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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 660 For DECEMBER 2010
EXCEPTIONALLY COLD UNTIL THE 9TH, AND FROM 16TH-27TH. FREQUENT AND SOMETIMES HEAVY SNOW.
Text Box: Mean monthly sea-level pressure was high over Greenland with a strong ridge extending to the British Isles, and low south of the Azores, reversing the normal westerly flow across the north Atlantic. Pressure anomalies over the UK ranged from +10mbar in the Western Isles to -2mbar in the Straits of Dover, and the anomalous flow was strongly northeasterly.

December opened in the midst of an exceptionally cold spell which lasted until the 9th. At first, strong northeasterly winds brought outbreaks of heavy snow to eastern Scotland, northeast England, the north Midlands and parts of the Home Counties, with falls amounting to 25-30cm in some areas. An accumulated snow depth of 40cm was logged at Copley (Co Durham) on the 2nd, with unofficial reports of 40-70cm elsewhere in northeast England. The cold spell relaxed temporarily over England and Wales on the 4th and 5th, but returned with renewed vigour between the 6th and 9th. The arrival of heavy snow coincided with the morning rush hour on the 6th in the Central Lowlands, resulting in gridlock on the region's roads; snow-depths of 20-30cm were typical. Lowest temperatures during this initial phase of cold weather included -21.1C at Altnaharra (Sutherland) on the 1st, -20.9C again at Altnaharra on the 2nd, and -20.4Cat Braemar (Aberdeenshire) on the 3rd. The day's maximum at Altnaharra on the 2nd was -14.0C.

A milder interlude followed between the 9th and 16th, allowing much of the snow on the ground to thaw slowly, although upland parts of Scotland and northern England retained a snow-cover. Cloud amounts were variable, with long sunny periods on some days especially in western districts, and there was little rain. Afternoon temperatures were typically between 3 and 7C, but 10.1C was logged on the 11th at Ronaldsway (Isle of Man).

A vigorous cold front travelled southwards across the UK during the 16th, introducing a strong northerly airflow. This was the windiest day of a quiet month, with a peak gust of 56kn at Capel Curig (Caernarfon).The front was accompanied by rain which was replaced Text Box: by snow as the temperature dropped, and on the 17th there were periods of snow, heavy at times, in northern and western Scotland, Northern Ireland, Wales and the West Country. The next day there were further substantial snowfalls in London, the Southeast, and the south Midlands, with 30cm accumulating at Charlbury (Oxon), and yet more snow affected chiefly Wales and the Midlands over the next few days. Altnaharra again featured as the coldest place in the UK, with a low of -20.2C overnight 21st/22nd and a daytime high of -15.8C on the 22nd itself. 

The Christmas weekend was intensely cold but mainly dry and sunny, the sun shining for 7.6h at North Wyke (Devon) on Christmas Day. Less cold air infiltrated from the west between the 26th and 29th accompanied by much fog; 30-40mm of rain fell over Northern Ireland and southwest Scotland during the 24h to 09GMT on the 27th. The temperature peaked at 11.5C at St Mary's (Isles of Scilly) on the 28th.

As measured by the CET, this was the coldest December since 1890, although in Scotland and Northern Ireland it was probably the coldest for a lot longer than that - for instance, there has been no colder December in the Royal Observatory, Edinburgh, series which began in 1764. The coldest 30-day period was 27 Nov to 26 Dec with a CET of -1.6C - surely unprecedented so early in the season. Also between those dates nine new date-records for low temperatures were established, with five other near misses. Parts of southeast Scotland, northeast England, Kent and the Channel Islands had above average precipitation, but elsewhere it was a very dry month, and the provisional monthly rainfall total was the lowest since 2001, but it should be emphasised that the proliferation of unmanned sites means that rainfall equivalents during snowy weather are now gross approximations. It was an exceptionally sunny month in Scotland, Northern Ireland and northern England, but a very dull one in southern England; aggregates ranged from 90h at Auchincruive (Ayrshire) to 9.5h at Charlwood (Surrey).
                                                                                                                                             
    TEMPERATURE   SUNSHINE   RAINFALL        
                                                                                                                                     
                                                                                                                                     
                                  Highest and lowest totals             Highest and lowest totals        
                                  on record for month    
Maximum fall in 24 hrs
   (beginning 09 h)
        on record for month    
Days with snow or sleet
 
Days with fog
(Vis <220 yards at 09 h)
 
                                                                                         
     
Difference from average
   
Difference from average
 
Highest maximum
   
Lowest minimum
   
No. of days with grass
  minimum below 0C
   
Days of no sunshine
 
Maximum duration
       
First year of record
         
Days of no rainfall
 (0.1 mm or less)
         
First year of record
         
Days with thunder
     
  PLACE  
Mean Maximum
   
Mean minimum
             
No. of air frosts
       
Total for month
                   
Total for month
                   
                               
% of average
                   
% of average
                 
                                                                     
                                   
Highest
   
Lowest
 
Year
             
Highest
   
Lowest
 
Year
       
             
Date
   
Date
         
Date
         
Year
         
Date
         
Year
           
                                                                     
    C     C     C     C           Hrs     Hrs       Hrs     Hrs       mm     mm       mm     mm          
                                                                                                                                             
