December CET

[Snowly does it]

Indeed, but in reality final CET figure does matter. Part of the problem we have these days is not that cold doesnt occur, it just occurs less frequently and is less potent compared to the mild. My disappointment is that despite 2-3 week cold spells, we struggle to record well below average months like we used too and especially well below average seasons (12 years and counting).

With regards to this month, we could well be sitting at a mean of 4.2C by the 22nd. This is despite the first half of the month being the coldest start to winter for 30 years. Even then, if the last 8 days had a mean of 2C, the month would end at 3.5C. So thats another winter-month failing to get sub-3C, despite what would essentially have been 85% cold. If we cant get a true 'cold' month (sub-3C - also 12 years and counting) in that scenario, when are we realistically going to these days?

Well, the cold is as potent as it is - it is the coldest start to winter for 30 years, that doesn't change because we have some mild weather now. I would hazard a guess that the period 20 November - 19 December would probably fit into the 'very cold' category.

December average is 5.1 - nearly a full degree above the January and February averages, so sub 3 would be exceptionally cold - witness the bitter Decembers of 1995 and 1996. A December finish of 3.5 would be the equivlent below to a January or February of 2.6 in terms of how far below mean it is

Sadly, 4 days of temps averaging 10 day and night will add about 1 degree to whatever December looked like being previously.

Phillip has just updated his header and its another 0.4 rise unfortunately.

[Duncan McAlister]

Another increase of 0.2C on the Hadley CET. Its now running at 3.6C to the 20th.

Today and tomorrow will be very mild, so we could be north of 4.0C by the update on Tuesday.

It seems a shame how quickly cold weather is negated by mild these days. Ill always remember March 2006, when the mean was around 3C to the 23rd but the very mild last week meant the CET increased by almost 2 degrees by ther end of the month. A sign of the times I think, the mild always seems milder than the cold is cold.

It would be an extreme disappointment not to finish below 4C when the first half has been so far below average. Hopefully the upcoming easterly wont be too cloudy and have some decent cold at the surface.

It almost seems like the colder the start of the month, the bigger the correction. I wonder if there is an actual synoptical explanation for this - for example how 'toppler' northerlies usually lead to Bartletts.

[Snowly does it]

It almost seems like the colder the start of the month, the bigger the correction. I wonder if there is an actual synoptical explanation for this - for example how 'toppler' northerlies usually lead to Bartletts.

well no, its just that the correction is necessarily bigger from a lower starting point

Lets say the 11th-20th averages 10 degrees

If the 1st-10th was minus 10 then the average comes to zero (a correction of 10 degrees)

If the 1st to the 10th had been zero, then it gets to 5 by the 20th (a correction of 5 degrees)

If the 1st to the 10th had been 5, then on the 20th it is 7.5 (a correction of 2.5 degrees)

We had the coldest start to winter in 30 years, hence a big correction for a few days mild weather.

[West is Best]

It would be an extreme disappointment not to finish below 4C when the first half has been so far below average. Hopefully the upcoming easterly wont be too cloudy and have some decent cold at the surface.

I think we'll finish well below 4C ...

[damianslaw]

A below average CET is almost a dead cert now, recording a sub 3 figure is I will say still achievable very much dependent on cloud as the rest of the month will be high pressure dominated. I expect something around the 3.2 figure as the finishing number so a decently below average CET month for a change.

[reef]

A below average CET is almost a dead cert now, recording a sub 3 figure is I will say still achievable very much dependent on cloud as the rest of the month will be high pressure dominated. I expect something around the 3.2 figure as the finishing number so a decently below average CET month for a change.

I think sub-3C is very unlikely at the moment, the first half of this week is going to see some big increases. Yesterday and today will both have averages close to or above 10C, this will ensure the mean ends up above 4C to the 22nd. The 23rd, 24th and 25th then still look above average, mainly due to cloudcover keeping up minima, though the daytime temperatures will slide closer to average.

Im betting we'll be at 4.3 - 4.5C by the time the update to the 25th comes on boxing day. We've then essentially got 6 days to see the average drop again to below 4C. That doesnt sound a tall order, but with if we're sat on 4.5C by the 25th, then we'd require 1.9C to do it. If the high stays cloudy, then chances of sub-4C are over too.

Edited December 22, 2008 by reef

[Guest North Sea Snow Convection]

I think sub-3C is very unlikely at the moment, the first half of this week is going to see some big increases. Yesterday and today will both have averages close to or above 10C, this will ensure the mean ends up above 4C to the 22nd. The 23rd, 24th and 25th then still look above average, mainly due to cloudcover keeping up minima, though the daytime temperatures will slide closer to average.

