Winter 2012 / 2013 Part 2

[feb1991blizzard]

I know this thread is for folk to have lots of fun but to those who may venture in here expecting some sensible comments about what may happen-forget it.

No one, no machine can predict the weather more accurately for 3 months ahead than the toss of a coin at the moment. 6 weeks in advance maybe to get more than an evens chance of being correct.

If you accept that then enjoy the fun.

I accept that 3 month forecasts are still at the experimental stage but GP's forecast for the last few winters have been really good, still a lot more research required of course but my bugbear is that the same organisation that stopped doing 3 month forecasts because they were inaccurate, tell us that in 100 years time we will be experiencing very mild winters.

[gottolovethisweather]

Where's the problem, Fred. Both natural and manmade signals are (almost) universally accepted...

I repeat.

Is this the Winter 2012/13 discussion thread?

Edited October 2, 2012 by gottolovethisweather

[gottolovethisweather]

Its impressive that you are looking through individual ensemble members in early October.

This activity does not normally become apparent until well into winter!

Sorry Cloud 10, I think you'll find that was me, however I do feel some signals are looking favourable for a colder October than we have been accustomed to, in many a recent year.

[Cloud 10]

Sorry Cloud 10, I think you'll find that was me, however I do feel some signals are looking favourable for a colder October than we have been accustomed to, in many a recent year.

I was referring to the post from BFTV

http://forum.netweat...20#entry2376628

Its inspiring to see such dedication.

[UV-RAY]

Where's the problem, Fred? Both natural and manmade signals are (almost) universally accepted...

Errrr, not always RP, some believe manmade signals are just, well manmade. Controversial in some circles I know.

Edit; Apologies to GLTW.

Edited October 2, 2012 by Seven of Nine

[gottolovethisweather]

This sounds quite hopeful, courtesy of GP.

http://forum.netweather.tv/topic/74600-model-output-discussion-october-2012/page__st__20#entry2376727

[bobbydog]

Straight away I'm not liking the report with htis para

The new cycle, called the Pacific Centennial Oscillation, was reported in the September 2012 issue of Journal of Climate. It provides a deeper understanding of how natural cycles may interact with manmade global warming to produce far-reaching climate impacts emanating from the Pacific region.

BFTP

the 'global warming' angle seems to have been thrown in as an afterthought. the study itself is quite interesting.

one for the pot?- http://forum.netweather.tv/topic/74566-the-hunt-for-white-december/

[BornFromTheVoid]

I posted this in the "Hunt for White December" thread, but here's a copy for those interested in here.

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Thought I'd best get this one finished before I start back in Uni tomorrow. This post turned out much longer than I'd anticipated, so apologies for that!

In this piece, I'm going (to attempt) to have a look at the relationship between Arctic Sea Ice Extent/Area and the usual Winter CET.

A little on Arctic sea ice.

The Arctic sea ice growths to a maximum extent (ocean surface covered by at least 15% ice) of around 16 million km2 each March before reducing to an average of 6 million km2 in September. In recent years, the maximum has declined by a small amount (Figure 1) while the minimum has been experiencing an accelerating decline (Figure 2)

Fig 1: Arctic Sea Ice Extent Maxima from 1979-2012

Average... 79-00... 15.9 million km2

Average... 01-07... 15.2 million km2

Average... 08-12... 15.1 million km2

Fig 2: Arctic Sea Ice Extent Minima from 1979-2012

Average... 79-00... 6.7 million km2

Average... 01-07... 5.6 million km2

Average... 08-12... 4.4 million km2

The rapid loss during for the minima is what most likely influences the weather. As the sea ice (especially when covered in snow) has a very high albedo (reflectivity), the sunlight during the 24 hours in summer is mostly reflected back into space. In recent years the, the ice has been reduced by several million km2, allowing large portions of the Arctic Ocean (which has a very low albedo) to absorb that solar energy and accumulate a lot of heat (which melts the ice even more).

When the Arctic enters Autumn and the air begins too cool, the energy which has built up in the ocean surface gets released into the air as heat, causing very large +ve surface air temperature anomalies in Autumn and early winter (Figure 3).

Fig 3: Surface Air Temperature for Sep 1st to Oct 31st, 2007-2011

This warming has several possible ways it can effect the weather in the northern hemisphere mid-latitudes.

