Monthly Summary - December 2011

   Following on from autumn December continued the theme of wet, dull and mild weather and whilst not as overly mild as recent months it certainly was wet and windy and quite different to the snow and cold of last December.

   In becoming the wettest month of 2011 it also broke three records for this site:

  rain was recorded on 30 days, the most in a single month.

  rain was recorded on 28 consecutive days (23rd Nov' to 20th), the longest ever such run.

  and with a mean wind speed of 12 Mph it was the windiest recorded month.

   The wind blew from a westerly quarter almost without a break throughout December making it the second most 'westerly' December, after 1974, in 139 years of records. As a consequence there were several extended periods of orographically-enhanced rainfall, especially in the Lake District. There were also frequent gales with six days recording gusts in excess of 50 Mph.

   Up to the 18th the month whilst not particularly cold saw a wintry mix of weather with snow or hail falling on eleven of the days. However, this was slight and fairly insignificant and despite the occasional dusting only the 6th was recorded as a 'Day of lying snow'.

   From the 19th the month became progressively milder and sunshine was a distant memory and after successive Christmas's with snow on the ground, this was to be a wet and green one and also the month's warmest day.

   Whilst the month only recorded 5 air frosts (the last 4 December's averaged 17), ground frost was frequent, being recorded on 20 days with only the 14th just missing out in the first 19 days of the month.

   After a few showery days for the 1st - 3rd, the 4th saw the first snow of winter as a brisk WNW'ly airflow brought cold air from the north Atlantic. Whilst heavy at times this snow struggled to settle, but then the 5th saw further snow showers as a cold Polar maritime airmass covered NW Europe. Relatively warm sea surface temperatures at this time of year caused unstable conditions with plenty of showers brought on numerous troughs within this flow. It also felt cold with a maximum temperature of 2.7°c.

   The first storm of winter arrived in the early hours of the 8th and had deposited 34.4 mm of rain by daybreak (credited to the 7th using 09-0900 hr readings) and during a very windy day had gusts up to 61 Mph with rain preceeded by wintry showers.

   The 10th saw the slight influence of high pressure and as a result there was a frost of -3.4°c and another dusting of snow to wake up to and some brighter conditions during the morning. But then the 11th was grim with more rain and then the 12th - 14th were just as miserable as a series of Atlantic depressions brought a strong Sw'ly flow that saw rain of 17.9 mm on the 12th and 14.4 mm on the 13th. A quieter day followed on the 15th that had some brighter moments but then then the airflow turned NW'ly and then followed the coldest spell of the month.

   That NW'ly flow saw the temperatures fall with the 16th the month's coldest day at 2.0°c (35.6°F) and that saw further wintry showers. The 16th saw a significant storm blow through the English channel and which had initially been forecast to hit us. Air frosts followed on the 16-18th with the -4.8°c (23.4°F) on the 18th the month's lowest temperature (ground frost of -8.5°c was jointly the year's lowest). The 18th was the month's sunniest day and whilst cold was lovely.

   A frost on the morning of the 19th quickly gave way to cloud and rain as a complex frontal system moved in. A weather front on the 21st marked a boundary between cold and warm air and it now became milder. However, using 09-0900 hr readings the 21st, whilst dull, became the only day of the month to record no rainfall and hence break a run of 28 days with at least 0.2 mm of rain.

   The Christmas/New Year week whilst very mild was overcast, wet and a little grim. Christmas day peaked at 12.0°c (53.6°F), but was wet and windy, gusting to 56 Mph. The 29/30th saw a cooler Polar air mass move in and a cold front in the early hours of the 28th brought heavy rain and the 29th saw us in a strong cyclonic NW'ly flow that was cooler and showery.

   The month finished back in warm and moist air on a SW'ly and the resultant murk and rain.

   Overall, a grim month, dull and in the end the lack of sun with the virtually ever present cloud sheet made it quite depressing.

 

   Rainfall totalled 180.1 mm for the month, with rain recorded on 30 days of which 24 were 'Wet days' (1.0mm +).

   The Mean Temperature for the month was 4.46°c+         --      The Mean Max' was   7.04°c   --    The Mean Min'   1.89°c.

   We had 5 Air Frosts in the month (year 39)      --      Grass frosts totalled 20 (year 79).

   The 30 cm soil temp ranged from 8.0°c on the 1st      to      3.0°c on the 19th      --      with a monthly mean of 5.4°c

  COMPARISONS:-

   * December 2011 rainfall was 196.8% of the December average for 2007 - 2010

   * December 2011 was 6.44°c warmer than December 2010



  * The 3 month mean for October/November/December 2011 is              TEMP'    7.82°c         --          RAIN    400.9 mm

* October/November/December 2010 was TEMP'    3.51°c -- RAIN    241.8 mm

* October/November/December 2009 was TEMP'    6.18°c -- RAIN    472.6 mm

* October/November/december 2008 was TEMP'    -- RAIN    395.6 mm

* October/November/December 2007 was TEMP'    -- RAIN    283.3 mm

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  A FEW NOTES ON 2011

   2011 saw a return to mild and wet weather in a complete contrast to 2010, with the rainfall and mildness most marked in the final four months. Summer once again disappointed and whilst autumn was exceptionally mild, by far the best month was April.

