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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 617 For MAY 2007
VERY WET AND DULL IN THE EAST AND SOUTH; VARIABLE TEMPERATURES
Text Box: Although Aprils high pressure persisted until the 5th, a cyclonic type prevailed for much of the rest of the month apart from a brief anticyclonic spell between the 21st and 24th. Mean monthly sea-level pressure was below normal over all parts of the British Isles (and practically the whole of Europe too), with anomalies ranging from  -3mbar in Cornwall to -7mbar in Shetland. The anomalous flow over the UK was WNW-ly.

With an anticyclone located just north of Scotland, east to northeasterly winds affected Britain until the 5th, maintaining the dry and settled weather which had characterised April. The best of the sunshine and highest temperatures were found in southern and western districts while eastern and central areas were cool and cloudy at times. Hurn (Dorset), reached 24C on both the 1st and 2nd, while Tulloch Bridge had a diurnal range of 24.4 degC (-2.1C to 22.3C) on the 2nd. Valley (Anglesey) logged 66h of bright sunshine during the first five days of the month, and at Tiree (Inner Hebrides) the sun shone for 118h between 26th April and 5th May. 

A very disturbed cyclonic/westerly type took over from the 6th until the 20th, with troughs and depressions crossing the country at frequent intervals, the depression of the 13th/14th being particularly active. Rain spread across all parts of the UK during the 5th/6th, and in parts of east Kent this was the first measurable rain since 30th March. The 6th was windy in northern Britain, with gusts approaching 60kn in the Western and Northern Isles, and showers fell widely over the next few days, locally accompanied by hail and thunder. Daytime temperatures were well up to normal, but there were local night frosts in Scotland. Rain fell widely on the 9th, 10th, and 11th as a sequence of three depressions crossed the country, and the 13th was exceptionally wet across England and Wales as another depression crossed the country; 25-50mm fell over a wide area of Southwest England, Wales, the Midlands and Yorkshire, and Preston Montford (Salop) collected 79mm. Scotland enjoyed a fine interlude with long sunny spells, but there were locally sharp frosts at night and Kinbrace (Sutherland) recorded -4.2C early on the 14th. It was briefly warmer on the 17th-18th especially in the Southeast where highs of 22-23C were observed, but Text Box: it became windy especially in Scotland where gusts of 55-60mph were widely reported on the 18th.

Pressure now built across the UK and the weather became quieter for a few days with warm sunshine in most districts except western and northern Scotland; the temp-erature reached 23-25C in the Home Counties on the 23rd, 24th and 25th, peaking at 25.7C at Heathrow airport on the 24th. A cold front brought sharply cooler weather from the northwest later on the 25th and 26th, accompanied by showers and local thunderstorms, and early on the 27th the temperature dropped to -5.7C at Kinbrace (Sutherland). A deep depression moved into the Southwest Approaches late on the 26th, whence it tracked eastwards across Cornwall and into northeast France. Rain spread northwards as far as southern Scotland, and it was heavy and prolonged south of a line from Pembrokeshire to the Humber. Some 50-75mm fell in a broad zone stretching from Dorset and Hampshire to Norfolk. At Luton (Beds), where extensive flooding led to the cancellation of the International Carnival, 99mm fell in 48 hours from 21z on the 26th. In the wake of the depression strong northerly winds uprooted trees and triggered power outages on the 28th, and in the Southeast this was one of the coldest late-May days on record with a high of just 6.4C at Whipsnade (Beds). The cool and unsettled regime persisted until the months end with thundery showers over England and Wales, and heavy rain over the east and north of Scotland (53mm at Loch Glascarnoch in Wester Ross on the 30th).

Mean temperature ranged from 1.0-1.5 degC above normal in southern England to 0.0-0.5 degC below in northern Scotland. Districts bordering the Irish Sea had slightly below average rainfall, but most other areas had a wet May, and new records were established at several long-term stations in southern England where over three times the normal monthly rainfall was reported locally. Sunshine aggregates ranged from 40 per cent above normal at Fair Isle, between Shetland and Orkney, to 40 per cent below in the East Midlands and East Anglia where it was locally the dullest May since 1991.
                                                                                                                                             
