December CET

[Thundery wintry showers]

I think the reason for that, however, is that December has tended to get a week or two of cold weather under mid latitude high's. I'm not one of these people that signs up to the whole "faux cold" thing - Cold is cold - But 95 and 96 are the only two months I can think of in the last twenty years where the cold has been delivered by proper cold synoptics (second half of December 2000 as well I suppose) rather than the AH building over us and giving inversion cold as it true of most of those cool Decembers. Until this December of course.

I don't think January and February have had less mid-latitude highs than December. The main differences are that Decembers in the last two decades have had more northern blocking, and zonality in recent Decembers has often tended to be less mild than in January and February- indeed the Decembers of 1993 and 1999 were cold zonal in the north.

Thanks Snowmaiden! Lovely as April was, I kinda wish it was more of a cool and dull month now.

Or it could have been cold and bright with night frosts- contrary to popular belief on N-W, cold in spring doesn't always mean dull!

Regarding global warming, Northern Hemisphere temperatures have warmed by no more than 0.5C since the mid 1980s, and since February 1986 returned a sub zero CET, it stands to reason that if we get cold synoptics it should still be possible for it to get very cold. The question was always whether those old-school synoptics could recur during the current regime of milder, more westerly-dominated winters, and this winter together with last is certainly making a fair stab at it.

[North-Easterly Blast]

First time since 2001, since we have had two sub 4C CET months within the same year.

The lack of really mild Decembers over the last two decades is notable considering how many notably mild Januarys and Februarys there have been in the same period.

Only 2 Decembers over 6C for the CET (There were 6 in the 1970s and 1980s)

1994 and 2006

Whilst there have been 4 Januarys and 5 Februarys

As a consequence, December has turned out the coldest month of the last 20 years (1990-2009) than either January or February

I make it six Februarys above 6*C in the 1990s and 2000s, not five. (1990, 1995, 1997, 1998, 2000, 2002). There were four Januarys (1990, 2005, 2007, 2008), and 1993 came very close at 5.9.

I find it a very strange aspect of the UK's winter weather how in the 1970s and 1980s, December was often the mild month and then January and in particular February were often much colder months. Whereas in the 1990s it all swung the opposite way and February was often the mild month and January much milder but less so than February, and December showed a cooling trend from the previous two decades. In the 2000s both January and February have often been the mild months with the cooling trend seen in December in the 1990s being maintained during the 2000s. Although there have been few significantly cold Decembers in the 90s and 00s, December has been close to the average for the twentieth century as a whole and January and February have averaged about 1*C warmer than the whole twentieth century average over the last two decades.

Of even more note Kevin, is that with December now looking very likely to come in below 3.5*C for the CET, it will be the first time since 1996 we have had two sub 3.5*C months in the same year. We have now already broken both the records for the longest interval in the CET record between sub 2*C months (18 years 10 months so far) and between sub 3*C months (12 years 11 months so far), and also the period of exactly eight years between Jan 2001 and Jan 2009 was the longest interval in the CET record between a sub 3.5 CET month.

Kevin, am I also correct that if this December falls below the 3.5 barrier, will it be the largest negative anomaly for any calendar month since the mid 1990s?

[Snowly does it]

Manley unchanged at 3.1 (3.05 rounded up) to the 30th - looks like it will finish rounded down to 3.0

Hadley is at 3.35 so will be 3.4 or 3.3 depending on 100ths rounding either side of 3.35

Last night was 1.4 so CET for the day will be in the high 2s probably and enough to see the finishing number unadjusted a rounded down 3.3

Adjustment may follow but probably not enough (0.4 required) to get us under 3

I think an adjusted 3.1 for Hadley and 3.0 for Manley is probably about the mark - 3.1 for Hadley would make December 2010 the first month to be 2 degrees below the 71-00 average since it came into being and the first month since May 1996 to be 2 degrees below the prevailing 30 year average (in that case 61-90) - December 96 was only 1.7 below the 61-90 average.

3.1 would also make Dec 09 the first month to be 1.5 degrees below the 61-90 average this century.

[Optimus Prime]

December 96 was only 1.7 below the 61-90 average.

