May 2011 Exceptionally wet in western Scotland; very dry in East Anglia

Authors

  • Philip Eden


May began with a large blocking anticyclone in Arctic latitudes and strong easterly winds affecting the UK. From the 4th to 10th a deep depression sat to the west of Ireland with southerly winds across the country, and from the 11th onwards lowest pressure was found to the west and north of Scotland with westerly and southwesterly winds delivering copious amounts of rain to the western upslopes. Over the British Isles this was the fourth most southwesterly May in 138 years of records.

The opening days were mostly dry and sunny with low humidity and a stiff northeasterly wind, and there were several reports of heath and woodland fires around the UK. The southwest had some thundery rain on the 1st and 2nd; a severe thunderstorm was reported from Penzance (Cornwall) on the late evening of the 1st. It was cool along the North Sea coast, but in the Scottish Highlands the days were warm and the nights cold and frosty. The sun shone for 15.0h at Tiree (Inner Hebrides) and Kinloss (Morayshire) on the 3rd, while early on the 4th the temperature fell to –6.3°C at Altnaharra (Sutherland). Winds veered southerly on the 4th and 5th bringing a rise in temperature to southern and eastern districts, but rain penetrated some western and northern parts of the country. It was very warm on the 6th and 7th: Weybourne (Norfolk) reported 25.4°C on the 7th, and a low of 16.0°C the following night. Outbreaks of heavy rain spread erratically eastwards across much of the UK on the 7th, with 40mm collected at Millport (Firth of Clyde), but amounts of rain east of the Greenwich meridian were very small. From the 8th to 10th the weather was changeable, warm and rather windy, but eastern, central and southern England remained largely dry.

Between the 11th and 20th winds varied between southwesterly and northwesterly bringing frequent changes in the weather. In northern and western Scotland, Northern Ireland and Cumbria there were substantial falls of rain each day, but once again eastern, central and southern England had trivial amounts. There was a good deal of sunshine at times and temperatures remained a little above the seasonal average.

The 20th and 21st were warm with sunny periods in eastern and southern districts, but a deep depression brushed past northwest Scotland on the 22nd delivering strong winds and heavy rain to northern regions, and an even deeper depression, 976mbar at its deepest, took an almost identical track on the 23rd, bringing the severest May gale to Scotland, Northern Ireland and northern England since 1962. Peak gusts at low-level sites included 70kn at Inverbervie (Kincardineshire) and 67kn at Drumalbin (Lanarkshire). Two people died and 30000 homes were temporarily without power. At Cluanie Inn (Wester Ross) 56mm of rain fell on the 23rd alone, with 135mm during the 72 hours to 0900 gmt on the 24th. The 25th was a bright and rather warm day in central and eastern regions, but a further depression tracked across Northern Ireland and southern Scotland on the 26th bringing heavy showers, accompanied locally by thunder and hail, even to East Anglia and the Southeast. Atlantic fronts brought further general rain during the 29th/30th (overnight 30th/31st in East Anglia and Kent), and the 31st was a day of sunshine and showers.

Mean maximum temperature ranged from near normal in western Scotland and Northern Ireland to 2.5 degC above in East Anglia, while mean minima were 1–2 degC above in all regions. Rainfall percentages ranged from over 300 locally in western Scotland to below 25 in East Anglia and Kent, with monthly totals ranging from 468mm at Cluanie Inn to 4mm at Manston (Kent). Sunshine percentages ranged from about 70 in southwest Scotland, northwest England and north Wales to 125 in the east of East Anglia and east Kent.

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All the charts on these pages are © Crown Copyright, Met Office. Charts on this page are based on NCEP Re-analysis data provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA.

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Data supplied by the Met Office:

www.metoffice.gov.uk

§ All averages are for the period 1961–1990.

The altitudes shown for the sites now conform with those shown in WMO Publication 9 Vol A.

The assistance of the Met Office in producing the maps and tables is gratefully acknowledged.

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