January 2011 Unsettled till just after mid-month, then anticyclonic
Version of Record online: 23 FEB 2011
© Crown Copyright, Met Office.
Volume 66, Issue 3, pages i–iv, March 2011
How to Cite
Eden, P. (2011), January 2011 Unsettled till just after mid-month, then anticyclonic. Weather, 66: i–iv. doi: 10.1002/wea.693
- Issue online: 23 FEB 2011
- Version of Record online: 23 FEB 2011
After an anticyclonic opening, a cyclonic spell followed between the 4th and 11th then gave way to a broad southwesterly flow between the 12th and 16th. The second half of the month was mostly anticyclonic. Sea-level pressure was 10mbar above normal south of Iceland, and the anomalous flow over the UK was northerly with an anticyclonic bias.
With high pressure west of Ireland, a southward-moving cold front brought some rain, drizzle and hill fog on the 1st, followed by drier and colder weather in Scotland. Most places were dry on the 2nd, but some rain or snow affected northeast coasts and southwest England, and this rather wintry mix became more widespread on the 3rd as pressure fell progressively. The next three or four days were cold and unsettled, with the heaviest rain (with hill snow) over southern England and south Wales, where it amounted to 25–45mm in several places. Between the 6th and 8th the lowest temperatures of the month occurred in Scotland where there were occasional outbreaks of snow and also some freezing fog; Edinburgh airport was closed by snow on the 8th. The temperature only rose to –3.9°C at Strathallan (Perthshire) on the 7th, and that night the minimum was –13.0°C at Altnaharra (Sutherland). Overnight 7th/8th milder air spread northwards as far as the Scottish border, but the 9th was rather cold though mainly sunny over England and Wales, whilst it turned wet on the 10th. A very mild southwesterly airflow covered the British Isles between the 12th and 16th bringing widespread rain; there were some heavy orographically-enhanced falls in upland western districts, including a 48-hour total of 149mm at Capel Curig (Caernarfon) and a seven-day total (10th–16th) of 267mm at Honister Pass (Cumbria). Over much of the country temperatures remained above 10°C for much of this period: the highest maximum was 14.5°C at Pershore (Worcs) on the 13th. Gusts to 66kn were noted at Capel Curig on both the 15th and 16th. On the 16th a cold front brought a drop in temperature, but the front lingered near southern England for 48 hours, during which period 25–40mm of rain fell widely.
From the 18th until the end of the month high pressure controlled Britain's weather. Until the 22nd it lay over the country, thence drifting to a position west of Ireland until the 26th, before returning to the UK as a slowly declining feature from the 27th onwards. Freezing fog formed widely between the 18th and 21st, clearing to sunshine in many places during the day, and most western districts enjoyed prolonged sunshine during this period, though with sharp overnight frosts: Katesbridge (Co. Down) recorded –9.8°C early on the 20th. As the high moved west, a cloudier northwesterly flow affected the country, bringing outbreaks of mostly light rain and drizzle, a good deal of hill fog and somewhat higher temperatures, but from the 27th onwards it became mostly dry and colder again with night frosts. There were snow flurries in some eastern districts, but western districts had plenty of sunshine and severe night frosts. Aberporth (Cardiganshire) recorded 8.5h of bright sunshine on the 28th and 8.6h on the 29th, while Sennybridge (Breconshire) had a low of –10.4°C early on the 31st. Heavy rain returned to western Scotland as the month closed.
Mean monthly temperatures were close to the 1971–2000 average in eastern districts, but up to a degree below in western Britain and Northern Ireland. It was a wet month over much of southern England, but notably dry in northeast England, parts of eastern Scotland and also in Northern Ireland. The month's total at Dishforth (North Yorkshire) was just 15mm. East Anglia and Southeast England had a dull month, but sunshine aggregates were above normal elsewhere, with excesses in Northern Ireland of around 60%.
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