OCTOBER PATTERN INDEX (OPI) MONITORING WINTER SEASON 2014-2015

[karyo]

And then another weather factor someone found which may or may not affect the weather ahead..

 

First it was Solar Index, Then Stratospheric Warming now it's the OPI

The OPI doesn't cancel the other two though.

[MarkTJ]

Suddenly the OPI is turning up everywhere and being used as "evidence" that we're about to have coldest winter for 100 years.

[johnholmes]

A less than scientific look at this latest phenomena

 

Is the OPI index reliable when comparing CET data with values for the OPI of lower than -1.7?

 

This is a very un scientific take on the possible link between the OPI and ‘cold’ CET winters. For cold I have taken winter months with 2 or more below average months. Winter being taken as December, January and February. Temperatures in degrees C.

 

The years of OPI below the figure quoted are:-

1976=-1.75      winter 1976/77

1978=-1.9                    1978/79

1984=-1.8                    1984/85

1985=-1.9                    1985/86

2009=-3.15                  2009/10

2012=-1.76, so -1.7 to the first decimal point.           2012/13

 

The CET data is that available on this site http://www.personal.dundee.ac.uk/~taharley/centralengav_temperat.htm

And has the average based on 1971-2000

December=5.1, January and February both at 4.2; this gives a mean of 4.5C.

1976/77=2.0, 2.8, 5.2

1978/79=3.9,-0.4, 1.2

1984/85=5.2, 0.8, 2.1

1985/86=6.3, 3.5, -1.1

2009/10=3.1, 1.4, 2.8

2012/13=8.5, 5.7, 6.2  can be discarded as no month fell below average

 

Before examining the above data we also need to see when the above criteria for cold winters CET values were satisfied but did not show an OPI of -1.7 or lower.

 

The following winters fell into this category

1981/82=0.3, 2.6, 4.8  mean=2.6

1982/83=4.6, 6.7, 1.7  mean=4.3 so requirement not really met with the mean

1990/91=4.3, 3.3, 1.5  mean=3.0

1995/96=2.3, 4.3, 2.5  mean=3.0

1996/97=2.9, 2.5, 6.7  mean=4.8, so again the mean makes this winter not relevant in spite of 2 ‘cold’ months.

2010/11=-0.7, 3.7, 6.4 mean=3.1

And the OPI very positive=1992=1.75, winter =1992/93=3.6, 5.9, 4.6        mean=

 

So tidying the above up leaves 1981/2, 1990/91, 1995/96, 2010/11 with CET fitting the criteria used, with one year 2012-13 when a very negative OPI did not lead to any month being below average in the following winter. A total of 3 years when the OPI did not come anywhere near -1.7, the actual values, in the same order as the CET years given above was:-

-0.4,0.55, -0.65.

 

We therefore have 5 years with the OPI and CET values agreeing with the theory of OPI indicating cold winters and 3 winters with cold CET values (as defined above) with the OPI giving no clue to this occurring. One year with a reasonably low OPI (-1.76 with no single cold winter month following.

 

Putting the OPI in order of negativity with the winters alongside gives

1          2009=-3.15      2009/10=3.1, 1.4, 2.8  mean=2.43      3

2          1985=-1.9        1985/86=6.3, 3.5, -1.1 mean=2.90      2

3          1978=-1.9        1978/79=3.9,-0.4, 1.2  mean=1.57      1

4          1976=-1.75      1976/77=2.0, 2.8, 5.2 mean=3.33      4

 

If we compare these figures with those years when the OPI did not give an indication, we have

1981/82=0.3, 2.6, 4.8  mean=2.6; this would rank 2 in the above winters

1990/91=4.3, 3.3, 1.5  mean=3.0: this and 1995/96 would rank joint 4^th

1995/96=2.3, 4.3, 2.5  mean=3.0

2010/11=-0.7, 3.7, 6.4 mean=3.1; even this one shows a mean winter temperature below the 4^th in the table above. None of the above had all 3 winter months below average whilst 2 of the winters in the above table did so.

 

Without doing any statistical tests on either of the above results it seems to me that the expectation, by some, on Net Weather, of this being the key to predicting winter are somewhat off the mark. As I suggested at the beginning it is a non scientific explanation and please feel free to shoot this post down if you wish.

