Thursday, January 26, 2012

Lookback: December 2011 Lookback - Frequent rain and gales, Jan 05 - 08:51

Westerly winds blew throughout the month, and there were several gales in northern districts, some of which caused structural damage - notably the Christmas Day gale in Orkney and Shetland. This was the second most 'westerly' December in 139 years of records. As is typical of westerly months, there were extended periods of orographically-enhanced rain over the western highlands of Scotland, the Lake District and Snowdonia.

Mean maximum temperature for December ranged from 11.0°C at Jersey airport (Channel Is) to 4.0°C at Dalwhinnie (Inverness-shire), while mean minimum temperature varied between 8.3°C at St Mary's (Isles of Scilly) and minus 0.6°C at Aboyne (Aberdeenshire). Mean maximum temperature was 0.5 °C below the 1981-2010 average in Northern Ireland but 1.5 °C above in the Midlands, East Anglia and the Southeast; mean minimum temperature ranged from 0.0-0.5 °C below in northern Scotland to 1.5-2.0 °C above in southern England and south Wales. The Central England Temperature (CET) of 5.9°C was 1.2 °C above the long-term mean making this the warmest December since 2006, and by this measure there have been only 17 warmer Decembers in the last 100 years.

The highest maximum at a standard site (i.e excluding rooftop and mountain sites) in the UK was 15.5°C at Fyvie Castle (Aberdeenshire) on the 26th, while the lowest minimum was minus 9.4°C at Loch Glascarnoch (Wester Ross) early on the 18th. The lowest daytime maximum was minus 3.0°C at Aviemore (Inverness-shire) on the 16th, and the warmest night was that of the 25th/26th with a minimum of 12.7°C at Murlough (Co Down).

Rainfall averaged over England and Wales during December was 113mm which is 114 per cent of the average for the standard reference period 1981-2010, the highest for this month since at least 2006; in the last 100 years 23 Decembers were wetter while 77 were drier. The equivalent figures for Scotland were 161mm and 147 per cent of the normal amount, and for Northern Ireland 97mm and 101 per cent. Monthly totals at routinely-available sites varied between 625mm at Cluanie Inn (Wester Ross) and 33mm at Loftus (Cleveland). In some western and northern districts rain fell on every single day during the month.

Sunshine averaged over England and Wales during December was 55 hours which is 105 per cent of the 1981-2010 mean; nevertheless, this is the lowest figure for six years. In the last 100 years 38 Decembers were sunnier while 62 were duller. The equivalent figures for Scotland were 33 hours and 88 per cent, and for Northern Ireland 42 hours and 98 per cent. Largest individual total in the UK was 80 hours at Wattisham (Suffolk) and the smallest was 13 hours at Lerwick (Shetland).

The windiest days of the month were the 8th with a gust of 98mph at Foula (Shetland), and the 25th with a gust of 97mph at the same site.

© Philip Eden


Source: http://feeds.weatheronline.co.uk/~r/weatheronline/~3/GR8YqZtw_Do/reports

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