Autumn And Winter

[blitzen]

That December chart looks too good to be true as the saying goes with an average temperature that is 4C below the long term average. It does look odd how in December the Northern Hemisphere suddenly is covered in an average of -6C anomalies with large areas having -16C anomalies. The November and October charts look normal whereas December looks like the beggining of a new ice age.

Take your seats ladies and gentlemen (with the popcorn!) when Daniel reads this we will be in for an epic "I told you so." and when SF reads what Daniel posts his reply will be rib-ticklingly funny. Honestly this is more entertaining than the Oscars!

[Dawlish]

Take your seats ladies and gentlemen (with the popcorn!) when Daniel reads this we will be in for an epic "I told you so." and when SF reads what Daniel posts his reply will be rib-ticklingly funny. Honestly this is more entertaining than the Oscars!

Completely potty.

The chances of this winter being colder than average are about 20% The chances of it being warmer than average are about 70%.

Since 1990, this percentage of warm as opposed to cold has actually been exceeded. There is nothing, apart from some highly iffy LRFs, that indicate anything different, The Met office reckon it will be a milder than average winter, but, quite frankly, I don't actually believe them either. Long-range forecasting is not good enough to predict the coming winter.

I can't see why on earth people who are desperate for a cold winter get all stirred up about this when, actually........no one knows. You are hope-casting. No more.

Damien; you really must qualify these, quite ridiculous assertions that you make that there is actually evidence for people to believe a cold winter is in the offing. It may be; but the odds are well in favour of it not being colder than average. I'd trust them.

Paul

[Damien]

Thanks for some interesting comments on the above guys.

It does rather give the impression of a disillusioned temp messing with the input data on their last day in the office. I think that chart is stretching the bounds of possibility a little to the extent that if I owned the data set I'm not sure I'd have published it; there is a common sense rule we tend to use about looking at the numbers just to see whether they seem plausible, and if they don't double checking the analysis. However, assuming that the source of these runs IS that rigorous, then it's an interesting looking data set. I can only assume that either a meteor strike is due or else the lid is ablut to blow off Iceland in a rather spectacular Reykjavik flattening sort of a way. I'd file it under "one to watch with amused interest" rather than "one to get excited about" at present.

In the run up to I think it was either winter 2003/04 or winter 2004/05 (I forget which one) the ECPC run for Europe quite consistently showed a long cold easterly stretching from St. Petersburg to Dublin beginning in either the first week of November or December, I can't remember which one. This was there for 6 weeks before being replaced with much milder conditions when the week came into the more *reasonable* range. Needless to say I was not happy! This however is blatantly bigger - but yes we need this chart to be at the VERY least 4 weeks away before we even START to consider what it may mean: never mind 4 months!

But Stratos this is a very important point: this week this forecast service (ECPC) release a "dynamic" NOAA-style LRF covering winter, probably around Friday. The last three runs have shown the winter to be significantly milder than average, and I had a feeling they would do so again - until I saw (and compared) these charts. If however - as I both fear and suspect - the *other* ECPC run (the aforementioned dynamic model) is based on other such data - such as separate (or inclusive) model runs, satellite data, human input, warming and other trends, etc. - then it will as I suspect show mild once again at this crucial stage for our winter prospects.

Take your seats ladies and gentlemen (with the popcorn!) when Daniel reads this we will be in for an epic "I told you so." and when SF reads what Daniel posts his reply will be rib-ticklingly funny. Honestly this is more entertaining than the Oscars!

Sorry, he's read it - and he'll probably be back anytime.

Edited September 3, 2006 by Damien

[Damien]

It may be; but the odds are well in favour of it not being colder than average. I'd trust them.

Do these odds include the continuing blocking period (easily comparable to the mid-1990s IMHO - although we have not yet really had the chance to see (AGW theory permitting) the fruits of the sun's lack of labour in the wintertime); the early cooling down over the Arctic; the cooling trend of recent winters in Central and even parts of Western Europe (though I acknowledge that this can suddenly end anytime - as winter 1997/into 1998 showed).

(And yes I am aware of the ENSO, warming, demographic trend, LRF, NAO, ice, and other situations. ( ))

Edited September 3, 2006 by Damien

[SMU]

Completely potty.

