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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 585 For SEPTEMBER 2004
DRY,SUNNY AND VERY WARM AT FIRST TILL THE 10TH, THEN CHANGEABLE AND OFTEN WINDY
Text Box: Mumbles, near Swansea, measured a gust of 74 mph. Amounts of rain were relatively small in some eastern parts of Scotland and England, but huge orographically-enhanced totals were recorded in the western Highlands, the Lake District, and Snowdonia. Largest 24-hour totals were 75mm at Capel Curig, Snowdonia, on the 12th and 70mm at Loch Sloy, Argyllshire, on the 19th. Here, 368mm fell in the 12-day period ending on the 21st. For much of this period temperatures were near normal, but it turned cold on the 23rd/24th as the wind veered; the maximum at Lerwick, Shetland, on the 24th was 9.6ēC, and the minimum at Redhill airfield, Surrey, overnight 24th/25th was -0.6ēC.

From the 25th till the month’s end high pressure lay over Biscay and France but a cloudy westerly airflow covered most of the UK, and most regions had occasional rain although amounts were small over England and Wales until the 30th.  Days were cool but nights were mostly mild, and Eskdalemuir had a sunshine aggregate of just 0.8 hour during the last six days.

Monthly mean temperature was around 1 degC above the long-term average in all regions, but this was almost entirely due to the warmth of the first ten days. In eastern, central and southern regions this was the third consecutive dry September, and only 10mm of rain fell at Dishforth, North Yorkshire, and12mm at Boulmer, Northumberland, where it was the driest September since 1971. By contrast, Loch Sloy collected 460mm, and an estimated 500-600mm fell in the wettest locations in the southwest Highlands, the Lake District and Snowdonia. Thanks to the exceptionally sunny start, monthly sunshine totals were above average nearly everywhere in the UK, and Aberdeen airport’s 181 hours was a new record for the site, making this the sunniest September in the Aberdeen area district since 1906.
Text Box: Pressure was high over the UK until the 9th, but winds from a westerly quarter blew throughout the remainder of the month. Mean sea-level pressure was above normal in the Europe/Atlantic sector south of latitude 55N and below normal further north, resulting in an enhanced westerly flow over the British Isles where it was the tenth most westerly September in the last 100 years.

High pressure lay over southern Britain from the start of the month, extending to all parts of the UK from the 5th-9th and the barometer climbed to 1040.6mbar early on the 7th at Inverbervie, Kincardineshire (a new UK record for the first half of September). A trough advanced from the southwest on the 10th as the high receded eastwards.  There was occasional rain in Scotland at first, notably on the 3rd, and showers over England and Wales on the 10th, otherwise the weather was dry, sunny and very warm throughout the first ten days. In fact this was the driest and sunniest start to September since 1991. The temperature widely reached 22-25ēC daily, peaking at 29.0ēC at Wisley, Surrey, on the 5th, while the 6th was the hottest September day in the Cardiff area since 1961. In Scotland, Glenlivet, Moray, touched 26.0ēC on the 9th. Bournemouth recorded 103 hours of sunshine during the first nine days.

Vigorous depressions tracked north-eastward past northern Scotland between the 11th and 14th followed by a transitory ridge on the 15th, then a large complex depression moved slowly eastward between Scotland and Iceland from the 16th-20th and settled over Scandinavia around the 21st-24th allowing a brief north-westerly intrusion across the British Isles. This was the most disturbed period of the month with belts of rain crossing all parts  of the country at frequent intervals, sunshine and showers between the rain-belts, and gale force winds especially in Scotland but also in Wales and south-west England on the 14th when
                                                                                                                                             
                       TEMPERATURE                                SUNSHINE                             RAINFALL                                                       
                                                                                                                                     
                                                                                                                                     
                   
No. of days with grass
  minimum below 0ēC
                      Highest and lowest totals    
Maximum fall in 24 hrs
   (beginning 09 h)
                Highest and lowest totals    
Days with snow or sleet
 
Days with fog
(Vis <220 yards at 09 h)
 
     
Difference from average
   
Difference from average
             
Days of no sunshine
                      on record for month                         on record for month        
                                                                                         
           
Highest maximum
   
Lowest minimum
         
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
           
                                                                     
      ēC       ēC       ēC       ēC             Hrs       Hrs         Hrs       Hrs       mm       mm         mm     mm          
                                                                                                                                             
