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Riccardo

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

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Plenty of mention 2009 in previous pages - Steve mentions the analogue, several times.

 

I plotted the October '62 500mb anomaly - it certainly doesn't have the Aleutian/cross pole positive anomaly that the other very negative OPI years show. Perhaps I'm missing some important element to get the whole picture.

 

compday.Y3kwhTTQYm.gif

 

 

For the October preceding the 10 most -ve AO winters, below is the 500mb GPHA composite anomaly.

 

gPIVtbF.png

 

For the 10 most -ve OPI October, we get the composite below.

 

IWNIHPf.png

 

Some very strong similarities, as you'd expect, especially the low heights over western Russia, southern Greenland and just south of the Aleutian islands.

 

 

The pattern for the first 6 days of this month?

 

4MqIwFH.gif

 

Low heights in western Russia, southern Greenland and south of the Aleutian islands. It will be interesting to watch as these change and develop during the month

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It may be a mistake or a strange quirk but from a quick look at the October 500mb height anomalies over 20 years from 1993-2012 it seems just a positive anomaly over the pole leading to negative winter AO and vice versa was correct 15/20 or 75%.

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OPI is going towards very negative values. These are still very uncertain values, but the situation is becoming interesting.

 

Riccardo

Is it the more negative the value the more colder it will be? Is it linear?

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Is it the more negative the value the more colder it will be? Is it linear?

The OPI is used to predict possible pressure anomalies. A negative value means a stronger chance of high latitude blocking (negative AO).

Edited by Radiating Dendrite

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The OPI is used to predict possible pressure anomalies. A negative value means a stronger chance of high latitude blocking (negative AO).

thanks mate

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I see the scale has been adjusted since yesterday to account for the increasingly negative figures. :D 

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If the OPI carries on this way - south of -2 then we will be left with very little to forecast at the end of October-

 

There will only be 3 Analogues

 

62 / 63

76 / 77

09 / 10

 

... What a choice.

 

Interestingly the lowest OPI on record for October was 2009 - Also 2009 has the lowest AO on record @ -1.5

If we look at the AO ensembles the first half of the months landing zone looks to be around -2....

 

Maybe the OPI can be used to forecast November?

 

If so,i look forward to it based on the composite from the 3 years listed above.

 

500mb..  850 temps.. 

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Maybe the OPI can be used to forecast November?

 

If so,i look forward to it based on the composite from the 3 years listed above.

 

500mb..attachicon.gifnovember.png  850 temps.. attachicon.gifnovember850.png

I have an analogue for November based on completely different years (except 1) and criteria that looks almost identical! Hmmm.

Edited by chionomaniac

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I have an analogue for November based on completely different years (except 1) and criteria that looks almost identical! Hmmm.

 

Are you doing the winter forecast this year?

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......According to GFS it’s not until around the 22nd of October that the PV finally muscles the high pressure residing over the pole out of the way. By then we would have 22 days actual and 9 days forecast to month end.

 

I know, I shouldn't watch each run for FI developments! But it is interesting to see this afternoon's GFS12z dismiss the idea of the PV muscling the high pressure away from the Pole on the Oct 22nd (see my earlier post). Tonight's 12z output continues with the cross-Pole high pressure right until the end of it's run on Oct 24th. Below, the comparison of 06z and 12z N. Hemisphere H500 charts for 24th Oct. This is looking a very interesting month indeed!

 

06z  post-20040-0-84954100-1412797681_thumb.p  12z  post-20040-0-06974900-1412797883_thumb.p

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Just remember there is 37 years of hindcast & only 1 year of forecast so far ....

 

Welcome to the forum!!!

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 I did the same plot for the three winter months, individually, and interestingly, January got the best fit, with R^2 of .47, followed by February at .43 and December "only" at .27.

 

Just speculation of course from my side, but is the reason to this "lag"  that the pattern established in October is affecting the Stratosphere, which in turn is feeding back to the Troposphere and this takes some time?

 

1984/1985 is maybe a good example here, where we had a -1,8 OPI, followed by a very mild december, before there was a big freeze in January and February (as predicted by OPI)

Edited by OlaL

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Yes, a joint venture with Tony (Lorenzo).

 

 

Look forward and good luck (as long as you predict a massive tanking NAO winter!!!)

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 I did the same plot for the three winter months, individually, and interestingly, January got the best fit, with R^2 of .47, followed by February at .43 and December "only" at .27.

 

Just speculation of course from my side, but is the reason to this "lag"  that the pattern established in October is affecting the Stratosphere, which in turn is feeding back to the Troposphere and this takes some time?