One other point is that the period of data is, relatively, small for predictive purposes. A minimum of 30 years is used for climatological records but for something of this type, an attempt to use a predictor much longer periods are the norm.

 

Maybe someone could discover in the winters I have highlighted what the QBO etc showed as well as this might refine the results? Were the winters that supported the theory west or east based NAO. Equally what about those winters with below average months what was the QBO and NAO showing?

 

I remain, sceptical of any claim that this will give a reliable indication ON ITS OWN, but it may be another indicator to use with others already in use. One thinks of the SAI and  Tropospheric influences to name just two.

 

Interesting to play around with the data though.

Edited October 30, 2014 by johnholmes

[Steve C]

Suddenly the OPI is turning up everywhere and being used as "evidence" that we're about to have coldest winter for 100 years.

 

The 100 year thing irritates me. Are they saying colder than the winter of '63, in which case you'd have to go back to 1740 for a colder one in the UK, or just more lazy / sensationalist journalism?

[Gael_Force]

John, your figures for '12-'13 are incorrect - should be 4.8, 3.5, and 3.2.

 

Look for other data on the Berlin site - remember, CWs and  SSWs, can change the overall winter picture very rapidly.

 

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/northpole/index.html

[Steve C]

John, your figures for '12-'13 are incorrect - should be 4.8, 3.5, and 3.2.

 

Look for other data on the Berlin site - remember, CWs and  SSWs, can change the overall winter picture very rapidly.

 

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/northpole/index.html

And 2009/10 was colder than 1981/82, but the gist of what he says remains. A negative OPI is still something we want to see. I think he's just saying don't place too much reliance one one indicator.

[LomondSnowstorm]

I think you've got the 2013/14 numbers mixed up with the 2012/13 ones John - 2012/13 was around average overall and I believe below average for both January and February (though I don't have the numbers to hand either). It's certainly true that you don't need an exceptionally low OPI for a cold winter but it does help, and the other winters on that list, with the exception of 90/91, all had negative OPIs.

If it were only the OPI pointing to a cold winter I don't think it would be taken as seriously, but given the SAI is likely to be one of the highest values in the series and we're in a -QBO+weak/moderate ENSO, which are also almost always winter with -AOs (and generally below average temperature wise for the UK as well), then it's difficult to look past the notion that we're more likely to see a cold winter than normal.

[Mucka]

Thanks John.

I think we are looking for correlation that a large negative OPI leads to a colder winter?

If this is so we need not mix in data of cold winters without a large negative OPI?

Also the OPI is no doubt just another tool (yet to be seen how useful) in helping with the winter forecast.

As mentioned above, by snowstorm, I think we need to check other measures traditionally used against those figures as they could reveal where overriding signals may exist where there is a negative OPI.

 

It seems natural that each feedback will have different weighting and more effect in some years than others.

I believe the OPI will have some use as a guide but as yet it impossible to know how much weight should be given to it against other measures.

Edited October 30, 2014 by Mucka

[The PIT]

Hold on hold.

What happens if we look at the winter of the northern hemisphere as whole? What happens then??

[johnholmes]

I think you've got the 2013/14 numbers mixed up with the 2012/13 ones John - 2012/13 was around average overall and I believe below average for both January and February (though I don't have the numbers to hand either). It's certainly true that you don't need an exceptionally low OPI for a cold winter but it does help, and the other winters on that list, with the exception of 90/91, all had negative OPIs.

If it were only the OPI pointing to a cold winter I don't think it would be taken as seriously, but given the SAI is likely to be one of the highest values in the series and we're in a -QBO+weak/moderate ENSO, which are also almost always winter with -AOs (and generally below average temperature wise for the UK as well), then it's difficult to look past the notion that we're more likely to see a cold winter than normal.

 

ta-I'll check that out when I have time

[Midlands Ice Age]

John,

The winter of 2012/13 was not very cold, but if you remember the weather abruptly changed in march 2013and April and May were exceptionally cold with persistent easterely winds.

Maybe the parameters for the out of kilter months needs to be adjusted a little bit for us snowies?

MIA

[snowking]

ta-I'll check that out when I have time

Hi john.

First of all just to say - kudos for the hard work that has gone in to compiling that report, and as unscientific as you may have suggested it is it is still a very valid observation.

