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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 637 For   JANUARY  2009
          DRY AND VERY COLD TILL THE 10TH, THEN SOMEWHAT MILDER BUT OFTEN WET AND WINDY
Text Box: January began with a week to ten days of anticyclonic weather, but southerly, southwesterly and cyclonic types dominated for the remainder of the month. Mean monthly sea-level pressure ranged from 4mbar below normal at Lowestoft to 10mbar below in the Western Isles. Overall, this was the most ‘southerly’ January since 1996 and the most cyclonic since 1994. High pressure controlled the UK’s weather throughout the first week, and it remained the dominant influence in southern districts until the 10th. The very cold weather of late December become even more entrenched during the first week of January with severe night frosts, daytime temperatures close to or below zero, and many areas had freezing fog at times with copious deposits of rime. There were also some moderate snowfalls, notably in central and eastern England early on the 5th, and in Scotland and northern England on the 7th. Snow lay over the Chiltern Hills for almost a week although the depth was never more than 4cm. Elsewhere there was a good deal of sunshine, and Aberporth (Ceredigion) recorded 79h in 15 days ending on the 9th. Overnight temperatures fell to -10°C or below on the 2nd/3rd, 5th/6th, 6th/7th and 9th/10th, and as low as -11.9°C at Chesham (Bucks) early on the 7th. Notably low maxima included -2.7°C at Sennybridge (Brecon) on the 1st and -3.0°C at Little Rissington (Glos) on the 9th. The cold weather slowly relented in Scotland and Northern Ireland from the 7th onwards, but it did not finally relax its grip in southeast England until the morning of the 11th. By this time strong south to southwesterly winds had delivered much milder but very wet weather to northern and western parts of the country. The rain was heaviest and most prolonged in upland areas, including the western highlands, the southern uplands, the Lake District, and the Welsh hills, with 150mm recorded at Shap (Cumbria) and 120mm at Tyndrum (Perthshire) in 48h on the 10th-11th. The mercury reached 13.8°C at Machrihanish (Kintyre peninsula) on the 11th, but the wind gusted to 60-70kn in the west and north of Scotland.
Text Box: A weak ridge crossed the UK on the 13th and 14th and was responsible for some thick fog patches and a sharp overnight frost, but the period 15th-26th brought the most disturbed weather of the month as deep depressions and associated frontal systems swept across the country at frequent intervals. The roughest day was the 17th when the central pressure of a depression near northwest Scotland dropped below 940mbar; maximum gusts included 85kn at West Gerinish on South Uist (Western Isles) and 81kn at Capel Curig (Snowdonia). Rain fell frequently throughout this period, and it was cold enough for snow at times over high ground in Scotland and northern England; temperatures fluctuated either side of the long-term average, and there were occasional sharp frosts, notably early on the 20th when Loch Glascarnoch (Wester Ross) registered -8.3°C. A very deep secondary depression crossed southern England early on the 23rd with a central pressure of 964mbar, the lowest in the districts since February 1989, and in its wake wet snow fell in some midland and southern counties for a time. During the closing days of the month the British Isles lay under a strong south to southeasterly airflow between low pressure west of Ireland and high pressure over Scandinavia. Eastern districts became dry and rather cold, but western regions remained mild and wet. On the 30th the temperature reached 14.0°C at Kinlochewe (Wester Ross), but 25-45mm of rain fell widely in western Scotland, west Wales and Northern Ireland, with 47mm at Killowen (County Down). Thanks to the very cold spell at the beginning of the month this was the coldest January since either 2001 or 1997 over most of the UK, although in northern Scotland it was marginally warmer than that of 2008. Rainfall was rather below normal in most eastern districts, but above in western and southern Britain. Over the country as a whole it was the sunniest January for six years.
                                                                                                                                           
                       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 0ºC
   
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
           
                                                                     
      ºC       ºC       ºC       ºC             Hrs       Hrs         Hrs       Hrs       mm       mm         mm     mm          
                                                                                                                                           
  *Hampstead   05.4   -1.0   00.9   -0.8   09.3   17   -06.0   07   19   11   05   06.5   06   076   175   1910   096   2003   020   1917   16   10.3   21   055   084   1910   131   1995   14   1914   00   02   02  
  Thorney Island   06.1   -1.6   01.3   -1.4   10.3   27   -07.5   10   15   13   02   08.1   06   077   128   1958   105   2003   035   1975   14   24.4   22   105   132   1941   160   1988   12   1987   00   01   01  
  *Wattisham   04.4   -1.4   00.0   -1.9   09.2   13   -07.3   07   25   14   11   06.9   06   057   101   1968   093   2001   022   1996   10   12.0   18   049   098   1960   133   1988   06   1997   00   04   02  
  *Wittering   05.1   -0.7   00.7   -0.9   09.4   22   -06.0   06   21   12   11   06.8   06   060   107   1950   096   1959   016   1996   14   09.2   18   042   078   1948   107   1948   12   2000   00   04   01  
                                                                     
