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

[Yarmy]

I would class a 1030mb high pressure over the pole at the end of October as pretty strong, not weak.

 

It's the geopotential height that counts for the OPI though apparently, not the surface pressure.

[easton888]

BOOM -2.86 on the 06z

[Yarmy]

BOOM -2.86 on the 06z

 

lol. So volatile.

 

I suppose if you're an optimist you could hope the 00z was a rogue run because the previous numbers (-2.91, -2.70 from memory) are closer to the latest update. From now on we should be getting more consistent because there are a solid 15-16 days of actual and 10 days of forecast of which 4 or even 5 days should be reasonably accurate.

[karyo]

BOOM -2.86 on the 06z

That's a great relief! Let's hope the 12Z will be similar to the 6z.

[Paul_1978]

BOOM -2.86 on the 06z

Steve Murr will have your guts for garters for using his 'BOOM'! ;-)

[Ali1977]

More established and professional forecaters including the METO are thinking everything is pointing towards a milder Winter, not saying they are correct. Does anyone know if they will use the final Oct reading of the OPI as an actual tool, or are we clutching at the only thing pointing towards a potentially colder winter.  I would love a cold winter, however none of the long range models used by the professionals are playing ball reading some of the forums posts.

[Yarmy]

More established and professional forecaters including the METO are thinking everything is pointing towards a milder Winter, not saying they are correct. Does anyone know if they will use the final Oct reading of the OPI as an actual tool, or are we clutching at the only thing pointing towards a potentially colder winter.  I would love a cold winter, however none of the long range models used by the professionals are playing ball reading some of the forums posts.

 

It's best to take everything with a pinch of salt. All the LRFs will have a very low certainty (you only need to browse back through past predictions to see this) even those from the major weather centres and even when we get a lot closer to winter. This index has a 40 year record of hindcasting and a 1 year record of forecasting. That's not to say it isn't intriguing.

[MattH]

I've been discussing the OPI on Twitter today with some respected Met's and scientists and the overal agreement is until this is peer reviewed it's open to questioning.

Also something to consider, according to one individual and analysis the OPI could go +ve second half of the month due the potential synoptic developments. Image attached to highlight this.

It'll be interesting to see what happens by months end but potentially prepare for a month of two halves!

Matt.

Edited October 16, 2014 by MattHugo

[Captain Shortwave]

Well the GFS and UKMO this afternoon still want to push an area of WAA from Scanivia northwards at around day 6, this might be enough to hold the +ive anomaly over the pole until the end of the month, especially if it is assisted by developments over the Pacific side.

Edited October 16, 2014 by Captain shortwave

[mulzy]

I've been discussing the OPI on Twitter today with some respected Met's and scientists and the overal agreement is until this is peer reviewed it's open to questioning.

Also something to consider, according to one individual and analysis the OPI could go +ve second half of the month due the potential synoptic developments. Image attached to highlight this.

It'll be interesting to see what happens by months end but potentially prepare for a month of two halves!

Matt.

 

Yep - caution is required.

 

the GFS 12z does seem to pick up on these synoptic developments.  Expect the OPI to be significantly less negative.  Of course it's only one run and things can swing back, but until we are very deep into the month, we are all speculating at best.

 

PS - if it pans out like the GEM, we are back in business (if a rather negative OPI is what we want...).  Couldn't resist at speculating!!!!

 

Edited October 16, 2014 by mulzy

[Midlands Ice Age]

I've been discussing the OPI on Twitter today with some respected Met's and scientists and the overal agreement is until this is peer reviewed it's open to questioning.

Also something to consider, according to one individual and analysis the OPI could go +ve second half of the month due the potential synoptic developments. Image attached to highlight this.

It'll be interesting to see what happens by months end but potentially prepare for a month of two halves!

Matt.

 

Matt...

 

Not by anymeans an expert but  I would have thought that composite pictures you have produced  both show a negative OPI.

