Monthly Summary - September 2012

   Despite a fine and settled start to the month which even gave a belated taste of summer, overall, September has been the coldest locally since 2001 and nationally since 1994. The second half of the month especially saw many cool days and an air frost on the 22nd is particularly early in the season.

   And whilst upto the 22nd rainfall had been relatively light, a significant and unseasonably deep depression on the 24-25th brought excessive rainfall that caused some disruption and localised flooding and ensured a fourth successive month to record over 100 mm of rain.

   September should be a quiet, possibly benevolent month and a slight case could have been made for this until that dreadful final week.

   Making comparisons with the Met' office site at Newton Rigg (Penrith) from 1961, using the averages for the (new) standard period 1981-2010 (mean temperature of 12.3°c and 76.3 mm of rain), 39 September's have been warmer, 11 have been colder, with one the same mean temperature. In the same period 3 September's have been wetter, with two virtually the same.


   1st - 5th    This was a settled and dry period that saw high pressure (HP) in charge, initially to our south then moving to our west and that provided a slight taste of a belated summer with some sunny days! The 1st-2nd whilst starting cloudy saw the sun out from late morning and then the 3rd-5th (3rd especially and with a temperature of 19.6°c) saw plenty of sunny spells.


   6th - 9th    Saw the HP slip south leaving us at its northern edge and which allowed weather fronts to progress east from the Atlantic. Whilst it was still dry, the days were cloudy and it initially felt much cooler in a brisk south westerly breeze. But the afternoon of the 8th was warm at 20.0°c and then the 9th was the month's warmest day at 20.8°c (69.4°f) with both days pleasantly sunny as that area of HP temporarily pushed back north.

   But the 9th also saw the gradual incursion of low pressure (LP) from the Atlantic and the next few days became unsettled.


   9th - 12th    The 10th saw 9.9mm of rain due to the passage of a cold front over the UK and behind this front it became much fresher and showery in a brisk westerly and the on-set of autumn was now upon us.

   From this point on the temperature took a noticeable dip and from the 17th, apart from the 26th, daytime maximums would fail to attain 15°c.


   13th    Saw a ridge of HP from the Atlantic that saw the day start with a ground frost, but once again LP was waiting to take over.


   14th - 20th    Saw Autumn kick in as LP (969 Mb) sat to the north of the UK and pushed a pair of cold fronts over the UK and that brought a little rain (14th), but much fresher conditions behind. The process was repeated on the 16th, but after the 15th had seen a sunny day.

   A slight ridge of HP on the 19th gave a day of sunny intervals, but was cool at just 12.2°c, with the 20th seeing a warm front attached to a shallow area of LP in the Atlantic bring 3.9 mm, but then followed a lovely weekend.


   21st - 23rd    Saw HP build and sit over the UK and this saw the 22nd start with the first air frost of the season and a month's low of -1.5c (29.3°f) with a ground frost of -4.4°c. But the 22nd (Saturday) was a glorious sunny day and after the cold start it did warm up to 14.9°c and then the 23rd whilst recording a ground frost just avoided an air frost (0.1°c). The 23rd started sunny but cloud soon encroached and it did feel cool at just 12.2°c as a brisk easterly wind picked up ahead of the next and a significant LP system moving north from Biscay.

   Those air and ground frosts saw the yearly totals go to 40 and 91 respectively, greater than the whole of 2011 - and we still have three months of the year still to go!


   24th - 25th    Upto this point rainfall had been patchy and at 37.4 mm fairly moderate, but now that was to change courtesy of a significant area of LP that had become established in Biscay and moved north over the UK. This LP had an input of warm tropical air dragged from ex tropical storm Nadine which gave it some extra energy.

   This LP then remained unusually active as it sat over the UK and as the LP system moved north across the UK, it has also pulled in cooler polar air from the north. When this cold air came up against the warm sub-tropical air it re-invigorated the depression allowing it to continue to deepen over the UK, 976.2 Mb at its lowest at this site.

   And our old friend from summer, the jet stream, played its meandering part, assisting the LP in lingering over the UK for longer than normal. Once again the effects on Cumbria were mixed, with some locations east of Carlisle being relatively unscathed, but at this site 68.9 mm fell during the event with 55.8 mm credited to the 24th (45% of the monthly total), making it the second wettest day at this site since June 2007 when records commenced.

   Both days were also on the cold side with the 24th seeing a month's low of just 11.2°c (52.2°f).


   26th - 29th    Was a mixed period as the LP that had brought the rain moved south and brought fresher and clearer air behind with a shallow ridge of HP building. But showers were never too far and the temperatures remained low.


   30th    The month ended wet and miserable as a series of fronts entrained around LP south of Iceland moved east over the UK and gave a strong and cool westerly flow.


   Rainfall totalled 123.7 mm for the month, with rain recorded on 20 days of which 17 were 'Wet days' (1.0mm +).

   The Mean Temperature for the month was 11.55°c      --      The Mean Max' was   15.42°c     --      The Mean Min'   7.68°c.

   We had 1 Air Frosts in the month (year 40)      --      Grass frosts totalled 3 (year 91).

   The 1 foot soil temp ranged from a low of 11.0°c on the 26th      to      a high of 15.6°c on the 3rd     --      with a monthly mean of 13.4°c

   The 1 meter soil temp ranged from a low of 11.6°c on the 30th      to      a high of 14.0°c on the 1st-3rd      --     with a monthly mean of 13.1°c



   * September 2012 rainfall was 140% of the September average for 2007 - 2011

   * September 2012 was 1.48°c colder than September 2011      --      1.05°c colder September 2010      --      0.85°c colder than 2009

  * The 3 month mean for July/August/September 2012 is                   TEMP'     13.29°c         --          RAIN    377.5 mm

* July/August/September 2011 was 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


* 2012 To date TEMP'     9.25°c -- RAIN    868.5 mm

* 2011 Jan - Sept 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


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    SEPTEMBER 2011    OCTOBER 2011    NOVEMBER 2011    DECEMBER 2011   

JANUARY 2012    FEBRUARY 2012    MARCH 2012    APRIL 2012    MAY 2012    JUNE 2012    JULY 2012    AUGUST 2012    SUMMER 2012   

   © Darren Rogers 2012

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