(i) The increase air temperature causes the air to expand upward, increasing the 500mb geopotential height during Autumn and Winter. This reduced the meridional (south to north) atmospheric thickness gradient, which causes the jet stream to have much higher amplitude waves and move slower. This causes slow moving or "stuck" weather patterns, as well as the higher amplitude waves carrying warmer air further north, and colder air further south than normal.

More details can be found in the study by Francis and Vavrus here

(ii)Another possible mechanism, relates again to the increased air temperatures in the Arctic and Siberian Autumn snow cover. The rate of increase of Siberian snow cover south of 60N (the SAI) during October is strongly related the the AO phase in winter. As you can see in figure 3, most of the very high temperature anomalies occur along the Eurasian coastline area, where the ice has melted back. This access to newly open ocean will allow the atmosphere to hold much more moisture, but the +ve temperature anomaly may be enough to reduce snowfall in September and early October, Later in October, while the air will still be milder and more moist than usual, the temperature may be low enough anyway to allow for snow to fall, causing a rapid increase in snow cover during October, giving a high SAI value, resulting in a -ve AO pattern later in Winter.

More details and the possible mechanisms for the SAI/Siberian snow cover and AO link can be found in these papers

http://web.mit.edu/j...dsetal_JC12.pdf

http://web.mit.edu/j...Jones_GRL11.pdf

http://web.mit.edu/j...henetal2007.pdf

Despite the above, there are several issues with with correlating sea ice changes and winter weather here. The main one is the short number of year. Consistent very reliable sea ice data only spans from 1979 to present, which doesn't offer up a long time for comparisons. Included with that, is the fact that the sea ice may only have reduced enough in the last decade for the mechanism described earlier to become clear, leaving even less time for correlation. We also have to consider the moderating influence of the open ocean, especially to the north and north west of Scandinavia. With so little time, the interference of the -ve PDO and the low solar activity, there is a lot of noise in the data, but I'll give the correlations a go anyway!

Right so. To take away the warming of the CET since 1979, the temperature data was detrended. Now I used the NSIDC sea ice extent data in the links in the opening post of this thread. From that, I used the September minimum extent to correlated with the winter CET.

The first correlation (Sea ice minimum with detrended winter CET), gave a weak but positive correlation of +0.13 (more ice=higher CET), which isn't statistically significant though, given only 33 years to compare with. Below is a graph of the Winter CET detrended and the sea ice extent minima.

All averages and lags I tried made the correlation even lower than +0.13. Correlations just using 10 and 15 year groupings did improve the correlation, especially before 1998 (the 1987-1996 correlation was +0.65, but still not passing statistical significance with so few data points.

The one method that did generate a statistically significant correlation, of +0.41 significant at p<0.2, was when I also detrended the sea ice extent minima, and then performed the correlation. The relationship between the 2 can be seen in the graph below.

So it seems there is some relationship present between the SIE minima and the following Winter CET

To see what kind of winter pattern follows low sea ice years, I picked the lowest detrended sea ice years, as well as the lowest without the detrending, and created some composite maps.

Lowest Detrended SIE Minima, 500 hPa Geopotential Height Winter Anomaly

Same as above, but based on actual SIE minima, not detrended

A clear signal for northern blocking on both those charts, but hints at the ridges being centred more towards Scandinavia, suggesting more of a easterly or northeasterly component to the upper flow. Perhaps a signal for a stronger Siberian high pressure extending west into Scandinavia?

[EDIT: For comparison the high sea ice years.

Both with a strongly +ve AO and NAO, the opposite of what you want for a cold winter.]

In conclusion, there does seem to be weak correlation between lower sea ice minima in September and below average winters in the CET zone. With the short timespan available for correlations and the rate of change in the sea ice observed, the strength of the correlation is not as strong as it might be if we had a longer time series. As it is though, it would appear to be another factor that's leaning towards a colder winter for the UK, along with the -ve PDO and weak ENSO signal

Edited October 2, 2012 by BornFromTheVoid

[Glacier Point]

Try it the other way round BFTV on the anomalis - we're looking for the mirror image to confirm the theory ?

[cheeky_monkey]

I posted this in the "Hunt for White December" thread, but here's a copy for those interested in here.

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Thought I'd best get this one finished before I start back in Uni tomorrow. This post turned out much longer than I'd anticipated, so apologies for that!

In this piece, I'm going (to attempt) to have a look at the relationship between Arctic Sea Ice Extent/Area and the usual Winter CET.

A little on Arctic sea ice.