The chances of this winter being colder than average are about 20% The chances of it being warmer than average are about 70%.

Since 1990, this percentage of warm as opposed to cold has actually been exceeded. There is nothing, apart from some highly iffy LRFs, that indicate anything different, The Met office reckon it will be a milder than average winter, but, quite frankly, I don't actually believe them either. Long-range forecasting is not good enough to predict the coming winter.

I can't see why on earth people who are desperate for a cold winter get all stirred up about this when, actually........no one knows. You are hope-casting. No more.

Damien; you really must qualify these, quite ridiculous assertions that you make that there is actually evidence for people to believe a cold winter is in the offing. It may be; but the odds are well in favour of it not being colder than average. I'd trust them.

Paul

Whilst the form horse would be an above average Winter we are in a period of Change & at these times historics become 'LESS' important-

Could you post a link to the Met office saying it will be a milder Winter- I wanted to know if was from their NAO model or general forecast as they run 2-

As I mentioned before - whilst the ACTUAL anomalies from the ECPC graphs look a bit iffy to say the least the regions they are pointing towards in terms of cold are pretty much what is the 'Educated view' from what I believe & also what I gather from reading some of the more professional posts from a another forum-

regards

Steve

[beng]

Could you post a link to the Met office saying it will be a milder Winter- I wanted to know if was from their NAO model or general forecast as they run 2-

http://www.metoffice.com/corporate/pressof...pr20060710.html

based on their NAO forecast.

[Damien]

Could you post a link to the Met office saying it will be a milder Winter- I wanted to know if was from their NAO model or general forecast as they run 2-

As I mentioned before - whilst the ACTUAL anomalies from the ECPC graphs look a bit iffy to say the least the regions they are pointing towards in terms of cold are pretty much what is the 'Educated view' from what I believe & also what I gather from reading some of the more professional posts from a another forum-

Steve, I'm gonna post both the current MetO dynamic forecast for winter and the latest ECPC one also for December so we can compare the two, principally to look at the cold and milder regions in the Northern Hemisphere.

Stick around....

Edited September 3, 2006 by Damien

[Roger J Smith]

I think there's a rational explanation for the week 13-16 map and its improbable anomaly patterns.

Somebody forgot to remove the actuals from week 9-12 so the n.h. anomalies are adding in the temp difference between Nov and Dec which is about 6-8 C degrees in many continental climates.

Meanwhile, land areas of the s.h. appear warmer than they should because December there is warmer than November.

In other words, sack the quality control guy.

As for an actual forecast for the UK from yours truly (speaking of the sack), my preliminary call subject to revision before the cut-off date is

December -- mild, perhaps very mild

January -- turning a lot colder and then becoming variable, overall about 1 below average

February -- cold tending to fade out mid-month with milder conditions returning.

Overall this gives a slightly above normal seasonal forecast but a good chance for some real winter weather as the coldest period is due when averages are lowest, 15 Jan to 15 Feb, and hopefully this time it won't be just a bunch of near misses and localized events but some more meaty winter-like weather to feast on.

[Damien]

UKMO vs. ECPC.

Round 1!

In the red corner, we have the Met Office dynamic forecast for the period November-December-January (NDJ):

Methodology.

And in the blue corner, we have the latest global GMS run from ECPC, covering the period November 25, 2006-December 23, 2006:

Methodology.

[Glacier Point]

Re: the potential long term pattern shift, February 2005 onwards....

February 2005 marked the beginning of what many members would consider as a significant change to our weather patterns. Some reanalysis which might prove of interest here, particularly in terms of what it might mean as our thoughts turn to winter.

500 hPa geopotential height anomalies

Clear evidence of +ve height anomalies (over the period January 2004 to present) existed over much of the mid and high latitudes of the northern hemisphere. This is akin to a cool or negative phase of the Arctic Oscillation. This essentially explains a period of high latitude blocking with notable anomalies across the southern tip of Greenland.

http://www.jisao.washington.edu/ao/

200 hPa zonal wind anomalies

Note here the negative (weaker than normal) flow over the normal track of the polar jet across the Atlantic towards the UK and the +ve anomalies towards Greenland supporting the theory of a poleward shift in the jet. But, note also the strong +ve anomalies for the sub-tropical flow across the Atlantic most probably related to weaker stratoshpheric pressure in the Atlantic (and a -ve phase Arctic Oscillation) and possibly sea surface temperature anomalies across the northern Atlantic.

