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Blimey !
This thread has woken us all up. Welcome Riccardo.
I don't know about others, but I would personally find it very useful if someone in the know could briefly set out the critical correlations and inferences that can be drawn from the OPI.I've heard that a strongly negative OPI has a good correlation with a weak PV and therefore a negative AO, which in turn makes it 'easier' for conditions that favour a cold winter in the UK to set up... but this is new to me, so I probably have it entirely wrong and it's entirely possible that I'm making up all those TLAs in an effort to fit in with the other kids and it's actually an LOB scenario? :)Thanks
I don't know about others, but I would personally find it very useful if someone in the know could briefly set out the critical correlations and inferences that can be drawn from the OPI.
I've heard that a strongly negative OPI has a good correlation with a weak PV and therefore a negative AO, which in turn makes it 'easier' for conditions that favour a cold winter in the UK to set up... but this is new to me, so I probably have it entirely wrong and it's entirely possible that I'm making up all those TLAs in an effort to fit in with the other kids and it's actually an LOB scenario? :)
Thanks
If you Google it you come up with last year's write-up also from Riccardo (looks like Google translate from Italian to English)
It does go into a little more detail about how the index works but it looks quite technical to my untutored eye
http://www.americanwx.com/bb/index.php/topic/41639-seasonal-winter-20132014-forecast-based-on-opi-index/
I found some other articles too but they need translating from Italian
Hope you are right mate because we havent had a decent winter since 2010/11 here.Andy
I'm amazed you can remember so far back!
(and wasn't winter 2012/13 pretty good with hindsight? Not a classic, but we had 3 or 4 decent snowfalls between Jan & the end of March in a winter that just wouldn't give up!)
Anyway, whilst hoping Steve M's excitement is merited and this OPI thing not only gives a very promising forecast, but we do actually get a good winter on the back of it, I've seen many a 'system' be heralded as THE big new thing in winter forecasting. And been totally suckered into the excitement of a forthcoming great winter (anyone remember Tom P's snowmageddon forecasts??). So I'll kep my keep on the ground about it.
a flick through the gefs members reveals little appetite to build a strong vortex in the next fortnigh
Question: are things looking better than this time last year?
Big shift in the latest OPI. Now at -1.67.
Is that where the OPI currently is or where it's projected to be by the end of today's GFS run?
Big shift in the latest OPI. Now at -1.67. Is that where the OPI currently is or where it's projected to be by the end of today's GFS run?
Think it's the projection based on the latest GFS run. I'm guessing it's picking up on the flatter pattern which is appearing in some of the runs now.
Big shift in the latest OPI. Now at -1.67. Is that where the OPI currently is or where it's projected to be by the end of today's GFS run?Think it's the projection based on the latest GFS run. I'm guessing it's picking up on the flatter pattern which is appearing in some of the runs now.
-1.67 to 27th October should still give us a negative OPI for October?
Big shift in the latest OPI. Now at -1.67. Is that where the OPI currently is or where it's projected to be by the end of today's GFS run?Think it's the projection based on the latest GFS run. I'm guessing it's picking up on the flatter pattern which is appearing in some of the runs now. -1.67 to 27th October should still give us a negative OPI for October?
btw, its not out to the end of the gfs run but to day 10. so we have a predicted opi at 21/10 of -2, based on todays gfs 12z out to T240 and the actual data from the first 10 days of october.
Daily figures up to and including 11/10 @ 18z: -1.2, -0.8, -0.3, -0.2, -2.2, -2.1, -3.42, -3.57, -3.85, -1.13, -2.0.Mean at -1.89Clem
as far as i know clem, the opi updates at the end of each gfs run to give a running figure based on the actual numbers up to the current day and the projected number based on the next 10 days. the mean of the previous days numbers should not be relevant.
incidentally, this from the latest ECMWF seasonal update for winter which was issued on the 8th:
It has a major negative AOIt has more blocking over Greenland now , but still has the strongest blocking over the NW part of N America and over the pole.
of course, this could well deliver a west based -NAO which would make nw europe fairly mild. promising though as it does tie in with what seems to be louder and louder background noise re a -AO winter.
Much better - hardly anyone's mentioned SSW yet
Thank you Riccardo for your contribution and your work looks interesting.
Daily figures up to and including 11/10 @ 18z: -1.2, -0.8, -0.3, -0.2, -2.2, -2.1, -3.42, -3.57, -3.85, -1.13, -2.0.Mean at -1.89Clemas far as i know clem, the opi updates at the end of each gfs run to give a running figure based on the actual numbers up to the current day and the projected number based on the next 10 days. the mean of the previous days numbers should not be relevant.incidentally, this from the latest ECMWF seasonal update for winter which was issued on the 8th: It has a major negative AOIt has more blocking over Greenland now , but still has the strongest blocking over the NW part of N America and over the pole.of course, this could well deliver a west based -NAO which would make nw europe fairly mild. promising though as it does tie in with what seems to be louder and louder background noise re a -AO winter.
I'm just using the running mean to take out the guess work of the next 10 days predictions to see where we stand as of now. The more days figures that are added to the running mean obviously the less uncertainty and less swings there are. If we can keep the figure sub -1.5 things could be getting very interesting!
Interesting piece on Joe B's Saturday Summary around the AO and NAO and the current CFS model contradicting its winter forecast with the positioning of above average heights across the Atlantic.
Clem
Riccardo why did you choose to correlate the OPI with the AO rather than the NAO?
Of course the NAO does not correlate exactly with UK CET-the correlation is around 0.60.
Based on the GFS12z run it's now down below -3 again. I'm surprised because at a glance the 6z and 12z runs both look pretty flat, though TBH I've not looked at them in depth. If Riccardo is around I'd be interested to know what the key differences are between today's 6z and 12z GFS runs in terms of the OPI.
i think it's to do with the angle of the vortex Brian. I wish I could get a better handle on this but I believe that the lower the angle, the more likely it is that a split vortex will ensue rather than an organised one.