December C.E.T

[damianslaw]

There looks like there going to be a rather large downward correction with a rather large stable high forming close to the UK in the middle of this week...whether or not it'll bring in cold enough air for snow is another matter but it'll be pretty cold regardless with daytimes maxes really suffering due to cloud cover and I'd have thought given past set-ups like this tmeps cold only rech 1-2C in fog...we could see quite a few days with CET's between 2-3.5C if this set-up comes off like currently progged.

Yes I to believe we have reached the peak for the december CET and it is a downward trend for the foresseable future. Next week looks like it could be a case of as some call it 'cold from the back door' with maxes in the CET zone struggling to get any higher than 6 degrees and mins close to freezing. As you say it will only need cold inversions to take place to get maxes down close to freezing especially if fog persists although the dirunal range in such conditions will be very small.

[Osbourne One-Nil]

My December mean is currently running at 6.6c which is startlingly above my 10yr December mean of 2.8c

[kold weather]

I think even if the less impressive of the set-ups were to occur we are still looking at 3 days of fairly cold weather and so we are going to see a pretty decent correction back towards normal I'd suspect.

I don't think I'll dare go beyond that stage right now but lest us forget that we are still a good bit below the CET for 2000 at this stage and as I keep saying that ended up not too greatly above average at 5.8C...and the rest of the moth bar the very last 6 days weren't really all that cold no reason why the next 10 days can't be pretty cold, IMO a CET of 3C is do-able from the 10th to the 20th IF current model runsd are close to the truth.

If I had to hone into a general region where the CET is likely to end up it'd be between 4.5-6.5C, rather large range but its still very early days.

Edited December 8, 2007 by kold weather

[Osbourne One-Nil]

Blimey - my average temp is 3c below the CET. Proof what a few miles north and a bit of height can do.

[Optimus Prime]

IMO a CET of 3C is do-able from the 10th to the 20th IF current model runsd are close to the truth.

Need to keep a sense of perspective, the outlook is cold, perhaps the coldest early December weather for a few years but it's still nothing particularly potent, a pretty mild easterly in comparison with what might had happened if those +3c anomolies weren't spread over the northern hemisphere.

GFS run indicates the period 8th-12th will average 3.75c.

The CET by the 12th should be aroubnd 7.2c. 1.6c above average for the first half of December.

Expanding the period 8th-15th, the average comes in at 2.2c. If this were to follow through to reality by the 15th the CET would be 5.8c, olnly 0.2c above the average for the first half of December.

There is still potential for a sub 5.0c month, whether or not the current pattern evolves into something similar to December 1946 is another matter but if it does it may well end up in the 3s.

At this early stage I'd go for the 5.0c mark. The cold won't last all that long.

[kold weather]

OP I weren't suggesting a 3C CET for the month but rather a 3C return for the period between the 10-20th of December which I think your stats would probably show quite nicely may not be al lthat far away from the turth if the HP lasts.

IMO something around the 5.5C mark would be where I'd place my mark right now..ironic that because 5 out of 6 last strong La Nina's came in between 5.1-5.4C!!!

[sundog]

I think its really hard to know what will happen during this december. But my best guess is that the atlantic will certainly wake up but may not have things all its own way and there could be some interesting battles between the atlantic and much colder air from the east,just a guess mind but we will see. I will go for the safer option for the cet with it coming in about average at 5.2c

I may not have been far off with my guess

[Stratos Ferric]

There looks like there going to be a rather large downward correction with a rather large stable high forming close to the UK in the middle of this week...whether or not it'll bring in cold enough air for snow is another matter but it'll be pretty cold regardless with daytimes maxes really suffering due to cloud cover and I'd have thought given past set-ups like this tmeps cold only rech 1-2C in fog...we could see quite a few days with CET's between 2-3.5C if this set-up comes off like currently progged.

I think the crtical point, kold, would be more the reference to HP close by. Irrespective of the airflow (almost certainly NOT cold enough by the way - the source is more SE Europe than Siberia / N Eurasia) HP is not conducive to precipitation in any form.

[Snowyowl9]

There is still potential for a sub 5.0c month, whether or not the current pattern evolves into something similar to December 1946 is another matter but if it does it may well end up in the 3s.

At this early stage I'd go for the 5.0c mark. The cold won't last all that long.

It does look like if this continental SE-ly or slack east even, then if high sticks around like the models suggest the SE will certainly get quite plummet in temps especially.