200 hPa meridional wind anomalies

Note the strong +ve anomalies indicating greater ridge activity in the mid-Atlantic, certainly confirming a blocked period of weather across the mid-latitudes in western Europe and no doubt key factor in 18 months of low precipitation.

Sea surface temperature anomalies (SSTA) and air temperature anomalies

Note here the relative warmth of the Pacific and North Atlantics, but also the incredible warmth of the pole.

So why does this matter ? Well, it could just be that this reanalysis just paints a very good illustration of what a -ve Arctic Oscillation phase looks like - there have after all been many such instances.

This could be put down to an isolated period but consider this, taking the 18 month period from February to August as a rolling mean, we have just experienced 11 out of the last 18 months with a -ve sign Arctic Oscillation (assuming August's return is a -ve). This is marginally greater than the 1950 - 2006 rolling average for the period Feb - August (10.2).

However, this is considerably greater than any period experienced during the 1970s, 1980s and the 1990s. In fact the 2000s have a rolling average of 10.2 and this places it on a par with the 1960s in terms of decadal comparisons for the same period (1960s = 10.4 months with -ve sign Arctic Oscillation).

There are a number of influences on stratospheric pressure - temperature of the upper layers being the key one. There is however some growing suggestion that mid and upper level tropospheric temperatures also exert an influence 'from below'. This is logical given that a warmed column of air will occupy a larger volume than cooler air and this may be seen to good effect during the mid and late summer period of 2006 where warming of the lower and mid troposphere around the pole lead to positive 500 hPa geopotential heights and a -ve Arctic Oscillation phase:

http://www.cpc.ncep.noaa.gov/products/prec...hgt.ao.cdas.gif

Now consider if we continue to observe strong warming of the poles way in excess of that around the sub-tropics (with some evidence that the strong sub-tropical jet flow will continue to prevent warming of sea surfaces at mid and low latitudes), there is the potential for warming to predispose the polar region to +ve height anomalies and a greater frequency of -ve Arctic Oscillation phases.

Negative Arctic Oscillation anomalies during the winter look like this:

http://www.cpc.ncep.noaa.gov/research_pape...DJF.z500.ao.gif

…with a strong sub-topical jet and blocking over Greenland in evidence - the ideal synoptics for winter cold for the UK, albeit moderated somewhat by elevated global temperatures.

Before we reach for the domesday comparisons, the sample comparison is just 3/5ths of the way through so we cannot draw any meaningful conclusions just yet but statistically this gives some weight to the theory of a long term pattern change delivering more continental type weather for the UK with colder winters and warmer summers.

What about this summer ? Why did we observe the second strongest +ve Oscillation phase in the last 56 years during June? Well I think here there was something of a 'bounce' factor going on. By this I mean that the sudden warming of the tropics and mid-latitudes during May (following on the back of a big stratospheric cooling event) coupled with a large amount of cold air at the pole lead to a large differential in stratospheric pressure over the Atlantic leading to strong westerly's which were modified by the underlying meridional flow to sustain more of a southerly wind flow.

The real test for this theory is during January. This is a month more typically associated with -ve phase Arctic Oscillation conditions

http://www.cpc.ncep.noaa.gov/research_pape...DJF.z500.ao.gif

yet we have struggled over the last twenty years or so to achieve this on a consistent basis - potentially the amount of energy in the system is the likely spoiler here and the reanalysis of zonal wind flow is horribly reminiscent of January's past.

The next couple of years should help us conclude one way or another whether the warming of our climate will accelerate or whether there will be some surprising and often perverse reactions related to massive distortions in the stratosphere.

GP

[John Cox]

Hi GP,

Quality post as usual and underpins the possibble reasons why what a lot of us on NW have said is happening for the last 18 months. As you say this winter will be a telling one.

[johnholmes]

superb post as usual GP with plenty of evidence to back up your points. We look forward to this winter with interest to see how it pans out.

