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July 1968 England and Wales dust fall storms

A weather map showing a front across the West Country, Wales and Northern England
Weather map at 18:00 on 1 July 1968
TypeDust fall thunderstorms
Formed1 July 1968 (1968-07-01)
Duration28 hours[citation needed]
Dissipated2 July 1968 (1968-07-02)
Largest hail75 millimetres (3.0 in)
Cardiff
Maximum snowfall or ice accretion450 millimetres (18 in)
Yeadon, West Yorkshire
Maximum rainfall184 millimetres (7.2 in)
Isle of Man
DamageWidespread
Fatalities4
Areas affectedSouth West England, Welsh Marches, Northern England

The July 1968 England and Wales dust fall storms were the most severe dust fall storms in the British Isles for over 200 years.[1] A layer of mineral dust blowing north from the Sahara met cold, wet air over the British Isles, resulting in thick, dense clouds and severe thunderstorms across most of England and Wales. These clouds completely blotted out the light in some areas and the rain and hail resulted in property damage and flooding, and at least four people were killed.[2][3] During the storm, Leeming Bar in North Yorkshire saw 35.7 millimetres (1.41 in) of rain in under 10 minutes – a UK record until 2003.[4]

Meteorology

The Hoggar Mountains in Algeria saw a number of severe thunderstorms on 26–27 June. These appear to have blown a large quantity of Sahara dust into the atmosphere, where it was caught in a southerly wind in an atmospheric layer between 10,000 feet (3,000 m) and 17,000 feet (5,200 m) in altitude, forming a classic Spanish plume. Unusually, no clouds formed as this dust blew over continental Europe, and the layer reached England on 30 June largely unrained out.[1]

The warm desert air brought a heatwave over Southern England, with temperatures in London on 1 July measured at 32 °C (90 °F), until it met the much cooler, moister Atlantic airstream. The boundary between the two formed a squall line stretching from Devon, along the England–Wales border and up across Northern England to the River Tees.[1] Thick clouds, darkened by the Sahara dust, rose to 44,000 feet (13,000 m), plunging areas along the squall line into total darkness. In some areas, the lightning continued for 24 hours, and ball lightning was seen at RAF Chivenor in Devon.[5]

The dust particles served as seeds for nucleation, causing water to rapidly precipitate out and form especially large raindrops and hailstones.[6] The thunderstorms resulted in one of the most intense hail falls ever recorded in the UK, with hail events in 9 separate places reported as "severe" (H3) or greater on the TORRO hail scale, and the strongest rated "destructive" (H6).[7] Hailstones 75 millimetres (3.0 in) across – the size of a tennis ball – were measured at Cardiff Airport, and the local newspaper for Hartland, Devon, reported the finding of "a piece of ice 4 inches (100 mm) long".[5][8]

Along with the hail came heavy rain, with the 9 minute 35.7 millimetres (1.41 in) fall at Leeming Bar setting a record for a sub-10-minute total. The Isle of Man measured 184 millimetres (7.2 in) of rain over the 48 hour time period associated with the storms. Areas south and east of the squall line saw less severe storms, but the rain that fell in the night of 1–2 July 1968 was rich in Saharan dust, turning it blood red and leaving dusty deposits on the surfaces it fell on – only the south coast and uplands of Wales avoided the red rain.[1] The last comparable storm associated with Saharan dust was seen in October 1755.[1]

Aftermath

The storms resulted in at least four fatalities. Three people were struck by lightning – a 72-year-old woman in Northallerton, a 14-year-old girl in Oldham, and an unnamed woman in Hampsthwaite – while an 80-year-old man drowned in flooding in Welshpool.[2][3][9] Hail broke windows and dented cars across a wide swathe of the country, and damage was reported at both Cardiff Airport and RAF Chivenor. At Yeadon, West Yorkshire, the accumulated hail piled 450 millimetres (18 in) deep, and in parts of Yorkshire the ice was so severe that roads had to be cleared with bulldozers.[5]

Bradford saw severe flooding on 2 July, with many streets in the centre left underwater, as did the Isle of Man.[10][11] The Met Office noted that many rivers across the West Country and the Midlands burst their banks, and said that every town and village in Devon was flooded, with damage to property and crops assessed as "a major disaster".[12] The summer of 1968 would prove to be one of the worst ever recorded for flooding in the UK, with further storms causing the Chew Stoke flood of 1968 just a week later and the Great Flood of 1968 that September, and would not be equalled until the 2007 floods.[13]

In the wake of the storm, a number of normally rare African and Southern European insects were reported across England, having been blown across with the Sahara dust.[14]

See also

References

  1. ^ a b c d e Stevenson, Catherine M. (1969). "The dust fall and severe storms of 1 July 1968". Weather. 66 (5). doi:10.1002/wea.780. Retrieved 2 October 2018.
  2. ^ a b "Two women and girl killed in freak storms". The Guardian. 3 July 1968.
  3. ^ a b "Multi-coloured rain on the hottest day". Birmingham Daily Post. 2 July 1968.
  4. ^ Harley, Trevor. "1968". British Weather. Retrieved 2 October 2018.
  5. ^ a b c Webb, Jonathan D.C.; Elsom, Derek M. (2016). "Severe Hailstorms in the United Kingdom and Ireland: A Climatological Survey with Recent and Historical Case Studies". Extreme Weather: Forty Years of the Tornado and Storm Research Organisation (TORRO) (PDF). pp. 181–185. Retrieved 2 October 2018.
  6. ^ Darwent, Thelma J. Flood studies conference: papers and discussion on the Flood studies report and discussion on Reservoir flood standards : proceedings of the Conference. Institution of Civil Engineers. p. 13.
  7. ^ "The 52 Most Intense Hailstorms, 1650 To Date". TORRO. Retrieved 2 October 2018.
  8. ^ Brockway, Derek (14 December 2011). "How hailstones are formed". BBC Weather. Retrieved 2 October 2018.
  9. ^ "Teesside remembers the Great Darkness of 1968". Teesside Gazette. 2 July 2008. Retrieved 2 October 2018.
  10. ^ Barnett, David (3 July 2009). "Memories flood back". Telegraph and Argus. Retrieved 2 October 2018.
  11. ^ Ayres, Odele (8 May 2018). "21 pictures of Bradford city centre underwater in 1968". Telegraph and Argus. Retrieved 2 October 2018.
  12. ^ "Monthly Weather Report – July 1968" (PDF). Met Office. Retrieved 2 October 2018.
  13. ^ Webb, Jonathan D.C.; Pike, William S. (July 2010). "Extreme thundery rainfall event in central and southern England, 19-20 July 2007: Part two: Comparisons to previous severe summer rainfall events" (PDF). International Journal of Meteorology. 35 (351). Retrieved 2 October 2018.
  14. ^ French, R. A. (1969). "Moth immigrations in the British Isles in July 1968". Entomologist's Gazette. 20: 37.