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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 649 For   JANUARY  2010
          EXCEPTIONALLY COLD AND SNOWY FIRST HALF; RATHER NONDESCRIPT SECOND HALF
Text Box: Although the second half of the month was unremarkable temperature-wise, the severity of the cold period during the first half was such that January turned out to be the coldest since 1987, and the ninth coldest in the last 100 years. Mean monthly sea-level pressure was almost uniform over the British Isles, and the anomalous flow was therefore north-easterly. The easterly component of the gradient across the UK was the greatest in January since 1996, and it was the 13th most ‘easterly’ January in 138 years of records. With northeasterly winds in charge, the first four days of the month were mostly sunny but very cold with severe night frosts and some early-morning fog patches, and in northern and eastern Scotland and northeast England there were frequent and occasionally heavy snow showers. At Braemar (Aberdeenshire) -16.7°C was logged early on the 3rd. A southward-moving cold front brought occasional rain and snow to northern districts on the 4th and it clouded over further south, then on the 5th and 6th a depression formed on the front resulting in widespread and prolonged snowfalls. Some 10-20cm fell widely, with 25-35cm in parts of Berks, Hants, Surrey and west Sussex, and also in the Scottish Borders and Northumberland. Pressure rose steadily over the next few days, and although snow showers continued in eastern coastal counties, most other districts became fine but intensely cold. Coldest nights were the 6th/7th with -17.7°C at Benson (Oxon), the 7th/8th with -22.3°C at Altnaharra (Sutherland), the lowest reading anywhere in the UK since late-December 1995, the 9th/10th with -18.4°C at Kinbrace (Sutherland), and the 10th/11th with -21.0°C again at Altnaharra. The 09-21z maximum at Altnaharra on the 10th was -13.5°C. Many places reported seven consecutive days continuously below freezing, and upland sites in Wales and northern England logged a run of 12 sub-zero days. The north-easterly flow strengthened for a time on the 10th and 11th (except in the far north) and further snow spread across the country from the continent, although heavy
Text Box: falls were confined to Kent and East Sussex.The next belt of snow advanced from the southwest on the 12th and 13th; heaviest snow in southwest England and south Wales was followed by a thaw, but slight to moderate snow persisted for much of the 13th in many other districts. From the 15th until the 22nd southerly winds dominated, bringing heavy rain and strong winds at times, and a rapid thaw as temperatures climbed above the seasonal average. Capel Curig (Snowdonia) recorded 45mm of rain on the 14th/15th, while Sule Skerry (west of Orkney) logged a gust of 65kn on the 16th - the month’s highest. Also on the 16th the temperature climbed to 12.4°C at Exeter airport (Devon). Many places had no sunshine at all during the week 10th-16th. The next few days were generally quiet with light winds, dull and damp at first, but much of Britain was sunny on the 26th. A cold northwesterly flow set in on the 27th and outbreaks of rain and sleet gave way to snow showers from the 28th onwards, especially in northern Scotland where 15cm of fresh snow accumulated at Lerwick (Shetland) by the month’s end, but most places also enjoyed good sunny periods. Mean temperature was 2.5-3.0degC below the 1971-2000 normal over most of the UK, but only 1.0-1.5degC below in the Northern and Western Isles; the long run of consecutive sub-zero days was probably the longest in January since 1963, while the proportion of the country failing to reach 10°C on any day was the greatest in January since 1979. Rainfall percentages ranged from 80-100 in eastern districts to 40-60 in northern and western Scotland and northwest England, and over England and Wales it was the driest January for four years. Sunshine percentages ranged from 90-110 in eastern regions to 150-plus in some western districts.
                                                                                                                                             
                       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 0şC
   
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
           
                                                                     
      şC       şC       şC       şC             Hrs       Hrs         Hrs       Hrs       mm       mm         mm     mm          
                                                                                                                                             
  *Hampstead   03.3   -3.1   -00.4   -2.1   09.4   17   -06.4   07   23   19   10   07.2   30   067   154   1910   096   2003   020   1917   11   12.5   16   065   099   1910   131   1995   14   1914   00   08   00  
  Thorney Island   04.3   -3.3   00.0   -2.7   09.3   17   -07.4   07   16   15   04   08.5   30   083   138   1958   105   2003   035   1975   09   19.6   22   084   104   1941   160   1988   12   1987   00   06   00  
  *Wattisham   02.8   -3.0   -01.0   -2.9   08.1   17   -07.4   08   22   14   17   06.9   17   051   090   1968   093   2001   022   1996   10   08.0   16   041   082   1960   133   1988   06   1997   00   15   01  
  *Wittering   03.3   -2.5   -00.3   -1.9   08.3   18   -05.7   04   20   16   13   07.9   30   067   118   1950   096   1959   016   1996   13   09.4   22   039   072   1948   107   1948   12   2000   00   14   01  
                                                                     
