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graphs CLIMATE-UK.COM'S REVIEW OF THE BRITISH METEOROLOGICAL SCENE
MONTHLY SUMMARY
No. 645 For SEPTEMBER 2009
A DISTURBED START, OTHERWISE VERY DRY AND RATHER WARM WITH BRIGHT PERIODS
Text Box: The opening days of September were cyclonic, but there was a rise in pressure over southern Britain on the 4th, and from the 9th onwards most of Britain experienced anticyclonic conditions although westerlies encroached across Scotland from time to time. Thanks to the cyclonic start, this September ranked only 22nd highest out of 137 for mean sea-level pressure over the British Isles.

The first four days were very unsettled and a deepening depression tracked northeastwards across the UK during the 2nd and 3rd. The weather was cool and windy, the wind gusting to 50kn or more at exposed sites, and a broad belt of rain crossed all regions during the 2nd and 3rd. The rain was heaviest and most prolonged in northern and eastern Scotland leading to serious flooding in Moray and Aberdeenshire; Capel Curig (Snowdonia) recorded 57mm on the 2nd and Lossiemouth (Moray) 87mm on the 3rd. Largest 48-hour totals were 101mm at Lossiemouth and 92mm at Aberdeen airport. Dalwhinnie (Inverness-shire) reported a high of just 10.1C on the 3rd.

Between the 5th and 8th an anticyclone crossed France and Germany and pressure rose sharply over England and Wales, but changeable southwesterlies continued to affect northern and western parts of the UK, and Tyndrum (Perthshire) collected 53mm of rain on the 7th, while Stornoway (Isle of Lewis) reported a gust of 63kn on the 8th. It became very warm in eastern, central and southern counties of England, with 25.1C at Manston (Kent) on the 7th and 28.7C at Swanscombe (Kent) on the 8th, while the temperature fell no lower than 17.5C at St Jamess Park (London) on the intervening night.

A renewed rise of pressure led to the establishment of an intense anticyclone over the UK from the 9th to the 13th, thereafter transferring to northern Scotland for a few days allowing strong northeasterlies to affect much of England and Wales, before returning southwards on the 17th and 18th. Early on the 11th a sea-level pressure of 1041.3 mbar was logged at Malin Head (Co Donegal), a new September record for the British Isles. Text Box: Except for the 15th, all regions were dry throughout this period; highest temperatures and best sunshine durations were found in western and sometimes southern districts including 12.4h bright sunshine at Southampton on the 10th, the months largest daily total, but eastern and central districts were often cool and cloudy. On the 15th a rejuvenated front became stationary across Essex, London, Surrey and Hampshire, delivering 8-10h of heavy rain which amounted to 60mm at South Farnborough (Hants) and 53mm at Hampstead (London). There were further isolated heavy showers in the Southeast on the 20th.

From the 20th-28th pressure remained high over England and Wales while a strong westerly airflow covered Scotland. An anticyclonic/northwesterly type affected the UK on the 29th/30th. Throughout this period, southern and central parts of England and Wales were dry with fair, warm days, and occasional cold misty nights. Further north it was somewhat cloudier with heavy rain and gales at times in western and northern Scotland. Broadford (Skye) collected 64mm of rain on the 21st, and Sule Skerry (west of Orkney) recorded a gust of 66kn on the 22nd. The months lowest temperature of -1.2C occurred at Kinbrace (Sutherland) on the 19th, and again at Katesbridge (Co Down) on the 20th. The high at Lentran (nr Inverness) was just 9.1C on the 29th. As September ended, many places in the Midlands and East Anglia had recorded no significant rainfall (no day with more than 0.2mm) for 28 consecutive days.

Averaged over England and Wales this was the warmest and sunniest September since 2006, and the driest since 1997. Mean maximum temperature was mostly between 0.5 and 1.0degC above the 1971-2000 average, whereas mean minimum temperature ranged from 1.5degC above in Scotland to 0.5degC below in Northern Ireland. Rainfall percentages ranged from less than 20 in parts of eastern England to over 200 in Aberdeenshire, Banffshire and Morayshire. Sunshine totals were mainly between 90 and 120 per cent of the long-term mean, although Stornoway noted its lowest September sunshine total on record.
                                                                                                                                             
    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   19.2   +1.0   11.2   +0.8   26.6   08   08.2   25   00   00   02   08.2   12   121   091   1910   224   1959   072   1945   25   53.2   15   066   108   1910   157   1918   02   1959   00   00   00  
  Thorney Island   19.8   +0.6   11.6   +0.6   23.8   19   07.2   27   00   00   01   12.4   10   183   114   1958   245   1959   129   1967   20   10.4   02   021   039   1941   159   1974   02   1971   00   00   00  
  *Wattisham   19.5   +1.4   10.3   +0.8   27.8   08   06.4   10   00   00   03   10.8   25   145   100   1968   232   2003   103   1984   20   12.4   02   021   045   1960   119   1968   01   1969   00   00   00  
  *Wittering   19.0   +1.3   10.7   +1.0   24.9   08   05.2   27   00   00   01   11.6   12   142   100   1950   207   1964   093   1967   26   08.6   02   015   032   1948   132   1992   02   1959   00   00   00  
                                                                     