The Arctic sea ice growths to a maximum extent (ocean surface covered by at least 15% ice) of around 16 million km2 each March before reducing to an average of 6 million km2 in September. In recent years, the maximum has declined by a small amount (Figure 1) while the minimum has been experiencing an accelerating decline (Figure 2)

Fig 1: Arctic Sea Ice Extent Maxima from 1979-2012

Average... 79-00... 15.9 million km2

Average... 01-07... 15.2 million km2

Average... 08-12... 15.1 million km2

Fig 2: Arctic Sea Ice Extent Minima from 1979-2012

Average... 79-00... 6.7 million km2

Average... 01-07... 5.6 million km2

Average... 08-12... 4.4 million km2

The rapid loss during for the minima is what most likely influences the weather. As the sea ice (especially when covered in snow) has a very high albedo (reflectivity), the sunlight during the 24 hours in summer is mostly reflected back into space. In recent years the, the ice has been reduced by several million km2, allowing large portions of the Arctic Ocean (which has a very low albedo) to absorb that solar energy and accumulate a lot of heat (which melts the ice even more).

When the Arctic enters Autumn and the air begins too cool, the energy which has built up in the ocean surface gets released into the air as heat, causing very large +ve surface air temperature anomalies in Autumn and early winter (Figure 3).

Fig 3: Surface Air Temperature for Sep 1st to Oct 31st, 2007-2011

This warming has several possible ways it can effect the weather in the northern hemisphere mid-latitudes.

(i) The increase air temperature causes the air to expand upward, increasing the 500mb geopotential height during Autumn and Winter. This reduced the meridional (south to north) atmospheric thickness gradient, which causes the jet stream to have much higher amplitude waves and move slower. This causes slow moving or "stuck" weather patterns, as well as the higher amplitude waves carrying warmer air further north, and colder air further south than normal.

More details can be found in the study by Francis and Vavrus here

(ii)Another possible mechanism, relates again to the increased air temperatures in the Arctic and Siberian Autumn snow cover. The rate of increase of Siberian snow cover south of 60N (the SAI) during October is strongly related the the AO phase in winter. As you can see in figure 3, most of the very high temperature anomalies occur along the Eurasian coastline area, where the ice has melted back. This access to newly open ocean will allow the atmosphere to hold much more moisture, but the +ve temperature anomaly may be enough to reduce snowfall in September and early October, Later in October, while the air will still be milder and more moist than usual, the temperature may be low enough anyway to allow for snow to fall, causing a rapid increase in snow cover during October, giving a high SAI value, resulting in a -ve AO pattern later in Winter.

More details and the possible mechanisms for the SAI/Siberian snow cover and AO link can be found in these papers

http://web.mit.edu/j...dsetal_JC12.pdf

http://web.mit.edu/j...Jones_GRL11.pdf

http://web.mit.edu/j...henetal2007.pdf

Despite the above, there are several issues with with correlating sea ice changes and winter weather here. The main one is the short number of year. Consistent very reliable sea ice data only spans from 1979 to present, which doesn't offer up a long time for comparisons. Included with that, is the fact that the sea ice may only have reduced enough in the last decade for the mechanism described earlier to become clear, leaving even less time for correlation. We also have to consider the moderating influence of the open ocean, especially to the north and north west of Scandinavia. With so little time, the interference of the -ve PDO and the low solar activity, there is a lot of noise in the data, but I'll give the correlations a go anyway!

Right so. To take away the warming of the CET since 1979, the temperature data was detrended. Now I used the NSIDC sea ice extent data in the links in the opening post of this thread. From that, I used the September minimum extent to correlated with the winter CET.

The first correlation (Sea ice minimum with detrended winter CET), gave a weak but positive correlation of +0.13 (more ice=higher CET), which isn't statistically significant though, given only 33 years to compare with. Below is a graph of the Winter CET detrended and the sea ice extent minima.

All averages and lags I tried made the correlation even lower than +0.13. Correlations just using 10 and 15 year groupings did improve the correlation, especially before 1998 (the 1987-1996 correlation was +0.65, but still not passing statistical significance with so few data points.

The one method that did generate a statistically significant correlation, of +0.41 significant at p<0.2, was when I also detrended the sea ice extent minima, and then performed the correlation. The relationship between the 2 can be seen in the graph below.

So it seems there is some relationship present between the SIE minima and the following Winter CET

To see what kind of winter pattern follows low sea ice years, I picked the lowest detrended sea ice years, as well as the lowest without the detrending, and created some composite maps.