 

The arctic circle on the second (although the jet appears to be roaring at our latittudes) still  seems to omnipresent in the Arctic.

I understood that it was supposedly measuring  in some way the strength of the developing polar vortex. Clearly the polar vortex

is struggling to take control of the high Arctic.

 

However, I could be totally wrong. 

 

 

MIA

Edited October 16, 2014 by Midlands Ice Age

[Mucka]

Yep - caution is required.

 

the GFS 12z does seem to pick up on these synoptic developments.  Expect the OPI to be significantly less negative.  Of course it's only one run and things can swing back, but until we are very deep into the month, we are all speculating at best.

 

I'm quite suspicious of the GFS 12z past day 4/5 as it sends all the energy NE but before that it develops a strong Scandi ridge. The UKMO also has a strong ridge but provides some undercut so likely that would be a much better run out to day 10 (re a negative OPI)

I can't see the PV getting organised any time soon as long as heights are being programmed to pump into the polar regions as they are and snow cover should continue to build and move West over Europe within the reliable 5-7 day timeframe which is good news for those who see this as aiding the Siberian high strengthen and ridge West in the winter months.

[bluearmy]

i assume you mean asia mucka ?   looking at NH plots and comparing GFS/UKMO/GEM at day 6, the GFS is fairly underamplified in comparison.  i think, as inertius has alluded, the axis of the pv is paramount in assessing how negative the OPI will be on any single run.

[shaky]

To be fair there is even more blocking across the Arctic on this 12z run than the 06z I think!!!this run should come out just as negative as the last run hopefully!

[Mucka]

i assume you mean asia mucka ?   looking at NH plots and comparing GFS/UKMO/GEM at day 6, the GFS is fairly underamplified in comparison.  i think, as inertius has alluded, the axis of the pv is paramount in assessing how negative the OPI will be on any single run.

 

I'm not sure which part of my post you are alluding to blue but if it is snowcover I think it should start to get into parts of Eastern Europe if the ridge is undercut.

Looking at UKMO and GFS ensembles I think the Op is probably wrong with its lack of undercut. 

I also expect the ECM 12z to be quite different to this mornings 00z by day 6/7 but we will see.

 

As far as a negative OPI is concerned I would assume that high pressure over the pole is key though I have limited understanding over how the precise measurements are arrived at.

Edited October 16, 2014 by Mucka

[LomondSnowstorm]

I've been discussing the OPI on Twitter today with some respected Met's and scientists and the overal agreement is until this is peer reviewed it's open to questioning.

Also something to consider, according to one individual and analysis the OPI could go +ve second half of the month due the potential synoptic developments. Image attached to highlight this.

It'll be interesting to see what happens by months end but potentially prepare for a month of two halves!

Matt.

 

It's certainly open to questioning seeing as how the only year of 'forecasting' we have to go by was a miss as far as the AO goes, but if it's going to increase it's going to have to hurry up since the D10 forecast is effectively factored in. 

Still doesn't look to me like the vortex is getting its act together in a hurry:

 

Troughing placement doesn't look too dissimilar to early in the month either (albeit again far more 'blue' as you'd expect and quite a bit flatter)

Edited October 16, 2014 by LomondSnowstorm

[Interitus]

 

 

As far as a negative OPI is concerned I would assume that high pressure over the pole is key though I have limited understanding over how the precise measurements are arrived at.

 

With regards to the geopotential anomaly part of the equation (in the Elypticization box) the formula is (Asia + America - Arctic)/10 so a high north pole anomaly can be cancelled out by smaller positive anomalies in the other two regions.

The axis angle has generally been the larger factor but is very sensitive to the locations of low pressures skirting round the edge of the vortex, both from timeframe to timeframe and run to run.

[Duane S.]

The volatility is so large that it would seem to make more sense to use a 5-day forecast instead of 10, since there will only be relatively minor changes (usually) in that output.