Last years was a mild 6.5c and it does look like being 1c lower at least if the high stays 2c.

I went for 4.9c which was dec 1989 cet who remembers that month it wasn`t exactly a memorable month as I remember.

Looks like there was an ineresting set-up here though.

http://www.wetterzentrale.de/archive/ra/19...00119891211.gif

[Stu_London]

Looks like CET is going to go south faster than a canoeist's widow with a suitcase full of life assurance cash if the 12z GFS verifies.

From a current position of 8.7C (Manley) in the fairly reliable timeframe we see a rapid cooldown to around 5.4C by the 15th.

Its at this time that the 12Z GFS draws what is likely to be a bitter southeastly off a rapidly cooling continent. Experience of this type of airmass tells me that the GFS may be overcooking the temps. If the airmass is clean and clear then widely in the zone we will see -6 or -7 at night with temps struggling above zero during the day.

If we draw a foggy regime, expect minima to be not quite as low, however daytime freezing fog could be extensive.

Either way, were the 12z to verify (and it has degrees of support from a lot of 06z ensembles and 0z ECM) a period of several days is likely where the net temperature is below zero.

My very rough outrun from the 12z suggest a CET of around 3.0C by the Xmas day, however this could be lower still as I have generally used the GFS temps and would expect surface temps might be even lower.

Look forward to SF rubbishing this post - but I will stick to my guns on this whilst the models support the said scenario (which might be as little as 6 hours)

[kold weather]

If ther eis one set-up that people under-estimat eits the one that is shown by the models with a slack flow from Europe, even in recent winters that has been one set-up that has given some pretty decent temps in the CET zone.

As I've said befor eits really cold through the backdoor, its not deep cold but shallow cold from Europe and I whilst it won't bring snow unless the high drags in a better airflow it'll be pretty damp and dull, i should think there won't be a single above average from the 10th onwards for at least 5-7 days IMO and given how high the CET is presently that'll really drag the CET down in a major way.

[Optimus Prime]

My very rough outrun from the 12z suggest a CET of around 3.0C by the Xmas day,

With that in mind I had to go and calculate it. The period 9th-25th the GFS has the average at 0.32c.

There were countless frost days in the unreliable time frame with minima coming down to -5c on a number off occasions.

So the average by the 25th would be 2.9(568 to be precise) so you weren't far out.

[West is Best]

Certainly in for a right royal hammering. Great to see

[kold weather]

Yeah its going to very interesting to watch, Tuesday actually looking like a rather cold day in the CET zone and I think a CEt day between 1.5-2.5C is certainly on the cards and with it a rather large downward turn...all this several days ahead of the drop that Dec 00 had and as I've said before that wasn't that much above average so every chance of getting a below average CET providing the high doesn't sink into bartlett.

[Snowly does it]

Looking good also for a sub 6 which will make the Jul-Dec period a below average second half of the year to follow the record warmth of the first half.

If December can finish at 4.5 or below then we will be below average for the second half of the year versus the 61-90 mean

Following on from the posts above, if December could hold this HP and finish at 2.7 or so then it would be the second coldest year since 1996 at below 10.30, it would also be the first sub 3.0 month since 1997. However please be aware that to reach 2.7, the CET from here on in needs to average a rather fanciful 0.65 for the entire remainder of the month.

Sub 4 is highly improbable.

EDIT - and I have just remembered that I ruled out sub-par on the 1st December, so there you go, I am as accurate as ever.

Edited December 9, 2007 by snowmaiden

[Stratos Ferric]

Looking good also for a sub 6 which will make the Jul-Dec period a below average second half of the year to follow the record warmth of the first half.

If December can finish at 4.5 or below then we will be below average for the second half of the year versus the 61-90 mean

Following on from the posts above, if December could hold this HP and finish at 2.7 or so then it would be the second coldest year since 1996 at below 10.30, it would also be the first sub 3.0 month since 1997. However please be aware that to reach 2.7, the CET from here on in needs to average a rather fanciful 0.65 for the entire remainder of the month.

Sub 4 is highly improbable.

Yes, I wouldn't be getting TOO carried away yet. As John has mentioned elsewhere, much depends on cloud, even assuming the pattern holds for as long as projected. It all ended more suddenly that anticipated just a couple of weeks ago. Definitely a downwards correction over the next week though, and if we get stagnant air and freezing fog then we might see an unusually dramatic switch.