    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   16.8   +0.8   08.7   +1.1   24.8   24   03.5   29   00   00   03   12.2   23   132   072   1910   297   1989   112   1932   12   29.0   27   095   163   1910   124   1979   04   1989   00   00   00  
  Thorney Island   16.8   +0.2   09.7   +2.2   23.0   17   04.9   29   05   00   02   13.8   22   196   090   1958   322   1989   151   1981   10   24.2   27   092   210   1941   103   1946   04   1989   00   00   00  
  *Wattisham   16.3   +0.7   08.3   +2.1   23.2   24   02.7   15   02   00   02   13.8   02   * 129   067   1968   331   1989   127   2006   12   54.0   27   * 119   271   1960   119   2006   05   1989   00   00   00  
  *Wittering   15.8   +0.6   07.6   +1.0   22.4   24   03.7   30   02   00   04   13.7   01   * 113   055   1955   299   1989   133   1969   15   25.2   27   106   226   1955   116   1983   09   1990   01   00   00  
                                                                     
  Lyneham   16.1   +0.7   07.7   +1.1   22.2   23   05.0   29   00   00   03   14.5   29   183   091   1945   288   1990   112   1981   12   36.6   27   133   229   1945   139   1967   05   1990   01   00   00  
  Ross-on-Wye   17.3   +1.6   08.7   +1.5   23.0   23   05.0   20   00   00   03   13.4   01   149   079   1915   285   1992   104   1932   12   43.1   13   130   217   1859   158   1967   05   1896   00   00   00  
  *St Athan   15.5   +0.5   09.1   +1.8   21.6   01   04.6   29   00   00   02   14.3   29   192   093   1954   318   1990   119   1981   14   31.2   13   111   179   1954   155   1983   05   1991   00   00   00  
  St Mawgan   14.9   +0.8   09.8   +1.8   21.6   02   06.9   29   00   00   02   14.5   22   204   092   1956   297   1990   125   1981   11   15.4   12   116   190   1956   149   1981   07   1991   00   00   00  
                                                                     
  *Edgbaston   15.8   +0.3   08.4   +1.5   22.5   24   05.6   30   00   00   02   13.2   12   159   095   1887   263   1997   094   1954   12   30.9   13   117   209   1887   173   1932   05   1896   01   00   00  
  *Valley   14.9   +0.6   09.1   +1.3   20.8   01   04.9   21   04   00   00   15.0   21   204   090   1946   306   1977   161   1970   14   12.4   13   044   079   1941   127   1993   10   1970   00   00   00  
  *Woodford   15.8   +0.7   07.2   +0.8   20.0   24   01.2   03   08   00   02   13.7   01   135   076   1945   258   1989   111   1991   12   15.6   16   071   119   1942   144   1967   08   1991   00   00   00  
  *Watnall   15.7   +0.5   07.7   +1.1   22.5   24   05.2   30   04   00   03   13.9   01   125   061   1948   276   1989   085   1983   13   26.4   13   096   205   1942   135   1969   11   1991   01   00   00  
                                                                     
  *Leeming   15.8   +0.8   07.2   +0.9   19.7   24   02.2   21   04   00   02   14.0   01   157   088   1945   238   1980   103   1983   17   20.8   13   049   101   1947   106   1983   09   1959   01   00   00  
  *Boulmer   13.6   +1.1   07.0   +1.2   19.5   23   03.3   26   01   00   06   14.9   31   150   085   1945   231   1989   098   1983   11   15.8   29   061   117   1945   151   1924   07   1992   00   00   01  
  *Eskdalemuir   13.4   -0.2   05.2   +1.1   19.5   02   -01.3   26   09   02   03   13.7   03   127   076   1911   268   1935   079   1969   08   25.4   09   134   141   1911   257   1986   04   1984   00   00   00  
  *Bishopton   14.8   -0.2   06.3   +0.3   21.4   02   01.9   28   08   00   03   13.3   01   157   083   1921   266   1975   098   1983   11   18.4   09   095   150   1921   156   1925   07   1991   00   00   00  
                                                                     
  *Leuchars   13.9   +0.5   06.4   +0.6   19.5   23   01.1   01   08   00   03   14.0   15   188   100   1922   256   1942   095   1969   14   15.2   29   057   112   1922   152   1969   14   1959   00   00   00  
  *Dyce   13.3   +0.5   06.0   +0.9   21.7   23   01.3   03   09   00   04   13.1   21   157   090   1941   256   2001   086   1983   09   32.4   29   116   194   1942   152   1969   14   1994   00   00   01  
  *Stornoway   12.1   -0.1   06.0   +0.0   15.9   31   01.1   13   07   00   05   14.4   01   173   091   1880   294   1994   093   1944   05   38.8   30   143   231   1943   145   1986   19   1978   00   00   00  
  *Aldergrove   15.4   +0.7   06.8   +0.7   20.8   03   02.4   30   03   00   01   14.1   03   202   102   1927   295   1946   115   1933   12   09.6   16   044   085   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   * New lowest   * Equals highest  
  sunshine figures are from a nearby site.