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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 640            For    APRIL    2009
    VERY WARM;  MAINLY DRY WITH LONG SUNNY PERIODS ESPECIALLY IN EASTERN ENGLAND
Text Box: Southerly winds blew frequently during the month, and the southerly component of the mean surface flow has been exceeded only seven times in 137 years of records, so it is no surprise that it was a very warm April. Although mean sea-level pressure was below normal in all parts of the UK, there were lengthy settled spells during the first week and from 18th-24th, and most regions were drier and sunnier than average. High pressure lay over or close to the British Isles for much of the first week, bringing mainly dry and warm weather to most parts of the country, but sunshine was hazy and rather variable at times, and there were occasional foggy mornings. Afternoon temperatures were typically between 14 and 18°C, and 19.8°C was reached on the 3rd at Kinlochewe (Wester Ross). An onshore wind kept eastern districts appreciably cooler, and also on the 3rd the temperature climbed no higher than 5.3°C at Inverbervie (Kincardineshire). Slight frost occurred widely early on the 3rd and 5th. Atlantic depressions passed close to Scotland between the 7th and 10th: 38mm of rain fell on the 7th at Tyndrum (Perthshire), while Capel Curig (Snowdonia) had the month’s highest gust of 56kn on the 8th. A cold front become slow-moving over eastern England throughout the long Easter weekend (10th-13th) maintaining rather cold, overcast and drizzly weather with persistent hill fog, and although there was an improvement during Easter Monday it was the dullest Easter holiday over much of eastern and central England since 1964. Ahead of the cold front the temperature reached 20.3°C at Weybourne (Norfolk) on the 10th, and behind it the sun shone for 13.6h at Inverbervie on the 12th. A southeasterly airflow developed during the 13th, backing northeasterly from the 15th-18th. High pressure then dominated the UK’s weather for several days before
Text Box: receding to southern Scandinavia on the 24th. It was warm from the 13th to the 15th with a high of 22.1°C at East Malling (Kent) on the latter date, but showers and local thunderstorms broke out across southern and midland counties. Killowen (Co Down) recorded a minimum temperature of 12.2°C overnight 14th-15th, the month’s highest. The 16th and 17th were dull and wet in many central and southern parts of England and Wales but further north it was generally dry and quite sunny although haar affected eastern coastal districts. Long sunny periods developed in most areas from the 18th-24th (13.9h in central Manchester on the 19th and at Shap, Cumbria on the 20th), and afternoon temperatures widely reached 16-20°C with 20.8°C at Kew Gardens (London) on the 21st. Widespread ground frost occurred at night, however, and an air minimum of -5.8°C was logged at Kinbrace early on the 19th. Pressure was low over England and Wales from the 24th-29th, and fronts became slow-moving over the UK on the 30th, so the last week of April was unsettled. A torrential downpour overnight 24th-25th produced a short-lived flash flood in south Cornwall; 85mm of rain fell in 24h at Penzance although appreciably more is likely to have fallen over the moor above Zennor. The 27th was rather cold and rainy in most districts, but temperatures again climbed above normal during the last few days of the month. Only five Aprils - 1943, 1944, 1945, 1987 and 2007 - were warmer in the last hundred years, although three others had the same mean temperature. Monthly rainfall was above the 1971-2000 mean in western Scotland, Northern Ireland and Cornwall, but below in all other regions, and in parts of Lincolnshire and Norfolk totals were below 10mm. Sunshine totals were near average in Scotland and Northern Ireland but above average over most of England and Wales, especially in East Anglia and the Southeast where monthly aggregates exceeded 200h at several sites and reached 217h at Weymouth (Dorset).
                                                                                                                                             
                       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   15.2   +3.0   06.8   +2.6   19.9   21   03.6   28   03   00   03   10.4   22   159   123   1910   240   1912   087   1920   19   05.7   16   024   044   1910   123   2000   02   1912   01   00   00  
  *Thorney Island   14.1   +0.8   06.8   +2.1   19.1   15   02.7   28   04   00   02   13.0   22   196   113   1956   262   1990   101   1966   19   15.8   14   045   086   1941   111   2000   00   2007   01   00   00  
  *Wattisham   15.3   +3.3   05.8   +2.4   18.7   01   01.7   21   04   00   01   13.0   24   195   140   1968   254   1990   123   2006   19   05.4   16   017   038   1960   109   1998   02   2007   00   00   01  
  *Wittering   14.4   +2.7   05.3   +1.6   19.0   21   00.7   05   08   00   05   12.5   22   158   107   1950   221   1984   077   1978   20   05.0   10   017   038   1948   142   1998   03   2007   00   00   00  
                                                                     