[Lettucing Gutted]

Countryfile have forcasted a "back door cold" scenario to develop by the end of this week after the initial Northerly and anticyclone arrival.

However I have got a bad feeling those dreaded warm Southwesterlies will win the battle instead. (They don't look to far away from the UK.)

[Stratos Ferric]

Countryfile have forcasted a "back door cold" scenario to develop by the end of this week after the initial Northerly and anticyclone arrival.

However I have got a bad feeling those dreaded warm Southwesterlies will win the battle instead. (They don't look to far away from the UK.)

Short-term runs always look robust, but this seems solid to my eyes. The HP to the E is a recurrent pattern in recent years, and from erlier this autumn, often by precisely the returning eddy in the flow currently programmed. The flip side is that the price of the HP to the E is a jet way north, and probably a continuation of the striking anomalies across the N Pole. At around t+168 there is something of a crux, with a huge returning eddy (almost implausibly long) sustaining HP. I can see a breakdown at that point, but the pattern between now and then seems fairly plausible. There may be a bit of variation at the surface, and the precise location of HP will impact surface temperatures, but that much is detail.

[kold weather]

Looks like Tuesday is still on track to return a CET between 2-3C at the moment, mins probably a little below freezing overall in the CET zone and maxes probably between 5-6C generally in the CET zone as well. Looks like we could be in for some pretty hefty drops over the next week.

Whats really interesting is both the ECM ensembles and the GFS ensembles suggesting maxes around 2-3C from Thursday-Friday onwards which will really hammer the CET downwards...though how long that'll last is anyones guess.

I wonder what is the biggest flip from a mild first 10 days to cold next 10?

Edited December 9, 2007 by kold weather

[damianslaw]

Looks like Tuesday is still on track to return a CET between 2-3C at the moment, mins probably a little below freezing overall in the CET zone and maxes probably between 5-6C generally in the CET zone as well. Looks like we could be in for some pretty hefty drops over the next week.

Whats really interesting is both the ECM ensembles and the GFS ensembles suggesting maxes around 2-3C from Thursday-Friday onwards which will really hammer the CET downwards...though how long that'll last is anyones guess.

I wonder what is the biggest flip from a mild first 10 days to cold next 10?

Yes it will probably be the CET zone that is the coldest part of the country as we head towards thursday and friday, the CET zone will do well out of the progged set up for returning coler than average CET values.

Many parts of the midlands and inland east anglia are quite likely to see some low maxima by thursday, wouldn't be surprised to see one or two stations to come in below 2 degree maxima.

[The PIT]

Well CET should take a dent this week. We're looking for only one day this week that's going to be average the rest well below and the story should be roughly the same for the CET area as well.

[Potent Gust]

Countryfile have forcasted a "back door cold" scenario to develop by the end of this week after the initial Northerly and anticyclone arrival.

However I have got a bad feeling those dreaded warm Southwesterlies will win the battle instead. (They don't look to far away from the UK.)

I am most likely been thick here but what do you/countryfile mean by "back door cold"?

[Stu_London]

Well CET should take a dent this week. We're looking for only one day this week that's going to be average the rest well below and the story should be roughly the same for the CET area as well.

Down to 8.4C on Manley now

An 'average' December day will knock off 0.2C to 0.3C off that figure each day at this stage of the month.

An 'ice day' would see the value drop 0.5C to 1.0C (depending on how cold the night gets)

[Stratos Ferric]

As at various times this autumn we're now staring at a nearby HP and the likelihood of some cold nights so CET is certainly going to fall sharply now. I'm not totally convinced the pattern will hold until Christmas, but we've had similar in recent Decembers, and it's in keeping with the surface of the last 3 months or so with the PFJ way north then kicking an eddy from the E as it corrects equatorwards.

Edited December 10, 2007 by Stratos Ferric

[Snowly does it]

Impressive drop over the last 3 days really given that we are not in the cold part of the cold snap yet.

Thats one way of looking at it, although if the first 6 days hadn't been so abnormally mild.....

Will be very interesting to see where the 16th puts us - halfway is always a more comfortable place to assess (trying to forget I wrote off a below average month on the 1st)

An 'ice day' would see the value drop 0.5C to 1.0C (depending on how cold the night gets)

Working it out Stu, a 3 degree day would drop 0.5 from our current position, an ice day at exactly freezing would lose 0.8 and 1.0 would go for a -1.7 CET day