Thermal Gradient

[Stratos Ferric]

The thermal gradient across the British Isles is unusually steep today. At Dublin airport the recent reading was 11C. 150 statute miles or so E, at LBA, it's a height assisted -2C (widely around freezing at the surface). Possibly almost one for the record books, and precisely the sort of variations we saw in the set-ups in 1979 when the S/SW would often be basking in termperatures of 10C whilst the N Mids north were at or below freezing.

To put this in context I think that this is not only an unusual battle in recent winters, it's unusual going back quite some way to have a straight W-E battleground. I'm sure TWS will have the data though.

[johnholmes]

would agree with you mate.

I'm sure Mr Data will tell us all the last time this kind of event happened. I would guess it must be at least 10 possibly nearer 20 years since such a wide spread of temps and such a wide and noticeable snowfall.

John

[Great Plum]

Did this ever happen frequently?

[Stratos Ferric]

Did this ever happen frequently?

Not frequently, and I suspect that even in 1979 the gradient was less wide although possibly just as steep. Now we're into March the warm sector air is that much warmer than it would be in Jan-Feb.

My imperfect records from the major events in 1979 are as follows:

Jan 14-15: Cornwall / SW Ireland 9C, NE England 1C.

Feb 1-2: N Mids - Scotland widely 0-2C, S Coast 9C.

Feb 13 range was aroun 1-7C S-N

March 17: N scot 3C - Borders / n england 0C - South 5-7C.

All of the above produced prodigious snowfall across the centre of the UK, and in each case the incoming frontal system was moving more N than E. I struggle to ehink of an ocasion when, as this weekend, the front has been spun to lie SW-NE along the gradient.

[kold weather]

So SF this set-up is rather an anomaly to the rule of the even larger teapot, infact as you say it was mighty rare even in the good old days, but now-days its unheard off.

intrestingly enough I remember the thread you made about the last frontal snow, I'm sure this one counts as just that!

Also, when was the last time the cold won the battle, at least at the surface when it was agaisnt the warm, I can't remember one in the 'even larger teapot' spell.

[crimsone]

Not frequently, and I suspect that even in 1979 the gradient was less wide although possibly just as steep. Now we're into March the warm sector air is that much warmer than it would be in Jan-Feb.

My imperfect records from the major events in 1979 are as follows:

Jan 14-15: Cornwall / SW Ireland 9C, NE England 1C.

Feb 1-2: N Mids - Scotland widely 0-2C, S Coast 9C.

Feb 13 range was aroun 1-7C S-N

March 17: N scot 3C - Borders / n england 0C - South 5-7C.

All of the above produced prodigious snowfall across the centre of the UK, and in each case the incoming frontal system was moving more N than E. I struggle to ehink of an ocasion when, as this weekend, the front has been spun to lie SW-NE along the gradient.

That's frightening!!!!! Wow!

Not that I'd want to start ramping, and not that I actually believe what I'm about to ask, but is it possibly that we might yet see a little more in the way of snow to match the falls we had in the late 70's and early 80's?

Are we seeing the end of the even larger teapot? and is the neo-even larger teapot going to come this much later in future?

[Stratos Ferric]

So SF this set-up is rather an anomaly to the rule of the even larger teapot, infact as you say it was mighty rare even in the good old days, but now-days its unheard off.

intrestingly enough I remember the thread you made about the last frontal snow, I'm sure this one counts as just that!

Also, when was the last time the cold won the battle, at least at the surface when it was agaisnt the warm, I can't remember one in the 'even larger teapot' spell.

Indeed, and I think i commented not long after posting the "demise" thread that it was a strange wonder that we suddenly then had precisely that, and now again for a second time. This is certainly the first occasion in my seven winters on the hill that frontal snow has not turned back to rain (I know it has in one or two places, and that in some locations in the far S all they had was rain - but these situations always had this sort of mix, it is a warm front after all). I think the quantities have been less than I'd have expected generally, although the SE half of Scotland has received a lot, and even in 1979 the main snowbelt was often not much more than 100-150 miles wide. What has been noticeable today is that western slopes seem to have picked up more, which is exactly what you'd expect were it rain not snow from this alignment. Critically, in 1979, the fronts were invariably tracking up the spine, rather than across it; this alone would dramatically change the pattern of snowfall.

So it's a very interesting event for several reasons, and I suspect that we are still far from seeing the back of this winter.

[Optimus Prime]

I wouldn't base a winter containing average temperatures (or veyr mild for Scotland) an end to the "even larger teapot". If we were talking about this in 1995/1996 with the record low set in December 1995 and the snow storm in February 1996 I bet we would all be saying goodbye to the mild winters.

An interesting winter synoptically. Most surprising are the very low maxima since mid November but on the other side the CET for December was only a little below average, January was slightly mild and February was slightly cold for England and Wales.