  Lyneham   05.2   -1.0   00.3   -1.5   10.0   16   -08.1   10   19   14   11   07.2   03   059   110   1952   088   1952   027   1996   10   11.1   21   074   109   1945   132   1995   06   1997   00   04   01  
  Ross-on-Wye   06.6   -0.3   00.1   -2.4   11.1   16   -07.2   06   19   14   07   05.5   09   053   096   1915   096   1952   017   1996   12   17.1   17   061   085   1859   161   1943   07   1898   00   03   01  
  *St Athan   06.2   -0.8   01.7   -1.3   10.3   17   -06.1   06   16   12   10   06.2   03   055   104   1954   085   1959   021   1996   12   16.6   22   108   119   1954   172   1995   09   1997   00   01   00  
  *Culdrose   07.8   -1.0   04.1   -0.9   10.6   17   -07.8   07   20   12   11   06.5   07   062   104   1961   092   1979   029   1982   09   21.2   24   157   131   1961   255   1984   22   1964   00   02   00  
                                                                     
  *Edgbaston   05.2   -1.5   01.2   -1.2   09.9   16   -05.8   06   21   09   04   05.7   18   057   116   1887   077   1952   007   1917   12   12.0   17   058   078   1887   153   1960   13   1888   00   05   01  
  *Valley   07.3   -0.6   03.0   -1.3   12.1   30   -06.1   06   16   07   12   07.2   26   058   098   1946   094   2001   024   1983   10   13.4   22   075   083   1941   195   1948   07   1997   00   00   00  
  *Woodford   05.4   -0.6   01.0   -0.5   09.8   12   -09.6   06   22   08   09   06.4   06   054   099   1945   074   2003   011   1953   13   10.6   21   061   087   1942   170   1948   08   1997   00   02   00  
  *Watnall   05.2   -0.6   01.3   -0.3   10.0   12   -04.5   10   20   10   10   06.7   18   045   079   1948   083   2000   013   1996   13   12.0   21   070   129   1942   149   1948   10   1997   00   04   02  
                                                                     
  *Leeming   05.6   -0.6   01.0   -0.4   10.9   12   -07.3   06   23   08   10   06.5   06   055   098   1945   091   1959   018   1996   13   07.6   27   047   079   1945   129   1948   06   1997   00   04   03  
  *Boulmer   06.1   -0.6   01.8   +0.2   11.1   11   -03.2   10   15   07   11   06.0   21   049   088   1945   104   1959   010   1996   12   09.6   21   052   076   1945   189   1948   09   1989   00   05   00  
  *Eskdalemuir   03.8   -0.8   -00.1   +0.1   07.9   11   -09.7   06   24   16   17   05.7   03   027   061   1911   096   1959   009   1996   10   50.6   11   195   123   1911   390   1928   38   1997   00   08   01  
  *Bishopton   05.9   -0.5   01.4   +0.1   10.6   11   -04.9   06   22   10   09   05.9   05   035   084   1921   069   1972   009   1940   07   27.2   10   164   160   1921   255   2008   18   1963   00   04   00  
                                                                     
  *Leuchars   05.8   -0.3   00.6   -0.7   11.1   11   -04.9   06   24   13   08   06.3   24   065   107   1922   101   1959   014   1996   12   11.0   24   052   082   1922   167   1993   12   1953   00   05   00  
  *Dyce   06.3   +0.7   01.1   +0.4   12.6   11   -03.5   03   23   12   09   06.0   26   071   134   1941   089   1959   010   1996   15   11.6   21   049   059   1941   157   1970   13   1989   00   06   00  
  *Stornoway   07.2   +0.3   03.7   +1.0   11.6   11   00.3   07   10   00   08   04.3   05   026   070   1880   079   2001   012   1907   03   16.6   10   136   112   1943   274   1993   26   1963   00   03   00  
  *Aldergrove   06.5   +0.1   02.0   +0.1   11.6   11   -03.6   07   19   09   11   06.1   12   065   139   1927   082   1959   024   1996   12   19.6   30   074   087   1927   151   2008   22   1997   00   02   00  
                                                                     
                                                                                                                                           
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's      
  sunshine figures are made at a nearby site.