientists warn of repeat of 1987 phenomenon". the Guardian. Retrieved 2022-02-19.
  9. ^ a b c Mass, Clifford; Dotson, Brigid (2010). "Major Extratropical Cyclones of the Northwest United States: Historical Review, Climatology, and Synoptic Environment". Monthly Weather Review. 138 (7): 2499–2527. Bibcode:2010MWRv..138.2499M. doi:10.1175/2010MWR3213.1.
  10. ^ Doyle, Chris; Ruping, Mo (16 December 2015). "A Rather Rare West-Coast Sting-Jet Event during December 12-13th, 2015" (PDF). National Laboratory for Coastal and Mountain Meteorology, Environment and Climate Change Canada, Technical Report 2015-001 National Laboratory for Coastal and Mountain Meteorology. Retrieved 14 April 2016.