Autumn and Winter discussion...

[TEITS]

I don't think being so near the north Pole really comes into it. The prevaling flow in the UK is south-westerly, and we are first in line from the Atlantic. Add to this the gulf stream and you can have all the cold you like to our north and east, if the west / north-west isn't right it won't come our way ... at least not for any sustained periods. The Atlantic will always return. Even with a blocked set up last year we didn't get a properly cold winter. The final nail in the cold coffin.

Whilst local variations to the general AGW trend are always possible, and it would be foolish to deny this possibility entirely, the chances become rarer with each passing year. As more and more warm records tumble around the globe it begins to look more and more desperate for those clinging to cold hopes for the UK. Personally I'd rate the chances of a below average winter now in the UK as 1/25 or 4%. This is reinforced by the full-blown return of the Atlantic this autumn.

I'm looking to record mild possibilities rather than the other way.

Morning Richard.

May I ask where you are getting the return of the full blown atlantic from??

http://www.wetterzentrale.de/pics/Rtavn1441.png

http://www.wetterzentrale.de/pics/Rtavn2641.png

As for the chances of a cold winter becoming rarer with each passing year may I ask you what would happen if the factor's that made the 90's so mild were reversed in the next few year's. GW is only a tiny part of the reason why the winter's since the 80's have been so mild and it look's to me the other reasons are on the change.

[SMU]

Welcome back sceptical West.

Your claim that the Atlantic is full blown is slightly erroneous. The story so far......

Low pressure manifested to our SW all the way to the Azores, and much above heights recorded over Greenland. Not a classic autumnal zonal pattern with low pressures crashing in on a strong jet.

The Autumn so far has been one of strong meridional flows and a very weak southward displaced west-east pattern. This could all reverse spectacularly over the coming weeks however, but right now it is no way full blown.

GP

Wheres the wall & Head bang smiley gone.....

Dont worry GP- Here Richard & Dawlish at home snuggled up in Devon this Winter....

Lol-

S

[Optimus Prime]

Octobers do look as if, since 2005 blocking is becoming established earlier. Which is why it's so warm, a lot like in the 60's when the winters were more blocked and colder.

There was only 1 cold October in the 60's, that's 1964 with a CET 8.9 (1.7c below the 61-90 average) The rest of them were mostly mild or very mild.

.

[Stratos Ferric]

To put a bit of persepctive into this, whilst the Atlantic is hardly a full blown conveyor this autumn, I find the inference that the weather this autumn has not been Atlantic dominated rather bizarre. We haven't had any northerlies or easterlies for weeks, all the surface activity has been from the S and W, and recent temperatures reflect that. Something more settled during October / November is not that unusual, whether it's warm or cool depends on precisely where any HP develops.

Regarding the outlook for a couple of weeks hence I'd be very cautious at this stage about sustained cold reaching the UK. Steve's technical assessment last night gave what I thought was a reasonable breakdown of the "ifs" and "buts" of the situation. The jet does look like becoming very unstable, but it looked the same in early September, and eventually restabilised. Even if it does retain a high amplitude flow over the Atlantic, forecasting the precise location of the decelerating air this far out is very hard, and expecting a sustained cold requires a low energy Pacific, or else a very southerly displaced PFJ. The former looks unlikely, the latter would require a huge cold pool to our NW.

The end of October shold be cooler than the start, it is THE cooling month of the year, but to determine just HOW much cooler this year we'll need to wait a few days yet.

[karyo]

Front after front has been crashing across our parts though Kevin, and moving through the east e.g. last night. Seems pretty Atlantic dominated to me!

This is only because low pressure has been near by. No matter how blocked the Atlantic is, there will always be low pressure around and we happen to be next to it (and to the warm side of it too).