Just to confuse things, some sources have the 61-90 DEC average at 4.6c but the official release by HADLEY is 4.7c.

[Nick L]

Just to confuse things, some sources have the 61-90 DEC average at 4.6c but the official release by HADLEY is 4.7c.

The exact value is 4.65333... so to 1d.p. Hadley is the correct one.

[Weather-history]

11th-30th December CET: 1.8C

[ukmoose]

Yes, it is looking unlikely to go below 3.0 which is unfortunate. If only we could have a clear night tonight rather than the blanket of cloud!

A sub 3.0 month would have shut many (global warming) mouths! Nevertheless, it is a very good result for an el nino December!

Karyo

No it wouldn't. One month or two months or a whole bunch of months makes no difference to the overall scheme of things does it?

[Guest North Sea Snow Convection]

I would concur with Karyo. He was being slightly tongue in cheek, but you might have missed that it seems.

The underlying point that Karyo is making is that last winter some members, yourself included (I think) made a lot of the 3C being some sort of 'psychological cold barrier' that the UK somehow had to overcome in order to suggest that this Island could still achieve what one would deem signifcantly cold enough winters.

Regarding the general scheme of things that you mention - it seems to me no coincidence that we have seen synoptical changes and patterns exactly in tandem with a solar minimum as well as other factors. Such factors being one's that don't fit in with the man made reasons for recent warming trends which you and others would strongly eshew. Two cold UK winters doesn''t make a cold climate, but it is a short term demonstration that the variables aren't as clear cut in terms of the drivers - as they seem to some. And they counter the turning tide post 1987 remarks that we were supposed to not be able to see these sort of synoptics again in a 21st century winter.

Edited December 31, 2009 by North Sea Snow Convection

[Nick L]

Some members even believed that a sub-3c was impossible, so it would at least shut those up!

[ukmoose]

I would concur with Karyo. He was being slightly tongue in cheek, but you might have missed that it seems.

The underlying point that Karyo is making is that last winter some members, yourself included (I think) made a lot of the 3C being some sort of 'psychological cold barrier' that the UK somehow had to overcome in order to suggest that this Island could still achieve what one would deem signifcantly cold enough winters.

Regarding the general scheme of things that you mention - it seems to me no coincidence that we have seen synoptical changes and patterns exactly in tandem with a solar minimum as well as other factors. Such factors being one's that don't fit in with the man made reasons for recent warming trends which you and others would strongly eshew. Two cold UK winters doesn''t make a cold climate, but it is a short term demonstration that the variables aren't as clear cut in terms of the drivers - as they seem to some. And they counter the turning tide post 1987 remarks that we were supposed to not be able to see these sort of synoptics again in a 21st century winter.

Hello.

Tongue in cheek perhaps; but meant.

The climate has warmed for the last 100 years, especially so in the last 10 to 20. Whether this will reverse anytime soon, who knows. I am merely pointing out the obvious - that it is warmer now than it was and (as I have said many times) this pattern has been repeated throughout history. Climate fluctuates. Always has, always will I should think.

Man made factors play a part in this (probably) but we don't know how much.

You are right. I did question whether the 3 barrier could be breached anytime soon. I think 20 odd years without it being breached was a fairly good yardstick don't you? I will be delighted if it is broken mind you - and would be very happy to be proved wrong.

I don't want to see a continuing warming trend with all the horrors it would bring for millions in the world and hope that it stops soon. I just think the trend, for now, is less rapidly upwards.

Have a snowy, Happy New Year and a sub 3 January.

[Optimus Prime]

Sorry to be a pain but after seeing the ECM I'm revising upwards to 2.8c.

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

Sorry to be a pain but after seeing the ECM I'm revising upwards to 2.8c.

That's a pretty late change, there's only less than 5 hours of December left!

[Weather-history]

Three sub 4C Decembers in the 1970s and 1980s but six in the 1990s and 2000s.

The more you look at that December 1981 value, the more freakish it looks.

Edited December 31, 2009 by Mr_Data

[Guest North Sea Snow Convection]

Hello.

Tongue in cheek perhaps; but meant.

