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

[Wilxy]

It seems that this GFS oper has the least blocking if you compare with EC00z and GEM12z. Looking forward to EC12z.. Hopefully the OPI doesnt becomes more then -2.5.

 

Its dropped to -1.86 now but I am not concerned, if anything I am still feeling optimistic but also cautious.

[MR EXTREMES]

Yes, the GEM has generally been looking better for blocking! 

ecm has been showing continued blocking for days now and so has the gem i rate the gem above the gfs for longterm trends the gfs loves low pressure i dont see the gfs beyond t144 even being close.

so id expect the OPI to continue into neg territory through the rest of october.

[feno13]

- 1.86 12z

[Continental Arctic Front]

OPI update.. -1.86, well i didn't see that one coming! Especially when you saw the graph of past year when it was stabilizing.

[Yarmy]

That's a huge drop when you think it would be stabilising. (It was -3.04 after the 00z)

Edited October 20, 2014 by Yarmy

[feb1991blizzard]

It hasn't dropped, it has risen!

[mulzy]

That's a huge drop when you think it would be stabilising. (It was -3.04 after the 00z)

 

Not sure if heights at the pole are a driver for the index but GFS 12z does how low heights in the polar region at days 9 and 10. 

 

ECM could be cruicial tonight - this is just like chasing a cold spell in the depths of Winter...

Edited October 20, 2014 by mulzy

[karyo]

OPI update.. -1.86, well i didn't see that one coming! Especially when you saw the graph of past year when it was stabilizing.

I knew that the 12z gfs was not a good run but I didn't expect such a rise in the index! 

 

The UKMO is not great either to be honest. Would it have followed the gfs if it was going further than 144 hours? You can see the high pressure cell that was originally in East Scandinavia slipping into Russia and a westerly taking over to the north of it.

Edited October 20, 2014 by karyo

[Cheshire Freeze]

I knew that the 12z gfs was not a good run but I didn't expect such a rise in the index! 

 

The UKMO is not great either to be honest. Would it have followed the gfs if it was going further than 144 hours? You can see the high pressure cell that was originally in East Scandinavia slipping into Russia and a westerly taking over to the north of it.

 

Yep, the high faces just too much pressure from low heights around....you guessed it....Greenland (+stronger/tighter resultant jet streak) . A place we don't want to see low heights manifest themselves. As we all know, it can be a hard slog breaking those low heights up!!

Edited October 20, 2014 by CreweCold

[Continental Arctic Front]

I knew that the 12z gfs was not a good run but I didn't expect such a rise in the index! 

 

The UKMO is not great either to be honest. Would it have followed the gfs if it was going further than 144 hours?

Me neither, but -1.8 is also a good value, the "breaking point" was -1.5 OPI i thought?

 

And thats true about UKMO, but the model calculates more pressure over eastern Siberia on 144hr, i dont see that in the EC and GFS run.

[terrier]

I think there is been far too much placed on our winter hopes on this opi even mad madden is blurting about it now. We may see a weak vortex but remember the uk can still end up on the wrong side of a blocking high. Leaving us in a westerly based set up. Yes I do think we won't see a winter as bad as last year. But I also don't think we will see heavy snow and freezing conditions for weeks at a time. My thoughts are a mixed winter ahead with more of a Atlantic influence going into mid jan.

[Ali1977]

OPI went from -0.2 to -3.8 in 5 days early in the month, would base anything on 1 run. If in 3-4 days it's down to 0 then we'll just have to clutch at other straws. The express maybe.

[SMU]

The GFS has gone all default on us in the last 5 days. If you look at my AO images I have uploaded to the model thread you will see how its modelling of the polar field has been pretty poor.

 

Saying that the next 4 days does see a burst of Westerlies, however its in isolation & expected to break up again by day 6.

 

No cause for concern.
S

[karyo]

Me neither, but -1.8 is also a good value, the "breaking point" was -1.5 OPI i thought?

 

And thats true about UKMO, but the model calculates more pressure over eastern Siberia on 144hr, i dont see that in the EC and GFS run.

-1.8 would be a good finishing value but it is a surge upwards which is very worrying!

[karyo]

The GFS has gone all default on us in the last 5 days. If you look at my AO images I have uploaded to the model thread you will see how its modelling of the polar field has been pretty poor.

 

Saying that the next 4 days does see a burst of Westerlies, however its in isolation & expected to break up again by day 6.

 

No cause for concern.

S

But Steve, the ECM has struggled just as much! Compare yesterday's dreamy 12z with the 0z as an example.

[Continental Arctic Front]

But Steve, the ECM has struggled just as much! Compare yesterday's dreamy 12z with the 0z as an example.

 The current 12z is also not good, the vortex is activating it seems.

[Weather-history]

-1.8 would be a good finishing value but it is a surge upwards which is very worrying!

What is worrying me is that people are getting too hung up on this.

Great for research, not great if people are hanging on every nuance of it.

[LomondSnowstorm]

OPI went from -0.2 to -3.8 in 5 days early in the month, would base anything on 1 run. If in 3-4 days it's down to 0 then we'll just have to clutch at other straws. The express maybe.

 

2/3 of the final value is already set in stone, so it would take some massively positive values at the back end of the month to get up to -1, never mind 0. 

[radiohead]

I think that as long as the OPI is being calcuated with days 7-10 from the GFS included then you have to expect changes like this from run to run as you are still including output for the FI period of each run, which as we all know too well, can change on a dime. I think once we get to around the 24th we'll see a more stable OPI figure as the FI element will have been removed. Until then, we'll just have to wait!

[karyo]

What is worrying me is that people are getting too hung up on this.

Great for research, not great if people are hanging on every nuance of it.

The models are going for a mild winter so the OPI and the snow cover are the only positives for us coldies at the moment!

[LomondSnowstorm]

The models are going for a mild winter so the OPI and the snow cover are the only positives for us coldies at the moment!

 

Well, that and a weak El Nino coupled with a -QBO and some decent early signs for the stratosphere. Even without the OPI the analogue years would suggest an increased chance of a negative AO and high latitude blocking.

[karyo]

 The current 12z is also not good, the vortex is activating it seems.

Indeed, much less high pressure up in the Arctic than the 0z. Also, it projects a southwesterly penetrating well into Russia which can do some serious damage to the fresh snowcover. It is not as bad as the gfs though.

[mulzy]

Indeed, much less high pressure up in the Arctic than the 0z. Also, it projects a southwesterly penetrating well into Russia which can do some serious damage to the fresh snowcover. It is not as bad as the gfs though.

 

 

Yep both the 12z GFS and 12z ECMWF not great - if these runs came to fruition then the OPI would take a hit (like it did this evening) - however just one set of runs and let's see what tomorrow brings....

[karyo]

Yep both the 12z GFS and 12z ECMWF not great - if these runs came to fruition then the OPI would take a hit (like it did this evening) - however just one set of runs and let's see what tomorrow brings....

Agreed! Hopefully an overeaction to a signal. The difference to what we were seeing 24 hours ago is outstanding!

[blizzard81]

Would it still be possible to end up with a neutral or even positive OPI ?