However, the thing I would say is that you can simplify the OPI - CET correlation a lot more than this given the situation we are in this year. If we take a look at all years with an OPI value below -1 (approx.), as per the link below (taken from my post in the seasonal thread, bottom of page 30):

https://f1.nwstatic.co.uk/forum/uploads/monthly_10_2014/post-1038-0-15246200-1414251715.png

We can see that in fact every single winter finished below the 71-00 average (any figures below this average are coloured blue and vice versa for red), along with all but a few months.

Further down in that post I also broke that down further in to the three closest years in terms of composite matching, which include El Niño conditions (despite the current position hovering around Neutral to El Niño, the atmosphere is very much exhibiting a Nino like state) and eQBO - and quite obviously from the previous table, these winters all finished below average overall.

So whilst indeed in more neutral years (> -1, <1) we see some real variance with the CET, when the OPI becomes as clear cut as this year then according to all the data we have available the CET follows suit.

Of course to add some caution, ultimately weather does not always follow statistics.

SK

[ukpaul]

-2.13 from the 12z, that's pretty much it for the final figure I would have thought.

[mcweather]

Just a couple of points.

 

Number 1

 

Why the obsession with CET in relationship to cold weather brought about in negative OPI winters?

 

One could have a mild first two weeks of January a cold and snowy second two weeks which continued into the first two weeks of feb before a mild second two weeks in feb. You would have had a very significant spell of wintery weather. which would tie in with the negative OPI suggestion of colder weather regimes. Yet official CET records used by Metetorologists would register two average months whereas the rest of us would be talking about the amazing month long cold and snowy spell . In other words the real weather as opposed to the statistics

 

Number 2

 

The way I view  a Negative   OPI below -1.5 is that it equates to an atmosphere more predisposed to allow cold set ups to affect the UK.

 

So this time round with a sub -2 OPI , although in the UK ,cold weather is never 'in the bag' until  it's 'in the bag'. This year we have a bag that is being held open and the right way up whereas last year we didn't even have a bag.

[snowking]

Just a couple of points.

 

Number 1

 

Why the obsession with CET in relationship to cold weather brought about in negative OPI winters?

 

One could have a mild first two weeks of January a cold and snowy second two weeks which continued into the first two weeks of feb before a mild second two weeks in feb. You would have had a very significant spell of wintery weather. which would tie in with the negative OPI suggestion of colder weather regimes. Yet official CET records used by Metetorologists would register two average months whereas the rest of us would be talking about the amazing month long cold and snowy spell . In other words the real weather as opposed to the statistics

 

Number 2

 

The way I view  a Negative   OPI below -1.5 is that it equates to an atmosphere more predisposed to allow cold set ups to affect the UK.

 

So this time round with a sub -2 OPI , although in the UK ,cold weather is never 'in the bag' until  it's 'in the bag'. This year we have a bag that is being held open and the right way up whereas last year we didn't even have a bag.

Just on point 1 - absolutely true, but the positive point is that up until now all <-1 OPI years have featured below average Winter CET's.

So actually in the context of this winter and people searching for cold the CET relationship provides hope. You are absolutely correct, and who knows perhaps something such as that may occur this winter, but up until now the CET actually provides a good correlation to the OPI, which I'm sure is comforting to many

SK

[mcweather]

Just on point 1 - absolutely true, but the positive point is that up until now all <-1 OPI years have featured below average Winter CET's.

So actually in the context of this winter and people searching for cold the CET relationship provides hope. You are absolutely correct, and who knows perhaps something such as that may occur this winter, but up until now the CET actually provides a good correlation to the OPI, which I'm sure is comforting to many

SK

 

Thanks Snowking and I do take your point and the CET-OPI relationship is a fascinating one.

 

I think what I wasrather clumsily trying to get across is that CET is not a great way of showing what the weather actually was, just what the average temps were and that can quite misleading in that in an average CET month the actual weather may have been anything but average.

[bobbydog]

I think some are missing Johns point here.

The point is, that a negative OPI does not necessarily lead to a cold winter in the UK.

It increases our chances as it correlates to a negative AO. That is the whole point of the OPI.

A negative AO (along with other factors) increases the chances of a colder winter for EUROPE of which we are a little island on the fringes.

Johns study is specific to the UK, not Europe as a whole

In short, it doesnt guarantee the coldest winter since the Ice Age but it does give us a fighting chance of being able to build a snowman this year! ⛄

[mcweather]

I think some are missing Johns point here.