I wouldn't be surprised if next winter was warm and wet like many of them since 1988. We will always get winters that are close to average or even cold with some good snowfalls like in December, February and March this winter but it doesn't mean it's the end of the "even larger teapot".

I wouldn't be surprised if next winter was mild again.

Edited March 12, 2006 by Optimus Prime

[Stratos Ferric]

That's frightening!!!!! Wow!

Not that I'd want to start ramping, and not that I actually believe what I'm about to ask, but is it possibly that we might yet see a little more in the way of snow to match the falls we had in the late 70's and early 80's?

Are we seeing the end of the even larger teapot? and is the neo-even larger teapot going to come this much later in future?

As I always say, one data point proves nothing: there are always outliers in both directions around a trend. You could see this winter two ways: either it's been more wintry than recent winters (though looking at the snow league table for last year it may not have been more snowy, it's certainly been colder), and as such it's bucking a recent trend. On the other hand, against an older baseline, it's actually been somewhat disappointing. As I keep mentioning in my posts, although there have been a lot of snow and cold occurrences, quantities and extremity have been unspectacular to say the least. What IS undeniable about this winter has been the lack of sustained warmth. It's possible to hypothesise, therefore, that what we've had here is a winter which, twenty years ago with the same synoptics, would have been rather more wintry.

It will be interesting, if the likes of Bingley STRI don't warm up this evening, to compare max temp across the British isles today because I fancy that there's a chance of a record being broken for March for the range, or at the very least of us coming close to it.

[kold weather]

Indeed I'd agree with that SF, then again I've always said if you were to have another severe winte rin this country you'd need at least 2 cool-down winters that lacked any real mildness before the continent gets something back to what it was like in the past, only once that happens do I believe the temps will be good enough for at least a shot at a severe month.

So I feel that this winter is a step in the right direction and has progressed from the set-up in Feb-05, which was intresting snyoptic-wise.

[patrickshere]

The other thing is that because one or two people have heavy snow, they seem to think the whole country was effected which is very much not the case. Over the past few days we've not had a single snow flake here and I know it's the same case for most of England. Only really Wales, Scotland and N/NW England have seen anything from it..

[Weather-history]

.

To put this in context I think that this is not only an unusual battle in recent winters, it's unusual going back quite some way to have a straight W-E battleground. I'm sure TWS will have the data though.

10 years to the day, 12th of March 1996

http://www.wetterzentrale.de/archive/ra/19...00119960312.gif

The mild westerly flow from the Atlantic made in roads to the UK giving intially rain but a colder easterly flow undercut the systems and turned the rain to snow and pushed it back westwards. The eastern slopes of the Pennines received several inches of snow.

As for thermal gradients, I remember on the 22nd of February 1994, Plymouth was something like 10 or 11C but the Midlands was 0C with snow.

Also happened on the 25th of January 1995, with a low tracking across the north Midlands. To the south of the low it was 12C but to the north over parts of northern England, it was 0C

Edited March 12, 2006 by Mr_Data

[Dave J]

You get even more impressive thermal gradients in the summer between the north and south of a slow moving frontal wave. It can set off some impressive thunderstorms too!!

[crimsone]

The other thing is that because one or two people have heavy snow, they seem to think the whole country was effected which is very much not the case. Over the past few days we've not had a single snow flake here and I know it's the same case for most of England. Only really Wales, Scotland and N/NW England have seen anything from it..

Erm, that's most of the country I believe? Far more than one or two people.

Besides, my question was only really a question to prompt a discussion of a balanced and realistic point of view of the relevance of this winter/event in a changing climate in terms of a view of future winters and past ones (and so giving the answer on the subject of this thread) - hence my statement that I didn't really believe what I was asking too much. It's more about the setups and how they may or may not be changing than it is about the actual snowfall on the ground in this context.

Edited March 12, 2006 by crimsone

[Stratos Ferric]

You get even more impressive thermal gradients in the summer between the north and south of a slow moving frontal wave. It can set off some impressive thunderstorms too!!

Dave, agreed, though in summer the potential for variation in insolation is higher, over and above any air-mass viaration, so that would be expected.

[AtlanticFlamethrower]

I've always said if you were to have another severe winte rin this country you'd need at least 2 cool-down winters that lacked any real mildness before the continent gets something back to what it was like in the past, only once that happens do I believe the temps will be good enough for at least a shot at a severe month.

What do you mean by this? What on the continent needs to cool down?

- forests?

- soil?

- cities?

- north sea?

- lakes?

- mountains? (larger glaciers?)

Etc.

[Stratos Ferric]

Indeed I'd agree with that SF, then again I've always said if you were to have another severe winte rin this country you'd need at least 2 cool-down winters that lacked any real mildness before the continent gets something back to what it was like in the past, only once that happens do I believe the temps will be good enough for at least a shot at a severe month.