The climate has warmed for the last 100 years, especially so in the last 10 to 20. Whether this will reverse anytime soon, who knows. I am merely pointing out the obvious - that it is warmer now than it was and (as I have said many times) this pattern has been repeated throughout history. Climate fluctuates. Always has, always will I should think.

Man made factors play a part in this (probably) but we don't know how much.

You are right. I did question whether the 3 barrier could be breached anytime soon. I think 20 odd years without it being breached was a fairly good yardstick don't you? I will be delighted if it is broken mind you - and would be very happy to be proved wrong.

I don't want to see a continuing warming trend with all the horrors it would bring for millions in the world and hope that it stops soon. I just think the trend, for now, is less rapidly upwards.

Have a snowy, Happy New Year and a sub 3 January.

My blunt answer to your question, is that the yardstick of twenty years, within the context that you believe, is totally and utterly meaningless. We all might imagine horrors - my own don't extend that far in terms of gazing into a man made crystal ball, but if they did extend into a contemporary equivalent then they would be in a very different direction to AGW supposed 'catastrophies'

But I would echo you very charitable wishes and hope you have a very Happy New Year

Edited December 31, 2009 by North Sea Snow Convection

[Optimus Prime]

We will soon find out what Decembers final temperature will be. Something to perhaps add a bit of spice. November and December 1939 (a year before the big change to very cold winters;

"November.Another very warm month (8.7C CET) - bettered only by 1994 and, incredibly, 1938. It was one of the three occasions this century when November has been warmer than the preceding October. It was also a wet month.

December. 3.2c CET A dry month and dull in Scotland. Slightly cooler than average. The month ended with a northerly airstream and a cold spell, auguring what was to come in. Several places were snowcovered by Boxing Day 1939.

1940;

"The first three decades of the century showed a gradual warming trend. Things were about to change."

"January. The coldest month of any kind since 1895 (-1.4C CET), and eventually the second coldest January of the century (after 1963). The month started with a northerly airstream, but early in the month the winds turned to the east, bringing very cold continental air. It was clear and sunny, with hard frosts at night and several frost days. There was a severe blizzard on the 16th. On the 17th, the Thames was frozen over for the first time since 1880. The morning of the 21st gave the lowest temperature of the month: -23C was recorded at Rhayader (Wales), with many places continuously well beneath freezing (e.g. only -4C maximum at Boscombe Down, Wilts.). There were heavy snowfalls in Scotland, with many places cut off. By the third week the Atlantic westerlies tried to return, bringing some heavy snowfalls. Most remarkably, there was a great snow and Ice Storm during the 27-30th, peaking on the 28th, but continuing in parts into February. Mild air approaching behind warm fronts from the SW met the cold easterly all the way from Russia. There was heavy snow over the north; four feet of snow in Sheffield on the 26th, and 10' drifts reported in Bolton on the 29th. Further south the lower air was warming up and was too warm for snow, but the rain froze as it fell, coating everything with a thick layer of glaze. The effects of the freezing rain was one of the most extreme weather events of the century. The south was particularly badly affected. Everything was coated in a thick layer of ice: phone wires 1.5 mm thick were coated with a 300mm diameter sheath of ice - up to 15 times their weight. Many large tree trunks and power lines were brought down. The area affected by the glaze reached from Kent to Exmoor and the Cotswolds, and from Sussex to Cambridgeshire and the north Midlands. It was a week before all the ice thawed; some places had snow on top of the glaze, with both remaining until the 4th February. Heavy snow and a violent gale swept the southwest.

February. Very cold for the first three days. The melting of the effects of January's great Ice Storm on the 3rd led to widespread flooding on the 4th. Foggy between the 5th and 9th. Very cold between the 10th and 19th. Colder than average overall, and a dull month everywhere."

From brit weather years.

Happy New Year.

[Weather-history]

Well Philip Eden in his notes for the month confirms the minimum date record for Christmas Eve with Braemar recording -16.0C and the old record was -15.6C set in 1935

[Eugene]

Coventry looks like having its coldest December since 1995(2.1C below average).

