Monthly Summary - September 2011

   The weather may often disappoint, but it is very rarely uneventful for very long and September is just one more example of this. It saw the remnants of an ex hurricane (Katia) and ended with a quite glorious and belated taste of Summer weather that was actually the warmest and most sustained warm spell of 2011 - but otherwise it was very much a 'South westerly' month and hence unsettled and wet, although relatively mild.

   A mean temperature for the month of 13.03°c (55.5°F) is well above the long term average with the main contributory factor being a large number of mild nights caused by the cloudy conditions trapping any heat in. Fourteen nights had minimum temperatures over 10°c, whilst daytime maximums were just very slightly above average. The mean minimum temperature of 9.21c is the same as that for August, but a wopping 0.78°c warmer than that for July! The impact of the warm spell at the month's end on those mean figures was actually relatively small.

   The month started with a warm sunny day as high pressure (1017 Mb) was centred on the UK, but then it was very much a return to the rain and cloud as the month became very cyclonic. Indeed apart from the final five days, high pressure was only present on two other days.

   That high pressure slipped away East on the 2nd allowing low pressure (981) to move in from the Atlantic, this brought two poor days with the 3rd especially quite a bleak day.

   The 4th saw us sit in a slack area behind the fronts of the previous days and hence it was quite pleasant, but it clouded over from tea-time ahead of yet more rain into the 5th. However, once the rain had cleared (by 0900 hrs) the 5th was a reasonable day. But a significant depression in the Atlantic was to bring very heavy rain through the night of 5/6th.

   At least the rain had the good grace to arrive overnight and clear by 0800 hrs on the 6th. All in all 29.9mm fell overnight (months wettest day), brought on low pressure (978) that had a cold front wrapped around an occlusion. The evening of the 6th saw yet another 9.4mm of rain as those fronts were slow to move away.

   After a few generally cloudy days the 10th saw a deep depression (984) west of the UK gradually move NE and bring rain (14.8 mm) and windy conditions. A temperature of 20.1°c (68.2°F) only made a dull and damp day feel worse with high humidity. That high temperature was brought on a southerly flow of humid air of Tropical Maritime origins. But by now attention had been cast to the eastern seaboard of America and Hurricane Katia which had been making swift progress across the Atlantic and was heading our way.

   Ex hurricane Katia arrived on the 12th - where exactly would it arrive in the UK and how wet and windy would it be? It arrived with a steep pressure gradient on its southern flank and it was this that brought the strong winds. We had had heavy rain overnight, 12.3 mm and then the strongest gust of 58 Mph came at 1345 hrs. In the end not quite the event some of the media had hyped it up to be.

   After Katia had moved away we remained in a strong Westerly flow and showers were now the order of the day until high pressure overnight 14-15th brought the months coldest temperature of 1.9°c and those two days were quite agreeable with the 15th a beautiful clear sunny day.

   The high pressure was soon gone and the 16+17th were wet days, 14.7mm on the 16th as low pressure (1000) was to the NW of the UK and a series of fronts brought that rain.

   We then entered a period of mixed days, some good, some bad but the 16-26th was still dominated by cyclonic conditions and the maximum temperatures in this period were more typical for the time of year at 14-16.5°c; fresher conditions on brisk Westerlies. Rain on the afternoons of the 18th and 19th had followed reasonable starts to the day and the 20th was another lovely albeit fresher day. But the 21st was a poor day as a band of rain arrived mid a.m. and brought another 8.0mm of rain and saw the wind gusting to 45 Mph and it also saw the months lowest day-time temperature of 13.5°c (56.3°F).

   We had more rain, 7.0 mm, through the night of the 25-26th but now it was a case of waiting for that warm spell and it didn't disappoint.

   Maybe an indictment of our Summer, but the four days of 28th to the 1st October all attained 70°f (21.1°c), the one and only time this year to have done so!! High pressure (1033) over Germany then Poland slowly migrated west and just far enough west to save us from Atlantic depressions that did bring rain to Scotland and Eire. This time we did reap the benefits as the high pressure drew up warm and dry air from southern France.

   24.8°c on the 28th was warm and after 'just' 22.5°c on the 29th the 30th was simply balmy at 25.4°c (77.7°F). This is by far the warmest September day at this site and whilst such temps do occur in September they wouldn't be expected at the month's end. Also not forgetting that all three days had been sunny and virtually cloudless, especially the 28th and 30th.

   So the month ended on a positive but fairly brief high, but maybe just a big enough high to disguise an otherwise poor and damp month.

   Rainfall totalled 126.9 mm for the month, with rain recorded on 20 days of which 15 were 'Wet days' (1.0mm +).

   The Mean Temperature for the month was 13.03°c+         --      The Mean Max' was   16.85°c   --    The Mean Min'   9.21°c.

   We had 0 Air Frosts in the month (year 30)      --      Grass frosts totalled 0 (year 50).

   The 30 cm soil temp ranged from 12.7°c on the 23rd      to      15.1°c on the 11th      --      with a monthly mean of 13.7°c


   * September 2011 rainfall was 161% of the September average for 2007 - 2010

   * September 2011 was 0.43°c warmer than September 2010 +

  * The 3 month mean for July/August/September 2011 is                   TEMP'    13.42°c         --          RAIN    305.2 mm

* July/August/September 2010 was TEMP'    13.58°c -- RAIN    254.7 mm

* July/August/September 2009 was TEMP'    14.00°c -- RAIN    341.4 mm

* July/August/September 2008 was TEMP'    -- RAIN    364.7 mm

* July/August/September 2007 was TEMP'    -- RAIN    276.5 mm


* 2011 To date TEMP'    9.62°c -- RAIN    904.5 mm

* 2010 Jan - Sept TEMP'    8.74°c -- RAIN    461.1 mm

* 2009 Jan - Sept TEMP'    9.74°c -- RAIN    791.9 mm

* 2008 Jan - Sept TEMP'   -- RAIN    985.7 mm

 + Met office figures for September show that NW England/N. Wales had a mean temp' of 13.7°c, this being +1.4°c warmer than the reference period 1971-2000 (+1.5°c warmer than reference period 1961-90)


JANUARY 2010    FEBRUARY 2010    MARCH 2010    APRIL 2010    MAY 2010    JUNE 2010    JULY 2010    AUGUST 2010    SEPTEMBER 2010    OCTOBER 2010    NOVEMBER 2010    DECEMBER 2010   

JANUARY 2011    FEBRUARY 2011    MARCH 2011    APRIL 2011    MAY 2011    JUNE 2011    JULY 2011    AUGUST 2011   

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