Kentish Kiwi

Remarkable, and the third coldest on record it would seem. Do you have any information on how the three day period of Christmas Eve, Christmas Day and Boxing Day (the Christmas 'trifecta' if you will) stacks up to historic records in term of CET?

Yes, the AO and NAO are simply indexes, measurements or representations of pressures patterns. They are certainly not atmospheric 'drivers'. Its almost as though saying that the CET is a driver of the temperatures we experience in the UK. Although that said the values the AO and NAO display and the pressure patterns that are reflected by this are particularly important as to what weather this part of the world sees. As to what is causing these negative values and the associated northerly blocking they relfect, no one knows for sure and this has been particularly obvious this winter, especially when compared to last winter where there were some clear-cut variables/drivers that we expected would prove favorable to produce northerly blocking, and these delivered. However, there are certainly many many factors that affect this and it has become clear during the last month or so that the temperature of the polar stratosphere and what we normally expect from such temperatures can be 'over-ridden' by other variables to produce blocking at northerly latitudes, as the stratosphere has been overwhelming below negative for at least the last month yet we have still seen a disrupted vortex. I get the feeling, though, that the consistently cool temperatures experienced over the polar stratosphere will begin to show their hand much more obviously throughout January (as can be seen by some of the zonal outputs from the models in the medium term), unless an SSW is able to break this down before the vortex really gets going.

Do you still think February will be the coldest month out of the three this winter ala your forecast? Or at least do you still see it being notably colder than January?

That's what I was thinking!

I'm beginning to get the feeling my 2.3C may well be a couple of degrees too low. The stratospheric elements certainly don't seem to be developing as I had hoped, and an SSW was my main hope in what would bring another cold month...

Although it is likely this month will end up relatively comparable to February 1986 in terms of temperatures, I thought 1986 was notable for how dry it was. If so, is it fair to assume December 2010 was a better winter month on the whole, as snowfall seemed to be relatively widespread and pretty frequent?

Any idea where that was filmed? Surely not in the UK...?

Apologies, it must be the +QBO I was thinking of that usually limits the potential for SSW's not the ENSO

2.3C please. Looking like a blocked, quiet but below average start due to the so-called 'faux cold' (below average for one of the coldest times of year = cold) unless North Sea low cloud scuppers the chances of inversion. The possible SSW could throw a spanner in the works for the middle half of the month and make it notably colder than what I'm predicting, while I think it will turn milder and more unsettled for the last week. Obviously absolute guesswork (as I suppose everyone else's is) it should be noted though. Love this. :lol:

An SSW would be particularly remarkable would it not? At the beginning of the winter it was noted that it is extremely rare to get such occurrences during La Nina (or maybe it was +QBO's?) and they were almost completely ruled out... Wasn't 2009 the first such SSW recorded during a La Nina, or at least something along those lines? And if so, could we not see a similar atmospheric reaction to the event ie. it not being as favourable for cold in the UK as initially forecast? (Sorry for all the questions Chiono, appreciate the effort you put into this thread, especially given the time of year. The prospects are certainly very exciting. If we saw a complete disruption of the vortex, this winter as a whole could turn out to be historic/memorable, not just December.)

So your telling me that everyone of the above temperature records will now have 2010 next to the figure? Astonishing. It would be interesting to see what the longest run of broken records is in regards to the date minima. Probably quite a specific/difficult statistic to conjure up though... Alas, it looks like that figure of -18.3 will not be broken by Altnaharra tonight (possibly by other stations though). Was down to -17.9 at 22:00 but has 'rocketed' up to -14.1 now that cloud has rolled in... I suppose it could have gotten lower than -18.3 somewhere between those two figures though.

How far back do the records go for December CET means?

The idea of a mid latitude high over, or very close to, the UK seems to fit in nicely with GP's thoughts for January.

Do we not already? (wasn't sure if you were being sarcastic or not!)

Thanks for that Stu, some very interesting results, was certainly a far more common occurrence during the 19th century than that just gone.. Looks like we're on track for only the fourth time of this happening in over 100 years, quite remarkable. Also, interesting that this happened to have occurred during (and before) the famous winter of 1962/63. The figures for 1796, 1830 and 1870 look insane. Were they particularly severe winters or more just a case of the timing of a severe cold spell falling over the Christmas 'trifecta'? Just to clear this up, because I'm a little unsure. Are the above 'hits' you've researched all for the CET mean being below zero over this specific three day period? And if so, does this mean that a CET 'ice day' only constitutes the mean being below zero and not the the CET max being sub-zero too?

To my inexperienced eye, and its probably already been covered previously in this thread, it looks likely that Christmas day will record a CET 'ice day'. Would I be correct in this thought, judging from the GFS? (although that said, I'm unsure if an ice day is counted as the absolute mean of the day recording below zero, or if it has to be the mean CET max for the day that records below zero - although I assume the latter is more logical/likely)... If so, when was the last time an ice day was recorded on Christmas day? It also looks possible that CET ice day's will be recorded for Christmas Eve day and Boxing Day. Surely having this three day period below zero is pretty unusual/rare?

I know its kind of irrelevant, but isn't it bizzare to think that on possibly the coldest December CET max day on record large swathes of the south coast still receive rainfall from a precipitation band... Incredible cold on offer across the UK at the moment though. A truly historic cold spell. I guess there no doubt this is more severe than what we experienced between the 1-15 of January earlier this year?

But the question is, is it forecast to?

When was the last year in which we had an above average December? Decembers in the 2000's (I'm assuming this one will be counted with the 2000's) will surely come in as the coolest compared to average of all the months? It truly is astonishing to think that we are now odds on to have a colder month than anything the 'historic' winter of 2009/10 could conjure up. Has anyone got any likely figures for what the period Mr Data highlighted of 24 November to 23 December will possibly come in at?

Kold, with the recent changes in models, notably the GFS, increasing the tendancy to have the trough further west and then settle over the top of the UK with very cold upper air and slack winds, would it not be the case that overnight lows will be a lot lower than if we continued with a moderate/strong northerly flow? Could this not help to aid chances of a lower CET, especially if inversion/freezing fog conditions come into play in the CET zone to keep day time temperatures below zero for a few days? I agree the length of the cold spell is becoming shorter and shorter on the various models, most probably to do with the section of the polar vortex likely to be dropping further west and less south than was modelled a few days ago, but could this slack set-up that results not make the period Mr Data mention of the 24th of November to the 23 of December even colder? (if you can get what I'm trying to say here)

I think most people are, I was just interested in how this 7 day period of November compared with other 7 day periods in November in history, ie. It may have been the coldest final 7 days on record, but is it the coldest 7 day period in November outright. And it appears this is not the case.

Possibly, but isn't that only the coldest 'last' week of November, not the overall coldest week of the month on record? Or is it just a given that the coldest last week will be the coldest of all the weeks on record?

Could anyone provide figures for the coldest weeks in November and how this compares with the spell we have just experienced (coldest last week of November)? Surely, being the coldest last week, it must be close to the coldest November week on record?

I wouldn't be surprised if it was more ignorance than anything else, either that or the fact that it hasn't been until today that London and the South East has seen snowfall.

Why wasn't the SE like that at all? On that image the SE is green, as it was yesterday? You may be confusing EA (which is white on that image) with the SE...