  *Hampstead   02.3   -5.4   -01.4   -3.8   07.9   11   -06.1   20   26   22   16   05.8   24   035   078   1910   086   2001   008   1956   15   07.5   18   031   050   1910   175   1914   10   1933   00   09   02  
  *Thorney Island   03.8   -4.8   -00.9   -4.6   07.6   28   -06.6   03   25   21   06   07.6   12   043   078   1958   114   2001   037   1966   17   10.2   20   037   051   1941   165   1993   19   1953   00   07   02  
  *Wattisham   02.0   -4.5   -02.3   -5.1   07.7   11   -10.6   20   24   22   15   06.8   17   039   079   1979   082   2008   022   2002   16   04.0   16   * 020   038   1964   120   1965   24   1988   00   16   03  
  *Wittering   01.8   -4.7   -02.5   -5.1   09.0   11   -10.9   07   23   21   16   07.1   06   070   140   1950   082   2001   020   1956   17   06.2   27   014   026   1948   130   1978   07   1963   00   15   03  
                                                                     
  *Lyneham   02.1   -5.1   -02.2   -5.0   06.8   29   -08.6   20   26   22   19   07.1   05   044   088   1952   083   2001   017   1956   21   04.4   27   * 013   018   1945   159   1959   16   1988   00   10   04  
  Ross-on-Wye   02.7   -4.7   -04.0   -7.4   08.5   16   -14.5   25   29   24   16   09.1   09   036   074   1915   078   1948   012   1989   23   11.0   19   022   031   1859   197   1929   11   1991   00   10   03  
  *St Athan   03.7   -4.3   -01.7   -5.8   09.2   28   -09.6   25   25   20   15   06.2   13   058   126   1954   072   2008   003   1956   15   08.0   27   * 028   030   1954   208   1965   31   1988   00   08   02  
  *Culdrose   06.1   -3.5   00.7   -5.4   09.8   28   -06.3   25   25   20   15   06.8   06   077   147   1961   088   2009   021   1988   17   08.2   03   039   035   1961   246   1978   27   1975   00   05   01  
                                                                     
  *Edgbaston   02.0   -5.4   -01.6   -4.9   07.5   11   -08.9   20   26   20   06   05.9   25   050   114   1887   090   1891   005   1890   23   04.0   27   020   008   1887   166   1965   10   1926   00   15   04  
  *Valley   05.0   -3.9   -00.3   -5.7   08.8   30   -09.3   25   22   16   13   06.3   08   062   126   1946   080   1960   025   1998   08   10.2   03   054   058   1941   179   1964   17   1963   00   06   00  
  *Woodford   02.5   -4.3   -04.4   -6.7   07.9   29   -14.8   20   24   21   11   06.7   08   056   123   1945   075   2001   016   1947   10   05.0   27   023   029   1942   180   1965   11   1963   00   12   02  
  *Watnall   02.0   -4.5   -02.0   -4.6   08.4   11   -12.0   07   19   20   13   06.9   06   061   122   1948   078   2009   012   1956   12   09.2   04   034   063   1941   180   1965   19   1963   00   15   03  
                                                                     
  *Leeming   01.8   -5.2   -05.2   -7.5   08.3   11   -17.9   03   27   21   07   06.2   20   072   170   1945   077   1967   014   1972   14   06.2   27   018   030   1945   125   1978   16   1988   00   14   02  
  *Boulmer   03.0   -3.9   -01.1   -3.5   08.0   10   -06.8   21   12   19   08   05.7   08   042   094   1945   082   2006   021   2002   06   08.6   27   055   092   1945   205   1978   17   1975   02   16   01  
  *Eskdalemuir   01.1   -4.3   -05.7   -6.5   08.3   11   -14.6   03   26   24   10   06.2   08   066   179   1911   074   1967   003   1912   13   13.6   26   046   029   1911   351   1993   33   1933   00   16   05  
  *Bishopton   01.3   -5.9   -04.1   -6.3   08.6   10   -12.5   08   23   22   10   06.5   05   069   217   1921   072   2001   009   1956   12   08.6   26   045   042   1921   295   2006   15   1933   00   12   01  
                                                                     
  *Leuchars   01.9   -4.8   -03.5   -5.6   08.1   10   -10.0   22   30   23   08   05.8   07   074   145   1921   082   1967   016   1934   19   04.0   26   019   030   1921   155   1978   08   1926   01   11   01  
  *Dyce   02.6   -3.8   -02.6   -4.1   08.7   10   -16.8   03   15   19   09   05.2   07   050   112   1941   088   2006   016   2002   15   22.2   09   061   076   1941   160   1978   20   1991   01   12   02  
  *Stornoway   04.6   -2.9   00.2   -3.1   09.3   10   -06.7   02   22   17   09   04.5   23   038   153   1880   057   1995   006   1884   11   14.4   02   043   035   1943   222   1985   29   1977   00   09   00  
  *Aldergrove   02.5   -4.6   -03.5   -6.4   08.5   28   -14.2   21   23   22   11   06.6   05   * 078   222   1927   077   2001   017   1954   11   21.8   26   046   051   1927   195   1978   15   1963   00   07   01  
                                                                     
                                                                                                                                             
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's   * New high record   * New low record  
  sunshine figures are made at a nearby site.