John

[carinthian]

Hi GP,

Quality post as usual and underpins the possibble reasons why what a lot of us on NW have said is happening for the last 18 months. As you say this winter will be a telling one.

Hi,

A lot of research and interesting dccumentation from GP latest post. We may be a long way from the "6th Winter Scenario" , but another winter of negative AO will allow anticyclone extention to influence our weather type in the British Isles to become more "polar continental" as GP suggests. The polar limit of the westerlies is driven nearer and nearer to the limit of the trades, the pressure gradient becomes steeper and who knows what could happen ?

C

[VillagePlank]

Great post GP

[BrickFielder]

Great post by GP as usual and I think I would go along with the idea that there was a pattern change around February 2005. I am not so sure about the source of the change and indeed whether there was a further pattern change towards the end of July.

It looks as if AO is linked to the strength of the polar vortex in the stratosphere which in turn is affected by conditions in the upper troposphere. Specifically rossby waves seem to affect the vortex and one of the main triggers for rossby waves is ENSO. There is no clear link between the AO index and the ENSO index but it does look as if cooling water off the coast of south america (end of el nino and start of la nina) may be linked to a negative AO. This suggests that there might be a possibility that ENSO conditions changing with water warming might lead to a more positive AO. I would contend that where we have had one pattern change we may have had another very recently and would wait a while to see how things play out before suggesting we are likely to have a very blocked pattern with easterlies this winter.

[Damien]

The latest from Mr. Mallett:

http://www.btinternet.com/~highdown/

November is the headline, expected to be at -0.6°C below average in the latest run. September is still expected to be +5°C above average and October -10°C below average - so no change from previous years there then.

That said he said that last October would return a CET of about 9.3°C (which is also about 10°C below average), and what happened at the end of the month? :blush:

Edited September 4, 2006 by Damien

[Snowly does it]

Going back to yesterdays conversation regarding an old wives forecast, would there be some advantage to having a thread here dedicated to weather lore? Having people post their lore and their observations will permit an old crone such as myself to conjure up a forecast based solely on natural observations that could be updated at the end of Sept, Oct and then finally November, it also lays open the 'evidence' used for anyone to look at. As I said, its really just for the purposes of experimentation, it will be interesting to see where a forecast based on weather lore ranks against the MetO, forecasters here and other places and it can be repeated for next years seasons. If its reasonable, I can start a thread, if its not I'll just continue to incant silently and with a mischievous look in my eye on the qt.

[Anti-Mild]

If I remember there was a dedicated thread on the subject last year over in Science and Nature. My advice; start one up and see what happens :blush: !

[The Eagle]

UKMO vs. ECPC.

Round 1!

In the red corner, we have the Met Office dynamic forecast for the period November-December-January (NDJ):

Methodology.

And in the blue corner, we have the latest global GMS run from ECPC, covering the period November 25, 2006-December 23, 2006:

Methodology.

Interesting contrasts there Damien. The Metoffice outlook, I must say, looks far more credible to me then the ECPC outlook (which is below average practically right across the Northern Hemisphere). My own instinct is (and I have not looked into it in any detail yet) that this may be an average Winter, with below average rainfall and average temperatures. I will gather my thoughts and explain my reasoning soon enough. Its interesting to see the conflicting views amongst various organisations. It only complicates things but either way someone is wrong. Indeed if we do end up average they will both be wrong and that would be a step back from the UKMO's superb call last Winter. Since it they only go to January it would be hard to characterise an entire Winter on those charts. :blush:

Edited September 4, 2006 by Icicles

[tinybill]

Going back to yesterdays conversation regarding an old wives forecast, would there be some advantage to having a thread here dedicated to weather lore? Having people post their lore and their observations will permit an old crone such as myself to conjure up a forecast based solely on natural observations that could be updated at the end of Sept, Oct and then finally November, it also lays open the 'evidence' used for anyone to look at. As I said, its really just for the purposes of experimentation, it will be interesting to see where a forecast based on weather lore ranks against the MetO, forecasters here and other places and it can be repeated for next years seasons. If its reasonable, I can start a thread, if its not I'll just continue to incant silently and with a mischievous look in my eye on the qt.

all i say is this year winter weather is looking miles better, tress full of berries, plus there i hope no nastry things being in the wong place, to give us a loverly cold and snow bound winter for a change!!!!! :blush:

[Anti-Mild]

I would tentatively suggest that the offering from ECPC is like that because of a glitch in their system. I would further suggest, although I could be wrong, that it would surely be practically impossible for the entire N.Hemisphere to be below average.