Im betting we'll be at 4.3 - 4.5C by the time the update to the 25th comes on boxing day. We've then essentially got 6 days to see the average drop again to below 4C. That doesnt sound a tall order, but with if we're sat on 4.5C by the 25th, then we'd require 1.9C to do it. If the high stays cloudy, then chances of sub-4C are over too.

I think that lowering dewpoints as the easterly kicks in from xmas will mean that clearer conditions come in from the continent by the weekend. This should assist some sharp night time frosts, especially in sheltered central and western areas along with the low daytime temps (assisted by that lovely 'refreshing' breeze! )

I think that sub 4 is very much on the cards

[AtlanticFlamethrower]

Latest 2m temp on GFS suggests rising CET until 26th and thereafter quite a bit of cooling. If it's 3.6C now and goes up to 4.5C I can imagine at least another 1C off that, so a final CET about what it is now.

3.2 - 3.7C

[reef]

Latest 2m temp on GFS suggests rising CET until 26th and thereafter quite a bit of cooling. If it's 3.6C now and goes up to 4.5C I can imagine at least another 1C off that, so a final CET about what it is now.

3.2 - 3.7C

Theres very little chance of a 3.7C finish if we're at 4.5C by the 25th. That would require the last 6 days to average -0.3C. This bearing in mind that the GFS is showing temperatures during the day of 3-5C and 2 degrees either side of freezing by night in that timeframe.

It could well be very very cold, but so far theres no evidence of it. We can only go by what the models are showing and until that changes or the weather does different, at present its not going to happen.

Edited December 22, 2008 by reef

[Guest North Sea Snow Convection]

If the predicted airflow was north easterly without drawing in an upper cold pool to provide snow showers, then the outcome could predominate with stratocumulus and keeping the night temps up.

However, the airflow looks increasingly likely to be coming from due east off a very cold continent with shorter sea track for most areas within the CET range. This should do two things:-firstly, irrespective of what the 850 temps show, there will be, at the very least, surface cold that will not be tempered much due to the very short sea track, especially across southern most parts, and secondly with the air coming off a land locked continent the dewpoints should be low.

The winds will be lighter further north too so that will assist lower night time temps, with any cloud or temp modification from the north sea kept to a minimum.

In the event of the suggested (and increasingly likely) retrogression pattern arising - some deeper upper cold air could arrive anyway with more instability so that sun and north sea convection snow showers could come on the menu as we arrive at New Year time - that will knock the temp down for months end anyway.

[Kentish Man]

Hadley is now on 3.9C (Dec 1 - 21)

Climate UK (Manley) stats at the end of week 3 stand at:-

CET: (Dec 1-21): 3.6°C (-1.7 degC)

E&W Rain: (Dec 1-21): 62.6mm ( 91 per cent)

E&W Sun: (Dec 1-21): 55.0hr (171 per cent)

Edited December 22, 2008 by Kentish Man

[Snowyowl9]

Climate uk is on 3.6c upto the 21st so today is very much on the mild side as mild as this week gets,as each day will cool off and by going by this morning forecast 2c was shown for saturday.

GFS maybe overdoing the maxes slightly as the wind may not be that strong.

http://91.121.93.17/pics/Rtavn10817.png

http://91.121.93.17/pics/Rtavn1087.png

This could be the coldest december month since 1996, 2.9c

3.6c is the target to beat 2001.

Edited December 22, 2008 by Snowyowl9

[reef]

Hadley is now on 3.9C (Dec 1 - 21)

Climate UK (Manley) stats at the end of week 3 stand at:-

CET: (Dec 1-21): 3.6°C (-1.7 degC)

E&W Rain: (Dec 1-21): 62.6mm ( 91 per cent)

E&W Sun: (Dec 1-21): 55.0hr (171 per cent)

As I suspected, yesterday came in a 9.8C. Tomorrow will likely see an increase to 4.2C, as the minimum temperature came in for today at a colossal 9.2C:

http://hadobs.metoffice.com/hadcet/cet_min_est_2008

The 23rd and 24th then look to be slightly above average too, so we'll be in the 4.3 or 4.4C range by the christmas day update.

[Optimus Prime]

It's 3.9c upto the 21st with mean max at 7.3c (-0.2c) and Mean Min 0.9c (-1.2c)

GFS has the mean temperature for the 22nd - 31st at 3.2c. The CET by the 31st should be around 3.7c. So a cool month looks likely, with the final adjustment closer to 3.5c.May just get the coldest December since 1996, unless it turns very cold (easterly shown once again this time around isn't too cold) there is no chance 1996 will be beaton, but with a decently cold North Easterly during the last 4 days, it's possible.

[kold weather]

Does look just about odds on now this December will be coming in below that of 2005 and that is a good start to getting a below normal winter.