Lowest Detrended SIE Minima, 500 hPa Geopotential Height Winter Anomaly

Same as above, but based on actual SIE minima, not detrended

A clear signal for northern blocking on both those charts, but hints at the ridges being centred more towards Scandinavia, suggesting more of a easterly or northeasterly component to the upper flow. Perhaps a signal for a stronger Siberian high pressure extending west into Scandinavia?

In conclusion, there does seem to be weak correlation between lower sea ice minima in September and below average winters in the CET zone. With the short timespan available for correlations and the rate of change in the sea ice observed, the strength of the correlation is not as strong as it might be if we had a longer time series. As it is though, it would appear to be another factor that's leaning towards a colder winter for the UK, along with the -ve PDO and weak ENSO signal

Maybe a better correlation would be to compare sea ice extent with northern hemisphere winter temps rather than just central England winter temps?

[BornFromTheVoid]

Try it the other way round BFTV on the anomalis - we're looking for the mirror image to confirm the theory ?

Do you mean this?

High sea ice years detrended

High sea ice year with trend

[BornFromTheVoid]

Maybe a better correlation would be to compare sea ice extent with northern hemisphere winter temps rather than just central England winter temps?

Northern hemisphere is showing a general increasing trend in temperatures like the rest of the world. Where you got cold outbreaks, it would be balanced by milder weather somewhere else.

When I set out to do this stuff, it was just with the CET in mind. If I find I have time, I might try something similar with European temperatures though...

[Glacier Point]

Evening All-

Nice blog from Matt- very good - to support people learning about the winter factors.

I wanted to put some commentary on what I think she be presented in a winter outlook - this I think correlates to our current level of understanding-

By this I mean we have a lot of teleconnection data coming online & each year another 'fluid' dynamic seems to enter the fray.- I hear a lot of people saying that its the new 'fad'-

Last few years have been the stratosphere & its impacts, this year is arctic ice, in years prior to that was ENSO & the Jet in the Mix- & that old chestnut- the even larger teapot-

Bottom line is this-

Our sample size & dataset is to thin to create a representative analogue.- To create and predict a good match to cover the following-

Arctic Ice,

PDO,

QBO,

ENSO,

Solar flux,

Stratosphere,

Ozone levels

SST

I think we would need at least 500 years worth of consistent reporting data,- even if we rationalise each Variable to a low level tangable rating of Strong, Neutral & Weak signal I bet on all of the above with the data we have you might get one match that had a strong Signal for the winter forecast,

Also with forecasting its about attributing 'weighting' to the signals & their apparent influence to the OVERALL hemispheric pattern-

Im sure with enough data the scientific community could complete an algorithm whereby each signal could be fed in & generate a 'type' of outcome. The current CFS is what we got but sadly its very limited on capability & data capture -

anyway-where we are in 2012 that 500 year dataset doesnt exist so we have to go on the SMALL dataset we have & try to decipher what that means in the mix of other factors-

it ALL boils down to 2 things- which is especially important to the 55 N line around the mid lattitudes-

* Net overall projected anomaly of the mean zonal Wind.- IE- are we facing blocking scenarios or zonal conditions-

* Focal points of where the rossby waves are likely to show the greatest wavelength against the norm & in relashon to that where the zones of strong CAA & WAA are going to be - as these areas will have the biggest +VE & -VE temp anomalies V the norm.

What could & should a Winter forecast offer-

If you are reading about specific events around specific dates then at worst its a hopecast, at best a forecaster has reviewed the historic datelines around winter - in terms of dates that generally have colder periods & so on-

Forget dates & events- We dont have that capability yet to forecast.

A lot of these are sensationalist forecasts & headline grabbers-

Interestingly in the last 10 years how many sensational winter months have we had( in terms of extreme cold temps V the norm- maybe 2 or 3 ( AKA Dec 2010 )- & yet every year we are subjected to forecasts of extreme weather-

Sorry people, we have a run rate of probably 2 in 30 months of severe 'events' but a forecast run rate of 1 in 3-

IE 1 extreme month from every winter forecast from all these people that appear- its laughable.

