Duane S.

Thats a bit too much A+B=C, as It’s just one ingredient in the cauldron. Other factors combined could still very well override this primary driver. But when the QBO is in its Easterly phase, as well as increasing the probability of SSWs, the atmosphere loses the ability to super charge our own jet stream / vortex in the same way as when we’re in a Westerly phase QBO. When the QBO is in its westerly phase, it can add energy in, to increase the westerlies in our tropospheric jet stream – leaning towards there being a greater risk of a stronger and persistent jet stream, with associated Atlantic storm systems.

Yep, I really think that has played a huge part Mike, just as you’ve put it. The strat vortex hasn’t been able to strengthen unabated through November/ December as it normally would. I think the E-QBO has played (and still is playing) its part as well.

The excellent Amy Butler putting out quite a few really interesting tweets right now. Essentially emphasising it’s tropospheric led disruption that is doing the damage to the vortex. “4/) Practically speaking, what matters for surface impacts/predictability is what happens in the lower stratosphere, where the polar vortex will be fully disrupted. So in that sense this event could still have persistent effects on tropospheric weather patterns”

Yes, it does make me laugh how once someone states it will be dry, they then have to go to great lengths to ‘prove it’. Surely the irony of desperately trying to prove a point, based on something (that hasn’t yet even occurred) that will be missing all sorts of macro details at this far out stage, isn’t just lost on me?

Just the envelope, doing its thing.

Yep, think it was around that. Continental airmass undercut versus moisture laden system in from the SW. The absolute definition of high risk, high reward

My words from last Saturday, still stands… ”I’m a little lost as to why so many people are so shocked at the variable deterministic output from the models. This warming and u-wind slow down is not your usual NH standard winter stuff. The models will struggle accordingly, more than normal, and head off earlier down different paths at times. For a brief time this coming weekend, for the south at least, there has been a strong signal pointing to more average 850s for the past few days. Milder blip before the main event starts from early the following week. That has not altered. The detached Atlantic low is going to be a huge player in all this I feel. Watch this be friend then foe and back to friend and then back to foe from run to run to run over the coming days” To be fair, if everyone was posting at the frequency I’ve been this winter it would be a pretty dead place , but when I’ve had the time I’ve been all over this. There has been some outstanding contributions on this forum by some, please keep it coming It’s a shame some don’t seem able to just enjoy what’s going on right now (with the inevitable associated ups & downs reflected in the chart outputs). Who knows how many more years it may be before we get such a set of background signals pointing to cold (and longitivtiy of). Call out the bad runs by all means, but perspective please. As Feb’78 got brought up, it’s time to wheel out my favourite ever chart. If only to remind folks it ain’t all about the 850s . The biggest snowfall in my location, on the south coast, in my lifetime. 18 hours of non stop snow with 20 foot drifts a few miles north of me. A product of embedded cold air and being JUST on the right side of marginality..

It would be nice to see this being somewhere near accurate as well. Certainly has support in the early stages of progression

A few days ago we had this stunning 10 day chart from GEM. Clearly this would be right at the top end of outcomes, it was stunning. And on that basis the outcome unlikely to end up quite as good as that was showing. Move ahead in time, through all the knee-jerk doom and gloom, all the wheels falling off the bus, huge disastrous downgrades and the such, yet still… OPs are still there sticking to the general theme, that envelope. Nothing has changed Moreover, that Atlantic low remains primed to cause a forecasting nightmare come the time.

No, this hasn’t all gone. Bar some more progressive runs that were showing it early weekend, any interaction has generally been modelled late weekend / early the following week. This is subject to big changes yet, because of its interaction with the jet. At the moment the models are clearly struggling with this. There are several options on the table, and will be for a while yet. Some good, some bad, some indifferent.

Too much weight is being given to GEFS trends mid term IMO. The 00z - 06z differences highlight this well. In these non-standard evolving cold spells, there’s often little to be gained by making these too big an egg in the proverbial basket. There is an enormous amount going on right now, none of which is your standard zonal. Never mind the Shannon Entropy involved downstream from events in the stratosphere…troposphere wise… Pacific ridging interference, that Azores low, inflated Iberian heights, retrogression of the UK high are very difficult to model. They are all intertwined with each other to different degrees as well of course, and not to be taken as isolated entities. Then you add in primary long term drivers like ENSO and QBO and short term the MJO route/amplification. Well, good luck being confident on our weather in 2 weeks time. The take any has to be though, there are way more background signals in our favour than often is the case, so sit back, relax, and try to enjoy the inevitable ups and downs (still to come ), we’re in a really good place still.

In my view, this is a very big factor. Specifically the ENSO state and E-QBO together.

