Monthly Summary - December 2010

   Quite simply December will live long in the memory, its place in the history books assured and surely lasting for a long time. The coldest December in at least 100 years and one that has shattered many a record at sites all over the country. Unusual in that the cold has come so early in the winter season, but to say that it was COLD does not do it any sense of justice - it, as the say in these parts, was BALTIC.

   A remarkable month that was in many ways typical of the whole year, cold and dry. Had this not been such a cold year the headline would have been just how dry a year we have had. December was also dry, the third driest in 100 yrs, but I look at list of nine (9) separate records for my site that December now holds and I expect that some of those will last a long time. It again doesn't do the month justice to say that it was cold.

   Apart from a weeks lull mid month and a return to 'normal' conditions at the end of the month, the main theme was for air of an Arctic origin to sit over us, with any warmer Atlantic depressions 'blocked' from reaching us, with the occasional front or trough bringing outbreaks of snow.

   So what are those nine records? And both individually and collectively, they underscore the severity and extremeness of Decembers weather:-

   * At -1.98°c (28.4°F) the coldest recorded month.

   * The coldest mimimum temp' of -14.6°c (5.7°F)             * The coldest minimum grass temperature of -18.3°c (-0.9°F)

   * The coldest maximum temp' of -4.3°c (24.3°F)

   * The most number of ICE DAYS with 12      * The most number of Days of laying snow with 22      * The most number of Air Frosts with 23      * The most consecutive days to record a minimum temp' below freezing with 17

   The 9th record I will save for later.

   At the month's start we were already deep in the grip of winter and snow of 1.5 cms overnight into the 1st took the level depth to 12 cms. Then behind the trough line that brought that snow was an area of high pressure (AHP) (1037 Mb) to the north of the UK and this gave a cold NE'ly airflow and this extended into the 2nd, with a further 3 cms of snow and with it consecutive 'Ice Days' - it was bitter.

   Generally we were saved from the main belts of snowfall during this time as the Pennines present a natural barrier to any weather getting to us when it originates from the east. The Pennines are no barrier to the bitter cold though and early on the 3rd the mercury dropped to -11.3°c and we had some occasional snow showers that did manage to travel far enough west.

   The 4th was slightly warmer as an elongated area of low pressure (ALP) (995 Mb) sat north of the UK and with an AHP to the south and occlusion fronts to the north and east and in central parts of the UK, there was more cloud, but we still had a little more snow - but now it did get cold - very cold.

   The weather was still influenced by cold Polar air and the 5th was a foggy day as we sat in a slack area between pressure/frontal systems, but with a maximum temperature of just -3.1°c and dropping away to -10.0°c at night it was, upto that point, the coldest maximum that I had ever recorded. Snow in the early hours of the 7th was followed by a sunny day as a blocking AHP (1028 Mb) sat in the Atlantic and another AHP (1005 Mb) was over central UK - perfect conditions for still, stable and cold weather.

   The 7th saw a minimum temperature of -12.9°c (then a record), but at 0906 Hrs on the 8th the mercury fell to -14.6°c (5.7°f) and the ground temperature of -18.3°c. We had hazy sun and 10 cms of level snow and was there ever such a winter wonderland?

   The 8th was truly a record breaking day, apart from the lowest minimum and ground temperatures, the maximum that day was just -4.3°c (24.26°f), yet another record and the mean temperature for the 8th was an amazing -10.9°c - this is why your water pipes may have frozen!

   The thaw was swift on the 9th. The AHP (1038 Mb) in the Atlantic now started to bring less cold polar maritime air from the NW Atlantic circulating around the AHP's top edge and additionally a warm front was travelling south with it. Still below freezing at 1400 Hrs, the temperature zoomed up and by 1515 Hrs stood at +4.3°c - enough to thaw and burst water pipes, mine included.

   The 10th saw the temperature remain above freezing and thus ended a sequence of 17 days (23.11.10 - 9.12.10.) that had had a minus minimum temperature - another new record.

   We then had a week of milder conditions (average for December), but the weather was still generally quite settled, although with the warmer and moist air this meant cloudy and dull. High pressure was never far away in the Atlantic (13/14th 1030 Mb over Scotland - 15th 1045 Mb centred NW of Eire) and weak cold fronts brought us a little rain. The 16th saw rain on a cold front moving south from Scotland but that later turned to snow with clearer and much colder conditions behind the front and a a return to Arctic air taking control.

   We now entered a truly remarkable phase. The afternoon of the 16th through to the afternoon of Christmas day saw Winter take hold and grip tightly.

   The mean temperature for the ten days of 17-26th was -5.45°c (22.2°F). The 17-24th were all Ice Days and whilst no one day broke any records, the daytime maximum temperatures for the 17-21st read thus: -2.5°c, -2.1°c, -3.3°c, -2.3°c and -2.9°c. Night-time minimums were all below -11.0°c and the snow was back as well. The fall on the 16-17th had only been slight, but overnight 17-18th we had a further 3.75 cm brought on troughs associated to a complex ALP (988 + 993 Mb).