Karyo

[TEITS]

As you know Dave the blocking was there for August - just 300 miles to our west. However, August may have seemed poor to you and some others but this is where statistics provide a useful corrective to mistaken personal perceptions. At 16.1C August was within 0.1C of the 1971-200 average, and comfortably warmer than both the 1961-1990 average (15.8C) and the 100 year rolling average (15.9C). It was of course a relative dull month, and whilst wet in much of eastern England it remained bone dry in much of the west (30% of rainfall totals in our parts!). All in all it was therefore an average month. The mood was lightened by a thumping warm September breaking the all-time record.

Statistics do have their uses, providing the source is rigorously tested.

August didn't seem poor it WAS poor!.

It doesn't matter what the temps were the fact is it never stopped raining here in Peterborough and this is why I classed it as a poor month. The garden was proof of this because as you may remember the pic's on my sig used to show the brown dead grass of July which was changed into a lovely lush green within a couple of weeks in August.

[nick sussex]

I wondered how long it would be before the old chestnut( full blown atlantic or not would appear on here! )

This always ends up with differing views as to what people decide is full blown zonality or not. IMO with no strong jet piling into scandi and higher than normal heights over greenland then in my humble opinion this is not a typical autumn pattern or proper zonal weather.

Anyone want to argue.....!!!

If you must do it nicely!

Edited October 9, 2006 by nick sussex

[Joneseye]

I wondered how long it would be before the old chestnut( full blown atlantic or not would appear on here!

This always ends up with differing views as to what people decide is full blown zonality or not. IMO with no strong jet piling into scandi and higher than normal heights over greenland then in my humble opinion this is not a typical autumn pattern or proper zonal weather.

Anyone want to argue.....!!!

I agree with you Nick, that pretty much sums up Zonal weather for me too. Add in the conveyor belt stretching back to the east coast of America and that is nail on the head time for me. I think the original comment was intended as bait...

[nick sussex]

I agree with you Nick, that pretty much sums up Zonal weather for me too. Add in the conveyor belt stretching back to the east coast of America and that is nail on the head time for me. I think the original comment was intended as bait...

Morning Jonesye

Well I agree with you there, this is it zonal or isnt it always brings such differing opinions on here.

[Weather-history]

Front after front has been crashing across our parts though Kevin, and moving through the east e.g. last night. Seems pretty Atlantic dominated to me!

Atlantic dominated? Yes I buy that but full blown? Nope, I would call it full blown, to me that is one low pressure after and another steamrolling through.

[BrickFielder]

It is now agreed warm anomalies encourage ridging, cold troughing, but two years ago there were people forecasting on the basis it was the opposite way round! Remember when cold anomalies off Western Europe were the purported reason for a persistent Bartlett high (label Bartlett is I think incorrect for this image - I use the word to express high pressure of western Europe pumping warm air our way from the Azores).

A little bit of a generalisation and partially true.

Two types of atmospheric response are desrcibed in the literature. One is baroclinic, shallow and thermal, with anomalously low (high) pressure over anomalously warm (cold) SST (Lindzen and Nigam (1987)). The other is barotropic, involves changes in the surface baroclinicity and in the statistics of the transient eddies (Palmer and Sun (1985)). The latter generally results in anomalously high (low) pressure downstream of a positive (negative) SST anomaly.

In our latitude the response is generally baroclinic or shallow because wind moves the air away before any deep heating from the warm water can take place (this may not be true mid winter). This according to Lindzen and Nigam would give troughing over a warm anomaly. Yet this is not quite what happens and the response in the north Atlantic seems to be high pressure to the north west and low pressure to the south east of a warm anomaly and this is much more in line with the updated research by Frankignoul. What we should expect according to literatures is for winds to tend to blow easterly across warm anomalies. In this respect we should expect ridging to the north of a warm anomaly.

