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Riccardo

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

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Whilst one would normally need ones bumps feeling to predicate something on gfs low res, the fact that the OPI is a rolling number updated every 6 hours should flatten out the effect of any strange runs. something does seem very odd about the sudden change seen today. As the 18z isn't used, we will have to wait for later tomorrow morning to see the update based on the 00z run.

 

So the 18z GFS is not used: so what's the Italian for 'pub run'? :D

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So the 18z GFS is not used: so what's the Italian for 'pub run'? :D

 

Funnily enough its 'run pub'

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Do the MetO accept the basic meteorology and maths behind the OPI algorithm?

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Paging Riccardo... :help:

 

Hopefully he can shed some light on what changed from earlier today to cause such a sudden swing.

Edited by radiohead

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It is not just about the AO - look at all the other aspects that make up the calculation. I found the cached version of yesterday's 06Z and when compared to today's 12Z run, there are quite big changes to the regional geopotential anomalies and axis parameters.

 

RjVwvCX.png  VtjyE8p.png

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Do the MetO accept the basic meteorology and maths behind the OPI algorithm?

Unfortunately paper not published yet.

Plenty of other peer reviewed hints of negative AO other than OPI at present, some stunning analog years.

Great post today Tamara, Iceland certainly provides an unknown.

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It has to be remembered that it doesn't settle down til second half of month, particularly from 20th/21st onwards when there is data for all the days.

Here is last years, all over the place to start with - http://fiorentino.altervista.org/OPI002.png

 

Yes Gael Force I have started taking note of the numbers, the OPI value is simply the factor ε value plus the Î¦(φ) but how they are calculated is unclear yet.

Bit surprising that the result of a simple sum could approximate the AO but there you go.

So compared to earlier, the axis of the vortex is what has brought the score up, the geopotential anomalies have improved.

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Dont know if you have noticed, but as far as I can see based on the site, http://app.til.it/opi/, the index is the sum of following two components:

 

Elyptization[sic*]+axes parameters

 

 

Now, I dont know what they mean by eliptization (elyptization?), but what I can see that this parameter is not changed much from the 06z run. 

 

The big change is in the axis parameters.

 

 

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Dont know if you have noticed, but as far as I can see based on the site, http://app.til.it/opi/, the index is the sum of following two components:

 

Elyptization[sic*]+axes parameters

 

 

Now, I dont know what they mean by eliptization (elyptization?), but what I can see that this parameter is not changed much from the 06z run. 

 

The big change is in the axis parameters.

 

See my post above yours lol

The word should be ellipticity - how much the vortex is oval rather than circular. The long axis of this oval is the axis they are looking at and normally runs roughly between the Pacific and the Atlantic over the pole. Elliptical diagnostics has been used to study and describe the stratospheric vortex for a while, but I've not managed to find any application of it to the troposphere yet.

Edited by Interitus
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IS the OPI  based only on the GFS  model?

 

Yes, but it doesn't really matter, at the end of the month it is the reanalysis of what actually happened, not forecast charts.

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It has to be remembered that it doesn't settle down til second half of month, particularly from 20th/21st onwards when there is data for all the days.

Here is last years, all over the place to start with - http://fiorentino.altervista.org/OPI002.png

 

 

Thanks for that. This certainly puts things into perspective as it shows wild swings were common last year too until later in the month. It looks like we may have gotten a little too excited at the early negative figures!

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Yes, but it doesn't really matter, at the end of the month it is the reanalysis of what actually happened, not forecast charts.

 

Hopefully it won't end up like the 2013 graph posted above,otherwise Nick Sussex's helpline

will be inundated before winter has even begun!

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Interitus

 

Yes, you beat me with 5 mins there.

 

Thanks, elipticity makes sense.

 

Looking forward to reading the paper when it is released. In particular I want to see whether there is a reasonable link between the geophysics and the statistics. The correlation is obviously strong, but it should ideally be backed with a geophysical theory.

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Hopefully it won't end up like the 2013 graph posted above,otherwise Nick Sussex's helpline

will be inundated before winter has even begun!

Haha, indeed, look at the 10/10/2013 value and then the final result, think this will only start to be realistic around the 20th

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Yes, but it doesn't really matter, at the end of the month it is the reanalysis of what actually happened, not forecast charts.

 

Yes that was really my point: the GFS  can be very good at 'short range' but the further it forecasts,  it can  swing wildly it its output. I think I will wait for the final figure at the end of October.........

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Some great progress being made on cracking this puzzle this evening, good observation OlaL re: how figure is computed, talk about right in front of you and not seeing wood for trees etc.

 

Thanks for putting those two charts side by side Polar Gael. For me it's not about what figure is achieved, obvs. that is important for confidence in Winter, but more about the analysis on how this is constructed. SM at his best there ! Interitus, I would wager you have this cracked by the 20th.

 

The GPH anomalies,  Elypticization, we can readily envisage / put into context in a familiar manner via each GFS run, as these are output in certain locales from the completed runs and predicted runs (or cartes). The axes parameters however, appear to determine not just the final OPI figure but the other chart re: predicted wave intrusions. So these are my main point of interest in the telemappa materials.

