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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 653       For     MAY      2010
         COLD FIRST HALF WITH FREQUENT FROST; A WARM WEEK 18TH-24TH;  GENERALLY DRY
Text Box: Apart from brief cyclonic interludes on 1st-2nd and 27th-30th, high pressure was never very far from the British Isles and mean pressure was 2-6mbar above normal over the UK. For much of the first half of the month anticyclones lay to the west or northwest of the country, allowing cold northerly or north-easterly winds to affect all districts, but when highest pressure migrated to Britain between the 18th and 24th it became very warm. This was both the most northerly and the most anticyclonic May since 1991. A shallow depression moved slowly south-eastwards across the country on the 1st/2nd, bringing widespread rain which was heavy in a broad zone from mid-Wales across the south Midlands to Kent. Hampstead (London) recorded 67mm, Elham (Kent) 49mm, and Credenhill (Herefs) 40mm. The 1st was rather warm in southern districts but it was cold in the north with a high of just 5.7°C at Fair Isle (between Orkney and Shetland), and the cold air spread to all districts on the 2nd accompanied in eastern and southern districts by a strong north-easterly wind. From the 3rd until the 12th high pressure was anchored between Ireland and Iceland and the winds over the UK varied between north-westerly and north-easterly, feeding persistently cold air to all parts. Weak fronts embedded in the flow brought mostly light rain from time to time, and sunshine was in short supply especially in eastern districts, although the 7th and 8th were very sunny in Scotland and Northern Ireland. Daytime temperatures were typically between 10 and 14°C but failed to reach 10°C even in parts of southern England on the 2nd, 8th and 11th. Frost developed widely at night especially in Scotland and northern England; notable overnight lows included -6.0°C at Braemar (Aberdeenshire) overnight 7th/8th and -6.0°C again at Altnaharra (Sutherland) overnight 11th/12th. The mornings of the 12th and 13th were frosty even in counties bordering the Channel coast, and on the 12th several sites in England reported their lowest May minimum since 1980.
Text Box: Weak fronts crossed the country between the 13th and 17th, bringing scattered showery rain, but it became rather less cold. A ridge of high pressure developed during subsequent days, and a large high pressure system settled over the UK between the 20th and 23rd, bringing a spell of sunny and very warm weather, and the warm weather lasted until the 25th in southern districts. Temperatures climbed a little higher each day, peaking at 28.8°C at Heathrow airport (London) on the 24th, and the temperature fell no lower than 17.9°C overnight 23rd/24th at Olympic Park (London). However, many coastal districts remained comparatively cool thanks to onshore breezes and patchy sea mist. Thunderstorms broke out in eastern Scotland and northeast England on the 21st when upwards of 40mm may have fallen in the Banchory (Aberdeenshire) district. Colder weather with night frosts returned to Scotland on the 24th and 25th as the high pressure system receded to the Iceland/Greenland region. The last few days of the month were generally rather cool and changeable with variable amounts of sunshine; 39mm of rain fell at Guernsey airport on the 25th-26th, and 26mm at Kinloss (Morayshire) on the 29th, and eastern England was windy on the 30th. Mean maximum temperature was within 0.5degC of the 1971-2000 average in all regions, while mean minimum temperature was generally 0.0-1.0degC below. Over England and Wales it was the coldest May since 1996 though it only ranked 28th coldest in the last 100 years. Rainfall was near normal in parts of northern and eastern Scotland, but other regions had deficits of 30-60%, and a few sites, chiefly in Lancashire and Yorkshire, reported 10mm or less. Averaged nationally it was the driest May since 2001 and it ranked 17th driest in the last 100 years. Regional sunshine aggregates were typically between 100 and 120% per cent of the long-term average, and individual sunshine totals ranged from 128h at Aviemore (Inverness-shire) to 272h at Valley (Anglesey).
                                                                                                                                             
                       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   16.1   +0.1   07.0   -0.6   28.0   24   01.2   12   07   00   01   12.3   23   163   090   1910   297   1989   112   1932   20   62.8   01   086   148   1910   124   1979   04   1989   00   00   00  
  *Thorney Island   15.5   -1.1   07.0   -0.5   22.8   24   01.0   12   03   00   01   15.2   23   200   092   1958   322   1989   151   1981   19   04.0   01   015   034   1941   103   1946   04   1989   00   00   00  
  *Wattisham   15.2   -0.4   05.9   -0.3   25.7   23   -01.1   12   06   02   03   15.2   23   175   091   1968   331   1989   127   2006   17   08.0   01   026   059   1960   119   2007   05   1989   00   00   00  
  *Wittering   15.6   +0.4   06.3   -0.3   26.8   23   -00.9   13   01   01   01   14.8   23   200   098   1955   299   1989   113   2007   24   05.0   01   017   037   1955   116   1983   09   1990   00   00   00  
                                                                     