Where are we at -

If I had the time I would be dividing my forecast into 4 clear sections-

* data & Indices-

Aknowledgment of data used, assumptions made MUST be communicated & clearly indicated in a medium where its clear what type of winter you are expecting-

I wouldnt dwell on this info & spend to long on it as a chunk of this is just available data to cascade & present-

Importantly the most UP TO DATE data is required- therefor a forecast issued prior to November the 15th is not going to be as accurate to the degree as one issued on Nov the 30th as the rate of change that can occur in this time period can be a big influence over the winter- especially with respect to the stratosphere.

* Projected longwave pattern-

Get the 'MEAN' longwave pattern right & your 95% of the way there- Especially when forecasting 'non typical' weather types-

If you go for a flat longwave pattern with minimal waves in the jet you are essentially saying that the weather type & pattern is essentially the norm with minimal variance-

On the 500MB plot for the NH there would be minimal Height anomaly zones-

Vice versa ( & interesting in terms of all these sensational forecasts ) is forecasting waves in the jet for the season- & how that correlates to the UK-

the MAX stationary waves at any one time for the NH is usually 4, however across a season its very unlikely that ALL 4 will show as a strong positive anomaly- its usually just 2 teleconnecting Highs that appear on the plots.-

So outlining these shows hemispherically where the 2 biggest areas of below average will occur & of course where the 2 warmest areas will be-

Also you will have smaller zones of anomaly where the 500 height anomaly signal is weaker.

dividing these up into 3 months is TOUGH for Nov 15th-

I would say a 6 week anomaly & a 7th-12th week preliminary view would be the way forward on the 15th Nov- with an update on the first / second week of Jan for the second 6 weeks of winter.

* Seasonal Temp Probabililty :

I firmly believe that rather that going for irrational CET estimates is not the way to go- we should break the forecast down to degrees of probability of a particular range of temps-

For example-

With all the background signals & the projected longwave anomaly you then present a 'signal' of pattern- I would have a temp range like this

-3 to -1c anomaly ( strong COLD) -1 c to +1 ( Neutral ) +1 to +3 ( Strong Warm)

The strength of your signal dictates the probability scale - I think this is VERY similar to how the met office operate with percentiles. & the range above could be broken down again & have weak cold inserted & weak warm as well-

* Rain days V the Norm ---- NOT accumulated PPN V the Norm.

I think this is where my thinking is slightly different to most ( if I cast my brief flirtation with trading energy & weather) Its better to predict rain days V the norm as opposed to predict totals V the norm-

The reason I say this is the total rain for one area can be delivered in one short heavy burst of heavy rain in an amplified flow or consistently short amounts accumulating over a period of time from a semi zonal flow.

For me being a numbers man- statistically we must measure ave rain days per month-

if you are producing a forecast & a particular prevailing weather type it will then stack up that from this you can forecast the amount of rain days anomaly V the norm-

So for example - your insight says strong atlantic high is the form horse- Rain days will be reduced-

I would be dividing this up into some sort of range V the norm- with the neutral zone being average zonal conditions & the average number of rain days- then signal for blocked conditions correlates to negative days & highly zonal conditions = positive days.

In Summary-

I think I would need need to invest 40-50 hours to produce a semi authentic forecast these days, all based on probability,- the difficulty being that theres not enough data on the wildcards like the arctic ice & Stratosphere......

best regards

Steve

Nice post Steve, an pretty much agree.

A couple of thoughts on the issues you've raised.

Long range weather forecasting

I would liken long range forecasting to being rotated on a carousel with a bow and arrow trying to hit an archery target. Even if you don't hit the target, getting close on a reliable basis places you in a better position than just relying on models alone. The bottom line here is some attempt to understand and predict the dynamical processes in the weather - climate system must go hand in hand with use of climate models. Where the two methodologies agree, confidence is increased.

Fad / fashion

This one makes me smile, but ultimately I think it reflects more of a lack of understanding rather than a continual raising and discarding of variables. A few years ago the idea that sea surface height and temperature over the Equatorial Pacific would have an impact on global weather patterns was faddy. Now it is a case of routine monitoring. The idea that the temperature of the polar stratosphere (both colder and warmer than normal) has a significant influence on the circulation in the northern hemisphere in winter was until a few years ago, faddy. Now it is routinely monitored. You get my point?

Just because these variables are not shouted about does not mean they have gone away. All of our teleconnective analyses are like a complex spiders web. Whichever way you come at it, ultimately it leads to the same destination focusing on zonal wind anomaly and placement of ridges and troughs. I would also suggest that the state of the Arctic Oscillation is of most interest to us in Europe as the associated anomalies show a significant influence on winter / summer patterns.

