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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 689 For MAY 2013
THE COLDEST MAY SINCE 1996; SUNNY START, THEN SEVERAL COLD AND CLOUDY SPELLS WITH WIDESPREAD RAIN
Text Box: further deep depression crossed England on the 14th and 15th bringing heavy rain to most parts of the UK with 72mm on the 14th at Pembrey Sands (Carmarthen). Winds in the rear of the depression gusted to 58kn at Culdrose (Cornwall). 

Pressure remained rather low across the UK between the 17th and 24th with winds mainly from a northerly quarter. Heavy rain fell in Northern Ireland on the 18th with 44mm at Ballypatrick Forest (Co Antrim). Warm air had become entrained in the flow across Scotland, and the temperature reached 22.5C at Altnaharra (Sutherland) on the 19th and 22.3C at Strathallan (Perthshire) on the 20th while the overnight minimum early on the 21st at Thorney Island (W Sussex) was 14.4C. But by the 23rd and 24th it had become much colder with highs of just 4.1C at Braemar (Aberdeenshire) on the 23rd and 6.6C at Fylingdales (N Yorks) on the 24th. A fine Bank Holiday weekend followed from the 25th-27th though rain reached northern and western Britain on the 27th. The weather then became cold and dull in central and eastern districts for three days, though there was unbroken sunshine in northern and western Scotland with 16.1h at Lerwick (Shetland) on the 28th and 16.2h at Tiree (Argyllshire) on the 29th. The 31st was bright and much warmer over England, Wales and eastern Scotland with 23.0C reached at Lee-on-Solent (Hants).

Mean temperature during May was between 0.5 and 1.5 degC below the 1981-2010 normal in most regions, and only northeast England and eastern Scotland reported deficits of less than 0.5 degC; it was widely the coldest May since 1996. It was a rather wet month with all regional percentages between 100 and 150; the wettest place was Achnagart (Wester Ross) with 265mm while driest was Shoeburyness (Essex) with 31mm. Regional sunshine percentages were everywhere between 90 and 110; sunniest place was Guernsey airport (Channel Is) with 247h while the dullest was Eskdalemuir (Dumfriesshire) with 119h.
Text Box: With a low northwest of Shetland and a large high of 1029 mbar just north of the Azores, the mean monthly pressure pattern showed a marked northwesterly flow across the British Isles. This was the 18th most 'northerly' May in 141 years of records, so it was no surprise that this was the coldest May since 1996; in the last 100 years only 12 Mays were colder. 

The first week was changeable and rather windy in Scotland and Northern Ireland, but dry and sunny over much of England and Wales with fairly warm days and rather cold nights. The temperature exceeded 20C in central and southern parts of the UK on the 3rd, 5th, 6th and 7th, with a highest reading of 23.8C at Drumburgh (Cumbria) on the 7th. Northwest Scotland, by contrast, was much colder, with an overnight low of -4.8C at Tulloch Bridge (Lochaber) early on the 2nd, and an afternoon high of 4.5C at Cluanie Inn (Wester Ross) on the 3rd. Heavy, orographically-enhanced, rain fell in western Scotland between the 2nd and 6th, with a 5-day total of 133mm at Achnagart (Wester Ross) of which 64mm fell on the 2nd alone. Approaching 80h of bright sunshine was logged during the week with upwards of 14h locally on individual days. The warmest night came under cloudier skies at the end of the week, with a low of 13.6C at Morecambe (Lancs) overnight 7th/8th.

Between the 8th and the 16th a cyclonic/westerly regime held sway. The weather was unsettled, often windy, and generally rather cold. A depression headed north then northwest across Ireland on the 9th, deepening to 984 mbar, and strongest winds occurred on this date with gusts to 62kn at Mumbles (Glamorgan). The low then headed eastward across Northern Ireland and northern England on the 10th. Rain was heavy in some western regions with 58mm at Loch Shin (Sutherland) on the 13th, though comparatively little fell in East Anglia and the Southeast.
                                                                                                                                             
    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   15.3   -1.1   06.9   -1.1   21.6   06   02.2   01   07   00   01   12.3   26   144   079   1910   297   1989   112   1932   10   11.9   28   054   093   1910   124   1979   04   1989   00   00   00  
  *Thorney Island   15.2   -1.8   07.2   -0.7   18.8   31   01.9   16   02   00   00   14.4   18   220   102   1958   322   1989   151   1981   13   09.0   14   038   086   1941   103   1946   04   1989   00   00   00  
  *Wattisham   15.1   -0.9   05.8   -0.8   20.8   07   -00.9   02   06   01   05   14.6   27   186   097   1968   331   1989   127   2006   16   09.4   14   045   100   1960   119   2007   05   1989   00   00   00  
  *Wittering   15.1   -0.5   06.2   -0.8   21.0   07   -00.8   01   03   01   04   14.2   26   179   088   1955   299   1989   113   2007   17   19.4   14   057   120   1955   116   1983   09   1990   00   00   00  
                                                                     