 

1984/1985 is maybe a good example here, where we had a -1,8 OPI, followed by a very mild december, before there was a big freeze in January and February (as predicted by OPI)

Hi OlaL and welcome to the forum.

 

I supsect that your speculation is well founded and that it will be a pretty safe bet that the pattern will feed back stratospherically later in winter. I wonder how well a negative OPI correlates to the SAI.

 

I think it has been suggested before that this is an extrapolation of Cohen's work regarding the 6 stage process following rapid expansion of the Eurasion snow cover south of 60ºN in October.

 

post-4523-0-91281200-1412802781_thumb.pn

 

Taken from here: http://www.aer.com/node/740

 

And to edit - that November H500 composite for negative OPI years suggests an early westward shift of the Eurasion high towards Scandi as would be expected with the higher SCE and SAI years.

Edited by chionomaniac

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While working on my own research output for the winter forecast, I noticed some strong indications of a "front loaded" winter season ahead, meaning anomalous cold would dominate early in the season.

 

To study this further, I created a "front half index" which is basically the change in anomaly from the NOV-DEC period to the JAN-FEB period of each winter. The higher this index, the more front loaded the winter season would be. These are the top ten "front loaded" winters of the CET period (using daily data from 1773 to 2014 and using monthly anomalies from the entire period for 1660 to 1772.

 

The list is followed by the three other cases since 1961 that exceed 1.5. Other than our recent record-breaker, this tendency for front-loading seems to be gradually fading out of the records, of the top ten cases, only two have been since 1880. The eleventh ranked winter was 1915-16 (+3.09). 

 

WINTER ____ Change in average anomaly (ND to JF)

 

2010-2011 ___ +4.23

1925-1926 ___ +3.92

1871-1872 ___ +3.91

1732-1733 ___ +3.70

1796-1797 ___ +3.37

1816-1817 ___ +3.36

1874-1875 ___ +3.27

1676-1677 ___ +3.25

1742-1743 ___ +3.25

1786-1787 ___ +3.12

 

1989-1990 ___ +2.81

2001-2002 ___ +2.17

1973-1974 ___ +1.69

 

These winters fall into two groups, one could be labelled deep winter cold to milder than average, and the other near normal to very mild.

 

It looks to me as though there is some value to this OPI research, and I can also report that the QBO index value that I use shows a significant negative anomaly in NOV-DEC followed by above normal in JAN-FEB. My own final winter forecast should be available in about a week or two.

I've followed you work for a number of years Roger and have found your forecasts to be never that far out in terms of pressure anomalies, are you seeing something similar to Dec 2010 in terms of HLB this time around?

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The OPI Continues to tank-

The rolling period + 10 day forecast Period is @ 3.54-

 

Rolling period currently @ -13.6 / 8 = -1.7.

 

Assuming the GFS 5-7 day is correct we are now going to hit a sub -2.5 OPI for the first half. Which will deliver an almost guaranteed negative by the end of the month.

 

If we land anywhere lower than -2 with an Easterly QBO I doubt many will be able to contain their excitement for the winter forecast....

As mentioned though there is 1 more check for November as well not relating to the OPI.

 

Also, 2-3 days ago the AO ensembles trended positive as they usually do however are now picking up a double dip, which could spell the most negative October AO in recorded history ( topping the record holder 2009 @ -1.54.....)

Relating to this the Second lowest negative AO was 2012 @ -1.51 - which delivered a record breaking -AO in march in 2013 of -3.1 which whilst isn't a Winter month because of the frequency of planetary waves fits into the 'cone' of influence from these events.

 

VERY exciting times currently.

nice to see you back steve notice you gone for 09/10 winter and my has the OPI update tanked very good indications indeed and just noticed in the model outputs the high lat blocking starting to show some signs of coming to life already although this is still far to early it certainly gives an the idea that possibly the north could have some cold weather before october ends.

 

its only a small chance at the moment but its there the last few model runs showed tiny signs but now with low pressure starting to sink futher se possibly running into southern england the more this happens the better for greenland to establish heights there.

 

so the OPI update tanked at -3 is certainly a good sign i expect a less strong polar vortex this year and am certainly looking at a 09/10 winter type of coarse we must remember although it may not be identical to 09/10 it could well be dryer but colder but even with a dryer colder winter the chances of some of the white stuff are still far greater.

 

now all we need is a nice strat warming event to help things along.

Edited by emotional rollercoaster

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