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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 693 For SEPTEMBER 2013
WARM EARLY AND LATE; EXTENDED COOL AND UNSETTLED SPELL FROM THE 6TH TO THE 19TH
Text Box: For a second successive month mean sea-level pressure was not far from normal during September; anomalies ranged from +1.5 mbar in northwest Scotland to -1.0 mbar in southeast England, and the anomalous flow was weakly north-easterly.

During the first five days of the month (four days in Scotland and Northern Ireland) the weather became progressively warmer, with 28.8C recorded at St Helier (Jersey) on the 4th and 30.2C at Writtle (Essex) on the 5th. This equalled the highest maximum in September 2006, and there has been none higher in September since 1999. The temperature fell no lower than 17.7C at Manston (Kent) early on the 5th, the highest minimum of the month. Sunshine was plentiful, too, during these opening days, with 13.1h at Wokingham (Berks) on the 2nd and 12.5h at Manston (Kent) on the 5th. But cooler weather behind a cold front had already reached most of Scotland and Northern Ireland, and also parts of northwest England and north Wales, by the 5th.

There then followed two weeks of cool and unsettled weather between the 6th and the 19th. The 6th was almost 12 degC cooler than the 5th at Leeming (North Yorks), while the day's high at Carterhouse (Roxburghshire) was just 9.1C. Overnight 5th/6th the temperature fell to -2.4C at Kinbrace (Sutherland). There was widespread heavy rain in many parts of the country, especially in central and southern Scotland, Northern Ireland, northern England, north Wales and parts of southwest England, during the 6th with as much as 68.8mm at Normanby and 63.5mm at Redcar (both North Yorks), all of which fell in 10h between 0700 and 1730 GMT. There was thunder and hail locally in Cornwall on the 6th, and scattered thunderstorms also occurred in eastern England on the 9th. The 12th was the solitary rather warm day during the middle fortnight, with highs of 20-22C in the Midlands and South, but the 13th-17th was the coolest and most unsettled spell of the month; the high on the 13th was 9.0C at Salsburgh
Text Box: (Lanarkshire) and on the 17th 8.6C at Blencathra (Cumbria). Some 41mm of rain fell at Hampstead (London) on the 13th while the 15th was a windy day with gusts to 58kn at Aberdaron (Caernarfon). The day's high on the 19th was 8.5C at Braemar (Aberdeenshire).

High pressure developed over Biscay and France on the 20th, transferring to the UK on the 23rd, to the north of Scotland on the 26th, and ultimately to Scandinavia by the month's end. The weather became rather warm and largely dry during this period, but on some days sunshine was in short supply. There was some rain at times in northern Scotland, and showers broke out in southern counties of England and Wales between the 25th and 28th, with some thunderstorms in Devon and Cornwall on the latter date. The temperature climbed to 24.4C at Donna Nook (Lincs) on the 22nd, and to 24.9C at Trawsgoed (Ceredigion) on the 23rd, and highs remained between 19 and 23C over much of England and Wales until the month's end, even though a brisk easterly breeze picked up during the last few days of the month.

Both mean maximum and mean minimum temperature during September were within 0.5 degC of the long-term mean. Rainfall was near or below average in all regions, and the England and Wales figure was some 20 per cent below the 1981-2010 mean. Rainfall totals at routinely available sites ranged from 187mm at Cluanie Inn (Wester Ross) to 19mm at Bridlington and Leconfield (both East Riding of Yorkshire) and Cranwell and Coningsby (both Lincs). Sunshine percentages ranged from 116 in eastern Scotland and northeast England to 79 in southwest England and south Wales; sunshine totals varied between 178h at St Helier (Jersey) and 57h at Lerwick (Shetland).
                                                                                                                                             
    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   18.4   -0.1   10.7   0.0   29.1   05   06.2   17   00   00   02   09.8   02   104   075   1910   224   1959   072   1945   11   41.0   13   078   120   1910   157   1918   02   1959   00   00   00  
  *Thorney Island   19.4   -0.1   11.2   -0.1   28.0   05   04.6   15   00   00   00   11.2   04   149   091   1958   245   1959   129   1967   16   11.0   06   055   098   1941   159   1974   02   1971   00   00   00  
  *Wattisham   18.4   0.0   09.6   -0.2   29.7   05   04.6   15   00   00   01   12.7   02   147   099   1968   232   2003   103   1984   09   18.2   13   039   079   1960   119   1968   01   1969   00   00   01  
  *Wittering   18.8   +0.8   09.9   -0.1   26.7   04   05.5   09   00   00   02   12.7   02   151   104   1950   207   1964   093   1967   19   08.0   13   023   046   1948   132   1992   02   1959   01   00   00  
                                                                     
