[Model Output Discussion - Christmas and New Year]

Unfortunately the trend away from amplification in the Atlantic and over Greenland has been consistent for 48 hours now.

[Model Output Discussion - Christmas and New Year]

4 minutes ago, Broadmayne blizzard said:

Did objective opinion not consider the reamplifying process of the pattern.

But yesterday, and for a few days before that we were seeing successful amplification into Greenland. Now we're seeing potential of reamplification at the far reaches if FI. The output has become less amplified with every run since yesterday evening. That's not saying it's a totally flat pattern, but the trend is the wrong way today.

[Model Output Discussion - Christmas and New Year]

9 minutes ago, Frosty Winter said:

Wasn’t going to post today until I saw this. Not sure whether you’ve been on the sauce this afternoon but I think you’re losing perspective about what a flat pattern actually looks like.

Flat:

Not flat:

We’re in a great position going forward, especially with the SSW potential as well. Anyway, Merry Christmas everyone!

Compared to the output over the last few days? Definitely flatter compared to what had been consistent recent output, which was what I said. But nevermind, objective opinion clearly not welcome.

[Model Output Discussion - Christmas and New Year]

Cold in the medium term, but longer term a definite trend over the last 48 hours towards a less amplified NH profile in the long term. GFS dropping a Greenland high, with each run showing lower heights in that area. Hopefully not the beginning of a pattern change for the worst.

[Hunt For Cold: Model Discussion - Heading Into Christmas]

12 minutes ago, Nick F said:

There is a danger of assuming that the upcoming major SSW and forecast split will couple with the tropospheric circulation, unfortunately not all do, a recent study by Karphechko et al. (2017) suggested that 43% of SSWs do not strongly couple to the trop circulation. We've been lucky that in recent years that some of the major SSWs (Jan 2009, Feb 2010, Jan 2013 and Feb 2018) have downward propagated and given us the goods. Credit to Simon Lee: https://simonleewx.com/2018/12/27/not-all-ssws-were-created-equal/

However, there is a great deal of uncertainty how this SSW will affect the trop if at all, so a waiting game to see, given that it can take 10-14 days for the troposphere to respond from the date of the SSW. The ECWMF ops recently to varying degrees have been hinting at perhaps a response from the trop by building a ridge north over the N Atlantic while deep cold pushes south over NE / E Europe. GFS ops not really been keen at all, rather showing deepening and expanding trop PV to the north and strong westerlies, though jet stream tracking further and further south with potential for NW'ly or N'ly incursions.

We could also see the trop pattern respond to poleward wave propagation of the MJO wave if it goess through 7-8-1 at a decent amplitude too, so if the SSW doesn't have an impact on changing the pattern the MJO could do it.

Frustrating I know, when the models are not hinting with any confidence and continuity a pattern change to bring deep cold and wintry weather atm. So more sitting on the fence from me.

And exactly why we shouldn't be saying so certainly that the models are yet to smell the coffee because the trop isn't mirroring the forecasted strat profile the way we would like it to 

It's has been suggested repeatedly that the models are yet to "smell the coffee". This coffee being the strat or MJO output of those same models.

Is there any truth to the notion that models don't take account of the feedback of the very events they are forecasting? It doesn't seem likely that NWP would have a less holistic view of the atmosphere when compared to wx enthusiasts looking for one type of weather in one part of the globe 

[Hunt For Cold: Model Discussion - Heading Into Christmas]

Is there any actual evidence that models are slow to take the effects of a SSW into account until it's under way. Similarly, it has been suggested here that the models are yet to factor in the impacts of the MJO.

It doesn't seem logical to say the GFS is not taking the amplitude of the MJO phase into account. And then make an independent forecast based of a GFS MJO plot... Similarly with strat impacts.

It's seems likely that the GFS/ECM/UKMO take many more drivers, signals and data into account than any human ever could when coming up with a forecast. Perhaps it's us enthusiast's are the ones failing to take drivers into account. And within there lies the mismatch between our expectations and NWP output, not the other way around.