ATMOSPHERIC GCM RESPONSE TO EXTRATROPICAL SST ANOMALIES:

SYNTHESIS AND EVALUATION (Peng et al) The patterns of wintertime (December-March), anomalous SST, ocean-to-atmosphere turbulent heat flux (latent plus sensible), and surface wind vectors, associated (via linear regression) with the leading principal component of SST variability in the North Atlantic (a and c) and North Pacific (b and d). Panels a and b are for observations from 1949 to 1999 (data for from NCEPNCAR CDAS-1, Reanalysis). Panels c and d are for the mean of a 10-member ensemble GCM integrations forced with global, time-varying SST anomalies from 1950 to 1999 ECHAM 3.5 GCM data provided by Lisa Goddard, IRI). Heat fluxes are in Wm-2 with positive/negative values in solid/dashed contours every 3 and a thick zero contour. Arrows depict the wind vectors in ms-1 with scales shown in lower left (panel a, c) and upper right (Panel b, d). The SST anomaly values, in °C, are denoted in colors according to scale (note that scale is kept at the –0.5 to 0.5 °C range for overall clarity, however, values in eastern equatorial Pacific extend up to 1.2 °C).

Warm anomalies also tend to move north west with time so looking at current SST anomalies we should expect to see High pressure over greenland and low pressure in the central Atlantic which with time should equate to Icelandic or Scandinavian high by winter time. In between and we might expect an increasingly stormy time. This is all theory and the response to SST anomalies is notorious for changing during mid winter and I can not help feeling high pressure and easterly winds are likely to be too far north.

[SMU]

Full blown Atlantic :

http://www.wetterzentrale.de/archive/ra/19...00119990125.gif

This Friday:

http://85.214.49.20/wz/pics/Rtavn961.png

Quite different charts, but the main point should be that the synoptics required to bring prolonged 'warm' or 'mild' conditions to the UK outside of the winter months are generally quite different to what is required to bring a mild winter. Richard (WIB) suggested last Autumn that the ongoing warm months would likely lead to a 'stonkingly mild winter'.

Not so. One of the major factors is the track of depressions across the Atlantic and what many of us were able to pick out last Autumn is the lack of depressions making it past the Meridian - i.e - no long jet pattern at Northern latitudes into Scandinavia. Whilst this brings warm conditions in Autumn with blocking over Europe and southerly flows for the UK, in winter it means the potential for blocking to build at higher latitude and advect colder air our way.

The Bartlett is not a blocking High, it is a downstream ridge which develops as a result of the forcing in the jet.

As for August, yes it was pretty wet but seemed cooler than it was due to the exceptional July that had preceeded it. There were never any long draw northerlies that occurred in August 93 for example, so for it to return an average CET was not a surprise given the synoptics.

Good post-

S

[The Enforcer]

Just picking up on a few of the recent points on here:

1. In terms of historical statistics, they are not the be all and end all, but they cannot be ignored. If winter 61/62 had not turned out the way that it did, then surely winter 62/63 would have been different - a kind of chaos theory. I would interpret it as the statistics set the context in so much as if specific factors are suggesting a colder winter is in store, then it is only likely to be 'colder' in comparison with recent winters and not to sit alongside those of the Dickensian era.

2. It seems to me that an 'almost' event (i.e. the cold pool in January 2006 that went to our south-east) is given more weight by some than an actual event (i.e. the dull fairly mild snowless January 2006 that was actually experienced). The former gets more airtime than the latter. This cannot be right.

3. All this hullabaloo about October. It doesn't matter. There's no real pattern or link between October and the coming winter. If this month was really blocked/cold many would be saying how this is obviously setting the stall for a cold winter. On the other hand, a zonal/mild October, which seems more likely at this stage, encourages people to say how quickly patterns can reverse (I don't dispute this - as evidenced by last November).

4. I totally agree with SF's assertion that delivery never matches up to the expectations that went before it, such that 'wonter' is always better than winter. To emphasise this point, can anyone think of a recent winter where the general consensus was it was going to be a mild one and it turned out colder (Ok perhaps less mild) than expected? Obviously, the individual is entitled to make any projections they like. What I would say is that a high wonter value has (at least) two effects:

a> The newbie registers and reads all these cold winter forecasts from people with 1000's of posts and races off to stock up on supplies.

b> The grizzled member who's suffered more letdowns than (s)he'd care to remember reads all these cold winter forecasts and thinks "Oh, here we go again".