So I feel that this winter is a step in the right direction and has progressed from the set-up in Feb-05, which was intresting snyoptic-wise.

It certainly makes next winter and interesting one to watch, and it also supports the theory that we're entering a cooler phase in the cycles: the question then would be would we bottom-out at anything like the cold temperatures we saw twenty or so years ago? I'd have to doubt it personally, but we shall see.

[reef]

Didnt 27th May 2005 have an impressive gradient aswell. I remember that day being 32°C in London while in Edinburgh it was only 9°C!

Not quite a winter setup, but equally impressive. -5°C 850hPa air just to the north of Scotland and the 15°C isotherm touching southern England!

[kold weather]

Just about everything Af, though to be fair this winter has, at least in terms of the synotpics seems to have been, if anything slightly below average though I've not really got a clue what is average anyway!

SF, yeah I'd have thought that the bottom-out temps will be higher then they would have been 20 years, simply because the base line is that bit higher. I'd have thought winters inbetween the 80's and 1995-1996/7 would be most probable in terms of how cold things could get when we bottom out, which I still think we are at least 1 winter away from doing.

[Stratos Ferric]

What do you mean by this? What on the continent needs to cool down?

- forests?

- soil?

- cities?

- north sea?

- lakes?

- mountains? (larger glaciers?)

Etc.

AF,

There is some statistical support for this I'm afraid. Very cold winters have never come out of the blue. As the chart below shows year on year changes in winter (D-M) ave temp of >2C are rare. We're just getting to the point now where, taking an agreesive view for March of a CET of 4.5C (it's unlikely to be this cold) something like 1979 starts to become possible next year.

However, whilst well within bounds (though unlikely) as a singleton, if we stack the data up to look at two year changes in temperature, then the requirement for us to get down to a 1963-like winter would be for a two year winter drop of 4C. This has occurred only three times in the CET record, the last time being 1963. It is possible, therefore, but against temperatures that are now about 1C higher on average acros the year such a marked drop becomes unprecedented.

[summer blizzard]

I personally feel that we are in a cooling trend and that next winter will be similar in to 1991 temperature wise with a winter CET around 3C and that the winter after will have a CET around 2C, which is comparible to the worst of the 1980's.

[AtlanticFlamethrower]

kold weather,

//Just about everything Af//

What?

It seems to me "continent needs to cool down" is one of those phrases people say without thinking what it actually means, if anything. I'm sure you must have an idea what you mean, - soil temperatures, I suppose, would be higher than normal on continent after a run of modern winters. However I'd reply that during most modern winters you still get frozen soil and snow in Europe. Is the continent that hot or is it another factor that means air temps are too marginal for snow here by the time it is blown our way on Easterlies?

I'd thought if the source of the cold is intense enough cold will dominate regardless of latent heat sources on the continent. And I'd still like to know which "heat sinks" you're referring too, if not continental european soil temperatures.

Stratos Ferric,

//

However, whilst well within bounds (though unlikely) as a singleton, if we stack the data up to look at two year changes in temperature, then the requirement for us to get down to a 1963-like winter would be for a two year winter drop of 4C. This has occurred only three times in the CET record, the last time being 1963. It is possible, therefore, but against temperatures that are now about 1C higher on average acros the year such a marked drop becomes unprecedented.//

The chart that plots winter (Dec - Mar) +/-s is interesting viewing, thanks for posting it. The plots to the NE I suppose are mostly from recent winters and ones to SW from older ones. First, what I find incredible is the existence of winters that were over 3 degrees warmer than the year before that themselves posted a frigid D-M average of only 3 degrees!

However sadly, the plot suggests to me our coldest winters support the "surprise hypothesis."* Rather than an "incremental cool down" as kold weather is suggesting, the 5 winters you chose to name show cold can come out of the blue. They were 2 degrees out of whack from the previous year.

*Edited to add, on further reflection I don't know what I'm talking about. The plot might suggest the best that is possible is -2 from previous year. Which is kind of incremental and kind of a surprise.

2004/2005 = 5.7 C

2005/2006 = 4.2 C (Feb at 3.6C, March at 4.5C, the 1996 figure)

Current estimate is that this D-M will be -/+ of 1.5 degrees from last year. Is this likely to be about as cold as it gets in the even larger teapot? Is the blue vertical line your estimate of the best even larger teapot can achieve (4 degrees)? I think this would be my view.

The cool dip on a warming curve is the most attractive explanation for this winter and I'd expect at best we could if we get more like over the next few years is a 1996 winter. This is not because continental Europe has sources of latent heat that need cooling, but because on Earth there is more heat in the atmosphere/oceans making smaller and smaller pocket of cold air at the poles to go around winter times.

That's my own view, willing to look at others and change my mind. Little more exciting than possibility of more snowy winters.

Edited March 13, 2006 by AtlanticFlamethrower