Sample size

I'm not a statistician and I don't know the sample size for statistical robustness with climatic modelling. However, I would suggest that with all the white noise that exists in the atmosphere, any anomaly pattern that comes out of say 10 samples (and we have two winters / summers per year) is starting to show the way. If we can test the theory with the mirror image analysis (i.e does it work in the opposite direction), that adds to the confidence that we're onto something.

I do not need much more of an increased sampe size to be confident that certain variables are good or bad for European cold in winter. For example, strong La Nina evolving in the summer which will interfere with the Brewer Dobson Circulation and generate feedback loops which reinforce a strong polar flow and associated low heights across the Arctic.

Time scale for release of forecasts

October is the month for winter data. No doubt about that. However, I think it's worth while forming a private idea in say September and testing this in October, particularly in terms of stratospheric winds and temperatures.

Definately agree about measures for seasonal forecasts.

[ASW]

Nice work BFTV.

Potential snow cover increasing down into the Mongolian steppe in the coming week as low pressure develops in the region with associated 850hpa temperatures of 0-10 C around the low. Most of Mongolia above 1500m so potentially good for snow cover there, south of Siberia.

That brings me onto another Siberian snow cover point. I once read/in those journal papers that the further south snow falls and the earlier it occurs in October the better. According to this snow cover further south reflects more sunlight into the stratosphere and causes resultant warming/ozone formation.

I will look into doing a correlation between amount of snow in October at relatively southern laltitudes in Asia - Mongolian, Tibetian Plateau etc - and winter cet. See if there's any difference.

[ASW]

Nice work BFTV.

Potential snow cover increasing down into the Mongolian steppe in the coming week as low pressure develops in the region with associated 850hpa temperatures of 0-10 C around the low. Most of Mongolia above 1500m so potentially good for snow cover there, south of Siberia.

That brings me onto another Siberian snow cover point. I once read/in those journal papers that the further south snow falls and the earlier it occurs in October the better. According to this snow cover further south reflects more sunlight into the stratosphere and causes resultant warming/ozone formation.

I will look into doing a correlation between amount of snow in October at relatively southern laltitudes in Asia - Mongolian, Tibetian Plateau etc - and winter cet. See if there's any difference.

http://www.wetterzentrale.de/topkarten/fsavnnh.html

Low pressure development around Mongolia seen here.

[BornFromTheVoid]

Nice work BFTV.

Potential snow cover increasing down into the Mongolian steppe in the coming week as low pressure develops in the region with associated 850hpa temperatures of 0-10 C around the low. Most of Mongolia above 1500m so potentially good for snow cover there, south of Siberia.

That brings me onto another Siberian snow cover point. I once read/in those journal papers that the further south snow falls and the earlier it occurs in October the better. According to this snow cover further south reflects more sunlight into the stratosphere and causes resultant warming/ozone formation.

I will look into doing a correlation between amount of snow in October at relatively southern laltitudes in Asia - Mongolian, Tibetian Plateau etc - and winter cet. See if there's any difference.

You might be looking for the "snow advanced index", which is to do with snow cover south of 60N http://web.mit.edu/jlcohen/www/papers/CohenandJones_GRL11.pdf

[Glacier Point]

Do you mean this?

High sea ice years detrended

High sea ice year with trend

Bingo. Mirror image. Nice work and look at the relationship with the AO pressure anomalies, which are most relevant to Europe.

The sample size has some merit to it given this mirror image test and the variability of ENSO and QBO states included.

Edited October 2, 2012 by Glacier Point

[ASW]

You might be looking for the "snow advanced index", which is to do with snow cover south of 60N http://web.mit.edu/j...Jones_GRL11.pdf

Thanks, so much research out there! Afraid I'm struggling to open it, but I'll try later.

I read what you were saying about the SAI - below 60 N; however, I just wonder what happens if we take it to an even further extreme and below say only below 50 N - basically Mongolia southwards. I think the amount of sunlight increases exponentially - well not quite that quick! - as we go towards the equator? I know a lot of years in October barely see anything below 50 N but I just wonder.

[BornFromTheVoid]

Bingo. Mirror image. Nice work and look at the relationship with the AO pressure anomalies, which are most relevant to Europe.

Cheers.I'll add them into the original post so.

