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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 604 For APRIL 2006
THE MOST 'WESTERLY' APRIL SINCE 1977. VERY DRY IN EASTERN SCOTLAND & SOUTHWEST ENGLAND
Text Box: A northwesterly type lasted until the 11th, but winds were often southwesterly during the middle and latter parts of the month. Blocking was largely absent over northwest Europe and the northeastern Atlantic. With sea-level pressure 12mbar below normal to the north of Scotland and 2mbar above over France, this was the most westerly April over the British Isles since 1977.

A complex depression crossed the country on the first two days of April bringing outbreaks of rain followed by showers, including a fall of 36mm on the 2nd at Capel Curig (Snowdonia). But there were also good sunny intervals in most regions, and temperatures were well up to the seasonal average. It turned appreciably colder between the 3rd and 11th as the wind swung into the north and night frosts occurred widely; the temperature fell to -6.4C at Katesbridge (Down) overnight 5th/6th and to -6.9C at Tulloch Bridge (Lochaber) overnight 9th/10th, while the maximum reading on the 7th was just 2.9C at both Loch Glascarnoch (Wester Ross) and Dalwhinnie (Inverness-shire). Many days brought sunshine and showers, and the showers often fell as hail, sleet and snow, and on the night of the 9th/10th heavy snow fell for several hours in Kent, Sussex, Surrey and parts of London. Some 5-10cm accumulated over land above 150m, and there were credible reports of around 12cm in the Tunbridge Wells, East Grinstead and Crowborough districts with damage to trees, telephone and power lines. East Malling (Kent) recorded a rainfall equivalent of 31mm. Sunshine was plentiful with aggregates for the 1st-10th running 50-75 per cent ahead of the norm.

Winds backed westerly from the 12th-18th and although the weather remained changeable it became warmer (especially by night) and less sunny. Rain fell frequently, but amounts were generally small except over west-facing slopes where Kinlochewe (Wester Ross) recorded 39mm on the 12th and Cassley (Sutherland) 39mm in 48 hours on the 16th-17th.





Text Box: Between the 19th and 26th winds were mainly southwesterly although they backed easterly on the 21st as a cut-off depression slipped southwards from Ireland to Biscay, the associated rain largely confined to Cornwall and Devon. Most districts were warm and rather humid on the 21st with 21C at St Helier (Jersey) and 19.7C at Herstmonceux (Sussex) and it remained warm in the Southeast on the 22nd but temperatures were lower thereafter. A good deal of fog was reported early on the 24th in central and southern districts.

An anticyclone west of Ireland dominated from the 27th-29th and all parts of the UK were dry with sunny periods; nights were cold and locally frosty, and in most areas days were cool although central Scotland was warm on the 29th with 18.9C logged at Aberfeldy (Perthshire) on this date contrasting with just 7.2C at Thorncliffe (Staffs) on the 30th. An active frontal system advanced eastwards across the UK on the night of the 30th bringing widespread rain, and substantial snow fell above 600m in the Scottish highlands.

Mean monthly temperature was 0-0.5 degC below normal in northern and western Scotland, but up to 1 degC above in all other regions; nevertheless this was the coolest April generally for five years. The absence of warm days was a notable feature: for the first time since 1986 nowhere in the UK had reached 20C by 30 April. Rainfall distribution showed a strong orographic modulation as one would expect in a very westerly month, percentages ranging from over 150 in northwest Scotland to little more than 10 in eastern parts of Fife and Angus, and around 20 in east Devon. Sunshine percentages ranged from 130 or more in Shetland, southeast Scotland and Northumberland to below 90 locally in East Anglia, the east Midlands, and southeast England. Lerwick (Shetland) had it sunniest April since 1970, while at Leuchars (Fife) it was arguably the sunniest since records began in 1922 (the recent change in sensor means that exact comparisons are now impossible).
                                                                                                                                           
    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   13.4   +1.1   05.2   +0.9   17.4   22   -01.5   05   07   02   01   10.5   05   134   105   1910   240   1912   087   1920   15   13   30   041   080   1910   123   2000   02   1912   00   02   00  
  Thorney Island   13.1   -0.3   05.9   +1.1   17.7   21   -01.1   11   07   01   00   12.0   18   174   099   1956   262   1990   101   1966   18   14   01   036   072   1941   111   2000   <01   1984   00   00   00  
  *Wattisham   12.5   +0.4   03.8   +0.3   15.7   21   -02.4   05   12   04   03   11.0   05   * 123   088   1968   254   1990   125   1971   12   04   30   034   078   1960   109   1998   07   1997   00   01   00  
  *Wittering   12.5   +0.7   04.7   +0.9   17.1   25   -01.5   05   09   02   02   11.9   05   128   088   1950   221   1984   077   1978   13   09   19   036   082   1948   142   1998   05   1954   00   01   00  
                                                                     
