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Riccardo

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

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Another angle on this ... one thought in my mind has been that, though the PV has taken time to get its act together, it hasn't been far off at any point and now as the end of October approaches all the PV cards might fall into line, at least if some recent model runs are to be believed:

 

 

... also, some others on here have wondered if the state of the atmosphere at the end of October is more important than at the beginning - after all, why should the OPI limit itself to being a straight average across the 31 days of October?

 

So I dug out the NH charts for the end of October for some of the recent "super negative" OPI years:

 

So all of the previous years had a far more scattered PV come the end of October, I'd sure you'd agree from the above - and therefore I suggest the daily OPI readings at the end of these months were still contributing to the overly negative OPI score - whereas with this year, the OPI might be holding on based on "gains" from earlier in the month (though of course the chart for 29th October 2014 is merely a forecast that could be wrong).

 

Something to think about if this year's AO does not match up to previous years with -1.5 OPIs or less.

 

Whilst I agree that the last quarter of the month obviously factors into the overall OPI score, I think it's the pattern as a whole throughout the month that counts. So even if the last week of October had all positive values, once averaged over the entire month the final score could still be negative. 

 

The PV is by no means organised at the moment and whilst models are toying with the idea of it becoming slightly more organised, it's still no where close to where we were last year. 

 

In fact, i'd be a little surprised if the PV didn't get it's act together as we moved towards the end of October, it'd be very unusual.

 

The important thing is that the overall OPI score now is very, very likely to be negative. Factor in the -QBO and the Wave Breaking we're already seeing in the Statosphere I don't think we need to be too concerned at this juncture. 

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no model currently covering itself in glory with its arctic modelling post day 6 at the moment

When it comes to anomalous heights, do they ever get it right around 80N-90N at that range though?

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Thanks for the comments - Fair points Nouska, of course we're all still a little in the dark over what exactly goes into the OPI, from reading the thread I'm guessing the shape of the PV is important but obviously there's more to it. I would still argue that the chart I posted for 29/10/2014 is by the far the most organised PV of the 5 charts - almost a diamond shape - none of the others are anything like a shape. I do indeed hope that the OPI creators are right and my post is wrong! but like others, it is well worth anticipating where it could go wrong - that's the heart of good research, isn't it? :)

edit: to add balance to my original post - we won't of course know what the PV will look like on 31 October for many days yet - this month, there's already been more than one model turn around on the PV between the T192 and T120 stages - very possible it could yet happen again, and it wouldn't be without a trend.

Edited by rjbw

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According to the terminology used in explaining the OPI; the 0z coming up tomorrow morning will be the first run to factor in all of October (1-21 October actual, 22-31 forecast). I think from there, we can reach a more reliable and tight spread of solutions. If it's -2.13 at the end of the month, virtual pints on me.

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Thanks for the comments - Fair points Nouska, of course we're all still a little in the dark over what exactly goes into the OPI, from reading the thread I'm guessing the shape of the PV is important but obviously there's more to it. I would still argue that the chart I posted for 29/10/2014 is by the far the most organised PV of the 5 charts - almost a diamond shape - none of the others are anything like a shape. I do indeed hope that the OPI creators are right and my post is wrong! but like others, it is well worth anticipating where it could go wrong - that's the heart of good research, isn't it? :)

 

You have a point but there have been a heck of a lot of very good winters / winters which included brutal cold spells that had a very flat zonal November, im sure people will correct me but off hand I cant remember any years where we had a very dry blocked November FROM THE VERY START that went on to be corking winters apart from 95/96, which was blocked most of the way through.

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Thanks for the comments - Fair points Nouska, of course we're all still a little in the dark over what exactly goes into the OPI, from reading the thread I'm guessing the shape of the PV is important but obviously there's more to it. I would still argue that the chart I posted for 29/10/2014 is by the far the most organised PV of the 5 charts - almost a diamond shape - none of the others are anything like a shape. I do indeed hope that the OPI creators are right and my post is wrong! but like others, it is well worth anticipating where it could go wrong - that's the heart of good research, isn't it? :)

 

Hi RBJ - at first glance your ECM T+192 chart doesn't look so good but if you look at the placement of anomalies, you can see that the lobes of low heights are still well scattered with the core still positive.

 

VyQ0ZJh.png

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In hindsight all the signs were there in October 2009 for a cold winter to follow yet that same month the MetO issued it's now famous mild winter 2009/10 prediction. After forecasting a BBQ summer in 2009 the winter forecast was there last seasonal forecast.