Edited October 9, 2006 by The Enforcer

[West is Best]

Morning Richard.

May I ask where you are getting the return of the full blown atlantic from??

http://www.wetterzentrale.de/pics/Rtavn1441.png

http://www.wetterzentrale.de/pics/Rtavn2641.png

As for the chances of a cold winter becoming rarer with each passing year may I ask you what would happen if the factor's that made the 90's so mild were reversed in the next few year's. GW is only a tiny part of the reason why the winter's since the 80's have been so mild and it look's to me the other reasons are on the change.

So you are resorting to the tendency of which Steve Murr accused me in the summer i.e. arguing current synoptic patterns on the basis of future model output charts ...!

I don't know what next week will bring, but I do know we're in prevailing south-westerlies off the Atlantic at the moment. I'll agree with Keving to remove for the time being the two words 'full-blown' for the reasons he cites (and Ian Brown), but this is certainly Atlantic dominated at the moment for the UK, and has been for some time. Doesn't mean blocking won't return, but let's not pretend it's there now.

As for your comment on AGW, I think you exaggerate when you write that it's only 'a tiny influence' on recent UK winters. I think it has almost certainly had a huge impact both synoptically and in actual baseline temperatures here, in Europe, in the Arctic and in Siberia.

To put a bit of persepctive into this, whilst the Atlantic is hardly a full blown conveyor this autumn, I find the inference that the weather this autumn has not been Atlantic dominated rather bizarre. We haven't had any northerlies or easterlies for weeks, all the surface activity has been from the S and W, and recent temperatures reflect that. Something more settled during October / November is not that unusual, whether it's warm or cool depends on precisely where any HP develops.

Spot on ... as usual.

August didn't seem poor it WAS poor! ... The garden was proof of this because as you may remember the pic's on my sig used to show the brown dead grass of July which was changed into a lovely lush green within a couple of weeks in August.

I'm delighted to see Dave that you are using such tried and trusted quantifiable tests as the grasses of Peterborough. For the one who brought us the Bn'Q winter wallchart it would be disappointing to find anything else. Next time the Hadley CET differs from your lawn we must remember to write and correct them.

Edited October 9, 2006 by West is Best

[Stratos Ferric]

...I'm delighted to see Dave that you are using such tried and trusted quantifiable tests as the grasses of Peterborough. For the one who brought us the Bn'Q winter wallchart it would be disappointing to find anything else. Next time the Hadley CET differs from your lawn we must remember to write and correct them.

Whilst I know you're being firmly tongue in cheek, that last comment made me laugh. Perhaps we need to start a sticky thread for "new science". The grasses of Peterborough...classic.

Edited October 9, 2006 by Stratos Ferric

[acbrixton]

Now that Richard (WIB) has conceded regarding the exagerated term "full blown" it is worth pointing out that he never mentioned "zonality" which indeed has beem weak/lacking recently with eastern blocking. However as we have seen recently some quite high rainfall totals (especially in eastern areas most affected by that block) can result from a moderately awakened Atlantic whose attendant fronts' progress is slowed by the eastern blocking. The mention by SF of southerly and westerly wind predominance (as opposed to south west/north west) back that up as depressions have either tended to die out in the North Sea or be forced north rather than north east by the block).

Bit mean to attack TEITS whose point was the dullish and pretty wet nature of the month of August in the east as opposed to a discussion of the CET...

Regards

ACB

[nick sussex]

In response to Enforcers post who has suffered more snow let downs than you can shake a stick at! I agree with lots of that, however I think the words hope springs eternal come to mind for many on here who like the cold and snow.