  *Lyneham   18.3   +0.5   10.0   +0.1   26.4   04   05.5   15   00   00   05   12.1   04   120   080   1952   235   1959   100   1983   08   23.2   13   056   081   1945   142   1974   05   1959   00   00   01  
  Ross-on-Wye   19.1   +0.9   10.0   0.0   25.1   04   03.7   08   00   00   01   08.2   02   124   092   1914   205   1929   069   1945   16   13.6   08   047   068   1859   203   1976   02   1865   00   00   00  
  *St Athan   17.9   +0.2   11.7   +0.7   24.9   04   06.3   15   00   00   03   09.6   04   116   076   1954   249   1959   074   1956   12   19.4   17   062   064   1954   223   1974   14   1959   00   00   00  
  *Culdrose   17.2   0.0   12.2   +0.9   20.3   22   06.5   07   00   00   08   10.6   01   116   072   1961   212   1972   098   1983   12   11.2   06   046   051   1961   185   1974   23   2001   01   00   00  
                                                                     
  *Birmingham Univ   17.9   +0.1   10.0   +0.7   26.0   04   05.0   15   00   00   01   07.9   05   110   083   1887   216   1895   067   1909   19   10.6   05   043   072   1887   165   1918   04   1959   00   00   00  
  *Valley   16.8   -0.3   11.9   +0.4   21.0   27   08.0   06   00   00   04   09.3   14   101   068   1946   214   1949   096   1948   13   32.4   06   076   086   1941   174   1950   03   1986   00   00   00  
  *Rostherne   17.7   +0.5   09.5   0.0   24.3   04   03.8   09   01   00   05   09.1   28   100   079   1945   197   1959   069   1948   12   11.4   15   052   065   1942   171   1965   05   1959   00   00   00  
  *Watnall   17.8   -0.2   10.0   0.0   26.1   04   05.4   08   00   00   02   10.9   22   138   095   1948   177   1991   075   1993   18   10.6   09   034   067   1942   147   1957   02   1959   01   00   00  
                                                                     
  *Leeming   17.3   -0.3   08.5   -1.0   24.1   04   03.1   08   02   00   04   10.8   02   122   098   1945   200   1986   073   1976   17   15.6   06   036   069   1945   174   1976   04   1959   01   00   00  
  *Boulmer   16.2   -0.4   09.5   -0.1   23.1   04   05.0   08   00   00   08   10.7   02   150   113   1945   205   1986   075   2001   18   19.4   06   043   073   1945   147   1965   12   2004   00   00   00  
  *Eskdalemuir   14.7   -0.3   07.7   +0.3   19.6   14   02.6   18   01   00   08   10.2   28   067   065   1911   153   1959   046   2008   08   31.6   06   118   077   1911   308   1950   18   1972   00   00   02  
  *Bishopton   15.8   -0.8   09.5   +0.5   20.5   03   04.5   16   00   00   09   10.5   10   095   081   1921   169   1996   058   2008   11   16.4   15   080   078   1921   258   1985   11   1972   00   00   00  
                                                                     
  *Leuchars   16.4   -0.1   09.0   0.0   23.9   02   02.7   26   05   00   06   12.6   02   117   088   1922   181   1997   077   1956   18   11.0   06   036   065   1922   149   1950   05   1972   00   00   00  
  *Dyce   16.3   +0.5   09.0   +0.7   25.3   02   01.0   26   07   00   05   11.9   08   125   104   1941   181   2004   070   1968   19   10.0   06   034   049   1941   234   1995   15   1959   00   00   00  
  *Stornoway   14.6   +0.1   09.0   0.0   18.4   23   03.9   06   01   00   05   10.4   30   102   091   1880   175   1903   065   2009   13   18.8   14   058   053   1943   206   1981   34   1968   00   00   00  
  *Aldergrove   16.5   +0.1   10.4   +0.7   22.6   02   04.9   06   00   00   06   09.6   04   093   083   1927   177   1986   070   1962   14   12.4   06   045   053   1927   163   1981   06   1986   00   00   00  
                                                                     
                                                                                                                                             
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative.      
       
  Averages are for 1981-2010