I’m a little lost as to why so many people are so shocked at the variable deterministic output from the models. This warming and u-wind slow down is not your usual NH standard winter stuff. The models will struggle accordingly, more than normal, and head off earlier down different paths at times. For a brief time this coming weekend, for the south at least, there has been a strong signal pointing to more average 850s for the past few days. Milder blip before the main event starts from early the following week. That has not altered. The detached Atlantic low is going to be a huge player in all this I feel. Watch this be friend then foe and back to friend and then back to foe from run to run to run over the coming days As for heights to the south, just a natural response to a combo of retrogression and that low pumping up the Hadley Cell. IMO it should be temporary, if at all, as that low ought to drift SSE and fill eventually.

Stunning. As steep an ascent at this level that I can remember . I find a better correlation to incoming cold however is at 30mb. Worth watching in the coming days. That said it’s already been running above average for 3 odd weeks, so that is definitely already playing to our advantage.

I can’t stop looking at this chart. It is simply beautiful

Despite concerted and at times desperate efforts to drag down the mood on here, everything looks as expected this morning for a decent cold spell for us. All within the envelope. Unfortunately, at this early stage, the outer edges of said envelope will never be a wintery nirvana. This has forever been the case for the UK and a cold spell, notwithstanding AGW has likely slightly widened that envelope over the past 30 years. There is a fine line between excellent pragmatism (i.e. Nick Sussex, Blue Army) and oh look at me I told you (several-dozen-bleeding-times-a-day…) it wouldn’t be -20 uppers and a 3 month long cold spell (glossing over the fact that nobody had actually said anything remotely like that). I exaggerate of course, but I’m sure most get my point… Of course the Azores high is a massive driver. If you look back at my first post of the winter, back in early November I went to pains to point out that I felt the story of this winter will be a very ’active’ displaced Azores high. This has good and bad consequences. For a start a Euro high ought to be less of a concern. Retrogression likelihood to be a lot higher than usual but yes that brings about the potential of a negative NAO with it. I’ll take that risk thanks. There is no hard fast way to guarantee winter weather to our balmy shores, there will always be jeopardy involved. Thats why 95% of people,like myself, visit this forum every winter. It’s as much about the chase and the enjoyment (and otherwise ) of it all along the way. Most on here are long enough in the tooth to know things will likely go wrong, to a degree or another, thanks. Ignoring a user is all well and good but it doesn’t stop them being the centre of attention and thus part of half of the thread posts quoting them. Again. There will be no kudos for pointing out what could go wrong every time there is a cold spell chase. Anyone could just as easily copy and paste that every time as well. And guess what? They will end up being correct most of the time But that, I thought?, isn’t why the vast majority of us come on this forum every winter.

Jeez. If this run is ‘sobering’, it shows what a good place we are in!

However…This shows a quicker return to average than the last couple of days. Personally, I’d prefer to see us miss an SSW but maintain weak westerlies through January (and hopefully beyond). I think with this current ENSO/IDO/QBO combo, we will reap the rewards. Then factor in the wave breaking from recent momentum spike, this sees us through favourably to maybe 3rd week of Jan. An Atlantic incursion likely after that (may be a VERY good thing that mind), then favourable MJO to then kick in late month to set up a memorable February. Simples. What could possibly go wrong

This fresh in from the EC headquarters…

Incredible set . Thanks for doing these Mike by the way. They are an often overlooked tool when it comes to reading the charts. There’s a tad more to this than individual Ops and the ens. Taking in the respective clusters should always be included as part of the chart suite analysis

It’s all there if you go looking. I did this a while back for a previous cold spell build up ( I can’t remember which) It did make for amusing reading at times, especially with the knowledge in mind that the cold spell did materialise on that occasion.

Good luck with that on here! But seriously, looking fantastic for mid month. Anything before, as has always been the case, to be treated as a bonus

I have been off this forum for a day or so. I had a quick scan through the charts of the past 24 hours (and they are certainly starting to fit perfectly with the teleconnections). I then opened up the Model thread, clicked a few pages back and then this was the first post I read ! This will ALWAYS be the risk involved with retrogression. We almost certainly will see a period of time with a West based -NAO threatening on the charts. And yes, it could very well even end up being the case. But... why the need to point out the bleeding obvious so far back? We go through plenty of winters without anywhere near as good a signals (as we have right now) for a proper retrograde. Having to read everything (and there are many) that can go wrong, does get somewhat tiresome after a while.

But where has there suddenly been a trend for the block to now be too far north ? Of course, if a block IS too far north, it indeed opens the door to the Atlantic. If a block is too far west we are at risk of any mixing out the cold. Too far east, we miss it all together. Too far south etc…. I think all your post does is highlight the incredible fine margins involved with getting a cold snowy spell to the UK. Anyway, very decent chart suite this morning. A initial mid lat high seems to be gaining traction, but with forcings still likely to be in our favour, a further retrograde looks likely. It’s clear how we could have a memorable January if things fall right for us.

And that concludes my Netweather bingo card for this chase.