[Eugene]

Yes looks to me like the final figure will come in around 3.5C, i feel the 24th might come in around average as HP is going to be directly over us by tomorrow night and after a cold night fog may form and keep it pretty cold on wednesday, good news is the cloud is clearing now and it's sunny so i can't see a min of 9C tonight in the midlands like GFS is going for, outside chance of a ground frost tonight in the midlands(around 4C) if cloud doesn't come back over, BBC Ceefax page 402 is going for 6C min tonight in the west midlands which will most likely be just about right.

[ukmoose]

Another increase of 0.2C on the Hadley CET. Its now running at 3.6C to the 20th.

Today and tomorrow will be very mild, so we could be north of 4.0C by the update on Tuesday.

It seems a shame how quickly cold weather is negated by mild these days. Ill always remember March 2006, when the mean was around 3C to the 23rd but the very mild last week meant the CET increased by almost 2 degrees by ther end of the month. A sign of the times I think, the mild always seems milder than the cold is cold.

It would be an extreme disappointment not to finish below 4C when the first half has been so far below average. Hopefully the upcoming easterly wont be too cloudy and have some decent cold at the surface.

Indeed, but in reality final CET figure does matter. Part of the problem we have these days is not that cold doesnt occur, it just occurs less frequently and is less potent compared to the mild. My disappointment is that despite 2-3 week cold spells, we struggle to record well below average months like we used too and especially well below average seasons (12 years and counting).

With regards to this month, we could well be sitting at a mean of 4.2C by the 22nd. This is despite the first half of the month being the coldest start to winter for 30 years. Even then, if the last 8 days had a mean of 2C, the month would end at 3.5C. So thats another winter-month failing to get sub-3C, despite what would essentially have been 85% cold. If we cant get a true 'cold' month (sub-3C - also 12 years and counting) in that scenario, when are we realistically going to these days?

I have to agree with you reef. I think I have had the very same discussions with SM before and I know we disagree.

Part of the problem is that the night time minima are just not that cold. Minus 1, 2 or 3 (pretty much what we've had at best during the first two weeks of December) is not bone-chillingly cold (minus 5,6,7 and 8 would have cropped up in the past with a similar pattern) and it is these very low night time temperatures that helped to more than offset the mild days that most months do get.

When night time minima only dip a degree or so below freezing, there's just not much leeway and the milder temperatures win out overall meaning the CET is never going to be very low.

In short - nights are are much warmer than they used to be even in a 'cold' spell.

Moose

[DR Hosking]

I have to agree with you reef. I think I have had the very same discussions with SM before and I know we disagree.

Part of the problem is that the night time minima are just not that cold. Minus 1, 2 or 3 (pretty much what we've had at best during the first two weeks of December) is not bone-chillingly cold (minus 5,6,7 and 8 would have cropped up in the past with a similar pattern) and it is these very low night time temperatures that helped to more than offset the mild days that most months do get.

When night time minima only dip a degree or so below freezing, there's just not much leeway and the milder temperatures win out overall meaning the CET is never going to be very low.

In short - nights are are much warmer than they used to be even in a 'cold' spell.

Moose

I agree, when I was a lad in the 70's and 80's -5 would be a regular occurance on cold winter nights and -10 was not unusual, and that was in Surrey only 30 miles outside london. I live in deepest rural Northamtonshire now and you would expect some very cold nights being smack bang in the centre of England almost as far from the coast as you can get, however the coldest temperature reached here since 2002 is -7c the next coldest -6.4 and the next coldest -5.8c. In fact there has only been 5 days with sub -5c temperatures. So nothing like we would get 20 years ago.

Edited December 22, 2008 by DR Hosking

[Nick L]

With the Met Office predicting a below average winter overall now, do you reckon we will beat 2005/06 and possibly give 1995/96 a run for its money?

[kold weather]

The thing is if you look at the set-up, its never been quite right for wide-spread -5/6/7 sort of temps overnight, the cold has generally been shallow and fairly stale. I suspect if we had lower temps at 850hpa or the air would be allowed to stagnate further then it had with more widespread fog, then we would have got the lower mins. Still mins probably are generally a little higher then before.

Whether or not we come in below 4C is indeed dependant on how much cloud the easterly drags in.

Edited December 22, 2008 by kold weather

[acbrixton]

With the Met Office predicting a below average winter overall now, do you reckon we will beat 2005/06 and possibly give 1995/96 a run for its money?

The CET average for winter 2005/6 was 4.1c; 1995/6 3.0c and the 1971-2000 average is 4.5c.

If December's CET is, say, 4.0c then to beat 2005/6 would require an average of 4.0c or less for January and February; not unrealistic as both those months' long term average is 4.2c. However if December comes in at, say, 4.5c the rest of the winter would have to record 3.7c/3.8c to beat 2005/6; the last time that winter had two months at or below 4c was 1996/7.