I suppose one could find just as many reasons why the winter would be mild aswell as cold but being as that alot of people on here like the cold and snow during winter then I suppose we all suffer to a certain degree of selective hearing, hear the good stuff ignore the bad!

Where is the fun and interest in finding every possible milder outcome when we all realize that the status quo in the UK is by and large crappy mild winters with hardly any snow anyway.

Of course good discussion should cover the possibilities of both scenarios but wheres the interest in seeking the mild option when its normally the case anyway. More than likely this will be another snowless winter for many but on the other hand it might not. I'm afraid its just human nature that people trend towards what they want to happen even if its the longshot. Half the fun is the journey along the way, ie: the discussions on here, the humour, all the people holding their breath for the next installment of the gfs rollercoaster! so even if the journey ends up at the wrong station no harm done and no ones died!

[West is Best]

Now that Richard (WIB) has conceded regarding the exagerated term "full blown"

It was a conciliar moment Andrew! I decided that even though down here we have been battered by south-westerlies for several weeks, the fact that some of the low pressure centres haven't made it all the way across to Scandinavia required a less parochial approach. hence: 'Atlantic', yes but 'full blown', no.

In many ways the current situation is the worst possible set up for winter lovers, giving neither true easterlies nor meridionality. But it won't last like this. Either the eastern high pressure will yield allowing 'full blown' zonality (my current preference) or easterlies will strike back.

In the meantime we can look forward to further warm records.

Perhaps we need to start a sticky thread for "new science".

An excellent idea! The new sciences come to the fore around this time of year, and are much in evidence on the various threads.

[BLAST FROM THE PAST]

Now that Richard (WIB) has conceded regarding the exagerated term "full blown" it is worth pointing out that he never mentioned "zonality" which indeed has beem weak/lacking recently with eastern blocking.

Regards

ACB

ACB

Yes he does mean 'zoneality' read the coldest winter in 30 years thread

Quote WIB

Since September blocking has given way to the thoroughly familiar thumping Atlantic, and we're back in a full-blown extremely mild zonality.

West we are not in zoneality...simple IB post 'should' put that to bed

BFTP

Edited October 9, 2006 by BLAST FROM THE PAST

[TEITS]

I'm delighted to see Dave that you are using such tried and trusted quantifiable tests as the grasses of Peterborough. For the one who brought us the Bn'Q winter wallchart it would be disappointing to find anything else. Next time the Hadley CET differs from your lawn we must remember to write and correct them.

A very good idea :lol: .

My main point im making about August is that for my location it wouldn't of mattered if the temps were +25C it was a very dull/wet month and very disappointing.

[acbrixton]

ACB

Yes he does mean 'zoneality' read the coldest winter in 30 years thread

Quote WIB :lol:

Since September blocking has given way to the thoroughly familiar thumping Atlantic, and we're back in a full-blown extremely mild zonality.

West we are not in zoneality...simple IB post 'should' put that to bed

BFTP

True: but I had simply commented on the argument on this thread. I would not agree with "full-blown zone zoneality" as a current description and nor clearly does Richard now in his subsequent post dealing with my post as he sees it a possible/likely future development.

I certainly agree we face yet another month with the CET noteably above normal although I cannot see last October's levels (CET 13.1 from memory) reached on the basis that:

1. In a weeks time my guesstimate for the CET would be about 14c at most (approximately 2c above the average of 12c for the first half of the month)

2. the second half of what is the most rapidly cooling month would have to show a remarkable positive anomaly of 3.9 from an average of 8.3 in the second half to an actual figure of 12.2 to bring the average back to 13.1.

I have not checked the figures yet (literally scrawled out on the back of a fag packet)...

Please feel free to correct!

Regards

ACB

[AtlanticFlamethrower]

A little bit of a generalisation and partially true.