The point is, that a negative OPI does not necessarily lead to a cold winter in the UK.

It increases our chances as it correlates to a negative AO. That is the whole point of the OPI.

A negative AO (along with other factors) increases the chances of a colder winter for EUROPE of which we are a little island on the fringes.

Johns study is specific to the UK, not Europe as a whole

In short, it doesnt guarantee the coldest winter since the Ice Age but it does give us a fighting chance of being able to build a snowman this year! ⛄

 

Yes that's true but it does tend to lead to winters with substantial spells of cold/and or snowy weather, whether the winter is cold overall or not.

[throwoff]

One snow day with my kids is all I ask!

[johnholmes]

Hi john.

First of all just to say - kudos for the hard work that has gone in to compiling that report, and as unscientific as you may have suggested it is it is still a very valid observation.

However, the thing I would say is that you can simplify the OPI - CET correlation a lot more than this given the situation we are in this year. If we take a look at all years with an OPI value below -1 (approx.), as per the link below (taken from my post in the seasonal thread, bottom of page 30):

https://f1.nwstatic.co.uk/forum/uploads/monthly_10_2014/post-1038-0-15246200-1414251715.png

We can see that in fact every single winter finished below the 71-00 average (any figures below this average are coloured blue and vice versa for red), along with all but a few months.

Further down in that post I also broke that down further in to the three closest years in terms of composite matching, which include El Niño conditions (despite the current position hovering around Neutral to El Niño, the atmosphere is very much exhibiting a Nino like state) and eQBO - and quite obviously from the previous table, these winters all finished below average overall.

So whilst indeed in more neutral years (> -1, <1) we see some real variance with the CET, when the OPI becomes as clear cut as this year then according to all the data we have available the CET follows suit.

Of course to add some caution, ultimately weather does not always follow statistics.

SK

 

thanks for that sk, especially the ENSO and QBO info which is what I was asking for. Now all we need are the bits re the NAO, west or east for the years most close to any link?

[johnholmes]

Yes that's true but it does tend to lead to winters with substantial spells of cold/and or snowy weather, whether the winter is cold overall or not.

 

very true, a 'mild' winter by CET standards does not rule out a cold spell of 7-10 days, and more than once in the December to end of February. But it is the possible link with OPI and other possible links which is the interesting feature.Maybe OPI will be proven to another part of the jig saw. At the moment we do not know this and will not, irrespective of what the final OPI figure is this month or the subsequent winter values. There is still a lot of work to be done as the folk involved with the OPI openly acknowledge. 

[johnholmes]

looking again at the data sk gave in reply to my original post this evening. We still are left with a mix of QBO and ENSO. So any link, regardless of a deeply -ve OPI is not clear. It is highly interesting though and who knows, as |'ve just commented, it may be another link in the jig saw of trying to predict with reasonable accuracy what the winter may turn out to be.

[feb1991blizzard]

very true, a 'mild' winter by CET standards does not rule out a cold spell of 7-10 days, and more than once in the December to end of February. But it is the possible link with OPI and other possible links which is the interesting feature.Maybe OPI will be proven to another part of the jig saw. At the moment we do not know this and will not, irrespective of what the final OPI figure is this month or the subsequent winter values. There is still a lot of work to be done as the folk involved with the OPI openly acknowledge. 

 

Yes a lot of work to be done but surely the evidence Steve has presented is overwhelming regarding this.

[January Snowstorm]

Well done to all for making this such an interesting thread.Looking forward to an exciting winter ahead

[The PIT]

Just a couple of points.

 

Number 1

 

Why the obsession with CET in relationship to cold weather brought about in negative OPI winters?

 

One could have a mild first two weeks of January a cold and snowy second two weeks which continued into the first two weeks of feb before a mild second two weeks in feb. You would have had a very significant spell of wintery weather. which would tie in with the negative OPI suggestion of colder weather regimes. Yet official CET records used by Metetorologists would register two average months whereas the rest of us would be talking about the amazing month long cold and snowy spell . In other words the real weather as opposed to the statistics

 

And it's also possible to have a possible cold snap where the QPI is anything but conducive towards such a feature. Actually getting the data out though would be very difficult without going through numerous station records on a month by month basis rather than looking at final average for the month.