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graphs      CLIMATE-UK.COM'S  REVIEW  OF  THE  BRITISH  METEOROLOGICAL  SCENE
     MONTHLY  SUMMARY
     No. 609 For   SEPTEMBER  2006
EQUAL WARMEST SEPTEMBER IN 340 YEARS OF RECORDS                            EQUAL  WARMEST  SEPTEMBER  IN  340  YEARS  OF  RECORDS
Text Box: Once again a major change of type was synchronised almost exactly with the calendar: August’s northwesterlies gave way to southerlies in September resulting in persistently high temperatures throughout the month. This was the fourth most ‘southerly’ September over the British Isles, after 1901, 1903 and 1934. Mean sea-level pressure ranged from 2mbar below normal in Shetland to 9mbar below in western Ireland, and the main anomaly centre of -13mbar lay near 52N 19W. A moist SW-ly flow covered the country during the first three days, bringing strong winds and much cloud, and heavy orographic rainfall affected western upslopes: Capel Curig collected 47mm on the 2nd, part of a 7-day (30 Aug-5 Sep) total there of 184mm. It was quite warm in eastern England especially at night and the minimum overnight 2nd/3rd at St James’s Park (London) was 18.9°C. The period 4th-11th was largely anti-cyclonic; highest pressure lay over France at first, and moist southwesterly winds delivered more rain to northwestern regions including a fall of 53mm at Tyndrum (Perth-shire) on the 5th, but temperatures climbed to 25-27°C in the south and east. Highest pressure transferred briefly to the west of Ireland on the 7th allowing a short-lived northerly incursion which resulted in a couple of cold nights, the mercury slumping to -0.8°C at Braemar (Aberdeenshire) early on the 8th. However, the anticyclone moved steadily eastwards over the next few days and a sluggish southerly airflow sent temper-atures soaring to 25°C or more from 9th-14th and peaking at 30.2°C at Heathrow (London) on the 11th, the highest September reading in the UK since 1999. Between the 6th and 12th, the sun shone for a total of 60-70 hours in many southern, central and eastern districts, and Kinloss (Moray) logged the largest daily total of 12.5 hours on the 8th. Britain lay under a humid southerly flow from the 12th-21st, with high pressure still anchored over eastern Europe, while low pressure lay to the west of Ireland. Although temperatures were lower than hitherto, it remained rather warm especially at night (although an isolated cold night in Northern Ireland brought a reading of -0.1°C at Text Box: Katesbridge, County Down, early on the 16th). Heavy rain and thunderstorms broke out widely between the 12th and 14th, but eastern districts became mostly dry again for several days. However, it was very wet between the 18th and 20th in western regions, and Tyndrum collected 131mm of rain in 72h, 67mm of which fell on the 20th alone. On the 21st much of the country was spectacularly sunny and very warm, and the maximum of 29.0°C at Sutton Bonington (Notts) was the highest this late in the year since 1985. A small but intense depression, associated with the remains of hurricane ‘Gordon’ brought rain and rough winds to western parts of the UK overnight 21st/22nd with gusts to 69kn at South Uist (Western Isles); there were widespread power failures that night in Northern Ireland. The rest of the month was cyclonic with lowest pressure over or just to the west of the British Isles. Showers broke out widely on most days, there were some torrential downpours, and thunder was frequently heard. Most places remained rather warm, but at Dalwhinnie (Inverness-shire) the day’s high on the 24th was just 12.4°C. An unconfirmed fall of 110mm at Gorleston (Norfolk) was associated with serious flooding in Gt Yarmouth and Lowestoft on the 25th. South Uist logged a gust of 64kn on the 27th during the passage of former hurricane ‘Helene’. Mean temperature ranged from 2.0-2.5degC above normal in northern and western Scotland and Northern Ireland, to 3.0-3.5degC above in the Midlands, East Anglia and southeast England. Over a large part of the UK it was warmer by a substantial margin than any September in the last 100 years. Rainfall was much below normal in parts of southwest England where Portland (Dorset) received only 17mm, but much above in western and central Scotland and in parts of East Anglia. Sunshine totals were up to 25% above normal in central and eastern parts of both England and Scotland, but there was a large deficit in Shetland; totals ranged from 198h at Herne Bay (Kent) to 47h 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 0ºC