   Whilst it will come as no surprise that only three months in 2011 were colder than their counterpart in 2010, it only becomes depressing when one learns that those three months were the summer months of June, July and August!

   As a whole 2011 had a mean temperature of 9.17°c (48.5°F), some 1.75°c warmer than 2010, but the summer was -0.8°c colder than that of 2010!

   For our region as a whole, eight months were above the standard long term average for 1971-2000 with January, July and August being colder than average, whilst June was exactly average.

   January - was a month of two halves, the first being very wet and the second dry and settled with the month overall being a cool one. The 15th was the year's wettest day with 48.7 mm and winds up to 60 Mph; the 'rainfall event' of this storm giving 68.1 mm of rain over two days. January also provided the year's coldest temperature of -6.9°c on the 29th.    February - whilst milder than the norm was drab, very wet and dull. The 3rd-4th saw the year's main storm with winds gusting to 67 Mph (108 mph was recorded on Great Dunn fell) and another soaking.

   After an average, settled and reasonable March, April blossomed and in many ways was our main taste of summer weather as it broke both local and national records (warmest April on record). The first five days had been wet but from then on exceptional warmth, sunshine and dry weather prevailed and the best of the weather even coincided with weekends and bank Holidays. The 6th to the 4th May saw a 29 day partial drought that only recorded 1.8 mm of rainfall. The 9+10th both just fell short of the 20°c mark, but the 20-22nd saw the mercury hit 20.7°, 23.1° and 21.4°c and all of these dates enjoyed brilliant sunshine. A mean temperature of 10.24°c was exceptional.

   Despite a decent start May was a poor month, windy and wetter than the three previous Mays combined and the month managed to get colder as it progressed. Summer was cool with no sustained periods of warmth and whilst not as wet as might be imagined, rain fell fairly frequently, especially in a dull and wet August.

   June saw the year's warmest day, 25.9°c (78.6°F) on the 3rd, but the good start to summer soon faded away and the temperatures never recovered. July also started well and whilst day-time temperatures were quite respectable and it felt comfortably warm, an unusually high number of cold nights (just 3.2°c on the 1st), held back the mean temperature for the month. August epitomized the Summer as a whole, unsettled, dull and cool. Rain fell on 23 days and it was to be the first of five successive months to record in excess of 100 mm of rain.

   Autumn was remarkable for its warmth, but then it was also wet! September was poor but was spectacularly saved at the very end by a four day (28th to 1st Oct') warm spell that saw all four days attain 70°F, the only time this year to have done so. The temperature peaked at 25.4°c on the 30th, quite amazing for the end of the month. October created a new temperature record on the 1st with 24.7°c and the month was mild by both day and night, but it was very dull and rain fell on 25 days.

   November was even more unseasonable in its mildness (2nd warmest November on record), but it was fairly flat for the majority of the month before the final week saw it revert to type and it became wet and windy.

   December was mixed with the 4-18th having a wintry mix with snow falling on most days within this period. However, it was all very light and virtually insignificant. The final ten days were very mild, ensuring that the month was a little warmer than average, but rain fell on 30 days and with 180.1 mm was the year's wettest month. Rain had fallen on 28 consecutive days from 23rd November through to the 20th December with just one dry before the rain returned. Consequently it was also very dull and overall quite grim.

  TEMPERATURES the mean minimum temperature for the year (5.51°c) saw a greater percentage increase than that of the mean maximum (12.82°c) (warmer nights), but one curiosity is that the 3rd, 4th and 5th warmest days of the year all occurred outside of the summer months by some considerable margin. The year had 39 air frosts and 79 ground frosts and only 25 days attained 20°c or greater.

  RAIN a wet year with rainfall fairly consistent throughout, but with the last five months all recording over 100 mm. Rain was recorded on 230 days with 179 of those being 'wet days' (at least 1.0 mm) - a fairly average figure.

  SNOW was in short supply this year and only two days (19.2.11. and 6.12.11.) were recorded as 'days of lying snow' (at least 50% coverage of 1cm at 0900 hrs). It was seen to fall on 17 days (9 in December) with sleet/hail on a further 5 days.

  OTHER Thunder was once again a rarity, only heard on three days and none of these resulted in storms. Fog was only recorded on six days at 0900 hrs and the air pressure for the year averaged 1012.9 Mb at 0900 hrs. The highest reading was 1041.8 Mb on 21st January and the low was 973.9 Mb 12/13th December.

   Various facts figures for 2010 and other years can be found on this site, see 'Previous years' and 'Rainfall'.

 


* 2011 TEMP'    9.17°c -- RAIN   1305.4 mm

* 2010 TEMP'    7.42°c -- RAIN    702.9 mm

* 2009 TEMP'    8.84°c -- RAIN   1264.5 mm

* 2008 TEMP'    -- RAIN   1381.3 mm

 + Met office figures for December -- NW England/N. Wales had a mean temp' of 5.4°c, this being +1.1°c warmer than the reference period 1971-2000 (+1.4°c warmer than reference period 1961-90)

   PREVIOUS MONTHS REPORTS

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   

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