Good decision chaps.

I am really excited about the OPI as I always suspected that the seeds of winter were sown in October.

Andy

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I see we have team OPI with us - a very warm welcome and please do join the discussion.

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You have a point but there have been a heck of a lot of very good winters / winters which included brutal cold spells that had a very flat zonal November, im sure people will correct me but off hand I cant remember any years where we had a very dry blocked November FROM THE VERY START that went on to be corking winters apart from 95/96, which was blocked most of the way through.

excellent point. If we get a "good" negative OPI then we might not see fruition until Dec or Jan.

If we get a mild/zonal Nov then so be it - it's not even winter at that stage.

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Indeed, there's no clear link between a very negative OPI to a cold November - of the 10 lowest OPIs the average November temperature was 7C, 7 were above the 61-90 average, with November 2009 being the third mildest ever at 8.7C (a horrible month with a very active Atlantic and severe flooding) and the coldest November of the 10 was shared between Novembers 1986 and 2010 at 5.2C.

I think there's a decent chance we'll see some decent cold at some point during November, certainly if the stratosphere continues its promising start, but either way it doesn't mean that much for our chances of seeing a colder than average winter.

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If it was 2.19 I'd be crying right now

This time last year if it had been 2.19 hardly any of us would have cared.Bit different this year though.-2.19 looks around the mark.

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No update based on the 0z GFS which is probably a good thing as it wasn't a good run for blocking in the Arctic. The ECM is much better overall and it tries to raise the pressure over Greenland. The UKMO is the worst model for heights once again.

 

Karyo

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Given we're under the final ten day's of October and every day this month has been negative, surely the only question now is HOW negative will be the OPI be this October?

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Ukmo at day 6 looks to be lacking neg anomolys over the polar field. Strong positive anomolys perhaps lacking but they are positive nevertheless.

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Hi Karyo -

 

The artic is but a small part of the whole measurement for the day, the overall artic profile for the next days is negative ( V the norm ) however not quite as negative as the start of the month.

 

Offsetting this though is the over Pressure anomalies around 60N which are more stacked towards a negative OPI-

 

Supporting this will 100% be the angle of the vortex as its still very distorted....

 

All in all- its still looking pretty good.

 

s

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If we get an OPI lower than -2 we are in a great position, only winter 2009/10 will have had an OPI lower from 1976.

Edited by Barry95
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I would think after looking at the 06z that the OPI index forecast today will drop to around -2.2 to -2.4 ~ as there is more noticeable pressure + anomalies along 60N.

 

S

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A month is a long time in terms of weather. It looks like the first half of the month will potentially be more negative than the second half. Is there any correlation for that to deliver a colder winter with a weaker/positioned vortex or would it be better to trend positive and finish the month more negative where the vortex isn't developing?

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I would think after looking at the 06z that the OPI index forecast today will drop to around -2.2 to -2.4 ~ as there is more noticeable pressure + anomalies along 60N.

 

S[/quote 06z has stronger heights once again!!

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I would think after looking at the 06z that the OPI index forecast today will drop to around -2.2 to -2.4 ~ as there is more noticeable pressure + anomalies along 60N.

 

 

Steve, is there a particular area along/North of 60N that you are drawn to?. Other than than anomalies, where are you looking to see the vortex?

 

Thanks

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Well we don't have 100% clarity of how the angle of the vortex is measured, other than the alignment to the imaginary like from Ocean to Ocean-

 

Heres the loading pattern.

 

post-1235-0-62887400-1413978103_thumb.gi

 

Its clear that for OPI years you have a split vortex which correlates with an angle perpendicular to the imaginary line-

 

Day 6 on the GEM for example shows

 

http://modeles.meteociel.fr/modeles/gem/runs/2014102200/gemnh-0-126.png?00

 

Good neg anomaly over Eurasia, &  fairly good pos over the northern parts of Siberia with a weak pos ringing its way around to Alaska ( remember shallow low heights are a positive height anomaly)

 

As for the vortex alignment to the Norm its almost inverse to the average with a strong easterly flow all way across Siberia towards western Russia & over Greenland a North south flow-

So I image todays Angle will be overall negative across the 10 days, but in the near terms ( days 1-3) a little less negative with the burst of Westerlies....

 

S

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Cheers Steve,

 

So a split vortex with portions in S,Greenland, Siberia and around S Alaska with above average heights over the pole.

 

Thanks MS

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