Agree, it would make a lot more sense. But then the GFS should only really be run 2 times a day, but where would be the fun in that :-)

It also occurred to me that they really ought to to have one daily figure published once the 12z is in (i.e. The 00z, 06z and 12z consolidated). The confusion comes as much from the inter daily figure as the day to day figures themselves.

[NorthYorksWeather]

12z just updated -3.26

[Yarmy]

Agree, it would make a lot more sense. But then the GFS should only really be run 2 times a day, but where would be the fun in that :-)

It also occurred to me that they really ought to to have one daily figure published once the 12z is in (i.e. The 00z, 06z and 12z consolidated). The confusion comes as much from the inter daily figure as the day to day figures themselves.

 

Another possibility would be to run it for each ensemble member and then present a spread of OPIs with the op being the "main" one.

[phil nw.]

 

With regards to the geopotential anomaly part of the equation (in the Elypticization box) the formula is (Asia + America - Arctic)/10 so a high north pole anomaly can be cancelled out by smaller positive anomalies in the other two regions.

The axis angle has generally been the larger factor but is very sensitive to the locations of low pressures skirting round the edge of the vortex, both from timeframe to timeframe and run to run.

That makes sense Interitus as it could explain some of the varying readings we have seen run to run.

I am wondering how much effect the trending upwards of the overall AO will have come month end.

 

I would think the more fragmented the vortex remains the better chance of a -ve OPI by month end.

Not a straightforward measure to follow that;s for sure.

[Duane S.]

12z just updated -3.26

Caused by the axis angle aspect of the formula as the NH GPT anomaly is actually slightly positive.

[neige57]

That makes sense Interitus as it could explain some of the varying readings we have seen run to run.

I am wondering how much effect the trending upwards of the overall AO will have come month end.

4.gif

 

I would think the more fragmented the vortex remains the better chance of a -ve OPI by month end.

Not a straightforward measure to follow that;s for sure.

 

 

there is a good chance that the graph of AO suddenly changes tomorrow (see tonight) because the models projectent negative and not positive AO. There was a break last night this morning GFS / GEFS saw scenarios AO positive which explains the positive as shown in Chart

[Nouska]

In last years forecast Riccardo has annotated the October composite and made some comments about how he arrived at the result. It refers to some of the points being raised here.

 

The chart - 

 

 

 

The discussion -

 

 

From the careful analysis map, the primary October pattern characteristics are:

 

1)      central axis of the vortex (black line) moderately inclined, joining Labrador and eastern Siberia; the axis position and OPI value are output of “Telemappa Next Generation†software;

 

2)      very low elliptical component index of weake stationarity and intrusiveness of the planetary waves.

 

Also, in virtue of near correspondence between average October pattern and circulation model characterizing the focal cold event of the following winter (“key event†in which the planetary waves activity is more intense in the winter), from the above reanalysis map and in refer the montly axis (black line), is possible infer featured of the most relevant winter events. In our case you notice a Pacific wave (wave 1) translated, compared to the usual position, on the eastern sector of north Pacific (Alaska gulf) and the Atlantic wave (wave 2) in symmetrical position respect to the axis (black line) positioned on the eastern Atlantic (United Kingdom - Scandinavia).

This planetary waves configuration (wave 1 – 2) suggest a compact Polar Vortex condition and weake planetary waves intrusiveness (in particular for wave 2) also in the most strong activity pahses. On the other hand the high OPI value, as well as the large negative anomaly centered from noth Scandinavia and Kara sea, support the thesis of a favorable circulation schema in which the Altlantic wave (wase 2) isn’t intrusiveness on high northern latitudes however in AO neutral/positive context. About location of the Pacific wave (wave 1), it result centered into western eastern pacific sector (Alaska gulf).

This configuration should favor a strong advection of cold arctic air masses to the central-eastern areas of the American continent during the increased activity of the planetary wave.

 

 

 

[shaky]

12z just updated -3.26

as I thought mate!!!12z looked pretty damn good for a negative opi!!!