 

Comparing today and yesterday sees a massive switch in the Arctic Anomaly, which in turn I perceive as changing the angle/location of standing waves on the axis of the vortex.

 

I still have real confusion around the massive bust years. With respect to a plot that has great correlation, then goes off at a tangent inexplicably, this is not a criticism of the skill forecast in other years, just a curiosity as to why the atmosphere would deliver a curve ball on this seemingly regular scale ( a good question would be, is this the infancy of a new atmospheric mode, or a true anomaly).

 

It's a great debate and this thread is really attacking the subject with vigour, although a similar thread exists in other weather communities, again Net Wx has the most in depth, tracking and attention to the subject.

 

post-7292-0-59435100-1412977658_thumb.pnpost-7292-0-92689300-1412977664_thumb.pn

 

 

Couple of AO suites from GFS/ ECM this morning, linked re Arctic heights 3 trends towards neutral in varying degrees on that ensemble spread, still a fair amount of time to go in October..

 

 

Edit : re build of index ; As an aside, I would pick the occasionally intuitive GFS 18Z over the 06Z any day of the week...

Edited by lorenzo
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pity that the 18Z GFS is not used because its output is very different from 12Z after October 18. The IPO index would certainly dropped

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The most pertinent point yet.

 

After having a discussion on twitter last night I went back and looked at the previious OPI scores. And to me it looks like that the scores are the daily values ( go back and look at the daily scores) rather than the cumulative score with the addition of the average T+240 GFS score factored in. So the OPI indicated is the score today (yesterday now -1.13 ) rather than the cumulative score that perhaps Riccardo had led us to believe ( - this could be lost in translation).

 

However, all is not lost as I suspect that the next 10 days we will be near an average score. After that we may get a more positive daily OPI value as the AAM is set to rise and this will lead to a more pronounced polar jet stream. Perhaps not a bad thing to temper winter expectations at this point..... but I am likely to suggest a negative AO winter, unless there is a significant change in pre-winter conditions for the worse in the next 6 weeks.

To further illustrate this point, let's look at the anomaly charts suggested for the OPI and what we have yesterday and what is forecast anomaly wise for the ECM days 6-10

 

So courtesy of griteater of American Wx here are the OPI +ve and -ve anomaly charts

 

post-4523-0-81419000-1412986597_thumb.gi

 

And here is the ECM chart for the anomalies yesterday:

 

post-4523-0-29225400-1412986659_thumb.gi -looks closer to the neutral anaomly - ie neither +ve or -ve OPI

and the 6-10 cumulative ECM anomaly chart:

 

post-4523-0-53718100-1412986746_thumb.gi

 

To me it looks more -ve OPI but trending towards neutral.

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The most pertinent point yet.

 

After having a discussion on twitter last night I went back and looked at the previious OPI scores. And to me it looks like that the scores are the daily values ( go back and look at the daily scores) rather than the cumulative score with the addition of the average T+240 GFS score factored in. So the OPI indicated is the score today (yesterday now -1.13 ) rather than the cumulative score that perhaps Riccardo had led us to believe ( - this could be lost in translation).

 

However, all is not lost as I suspect that the next 10 days we will be near an average score. After that we may get a more positive daily OPI value as the AAM is set to rise and this will lead to a more pronounced polar jet stream. Perhaps not a bad thing to temper winter expectations at this point..... but I am likely to suggest a negative AO winter, unless there is a significant change in pre-winter conditions for the worse in the next 6 weeks.

By that reckoning, it's currently on around -1.8; and is expected to slowly rise.

For reference (thanks to BFTV), winter OPI's between -1 and -2 are 76/77, 78/79, 82/83, 84/85, 85/86, 86/87, 12/13; so it wouldn't be a bad point to be at one bit (of course it's one part of the jigsaw as Tamara, Chiono, SM etc allude to above).

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Further noting upon Phil n Warks excellent post #25, here is the CET-OPI correlation:

vYNTC.jpg

And there's a very striking correlation in fact; of course there are a few discrepancies but near enough 0.9 correlation w/ the CET. 

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Further noting upon Phil n Warks excellent post #25, here is the CET-OPI correlation:

vYNTC.jpg

And there's a very striking correlation in fact; of course there are a few discrepancies but near enough 0.9 correlation w/ the CET.

Wow - post of the day - amazing correlation. Looking forward to finding the final value at the end of the month already!
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The software analyzes the previous consolidated daily charts plus 10 forecast charts as given by the GFS model. 
For example on the 15th of October, the software calculates the OPI index based on the 15 
consolidated daily charts (1-15 October) adding 10 forecast charts as given by the GFS model (16-
25 October)

 

clearly, something must be awry with yesterdays figure derived from the 12z run or riccardo's prose above. as ed has posted, we saw wild swings in the daily numbers before. but they always reverted to the previous trend. the numbers from the previous 9 days of october are already set in stone so for one run to skew the OPI so significantly must show the 12z gfs run was odd. a similar figure derived from the 00z and 06z today will show that the modelling for the next ten days has undergone a significant shift wrt the vortex.

Edited by bluearmy
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