  *Lyneham   14.7   -1.1   05.9   -1.1   21.1   07   00.9   01   06   00   02   13.7   07   175   087   1945   288   1990   112   1981   15   14.0   14   060   102   1945   139   1967   05   1990   00   00   00  
  Ross-on-Wye   16.0   -0.1   06.1   -1.5   22.4   07   -00.2   01   09   01   00   12.6   02   207   111   1915   285   1992   104   1932   13   30.2   14   075   125   1859   158   1967   05   1896   00   00   00  
  *St Athan   14.5   -0.9   07.2   -0.5   21.3   07   03.1   01   01   00   02   14.4   26   219   106   1954   318   1990   119   1981   15   26.2   14   063   101   1954   155   1983   05   1991   00   00   00  
  Culdrose   13.1   -0.8   07.3   -1.4   16.1   31   03.6   26   03   00   03   14.2   26   229   102   1961   275   2004   124   1981   19   16.8   28   070   116   1961   141   1993   06   1991   00   00   00  
                                                                     
  *Birmingham U   15.0   -0.8   06.0   -0.6   21.8   07   -00.7   01   04   01   00   11.2   26   173   095   1887   263   1997   094   1954   11   25.8   14   080   139   1887   173   1932   05   1896   00   00   00  
  *Valley   13.1   -1.6   07.8   -0.4   21.5   07   03.4   02   04   00   01   14.6   25   183   080   1946   306   1977   161   1970   13   09.4   09   040   071   1941   127   1993   10   1970   00   00   00  
  *Rostherne   14.8   -0.7   06.1   -0.7   22.2   07   -01.3   02   05   01   03   15.0   25   153   086   1945   258   1989   111   1991   13   26.6   14   063   104   1942   144   1967   08   1991   00   00   00  
  *Watnall   15.1   -0.5   06.4   -0.6   22.3   07   00.3   01   04   00   02   14.6   26   166   082   1948   276   1989   085   1983   12   20.2   14   073   154   1942   135   1969   11   1991   01   00   00  
                                                                     
  *Leeming   15.2   -0.2   05.8   -0.9   22.1   31   00.6   16   10   00   05   13.8   26   162   091   1945   238   1980   103   1983   16   15.6   14   067   135   1947   106   1983   09   1959   00   00   00  
  *Boulmer   12.8   -0.7   05.9   -0.3   17.2   05   02.3   01   04   00   02   15.3   25   176   099   1945   231   1989   098   1983   13   08.6   18   048   092   1945   151   1924   07   1992   00   00   00  
  *Eskdalemuir   12.9   -1.1   04.0   -0.5   20.3   07   -03.2   02   09   07   05   14.4   25   119   072   1911   268   1935   079   1969   10   26.2   27   119   125   1911   257   1986   04   1984   01   01   00  
  *Bishopton   14.1   -1.3   06.0   -0.4   21.4   20   -00.9   02   04   01   04   14.9   25   164   087   1921   266   1975   098   1983   10   15.4   26   092   145   1921   156   1925   07   1991   00   00   00  
                                                                     
  *Leuchars   14.3   +0.5   06.0   -0.2   20.3   31   00.6   15   13   00   02   15.5   25   163   087   1922   256   1942   095   1969   17   19.8   03   067   131   1922   152   1969   14   1959   00   00   00  
  *Dyce   13.6   +0.4   05.6   +0.1   19.4   05   00.3   02   09   00   02   15.8   25   174   100   1941   256   2001   086   1983   16   16.0   18   047   078   1942   152   1969   14   2008   00   00   00  
  *Stornoway   11.5   -1.1   05.5   -0.9   16.5   28   00.2   04   02   00   02   15.7   29   182   096   1880   294   1994   093   1944   09   20.8   02   097   154   1943   154   2011   13   2008   00   00   00  
  *Aldergrove   14.0   -1.1   06.5   0.0   19.0   07   00.6   17   05   00   04   15.6   30   154   077   1927   295   1946   115   1933   10   18.8   26   084   160   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.      
  Reference period now 1981-2010