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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 616 For APRIL 2007
WARMEST APRIL SINCE AT LEAST 1659, DRIEST SINCE 1984 AND SUNNIEST SINCE 1893
Text Box: On the 16th highest pressure transferred to the west of Ireland allowing cooler air to travel around its eastern flank, but this new anticyclone moved back across the UK on the 19th and 20th, reaching Germany on the 21st. A moist south to south-westerly airflow affected the country for the next four days. A drop in temperature over northern Britain on the 16th affected all except southernmost counties over the next few days, and in Shetland there were snow showers with a high at Lerwick of 3.5C on the 19th; overnight frosts were widespread; Kinbrace (Sutherland) recorded  -3.9C early on the 20th. The next few days were much warmer (23.5C at Gravesend, Kent, on the 22nd), and overnight temperatures were remarkably high for the season on 23rd/24th and 24th/25th with a minimum at St Jamess Park (London) on the latter night of 14.5C, but it became generally cloudy with outbreaks of rain. The rain was heaviest in upland western districts with 90mm in 72h at Capel Curig (Snowdonia) of which 59mm fell on the 23rd alone, but amounts in eastern and southern England were derisory, and a few locations escaped altogether. High pressure re-established itself over the UK on the 26th, migrating to northern Scotland during the last few days of the month, and it became mostly fine and warm except near North Sea coasts which were plagued by haar. Districts bordering the Solent were particularly favoured with highs of 22-25C on each of the last four days.

Mean maximum temperature for April was well above normal everywhere, the anomaly ranging from +1.5degC in Shetland to +6degC locally in Sussex and Hampshire. Mean minimum temperature was 2 to 3 degC above in all regions. It was the warmest April in the entire Central England Temperature series which began in 1659, beating the previous warmest, 1865 (which had 10.6C), by a wide margin. This is the third monthly record equalled or beaten in the last ten months. April also ranked eighth driest in a record going back to 1766, and second sunniest (after 1893) in a series which began in 1881. Large parts of the UK had no significant rain (i.e. no day with more than 0.2mm) over a period of 25-30 days beginning in late-March, and at a small number of sites there was no rain at all during the month.
Text Box: High pressure lay over or close to the British Isles throughout the month, apart from the 21st-25th when a rather humid south to southwesterly airflow covered the country. Mean sea-level pressure was well above normal, anomalies ranging from +6mbar at Valentia and Scilly to +9mbar on the Northumberland coast; overall it was the eleventh most anticyclonic April in 134 years of records.

Highest pressure lay over Scotland and southern Scandinavia as the month began, but the anticyclone migrated to the west of Scotland between the 2nd and 4th, thence to Ireland and southern Britain from the 5th to the 11th, returning to southern Scandinavia between the 13th and 16th. 

The opening days were warm and sunny by day in spite of a stiff easterly wind over England and Wales, but cold and frosty at night especially in Scotland where the months lowest temperature of -5.6C was recorded at Tulloch Bridge (Lochaber) and Kinbrace (Sutherland) early on the 1st, but afternoon highs of 17-20C were typical in southern England. It was briefly colder and cloudier on the 3rd with maxima of 6 to 9C over much of eastern England, but warm and sunny weather soon returned to most parts of the UK although nights were frosty in many places; a noteworthy diurnal range of 22.8 degC (-1.8 to 21.0C) was logged on the 4th at Aboyne (Aberdeenshire). A potent Arctic outbreak which affected northern and eastern Europe from the 5th to 7th grazed Shetland bringing some outbreaks of snow here, while afternoon temperatures close to 5C at Lerwick contrasted with 15-20C over much of the rest of the UK. The next few days were cloudy with occasional rain in northwest Scotland, but the sunshine continued elsewhere: Ronaldsway (Isle of Man) measured 77.6h of bright sunshine during the first week and Camborne (Cornwall) 97.3h between the 1st and 10th. It became very warm between the 14th and 16th, the temperature widely reaching 21-25C; Lee-on-Solent recorded 25.0C on the 14th and 25.5C on the 16th, while the months highest reading of 26.5C was observed at Herstmonceux (Sussex) on the 15th. A few showers, locally accompanied by thunder, affected southwest England, Wales and the Channel Isles around this time.
                                                                                                                                             