To equal or beat 1995/6 is a long shot, to say the least: the winter CET was 3.0c. Thus if December comes out at 4.5c the remainder of the winter would have to record an average of 2.3c: in 1995/6 this was not achieved as the two coldest months recorded 2.5c and 2.3c. Even in 1990/1 the two coldest months averaged 2.4c. On that basis I would say very unlikely. If December was to record 4.0c the remaining winter months would have to average 2.5c to equal 1995/6 and even would entail two winter months colder than we have seen since 1995/6.

Regards

ACB

[Cymro]

The CET average for winter 2005/6 was 4.1c; 1995/6 3.0c and the 1971-2000 average is 4.5c.

If December's CET is, say, 4.0c then to beat 2005/6 would require an average of 4.0c or less for January and February; not unrealistic as both those months' long term average is 4.2c. However if December comes in at, say, 4.5c the rest of the winter would have to record 3.7c/3.8c to beat 2005/6; the last time that winter had two months at or below 4c was 1996/7.

To equal or beat 1995/6 is a long shot, to say the least: the winter CET was 3.0c. Thus if December comes out at 4.5c the remainder of the winter would have to record an average of 2.3c: in 1995/6 this was not achieved as the two coldest months recorded 2.5c and 2.3c. Even in 1990/1 the two coldest months averaged 2.4c. On that basis I would say very unlikely. If December was to record 4.0c the remaining winter months would have to average 2.5c to equal 1995/6 and even would entail two winter months colder than we have seen since 1995/6.

Regards

ACB

Yes but why do you say unlikely? It happened in 1996 why can't it happen now? Just because the scientist hype aload of trash about global warming which has over timed been changed to climate change etc. There is no reason why we can't get those sypnotics now and retain a cet like that. Take each week in it's stride you can't say it's unlikely because the past few winters have been generaly mild.

[kold weather]

Just too early to tell about the rest of the winter I think, but a decently below average December does set us up for a shot at the coldest winter since 95-96 at least.

Seems like a general falling range now of bewtween 3.8-4.2C, though I think the lower end of that range is looking more likely if we can keep some clear skies in a SE airflow.

[Stratos Ferric]

The CET average for winter 2005/6 was 4.1c; 1995/6 3.0c and the 1971-2000 average is 4.5c.

If December's CET is, say, 4.0c then to beat 2005/6 would require an average of 4.0c or less for January and February; not unrealistic as both those months' long term average is 4.2c. However if December comes in at, say, 4.5c the rest of the winter would have to record 3.7c/3.8c to beat 2005/6; the last time that winter had two months at or below 4c was 1996/7.

To equal or beat 1995/6 is a long shot, to say the least: the winter CET was 3.0c. Thus if December comes out at 4.5c the remainder of the winter would have to record an average of 2.3c: in 1995/6 this was not achieved as the two coldest months recorded 2.5c and 2.3c. Even in 1990/1 the two coldest months averaged 2.4c. On that basis I would say very unlikely. If December was to record 4.0c the remaining winter months would have to average 2.5c to equal 1995/6 and even would entail two winter months colder than we have seen since 1995/6.

Regards

ACB

Hard to disagree with the man from Brixton. This winter may become an interesting marker. I know my views on this matter don't always hang happily with those who hanker after extreme cold, but I've been arguing for years now that 3C may well be the realistic minimum for a month in the UK now. Natural variability in the weather will, occasionally, test any hypothesis, save for the most extreme. Philip Eden reckoned a year or so back that we were due a cold winter in the next two, maybe this will be it. If so, and in a warming climate, one could be forgiven for saying..."enjoy".

December still looks like landing around 4C, probably a smidge under. In that case, and after a month of what will have been almost unrelenting cool or cold, to have missed 3C by such a margin shows how hard it is now to get anywhere near an extremely cold month in the UK. I remember as a kid in the early 80s seeing documentaries about the bussing of blacks in the southern states of the USA, and having to shake myself to realise how much the world had (apparently) changed in less than a couple of decades. I have the same sensation now when I look back at temperatures in the 80s. It's only 27 years since the memorable December of 1981, when the Hadley daily mean temperature was -8.5C on the 12th, the day records were broken widely if memory serves me right. That was just one day in a sequence of 18, lasting to the 26th, during which the mean CET rose above 0C on only two days.

Rather puts the current sequence in context. By my reckoning we haven't had single day averaging below 0C yet this month, and at present my rough forward projection can only see one or two dipping just below zero before the month is up.

[The PIT]

Well we're up to average for Max temperatures now and still below for the mins. Our min is 1.4C below the average so the cooler air coming in should ensure a below average month.

For the CET zone how far below depends on how cloudy the high is. Recent easterlies have been cloudy with day time temps and night about the same.