  Lyneham   14.0   +2.1   05.4   +1.6   18.7   15   02.7   28   07   00   02   12.2   21   168   107   1952   243   1984   084   1961   12   07.6   27   039   072   1946   153   2000   01   1984   01   00   01  
  Ross-on-Wye   15.0   +2.8   05.2   +0.6   18.9   20   00.0   05   07   00   05   11.9   08   171   118   1915   229   2007   072   1920   16   09.0   28   042   082   1859   173   2000   00   1957   00   00   00  
  *St Athan   13.2   +1.3   06.4   +2.0   16.5   23   01.2   05   10   00   04   12.6   11   168   099   1954   253   1984   091   1966   12   12.2   26   042   069   1954   125   2000   02   1957   01   00   00  
  Culdrose   12.2   +1.0   06.0   +0.5   15.2   20   -00.5   05   10   00   04   12.2   20   188   109   1961   248   1984   127   1966   13   18.8   24   115   187   1961   152   1998   09   1984   00   00   00  
                                                                     
  *Edgbaston   14.2   +3.0   06.3   +2.2   18.4   20   03.6   05   00   00   02   11.0   29   149   118   1887   242   2007   091   1891   16   11.2   16   046   064   1887   137   1998   02   1938   01   00   01  
  *Valley   12.5   +1.1   06.7   +1.5   14.7   14   02.0   28   08   00   03   13.0   19   189   102   1946   247   1974   123   1996   11   14.6   26   049   081   1941   103   1961   07   1980   00   00   00  
  *Woodford   14.8   +3.2   04.8   +1.3   18.9   20   -00.2   05   19   02   03   12.2   18   169   129   1945   216   1984   095   1961   14   11.6   26   040   069   1942   107   2001   04   1980   00   00   00  
  *Watnall   14.5   +2.8   05.7   +2.0   19.2   24   01.7   05   10   00   08   12.8   20   139   094   1948   220   1984   071   1971   17   09.2   27   030   064   1942   135   2000   06   1957   01   00   01  
                                                                     
  *Leeming   14.2   +2.5   04.2   +0.7   18.9   20   -01.1   05   10   03   03   11.7   20   149   110   1945   213   2007   088   1971   18   30.8   28   057   126   1945   140   2000   05   1954   01   00   00  
  *Boulmer   11.2   +1.1   05.1   +1.6   15.7   01   01.0   12   14   00   07   12.1   12   126   086   1945   218   1984   083   1974   17   09.6   28   021   046   1945   156   1998   03   1980   00   00   03  
  *Eskdalemuir   12.6   +2.3   03.1   +1.6   18.0   20   -02.7   19   14   06   03   13.1   19   116   085   1911   197   1942   059   1996   16   12.6   07   078   077   1911   254   1947   17   1980   00   00   00  
  *Bishopton   13.2   +1.3   05.4   +2.1   18.2   20   00.3   19   10   00   02   13.2   19   125   081   1921   205   1962   073   1937   11   15.6   07   065   112   1921   159   1947   05   1974   00   00   00  
                                                                     
  *Leuchars   12.6   +1.6   04.9   +1.7   18.0   20   00.5   12   13   00   05   11.8   22   128   078   1922   217   1990   098   1937   18   08.4   07   029   064   1922   117   1934   02   1938   00   00   03  
  *Dyce   11.8   +1.4   04.8   +2.3   15.1   20   00.0   12   09   00   07   12.1   11   106   071   1941   212   1942   085   1941   20   08.8   07   026   045   1941   131   2000   10   1946   00   00   02  
  *Stornoway   11.2   +1.3   05.8   +2.3   14.5   13   02.0   19   07   00   03   13.0   28   170   107   1880   230   1962   095   1944   12   11.2   04   065   085   1943   144   1947   01   1974   00   00   00  
  *Aldergrove   13.0   +1.2   06.0   +2.1   17.8   20   02.3   19   04   00   04   11.5   02   136   090   1927   220   1974   057   1937   11   11.0   03   065   116   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      
  sunshine figures are from a nearby site.