[Snowly does it]

I would tentatively suggest that the offering from ECPC is like that because of a glitch in their system. I would further suggest, although I could be wrong, that it would surely be practically impossible for the entire N.Hemisphere to be below average.

Be fair A-M, a small section of the Aleutian Islands is positively baking!

[The Eagle]

I would tentatively suggest that the offering from ECPC is like that because of a glitch in their system. I would further suggest, although I could be wrong, that it would surely be practically impossible for the entire N.Hemisphere to be below average.

Thats exactly what im thinking. :blush:

Also the relatively warm SST anomally's currently in the Atlantic. Ultimatley less blocking this year perhaps??

Edited September 4, 2006 by Icicles

[Anti-Mild]

Be fair A-M, a small section of the Aleutian Islands is positively baking!

:blush: Thanks sm, I almost missed that one. No doubt the Aleutian Times will be jam-packed with GW stories after seeing that output !

[Dawlish]

OK.

GP. A terrific piece of postulation, superbly and engagingly written and underpinned by some excellent knowledge. Thank you. It is a piece that could only be written by someone with talent and understanding of a wide range of meteorological principles and there interrelations. No wonder, as a result of it, the comments from the cold-wishers are so complimentary. It gives them the straw that they wish to grab for.

Much as I love the writing (and I do) your piece is no more than speculation. No better, as a piece of accurate predictive science as me saying "it will probably be a milder than average winter". Indeed, your long, complex and erudite piece, which is hugely enjoyable to read, has, probably, much less chance of coming true than those 9 simple words.

There is nothing and nobody that can predict 3 months+ in advance with accuracy. Not even NOAA, with all its resources manages even a reasonable predictive record. The UKMO manages 2 out of 3 correct, on a short dataset, with a "fairly weak" correlation of only 0.45.

The "many" people who really feel there has been a "pattern change" on netweather, in the last 18 months, are those who wish there to be a pattern change. Globally, nearly every single month that goes by gets into the top 10 respective warmest months. In the face of such constant evidence of warming, it must be so difficult to close one's eyes to this and believe that the UK will somehow not be affected by this warmth and that we are undergoing a "pattern change" that will bring the back towards the snowier, colder winters that would satiate the desires of the cold-wishers, while the rest of the world continues to warm. Some realism is desperately needed.

There will still be colder winters than average, in the UK, but the years between them have got longer and will continue to get longer, as the planet continues to warm. This year could be one of those colder ones. I rather hope that GP's analysis is correct and his analyses are correct over the next few summers and winters as it would give me hope that progress may be being made in the field of LRF, by using patterns, measurements and synoptics that exist months before the coming season.

The realism that I'd like to bring to this is underpinned by the statistic that over 70% of all uK months, since 1990, have been warmer than average and the world is continuing to warm. Globally, the percentage of warmer months than the global average, since 1990 has been even higher. There is no evidence whatsoever that this warming has stalled and none that it has reversed.........so how can people believe so easily that we are on the cusp of a change????

The reason is simple.............Hope. No more, no less. The argument for a change to a colder pattern is underpinned by hope. It is manifested by an almost deperate need for it to happen and a willingness to believe anything, or anyone, that will tell the cold-wisher that there is a chance that what they are hoping for will actually come true.

Based on the last 16 years, ie 192 months; every month that goes by has at least a 70% chance of being warmer that the long-term Manley average temp, about a 10% chance of being close to the average and a 20% chance of being colder than the average. That last % is the % I've been using to predict the severity of winters since 1990 and may well, now, be conservative, in the light of what has actually happened. I'm not changing it yet, but if we don't get a colder winter than average in the next 4 years, I may change the possible chance of a colder than average winter to 10%.

Dispiriting, cold-wishers, I know, but cold realism.

Paul

Edited September 4, 2006 by Dawlish