Also just proving my point how cold airmasses bring sunny weather its looking like being the sunniest December since 2001 and the second sunniest since Dec 1894

Excellent cold month overall for my area

[Optimus Prime]

I keep having to remind myself December isn't a sunny month because in the last 15 years or so December for me sticks out as being sunny and cold. Take a look at these sunshine totals from manley;

2009 71.6 hours/ 155% CET 3.1c

2008 74.8 hours/ 157% CET 3.6c

2007 56.8 hours/ 119% CET 4.9c

2006 50.0 hours/ 105% CET 6.6c

2005 65.3 hours/ 137% CET 4.6c

2004 53.9 hours/ 109% CET 5.3c

Don't have the Manley figures for 2003 but I know that was sunny.

The only December I can remember being not sunny was 2006 and yet it was still above normal. An average 30% increase in sunshine since 2003.

[Weather-history]

Coldest 11th-31st December CET periods of recent times

2009: 1.4C

2001: 2.8C

1996: 2.5C

1995: 1.6C

1992: 2.7C

1981: -1.0C

1976: 2.0C

1968: 2.5C

1964: 2.4C

1963: 1.9C

1962: 1.8C

1961: 1.2C

1950: 0.6C

Edited January 1, 2010 by Mr_Data

[North-Easterly Blast]

Hadley December 2009 CET is confirmed at 3.1*C, (3.10), which makes it the 18th coldest in the past 100 years. December 2009 is the first calendar month of any to be 1.5*C below the 1961-90 average since December 1996. This makes the decadal average for the 2000s Decembers stand at 4.78*C, slightly warmer than in the 1990s but much colder than in the 1970s and 1980s, so the cooling trend seen in December in the last 20 years, out of kilter with most other months in the year has continued. December 2009 has been an old style winter month's weather in the UK, notably as the cold weather has been brought by proper cold synoptics (deep cold Arctic air), and not the mid-latitude Rex blocks (surface cold) often seen in the last 20 years, as seen in the likes of Dec 1992, Dec 2001, mid Dec 2007 etc. Many areas have seen more snow than average this December, and I would believe that it will be the snowiest December since 1995 or 1996. Some echoes of the even larger teapot era have still shown their faces this month, as it has been another very sunny winter month, typical of many winter months in the 2000s, and fog has been far less frequent this month than it used to be in years gone by. A notable feature of the 2000s winters is that most winter months have been sunnier than the long term average.

[stewfox]

Hadley December 2009 CET is confirmed at 3.1*C, (3.10), which makes it the 18th coldest in the past 100 years.

I'm surprised the figs have already been posted, before they have taken a few days to round up or usually down

Why so quick this time ??. Anyway comes in at 99 coldest December out of 352 !

http://hadobs.metoffice.com/hadcet/mly_cet_mean_sort.txt

[Snowly does it]

The adjusted figures also show that the 7 days 18-24 December inclusive were all below zero, the first full week of sub-zero CET days since the 12 in a row of Feb 1991.

December 2009 is the first month to be 2.0c below the 71-00 and 1.5 below the 61-90 (actually 1.6) this century and is the biggest negative anomoly this century and against the prevailing 30 year average since May 96 (2.1 below the 61-90 average) and for a winter month since Dec 95 (2.4 below the 61-90 average)

[Optimus Prime]

Mean Max; 5.8c (30th coldest ever)

Mean Min; 0.4c (23rd coldest ever)

Compare to;

2008;

Mean Max; 6.3c

Mean Min; 0.8c

2001;

Mean Max; 6.6c

Mean Min; 0.5c

1996;

Mean Max; 5.4c

Mean Min; 0.5c

1995;

Mean Max; 4.5c

Mean Min; 0.1c

1981;

Mean Max; 3.3c

Mean Min; -2.7c

1934;

Mean Max; 10.1c

Mean Min; 6.1c

[AderynCoch]

The adjusted figures also show that the 7 days 18-24 December inclusive were all below zero, the first full week of sub-zero CET days since the 12 in a row of Feb 1991.

18-24th December = -1.09C

First time five or more consecutive sub-zero CET days have occurred since January 2001. Quite a run!

[J10]

Latest CET results in and a big well done to Terminal Moraine who got 3.1 spot on, North Sea Snow Convection was 0.1c out and Polar Side was 0.2c out.

From that you can probably guess it was a cold month.

Dec 2009 CET.xls Dec 2009 CET.pdf