    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   17.9   +5.6   07.2   +2.9   24.0   15   01.7   04   06   00   00   10.9   21   220   172   1910   240   1912   087   1920   26   02   25   004   008   1910   123   2000   02   1912   00   00   00  
  Thorney Island   17.4   +4.0   07.2   +2.4   23.7   16   00.4   05   10   00   00   12.4   30   259   152   1956   262   1990   101   1966   28   00   00   * 000   000   1941   111   2000   <01   1984   00   00   00  
  *Wattisham   17.0   +4.9   05.6   +2.1   22.5   15   -00.7   05   09   01   00   13.2   30   230   165   1968   254   1990   123   2006   20   01   25   * 002   006   1960   109   1998   07   1997   00   00   00  
  *Wittering   16.2   +4.4   06.3   +2.5   22.5   15   02.0   05   08   00   01   13.5   30   202   139   1950   221   1984   077   1978   25   02   23   * 003   008   1948   142   1998   05   1954   00   00   00  
                                                                     
  Lyneham   16.8   +4.8   06.3   +2.4   22.6   15   00.8   04   04   00   01   13.0   18   231   148   1952   243   1984   084   1961   25   05   23   008   017   1946   153   2000   01   1984   00   00   00  
  Ross-on-Wye   17.7   +5.4   06.6   +1.9   23.0   14   02.0   08   00   00   01   12.0   30   * 229   159   1915   226   1984   072   1920   28   05   24   006   013   1859   173   2000   00   1957   00   00   00  
  *St Athan   16.3   +4.3   07.2   +2.7   20.8   28   01.7   04   04   00   02   12.9   19   229   136   1954   253   1984   091   1966   25   13   23   019   036   1954   125   2000   02   1957   00   00   00  
  St Mawgan   15.6   +3.9   08.1   +2.6   19.8   29   02.9   04   05   00   01   13.4   19   230   120   1944   266   1984   125   1966   22   05   23   014   027   1945   142   1998   02   1984   00   00   00  
                                                                     
  *Edgbaston   16.4   +5.2   07.2   +3.1   23.5   15   03.8   01   03   00   01   12.7   09   * 242   193   1887   235   1893   091   1891   25   04   23   006   010   1887   137   1998   02   1938   00   00   00  
  *Valley   14.3   +2.8   07.6   +2.3   21.7   14   01.4   04   09   00   03   13.8   30   227   124   1946   247   1974   123   1996   23   05   23   014   027   1941   103   1961   07   1980   00   00   00  
  *Woodford   15.8   +4.1   05.5   +1.9   23.0   14   -00.1   02   06   01   03   12.6   28   202   156   1945   216   1984   095   1961   20   11   23   016   032   1942   107   2001   04   1980   00   00   00  
  *Watnall   16.1   +4.3   06.5   +2.7   23.2   15   03.2   05   10   00   02   13.2   30   208   143   1948   220   1984   071   1971   23   06   23   009   022   1942   135   2000   06   1957   00   00   00  
                                                                     
  *Leeming   15.6   +3.8   05.4   +1.8   22.8   15   -00.6   04   13   01   00   14.1   30   * 213   159   1945   199   1984   088   1971   20   07   24   011   028   1945   140   2000   05   1954   00   00   00  
  *Boulmer   14.0   +3.8   06.5   +2.9   21.0   15   01.9   04   03   00   04   13.6   30   172   119   1945   218   1984   083   1974   21   07   24   011   028   1945   156   1998   03   1980   00   00   00  
  *Eskdalemuir   14.1   +3.7   03.8   +2.2   22.0   14   -03.1   07   16   05   04   12.2   30   174   129   1911   197   1942   059   1996   19   18   23   040   047   1911   254   1947   17   1980   00   00   00  
  *Bishopton   14.7   +2.7   06.0   +2.6   20.0   14   -01.0   02   16   01   04   12.9   30   179   117   1921   205   1962   073   1937   18   14   23   042   084   1921   159   1947   05   1974   00   00   00  
                                                                     
  *Leuchars   14.6   +3.5   05.7   +2.4   21.1   15   -01.9   02   16   01   03   12.4   04   191   118   1922   217   1990   098   1937   23   04   25   010   026   1922   117   1934   02   1938   00   00   00  
  *Dyce   14.5   +4.0   05.5   +2.9   23.0   15   -01.8   02   10   02   01   11.6   04   179   121   1941   212   1942   085   1941   20   11   21   027   053   1941   131   2000   10   1946   00   00   00  
  *Stornoway   12.8   +2.8   06.6   +3.0   16.5   13   00.8   01   04   00   03   14.3   27   158   100   1880   230   1962   095   1944   13   10   18   054   082   1943   144   1947   01   1974   00   00   00  
  *Aldergrove   15.1   +3.2   06.2   +2.2   20.0   14   01.1   04   07   00   03   13.4   30   195   131   1927   220   1974   057   1937   22   05   24   014   029   1927   117   1986   06   1938   00   00   00  
                                                                     
                                                                                                                                             
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's   *Higher than previous record,   * New low record  
  sunshine figures are from a nearby site.   although sensor may have changed