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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 592 For APRIL 2005
CHANGEABLE AND RATHER WET, BUT MOSTLY FINE IN SCOTLAND 16TH-26TH
Text Box: The month was characterised by enhanced cyclonic activity in the northern Atlantic, and mean sea-level pressure was below normal over much of northern and western Europe as well. The dominant anomaly centre was -7mbar just south of Iceland, while the anomalous flow over the British Isles was cyclonic/southwesterly. However, an easterly flow brought settled weather to much of Scotland between the 16th and 26th.

High pressure persisted over Europe until the 5th; a mainly southerly flow covered the UK at first, veering westerly on the 4th and 5th. A vigorous depression then crossed the country followed by a brief northerly outbreak around the 8th, with westerlies returning from the 9th-12th. Much of Britain was fine and warm until the 3rd, the temperature widely reaching 17-20C, and on the afternoon of the 2nd a patch of very dry air drifted north-westward across England with relative humidity around 20%. It turned cooler on the 4th with some showers, and wet and windy weather affected all areas on the 6th with gusts to 60kn; Capel Curig (Snowdonia) collected 59mm of rain in 48 hours. The rain-belt was followed by heavy showers accompanied by hail and thunder. The 7th and 8th were very cold with a strong to gale northerly wind, and the showers turned to snow even in the south. At Lerwick (Shetland) the maximum on the 8th was 0.1C, the lowest in April there since 1985. The following night was frosty, and Benson (Oxon) logged -5.2C. It turned warmer from the 10th as the flow backed westerly, and eastern and southern districts had long sunny periods.

A mainly cyclonic period followed from the 13th to the 19th. A slow moving frontal system delivered prolonged heavy rain and hill snow on the 15th and 16th over northern England and southern Scotland; over the 48-hour period Boltshope Park (Durham) recorded 76mm and Newcastle 74mm. After a frosty start, further heavy rain spread from the west on the 17th giving 37mm at Lough Fea (Tyrone), while Bishopton (Renfrewshire) had 39mm on the 18th. Thunder and hail occurred somewhere over southern Britain almost daily during this period.





Text Box: A strong ridge of high pressure extended southwards across northern Britain from the 20th to the 25th inducing an easterly flow over the UK but fronts were never far from southern districts. Scotland, Northern Ireland and northern England were largely dry with long sunny periods, and in the eight days ending on the 26th Kinloss (Moray) logged 89 hours bright sunshine and Stornoway (Western Isles) 88 hours. Nights were frosty but days were rather warm: Altnaharra registered a diurnal range of 21.9 degC (-4.6 to 17.3C) on the 25th. Southern and central parts of England and Wales, meantime, were cloudier with occasional rain - heavy in the West Country on the 23rd with 40mm at Exmouth - but a patch of very dry air drifted across England from the continent on the 21st, the relative humidity dropping to 16% in London.

The ridge declined on the 26th as a frontal trough advanced northwards across the country, and this was followed on the 28th by a vigorous depression. A sluggish southerly airflow developed on the 29th-30th. Belts of rain moved north-eastwards across all districts on the 26th followed by heavy showers and thunderstorms the next day, and widespread rain and gales on the 28th when Tyndrum (Perthshire) reported 42mm. Thereafter it became dry and warm in southern districts; the night of 29th-30th was unusually mild with minima widely of 12-13C (the highest in April since 1945 locally), and a maximum of 22.7C was recorded at Charlwood (Surrey) on the 30th. 

Mean monthly temperature ranged from near normal western and northern parts of the UK to almost 2 degC above at a few places in East Anglia and the Southeast. Averaged nationally it was a wet April and a number of sites in southern Scotland, northern England and Devon reported more than 2.5 times the normal rainfall. By contrast, just half the normal amount fell along the southern shore of the Moray Firth, while a relatively modest deficit in the London area meant that this was the 6th consecutive dry month here. Sunshine totals were mostly within 15 per cent of the average, but it was the dullest April since 1996 at Valley (Anglesey) with a 30 per cent deficit.
                                                                                                                                           
    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   14.1   +1.8   05.7   +1.4   21.5   30   -02.5   09   04   01   01   10.9   29   145   113   1910   240   1912   087   1920   15   10   07   045   089   1910   123   2000   02   1912   02   01   00  
  Thorney Island   13.3   -0.1   06.1   +1.3   19.9   30   -01.1   09   07   01   00   10.9   20   167   094   1956   262   1990   101   1966   15   06   17   045   091   1941   111   2000   <01   1984   01   00   00  
  *Coltishall   13.3   +1.7   04.9   +0.9   20.7   30   -00.3   22   05   02   03   12.6   21   145   100   1979   257   1990   125   1981   13   15   30   056   124   1964   107   1981   04   1974   03   01   00  
  *Wittering   13.5   +1.7   04.7   +0.9   21.1   30   -02.1   09   05   02   02   13.0   29   156   107   1950   221   1984   077   1978   14   05   30   029   066   1948   142   1998   05   1954   03   01   00  
                                                                     