In our latitude the response is generally baroclinic or shallow because wind moves the air away before any deep heating from the warm water can take place (this may not be true mid winter). This according to Lindzen and Nigam would give troughing over a warm anomaly. Yet this is not quite what happens and the response in the north Atlantic seems to be high pressure to the north west and low pressure to the south east of a warm anomaly and this is much more in line with the updated research by Frankignoul. What we should expect according to literatures is for winds to tend to blow easterly across warm anomalies. In this respect we should expect ridging to the north of a warm anomaly.

ATMOSPHERIC GCM RESPONSE TO EXTRATROPICAL SST ANOMALIES:

SYNTHESIS AND EVALUATION (Peng et al) The patterns of wintertime (December-March), anomalous SST, ocean-to-atmosphere turbulent heat flux (latent plus sensible), and surface wind vectors, associated (via linear regression) with the leading principal component of SST variability in the North Atlantic (a and c) and North Pacific (b and d). Panels a and b are for observations from 1949 to 1999 (data for from NCEPNCAR CDAS-1, Reanalysis). Panels c and d are for the mean of a 10-member ensemble GCM integrations forced with global, time-varying SST anomalies from 1950 to 1999 ECHAM 3.5 GCM data provided by Lisa Goddard, IRI). Heat fluxes are in Wm-2 with positive/negative values in solid/dashed contours every 3 and a thick zero contour. Arrows depict the wind vectors in ms-1 with scales shown in lower left (panel a, c) and upper right (Panel b, d). The SST anomaly values, in °C, are denoted in colors according to scale (note that scale is kept at the –0.5 to 0.5 °C range for overall clarity, however, values in eastern equatorial Pacific extend up to 1.2 °C).

Warm anomalies also tend to move north west with time so looking at current SST anomalies we should expect to see High pressure over greenland and low pressure in the central Atlantic which with time should equate to Icelandic or Scandinavian high by winter time. In between and we might expect an increasingly stormy time. This is all theory and the response to SST anomalies is notorious for changing during mid winter and I can not help feeling high pressure and easterly winds are likely to be too far north.

Thank you, and very interesting; it has advanced my knowledge. A very interesting chart. I do not totally understand what baroclinic/trophic means but if warm anomalies don't mean high pressure (or high pressure to the north of the warm anomaly) we can say they "stastically", favour Easterlies (as the Peng et al chart shows).

North Sea and NE Atlantic warm anomalies therefore, "stastically", should favour Easterlies over the UK. Will there be a cold pool?

SST map for OCT and DEC 2005 suggests a much weaker signal for Easterlies over the UK. Warm anomaly actually increased for FEB 2006 and we know what happened next

(SST Map 2 months later) :lol:

[Thundery wintry showers]

I tend to think TEITS has a point about August; I think temperatures are overrated when it comes to people's perceptions of a month. For example, Mays 2001 and 2004 were generally better received than May 1999 was, yet May 1999 was the warmest of the three. Sunshine and rainfall amounts are also important, and August 2006 was widely the dullest since the 1980s.

I can understand the desire for a cold October, mainly because of the positive SST anomalies, which need a bit of a cooling-off. It's all very well me getting excited about possible thundery wintry showers caused by strong airmass-SST temperature gradients, but that's a fat lot of good if the showers are of rain to begin with.

[Mark Bayley]

Colder winter?

If the trend towards blocking areas of high pressure building to the north of the UK does become established, this winter could turn out to be one of the coldest of the last 30 years.

[WhiteFox]

Now that Richard (WIB) has conceded regarding the exagerated term "full blown" it is worth pointing out that he never mentioned "zonality" which indeed has beem weak/lacking recently with eastern blocking.

Perhaps a re-definition of terms?

Zonality = Conveyer of Low pressures from West to East.

Atlantic Dominated = Winds predominately from the West, particularly South-West to West.

As for the coming winter, if you get sick of wonting winter, then move. I'm looking forward to this winter for the first time in many years. Of course, that is assuming that we don't get three equivalents of last January...