  Lyneham   15.8   +0.4   06.6   0.0   25.9   24   00.8   04   03   00   02   15.5   23   226   112   1945   288   1990   112   1981   15   11.4   01   032   056   1945   139   1967   05   1990   00   00   00  
  Ross-on-Wye   17.0   +1.3   07.0   -0.2   27.5   23   01.6   13   03   00   01   14.5   22   207   111   1915   285   1992   104   1932   18   34.4   01   046   077   1859   158   1967   05   1896   00   00   00  
  *St Athan   15.3   +0.3   07.8   +0.5   25.3   22   01.5   13   04   00   02   14.7   23   216   105   1954   318   1990   119   1981   12   06.8   06   047   076   1954   155   1983   05   1991   00   00   00  
  Culdrose   14.4   +0.9   07.9   -0.4   22.6   24   02.4   12   04   00   02   14.7   24   207   092   1961   275   2004   124   1981   16   14.6   23   050   083   1961   141   1993   06   1991   00   00   00  
                                                                     
  *Edgbaston   15.6   +0.1   07.7   +0.8   26.9   23   02.4   13   01   00   00   13.3   22   166   099   1887   263   1997   094   1954   18   13.4   01   027   049   1887   173   1932   05   1896   00   00   00  
  *Valley   14.2   -0.1   07.4   -0.4   23.3   22   02.7   13   08   00   02   14.7   23   272   120   1946   306   1977   161   1970   22   11.2   28   038   068   1941   127   1993   10   1970   00   00   00  
  *Woodford   15.5   +0.4   05.3   -1.1   27.1   22   -02.2   13   14   02   01   14.6   23   154   087   1945   258   1989   111   1991   22   04.8   27   014   023   1942   144   1967   08   1991   00   00   00  
  *Watnall   15.4   +0.2   06.8   +0.2   27.0   23   00.8   13   04   00   04   14.4   22   173   085   1948   276   1989   085   1983   23   10.8   29   023   049   1942   135   1969   11   1991   00   00   00  
                                                                     
  *Leeming   15.4   +0.4   04.9   -1.4   27.2   23   -03.5   13   10   03   01   14.7   23   184   104   1945   238   1980   103   1983   18   05.6   26   020   040   1947   106   1983   09   1959   00   00   00  
  *Boulmer   12.6   +0.1   06.3   +0.5   21.0   22   00.3   13   03   00   02   13.4   18   166   094   1945   231   1989   098   1983   14   07.2   29   028   053   1945   151   1924   07   1992   00   00   00  
  *Eskdalemuir   13.6   +0.0   03.4   -0.7   25.5   22   -02.9   13   14   07   01   14.3   22   144   087   1911   268   1935   079   1969   16   14.8   13   037   039   1911   257   1986   04   1984   00   00   00  
  *Bishopton   15.5   +0.5   05.7   -0.3   23.6   22   -00.5   03   06   01   02   13.6   22   199   106   1921   266   1975   098   1983   15   04.4   31   022   034   1921   156   1925   07   1991   00   00   00  
                                                                     
  *Leuchars   14.4   +1.0   05.0   -0.8   26.2   22   -01.2   13   17   03   01   14.5   12   207   110   1922   256   1942   095   1969   10   17.4   29   059   116   1922   152   1969   14   1959   00   00   00  
  *Dyce   13.3   +0.5   05.4   +0.3   22.4   22   00.3   03   08   00   01   14.9   18   184   105   1941   256   2001   086   1983   07   10.8   27   059   099   1942   152   1969   14   2008   01   01   00  
  *Stornoway   12.0   -0.2   05.7   -0.3   18.5   22   00.5   03   03   00   04   14.7   31   158   084   1880   294   1994   093   1944   08   14.0   21   068   110   1943   145   1986   13   2008   00   00   00  
  *Aldergrove   15.0   +0.3   06.3   +0.2   24.4   22   00.1   11   05   00   02   14.7   23   201   102   1927   295   1946   115   1933   16   05.4   31   034   065   1927   131   1993   07   1991   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.