  Lyneham   13.0   +1.0   05.1   +1.2   19.8   30   -02.1   09   07   01   00   10.3   18   139   088   1952   243   1984   084   1961   19   16   17   063   126   1946   153   2000   01   1984   03   01   00  
  Ross-on-Wye   13.8   +1.5   05.2   +0.5   22.0   30   -01.0   09   05   02   02   10.5   29   156   108   1915   226   1984   072   1920   16   10   18   053   109   1859   173   2000   00   1957   02   01   00  
  *St Athan   12.9   +0.9   06.5   +2.0   19.6   30   -00.4   17   02   01   00   10.5   02   156   093   1954   253   1984   091   1966   13   26   17   095   162   1954   125   2000   02   1957   02   00   01  
  St Mawgan   12.2   +0.5   06.8   +1.3   18.1   30   02.3   09   02   00   04   13.1   21   181   094   1944   266   1984   125   1966   15   17   17   095   165   1945   142   1998   02   1984   02   00   01  
                                                                     
  *Edgbaston   13.0   +1.7   05.5   +1.1   20.5   30   00.1   09   04   00   01   09.9   29   128   096   1887   235   1893   091   1891   16   08   17   043   067   1887   137   1998   02   1938   03   01   00  
  Valley   11.5   0.0   06.5   +1.2   18.4   02   02.7   17   02   00   02   11.0   02   131   071   1946   247   1974   123   1996   12   19   17   098   170   1941   103   1961   07   1980   01   00   00  
  *Woodford   12.9   +1.2   04.5   +0.9   18.7   30   -03.0   09   09   03   03   12.4   25   114   081   1945   216   1984   095   1961   16   14   15   067   121   1942   107   2001   04   1980   02   01   00  
  *Watnall   13.1   +1.3   04.7   +0.9   20.1   30   -01.3   09   06   01   03   10.5   29   124   084   1948   220   1984   071   1971   14   09   17   042   095   1942   135   2000   06   1957   01   02   00  
                                                                     
  *Leeming   12.7   +0.9   03.5   -0.1   17.2   03   -02.2   17   13   08   03   13.0   24   159   118   1945   199   1984   088   1971   17   24   15   106   247   1945   140   2000   05   1954   01   02   00  
  *Boulmer   11.0   +0.8   04.4   +0.8   16.4   29   -00.7   21   09   01   03   12.4   29   142   098   1945   218   1984   083   1974   13   21   14   086   195   1945   156   1998   03   1980   00   01   02  
  Eskdalemuir   10.7   +0.3   03.0   +1.4   16.1   02   -02.0   09   13   05   04   12.7   23   151   111   1911   197   1942   059   1996   11   36   05   123   129   1911   254   1947   17   1980   01   04   00  
  *Bishopton   11.7   -0.3   04.3   +0.9   16.5   02   -00.3   08   09   01   06   12.3   23   125   081   1921   205   1962   073   1937   06   42   17   117   213   1921   159   1947   05   1974   01   02   00  
                                                                     
  Leuchars   11.3   +0.2   04.2   +0.9   16.9   03   -00.5   13   08   02   02   13.5   29   170   105   1922   217   1990   098   1937   14   24   17   073   169   1922   117   1934   02   1938   00   01   01  
  Dyce   10.8   +0.3   04.1   +1.5   16.5   11   00.1   09   09   00   04   12.5   12   176   119   1941   212   1942   085   1941   09   14   07   058   105   1941   131   2000   10   1946   00   02   01  
  *Stornoway   10.4   +0.4   05.1   +1.5   15.9   26   -01.1   08   04   01   05   13.8   21   155   098   1880   230   1962   095   1944   06   31   28   108   148   1943   144   1947   01   1974   01   02   00  
  *Aldergrove   11.5   -0.4   04.5   +0.5   16.1   29   00.0   08   07   00   03   13.0   29   135   090   1927   220   1974   057   1937   13   13   18   056   106   1927   117   1986   06   1938   01   01   00  
                                                                     
                                                                                                                                           
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's      
  sunshine figures are from a nearby site.