  Lyneham   18.2   +0.7   09.9   +0.3   22.0   08   06.5   24   00   00   01   11.3   10   151   104   1952   235   1959   100   1983   25   07.6   02   009   014   1945   142   1974   05   1959   00   00   00  
  Ross-on-Wye   19.0   +1.1   10.5   +0.8   22.6   08   05.6   24   00   00   01   12.0   10   140   106   1914   205   1929   069   1945   27   13.3   01   024   037   1859   203   1976   02   1865   00   00   00  
  *St Athan   17.9   +0.5   11.0   +0.3   21.8   08   06.5   27   00   00   02   12.0   12   158   106   1954   249   1959   074   1956   23   09.4   03   020   022   1954   223   1974   14   1959   00   00   00  
  Culdrose   17.3   +0.4   11.1   +0.1   21.0   13   06.8   21   00   00   02   12.0   11   174   109   1961   212   1972   098   1983   23   17.2   02   027   032   1961   185   1974   23   2001   00   00   00  
                                                                     
  *Edgbaston   17.9   +0.4   11.2   +1.0   22.6   08   08.3   10   00   00   01   10.4   12   119   095   1887   216   1895   067   1909   26   12.8   02   016   023   1887   165   1918   04   1959   00   00   00  
  *Valley   16.7   -0.1   11.4   +0.2   19.1   13   07.2   11   00   00   03   12.1   09   127   089   1946   214   1949   096   1948   20   12.0   02   029   035   1941   174   1950   03   1986   00   00   00  
  *Woodford   17.3   +0.5   09.8   +0.6   23.4   08   04.0   13   00   00   02   11.8   10   096   078   1945   197   1959   069   1948   18   17.2   02   055   074   1942   171   1965   05   1959   00   00   00  
  *Watnall   18.2   +0.5   10.5   +0.8   23.7   08   07.6   25   00   00   01   11.8   12   125   089   1948   177   1991   075   1993   19   16.0   02   023   048   1942   147   1957   02   1959   00   00   00  
                                                                     
  *Leeming   18.1   +0.8   09.6   +0.4   23.7   08   04.1   26   00   00   05   12.2   12   121   099   1945   200   1986   073   1976   20   07.8   02   021   044   1945   174   1976   04   1959   00   00   00  
  *Boulmer   17.1   +0.8   10.4   +1.1   23.5   08   05.9   18   00   00   07   11.4   12   114   089   1945   205   1986   075   2001   19   18.4   03   043   078   1945   147   1965   12   2004   00   00   00  
  *Eskdalemuir   15.5   +0.6   08.2   +1.1   21.6   12   -00.9   20   05   01   10   09.3   15   082   081   1911   153   1959   046   2008   16   26.6   08   091   064   1911   308   1950   18   1972   00   00   00  
  *Bishopton   16.4   +0.1   10.2   +1.5   21.9   13   05.1   20   00   00   07   12.3   12   104   092   1921   169   1996   058   2008   11   23.0   07   095   100   1921   258   1985   11   1972   00   00   00  
                                                                     
  *Leuchars   17.0   +0.8   09.7   +1.0   22.2   12   04.9   17   04   00   03   11.3   12   135   104   1922   181   1997   077   1956   19   51.6   03   090   176   1922   149   1950   05   1972   00   00   00  
  *Dyce   17.0   +1.5   09.3   +1.3   22.2   08   03.6   20   01   00   05   10.6   26   120   102   1941   181   2004   070   1968   18   67.2   03   103   158   1941   234   1995   15   1959   00   00   00  
  *Stornoway   14.9   +0.7   10.4   +1.7   16.7   10   07.5   30   01   00   05   07.4   09   * 065   060   1880   175   1903   070   1965   08   09.6   05   086   084   1943   206   1981   34   1968   00   00   00  
  *Aldergrove   16.8   +0.7   09.9   +0.5   21.0   13   04.0   11   00   00   02   12.0   12   119   107   1927   177   1986   070   1962   17   08.0   02   032   040   1927   163   1981   06   1986   00   00   00  
                                                                     
                                                                                                                                             
  Stations marked with an asterisk record sunshine electronically; comparisons      
  with earlier records are therefore somewhat speculative. Thorney Island's   * New lowest    
  sunshine figures are made at a nearby site.