  Lyneham   03.0   -3.2   -01.3   -3.1   08.6   22   -08.3   08   23   21   11   08.3   30   066   122   1952   088   1952   027   1996   15   10.2   22   058   086   1945   132   1995   06   1997   00   12   01  
  Ross-on-Wye   04.7   -2.2   -01.5   -4.0   11.2   18   -12.0   08   28   18   13   06.8   07   057   104   1915   096   1952   017   1996   16   18.0   05   094   131   1859   161   1943   07   1898   00   11   00  
  *St Athan   04.7   -2.2   -00.2   -3.1   11.5   22   -08.5   08   22   16   09   07.4   30   070   131   1954   085   1959   021   1996   18   19.0   21   065   071   1954   172   1995   09   1997   00   09   00  
  *Culdrose   06.5   -2.2   01.1   -3.8   11.2   15   -05.9   08   22   16   09   07.0   23   * 107   180   1961   092   1979   029   1982   10   27.0   12   098   081   1961   255   1984   22   1964   00   06   00  
                                                                     
  *Edgbaston   03.1   -3.6   00.0   -2.4   08.5   18   -06.5   07   25   17   06   06.6   30   063   128   1887   077   1952   007   1917   18   12.0   22   050   066   1887   153   1960   13   1888   00   13   00  
  *Valley   05.5   -2.3   01.4   -2.8   10.1   19   -05.9   08   20   08   06   06.6   08   067   113   1946   094   2001   024   1983   09   11.2   28   055   061   1941   195   1948   07   1997   00   04   00  
  *Woodford   03.5   -2.5   -01.8   -3.3   08.3   18   -17.6   07   18   15   16   07.1   30   062   115   1945   074   2003   011   1953   10   07.8   15   046   064   1942   170   1948   08   1997   00   10   00  
  *Watnall   03.4   -2.4   -00.2   -1.8   08.2   27   -04.3   03   17   16   13   08.3   30   067   119   1948   083   2000   013   1996   09   12.8   22   051   094   1942   149   1948   10   1997   00   14   01  
                                                                     
  *Leeming   03.2   -3.0   -01.6   -3.0   09.2   27   -14.0   08   19   16   10   07.2   30   059   106   1945   091   1959   018   1996   08   07.8   15   048   081   1945   129   1948   06   1997   00   13   02  
  *Boulmer   04.2   -2.4   01.0   -0.5   11.3   27   -06.3   08   11   10   14   06.5   31   043   078   1945   104   1959   010   1996   04   12.4   01   077   111   1945   189   1948   09   1989   01   15   00  
  *Eskdalemuir   01.6   -2.9   -02.7   -2.4   08.7   27   -15.1   07   31   17   12   07.1   30   059   134   1911   096   1959   009   1996   12   19.8   15   072   045   1911   390   1928   38   1997   00   16   04  
  *Bishopton   03.6   -2.7   -00.9   -2.1   10.9   27   -09.7   08   20   15   08   07.9   30   067   162   1921   069   1972   009   1940   13   24.2   21   059   057   1921   255   2008   18   1963   00   11   00  
                                                                     
  *Leuchars   04.1   -1.9   -00.2   -1.4   11.3   27   -07.5   03   21   13   13   07.5   30   060   099   1922   101   1959   014   1996   12   12.4   21   054   086   1922   167   1993   12   1953   00   12   01  
  *Dyce   03.9   -1.6   00.2   -0.4   10.1   27   -13.7   08   13   12   18   06.1   18   042   079   1941   089   1959   010   1996   11   14.4   16   076   092   1941   157   1970   13   1989   01   14   01  
  *Stornoway   05.6   -1.1   02.0   -0.5   09.1   16   -03.1   08   18   08   10   05.5   10   049   131   1880   079   2001   012   1907   07   15.2   21   089   073   1943   274   1993   26   1963   00   10   00  
  *Aldergrove   04.4   -1.9   -00.1   -1.9   10.6   15   -09.9   08   16   14   14   06.7   08   055   118   1927   082   1959   024   1996   04   13.8   21   062   072   1927   151   2008   22   1997   00   09   00  
                                                                     
                                                                                                                                             
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's   * new high record    
  sunshine figures are made at a nearby site.