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The jet stream casts its shadow over the UK during October

October was an unsettled month, with frequent low-pressure systems influencing the weather of the UK, especially the south.

Jet stream positions for October 2019 and October 2018

The above maps show the composite mean for the position of the jet stream during October 2019 (top) and October 2018 (bottom). Images provided by the NOAA-ESRL Physical Sciences Division, Boulder Colorado  http://www.esrl.noaa.gov/psd/

The most notable influence on the month’s weather was the more southerly track of the jet stream when compared with an average October. This more southerly position brought more rain to southern parts and drier conditions to northern parts.

Although there were some calmer spells towards the end of the month, there were days with notable heavy rainfall, with over 100mm falling in 36 hours in the wettest parts of South Wales on the 25th and 26th.

Dr Mark McCarthy is the head of the Met Office’s National Climate Information Centre. He said: “The position of the jet stream has a major influence on the UK’s weather patterns, especially in autumn.  This October, the jet took a more southerly track, steering low-pressure systems towards southern Britain, bringing heavy rainfall to some. By comparison the northern parts of the UK, especially northern Scotland and Northern Ireland, saw less rainfall, more sunshine, but they were also slightly colder on average, reflecting their position on the ‘cool’ side of the jet stream.”

The UK received 109% (138.8 mm) of its average October rainfall. Although it was wetter than average for the UK as a whole, the rainfall was not distributed evenly, with many northern regions and Northern Ireland receiving less than their average monthly totals.

Scotland and Northern Ireland were the only regions in the UK to record drier than average totals for October, with 87% (152.7 mm) and 84% (100.3 mm) respectively. Caithness was the driest historic county, with only 68% (80.9 mm) of its average October rainfall.

Rutland was the wettest compared to average with 177% (113.0 mm) of its monthly total. For the UK as a whole this marks the fifth consecutive wetter than average month.

Temperatures throughout the month were unremarkable, with the nationwide average 0.5°C below the 1981-2010 mean. Each region recorded slightly below average temperatures throughout the month. Only Kent and Sussex were above average in October, and that was only by 0.1°C.

Provisional October 2019 Mean temp (°C) Sunshine (hours) Rainfall (mm)
  Actual  Diff from avg (°C) Actual % of avg Actual % of avg
UK 9.0 -0.5 87.9 95 138.8 109
England 10.0 -0.4 86.6 84 124.8 136
Wales 9.5 -0.4 78.1 84 198.5 117
Scotland 7.2 -0.8 89.5 118 152.7 87
N Ireland 8.7 -0.7 105.4 120 100.3 84
Channel website: http://www.metoffice.gov.uk

Original article link: https://blog.metoffice.gov.uk/

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