  Lyneham   12.6   +0.6   05.0   +1.1   16.7   21   -02.7   05   06   03   02   12.2   05   151   097   1952   243   1984   084   1961   15   06   30   033   067   1946   153   2000   01   1984   00   00   00  
  Ross-on-Wye   13.9   +1.6   05.2   +0.5   18.0   21   -02.0   05   06   02   03   10.5   05   156   108   1915   226   1984   072   1920   18   09   01   025   052   1859   173   2000   00   1957   00   01   00  
  *St Athan   12.2   +0.2   05.9   +1.4   18.0   21   -01.2   05   04   02   02   12.3   05   172   103   1954   253   1984   091   1966   19   03   30   021   036   1954   125   2000   02   1957   00   00   00  
  St Mawgan   11.7   +0.1   06.7   +1.2   16.3   21   -00.1   05   04   01   02   12.5   27   183   096   1944   266   1984   125   1966   18   05   30   035   060   1945   142   1998   02   1984   00   00   01  
                                                                     
  *Edgbaston   12.1   +0.7   05.7   +1.7   17.6   25   -00.7   05   06   02   01   10.5   05   131   099   1887   235   1893   091   1891   12   13   19   040   082   1887   137   1998   02   1938   00   01   00  
  *Valley   11.2   -0.3   06.3   +1.0   14.7   21   -00.5   05   02   01   02   12.4   23   191   104   1946   247   1974   123   1996   15   10   18   054   093   1941   103   1961   07   1980   00   00   00  
  *Woodford   12.1   +0.4   04.4   +0.8   16.5   15   -04.8   10   11   03   00   09.0   05   150   106   1945   216   1984   095   1961   7   12   20   059   106   1942   107   2001   04   1980   00   01   00  
  *Watnall   11.9   +0.1   05.1   +1.3   17.5   25   -01.2   05   08   02   01   12.1   05   120   082   1948   220   1984   071   1971   13   08   20   036   082   1942   135   2000   06   1957   00   01   00  
                                                                     
  *Leeming   12.4   +0.6   03.8   +0.2   16.0   27   -02.7   05   13   03   00   11.3   10   151   113   1945   199   1984   088   1971   19   10   02   029   068   1945   140   2000   05   1954   00   02   00  
  *Boulmer   11.2   +1.0   04.1   +0.5   15.9   25   -00.3   05   09   01   01   13.0   23   191   132   1945   218   1984   083   1974   13   04   08   016   037   1945   156   1998   03   1980   00   02   00  
  *Eskdalemuir   10.4   +0.1   01.8   +0.3   13.6   28   -04.2   10   18   09   00   11.5   23   140   104   1911   197   1942   059   1996   8   15   01   114   120   1911   254   1947   17   1980   02   05   00  
  *Bishopton   11.5   -0.5   03.0   -0.4   14.7   29   -02.8   10   14   03   00   13.0   28   163   107   1921   205   1962   073   1937   11   08   30   071   128   1921   159   1947   05   1974   00   01   00  
                                                                     
  *Leuchars   12.0   +0.9   02.4   -0.9   16.3   24   -02.4   10   20   06   01   12.9   23   206   127   1922   217   1990   098   1937   21   02   07   005   012   1922   117   1934   02   1938   00   03   00  
  *Dyce   10.9   +0.4   03.4   +0.8   14.9   26   -01.9   08   11   04   02   11.5   23   171   115   1941   212   1942   085   1941   13   06   08   022   040   1941   131   2000   10   1946   00   04   00  
  *Stornoway   09.7   -0.3   03.9   +0.3   13.0   27   -01.8   04   09   01   03   10.9   14   142   091   1880   230   1962   095   1944   03   12   30   118   161   1943   144   1947   01   1974   01   03   00  
  *Aldergrove   11.1   -0.8   04.0   +0.1   14.5   27   -03.4   10   08   03   01   12.1   23   142   095   1927   220   1974   057   1937   11   09   01   047   088   1927   117   1986   06   1938   00   01   00  
                                                                     
                                                                                                                                           
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's   * Lower than previous record, though change to KZ sensor    
  sunshine figures are from a nearby site.   means that direct comparisons are no longer possible