   Slightly unusual was the fact that low pressure was creating these cold conditions, but it was drawing in the Arctic air and this was helping create a slack area in the low pressure and thus giving the stable conditions. Come the 23rd and we now sat under a ridge of HP (1022 Mb) and which was building.

   Come Christmas day and snow was still on the ground, the second successive Christmas winter wonderland!! AHP (1029 Mb) was now over the UK, but now cloud was moving in ahead of a warm front over Scotland and then at 1020 Hrs SNOWFLAKES, followed by further snow showers through a.m. - an official WHITE CHRISTMAS.

   THE NINTH RECORD - At 1255 Hrs on Christmas day the temperature rose above freezing, it had been below freezing since 1410 Hrs on the 16th - 75 mins short of nine days below freezing, or 214 Hrs and 45 minutes below freezing!!! Quite remarkable. In January this year when we had a spell of 83 hrs below, I thought that it would be some time before that record was broken - how wrong I was!.

   We had 'days of fog' on the 26th and 29th but milder weather saw us through to the month's end. The AHP was still in charge on the 26th but this began to slip into the continent allowing fronts to push in from the Atlantic. These fronts initially brought snow on the 27th as they met up with the still cold ground and air. But the snow had a high water content and was quickly melting as warmer conditions took over.

   The airflow was now from the S-SSE and the early hours of the 28th saw our wettest day with 9.1mm (credited to the 27th with 0900x0900 hrs readings) as fronts entrained around a fairly weak ALP (984 Mb) west of Eire pushed NE up the UK. Then a ridge of HP moved in on the 30-31st and the fog of the 29th was replaced with cloudy and dull conditions, but mild.

   And so ended a remarkable month, a highest max' of just 7.7°c - you would expect to reach 10.0°c at least once. A dry month with just 24.3 mm of ppt (snow+rain), but with snow on the ground for the majority, although the accumulated snowfall only totalled 9.75 cms. Ten days saw the temperature drop to -10.0c°c or below and it will always be the cold that December 2010 will be remembered for.

   The Mean Temperature for the month was -1.98°c+     - the Mean Max' was 1.64°c and the Mean Min' -5.61°c.

   We had 23 Air Frosts in the month (97 for 2010) and Grass frosts totalled 25 (145 for 2010).


   * December 10 rainfall was 21.3% of the December average for 07/08/09

   * December 10 was 3.92°c colder than December 2009 +

   * December saw 13 rain days of which 8 were wet days.

  * The 3 month mean for October/November/December 2010 is                   TEMP'    3.51°c          -          RAIN    241.80 mm

* October/November/December 2009 was TEMP'    6.18°c - RAIN    472.60 mm

* October/November/December 2008 was TEMP'    - RAIN    395.60 mm

* October/November/December 2007 was TEMP'    - RAIN    283.30 mm


   As already mentioned 2010 was both cold and dry. A mean temperature for the year of just 7.42°c (45.36°F) is quite clearly much colder than that of recent years and indeed this century. With the year getting off to a very cold start and continuing through the first three months it never recovered and Novemeber and December just topped the year off.

   April (whilst colder than recent Aprils) did buck the trend but the daffodils hadn't bloomed come Easter and whilst May had some good days it was also cold with many air frosts. A special mention then for June, undoubtedly the years best month for warmth. June was well above average and also sunny and our only real summer month. July deceived. Average temperature wise, but yet another wet and dull July and hence it never felt 'average'. August was below average and another dull month and whilst a true taste of Summer came at the start of September it to reverted to type.

   By the time we got to a rain lashed start to November it was clearly going to be a cold year and when winter spectacularly arrived at the end of November and then stayed to make December a record breaker, we were shivering.

   On the plus side it has been dry and we have had above average levels of sunshine and not endured too many storms. The first half of the year was too dry though. Only March saw anything near normal rainfall with both April and May especially dry. 'Dry Spells' and a 'Partial Drought' in April/May were common in Spring and with June continuing the trend a hosepipe ban followed.

   But the rain returned in July and this month has been very wet for all of the last four years, not what you want for the 'height of summer'. The Autumn saw rainfall back at monthly average figures, with November being wet once again, but we never got the drenching that was required to get the annual total back on track. With just 702.9 mm (27.67 inch) of rain, 2010 has seen far less rainfall than what would be expected.

   The year has been reasonably settled and stormy weather as been less frequent. 16th July saw an unseasonal storm and July was also windy as well as wet! The years main storm came on 11th November with gusts upto 56 Mph and plenty of rain, but the absence of westerly Atlantic flows as been notable with Northerly/Easterly airflows been a frequent visitor and the term 'blocking area of high pressure in the Atlantic' being well used this year.

   Other weather events have been fairly sparse, only 4 days of fog and thunder was only heard the once.

   But Winters are back with vengeance. As a weather watcher undoubtedly a good thing. 2010 has provided my complete list of 'Top Ten' coldest temperatures and not a single entry in the top ten warmest temperatures. But do winters come in pairs? There are have been occassions when this has happened. What does 2011 hold? Keep watching.

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

* 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 show that NW England/N. Wales had a mean temp' of -1.0°c, some -5.3°c colder than the reference period 1971-2000 (-4.9°c colder 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   

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