  *Hampstead   20.1   +1.7   11.6   +1.1   27.4   05   04.8   25   00   00   00   10.0   04   147   113   1910   224   1959   072   1945   11   06   12   024   036   1910   157   1918   02   1959   00   00   00  
  Thorney Island   20.0   +0.9   12.7   +1.8   27.9   05   04.7   25   00   00   00   10.9   05   172   102   1958   245   1959   129   1967   9   09   12   030   057   1941   159   1974   02   1971   00   00   00  
  *Coltishall   19.3   +1.5   11.1   +0.9   26.5   04   02.6   16   01   00   02   12.1   01   173   119   1979   220   2003   082   2001   11   15   22   044   085   1964   154   1994   08   1969   01   00   00  
  Wittering   18.9   +1.3   10.9   +1.3   25.6   05   04.4   16   00   00   01   12.5   04   179   130   1950   207   1964   093   1967   12   06   30   028   060   1948   132   1992   02   1959   01   00   00  
                                                                     
  Lyneham   18.9   +1.5   11.3   +1.8   26.9   05   05.9   25   00   00   00   11.8   01   169   119   1952   235   1959   100   1983   10   10   12   040   062   1945   142   1974   05   1959   00   00   00  
  Ross-on-Wye   19.8   +2.0   11.1   +1.5   27.0   05   05.0   16   00   00   00   12.1   01   179   140   1914   205   1929   069   1945   11   15   14   054   084   1859   203   1976   02   1865   00   00   00  
  *St Athan   18.3   +1.0   12.3   +1.7   26.1   05   06.6   25   00   00   01   11.8   05   128   089   1954   249   1959   074   1956   11   14   16   087   096   1954   223   1974   14   1959   00   00   00  
  St Mawgan   18.0   +1.0   13.1   +1.8   26.0   06   09.6   01   00   00   01   11.4   07   157   100   1945   258   1959   080   1956   11   13   16   050   062   1944   179   1974   10   1959   00   00   00  
                                                                     
  *Edgbaston   18.3   +1.6   11.6   +1.8   26.3   05   07.6   16   00   00   00   10.8   01   146   115   1887   216   1895   067   1909   11   11   22   054   075   1887   165   1918   04   1959   00   00   00  
  Valley   17.6   +0.9   12.7   +1.6   25.8   09   09.3   29   00   00   00   12.0   08   143   102   1946   214   1949   096   1948   12   15   12   085   102   1941   174   1950   03   1986   00   00   00  
  Ringway   18.3   +1.3   11.1   +1.1   24.5   05   06.3   24   00   00   02   12.2   01   148   122   1945   197   1959   069   1948   6   37   14   110   147   1942   171   1965   05   1959   00   00   00  
  *Watnall   18.2   +0.6   11.0   +1.4   25.7   05   05.4   16   00   00   02   12.5   01   147   106   1948   177   1991   075   1993   13   08   16   038   080   1942   147   1957   02   1959   00   00   00  
                                                                     
  Leeming   18.3   +1.1   9.5   +0.4   25.2   05   02.6   25   01   00   03   12.0   05   170   143   1945   200   1986   073   1976   9   03   10   016   032   1945   174   1976   04   1959   00   00   00  
  *Boulmer   17.1   +0.9   9.9   +0.7   23.0   04   04.8   25   00   00   09   09.3   08   126   100   1945   205   1986   075   2001   9   03   29   * 012   023   1945   147   1965   12   1971   00   00   00  
  Eskdalemuir   15.3   +0.5   8.7   +1.7   22.7   09   02.3   01   01   00   06   11.4   08   099   101   1911   153   1959   055   1980   9   30   19   213   150   1911   308   1950   18   1972   00   00   00  
  *Bishopton   16.3   +0.1   10.0   +1.4   21.7   09   04.2   24   00   00   04   12.4   07   106   096   1921   169   1996   068   1965   11   30   19   162   171   1921   258   1985   11   1972   00   00   00  
                                                                     
  Leuchars   16.8   +0.7   9.5   +0.9   22.9   04   03.3   29   00   00   07   10.3   15   154   122   1922   181   1997   077   1956   10   07   05   036   070   1922   149   1950   05   1972   00   00   00  
  Dyce   16.4   +1.0   9.6   +1.7   25.1   04   03.5   01   00   00   05   11.8   07   * 181   158   1941   171   1997   070   1968   11   04   27   024   037   1941   234   1995   15   1959   00   00   00  
  *Stornoway   14.8   +0.7   9.5   +0.9   19.6   09   05.1   14   00   00   01   12.4   08   118   111   1880   175   1903   070   1965   11   22   17   131   127   1943   206   1981   34   1968   00   00   00  
  *Aldergrove   16.3   +0.3   10.9   +1.6   21.5   04   05.5   24   00   00   05   12.1   08   108   101   1927   177   1986   070   1962   11   14   29   060   075   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 record   * Equals record  
  sunshine figures are made at a nearby site.