[bobbydog]

hi ASW, i thought you might be interested in my little effort on this subject

i found this article earlier- http://dotearth.blog...on-to-the-test/

i'm not sure how much weight it holds but its another interesting theory. the doubts i have with it are, that they are saying autumn siberian snow cover can affect the AO but surely the AO would affect the amount of snow in the first place. ( a "chicken and the egg" type situation)

i looked back at the last 3 years, covering 2 cold winters and a 'mild' one (bearing in mind its only really a small snapshot and would take a lot more work to get a more accurate picture) the thing i noticed, was it was not the amount as such but the placement of snowcover which seemed to have more influence. i posted some images in the snow and ice thread for comparison- http://forum.netweat...00#entry2376270

Nice work BFTV.

Potential snow cover increasing down into the Mongolian steppe in the coming week as low pressure develops in the region with associated 850hpa temperatures of 0-10 C around the low. Most of Mongolia above 1500m so potentially good for snow cover there, south of Siberia.

That brings me onto another Siberian snow cover point. I once read/in those journal papers that the further south snow falls and the earlier it occurs in October the better. According to this snow cover further south reflects more sunlight into the stratosphere and causes resultant warming/ozone formation.

I will look into doing a correlation between amount of snow in October at relatively southern laltitudes in Asia - Mongolian, Tibetian Plateau etc - and winter cet. See if there's any difference.

[Barry12]

I accept that 3 month forecasts are still at the experimental stage but GP's forecast for the last few winters have been really good, still a lot more research required of course but my bugbear is that the same organisation that stopped doing 3 month forecasts because they were inaccurate, tell us that in 100 years time we will be experiencing very mild winters.

That is called climate forecasting, which is completely different from forecasting what will happen in 3 months

[bobbydog]

Bingo. Mirror image. Nice work and look at the relationship with the AO pressure anomalies, which are most relevant to Europe.

hi GP, can you explain this briefly in laymans terms? i'm attempting to work with BFTV on these subjects but he's way ahead of me on the technical side, i'm slowly getting there with teleconnections but any help with 'getting my head around' it would be much appreciated

[ASW]

hi ASW, i thought you might be interested in my little effort on this subject

Thanks BobbdyDog, I need to start combing all the forums vigorously! Just want snow so much!

Interesting looking at what you've done. Quite a bit more snow in middle of October in 2009 and 2010 on the Tibetan Plateau - thats around 30-35 degrees north - than in 2011. Bearing in mind the SAI, I wonder how much snow at that latitude is "worth" in terms of reflectance/atmospheric disturbance value compared to snow between 60 - 50 N. Maybe that paper that I cant load has already explained this anyhow. Just so excited at potential this year..

[stewfox]

Evening All-

Bottom line is this-

Our sample size & dataset is to thin to create a representative analogue.- To create and predict a good match to cover the following-

Arctic Ice,

PDO,

QBO,

ENSO,

Solar flux,

Stratosphere,

Ozone levels

SST

I think we would need at least 500 years worth of consistent reporting data,- even if we rationalise each Variable to a low level tangable rating of Strong, Neutral & Weak signal I bet on all of the above with the data we have you might get one match that had a strong Signal for the winter forecast,

Are you saying if we had 10 cold winters in Europe and 10 very low summer artic ice levels we could be jumping the gun by saying a correlation looks likely ?.

I always thought 30 yrs can give us a good idea ? If there is a group of signals but one that has a larger influence, surely 30 years of good data collection gives reasonable predictive qualities ?

Why 500 years ? If there is no over riding factors ie it may take much longer to confirm there are none.

[Glacier Point]

hi GP, can you explain this briefly in laymans terms? i'm attempting to work with BFTV on these subjects but he's way ahead of me on the technical side, i'm slowly getting there with teleconnections but any help with 'getting my head around' it would be much appreciated

OK, here is the pressure anomaly pattern for the middle part of the atmosphere during the top ten most positive Arcitic Oscillation winters and alongside it the sea ice maxima (untrended) during September:

and reversed, the top ten negative AO winters and sea ice minima during September:

Note that the deepest anomalies are focussed around Greenland and NW Europe for both sea ice and AO. In other words, the predictive skill shown in forecasting the state of the AO would appear to be the key for European Winter forecasts amd this appears to have some correlation to the extent of sea ice cover in autumn.

What's interesting here is that we have a variable (anomalous sea ice extent) which appears to precede the AO winter state by some months and a proposed series of mechanisms by which it influences the subsequent state of the AO.

Edited October 2, 2012 by Glacier Point