Mike Poole

Great run so far from the GFS 12z. Here at T144, there is a good split of the vortex, leaving just enough on the Canadian side to fuel WAA west of Greenland. Leads to a decent and cold northerly at T180. Good to see this in the mix.

ECM clusters T192-T240: This is now the timescale we were tracking with the T264+ clusters a day or two ago, so let’s see what is currently being predicted and how it compares with previous. Cluster 1, while designated Atlantic ridge (purple border) in fact has the high stubbornly refusing to shift from the UK. Cluster 2, this one is similar to a couple of op runs recently with the Azores high sluggish to retract, but looks like it will get there in the end. Cluster 3, is the one we want with a proper northerly developing. Cluster 4, is also with much promise and a northerly flow. Most optimistic take, clusters 3 and 4 total 18 out of 51. That’s todays odds! It isn’t worth posting the T264+ clusters, there are 5 and look a complete mess, you can tell when there is just no signal whatsoever and that about sums it up. Finally, the spread at T168 is worth a mention: At later times than this, there is uncertainty all over the place, but not a localised hot spot like this between Greenland and Iceland. Make of it what you will, but I’d kind of mark it out as something that needs to be resolved before we put any faith in the later output.

One of those where you’d like to see the next two frames from ECM T240: I think a modest step away from cold today on the models, so a lower probability than yesterday of landing anything noteworthy, a decent short term toppler still very much on the cards. On to tomorrow.

Kind of asking a lot of this area on this one, T240:

Well it kind of has to from here, doesn’t it? (Know I said I wasn’t going to stay up for the pub run, but hey ho!). T204:

So where are we right now? I’m not staying up for the pub run, early start tomorrow! Well for a week or so now this place has been a strange place with those of a cold persuasion (I think it is fair to say) looking fairly long range for thin gruel, and of course cherry picking fruity ensemble members, while those who are convinced there is no cold to come at all in January (I think it is also fair to say) saying so repeatedly without backing it up with any evidence at all (I exempt @Catacol and @CreweCold from that generalisation because they have provided their reasoning). But I sense a shift based on the model output today: The evolution after the reliable relys heavily on where the bulk of the trop PV ends up, and while there is definitely an early movement to the east, whether it all stays there, how much remains as a Canadian lobe has been massively open to question. The 12z suite, and ECM clusters, seem to be reinforcing the idea that the shift of the PV to the east will be more substantial, allowing an Atlantic ridge to form and the Azores high to retract, thereby allowing a trough into Southern Europe. For a longer term cold pattern, this is now a 40% chance at most (going off the 12z clusters 20/51 - that could be a flash in the pan, need to see it repeated on next couple of runs). For shorter term northerlies (topplers), I would say there is a better chance than 40% (75%?) we will see something the week after next. Today, with the ECM 12z we now have something to work with within 10 days. There is still massive uncertainty about how the next 2 weeks pan out, and anyone saying they know now are talking out of their backsides. I think there will be some twists and turns to come if we are to get this down to T0! Best regards Mike

Also, in case you hadn’t spotted it, nerdy point here!, the representative perturbation chosen to illustrate the cluster was ‘perturbation 0’ - which is the control. (Op run obviously finishes at T240.)

ECM clusters T264+ And, well, the 20 member Atlantic ridge cluster 1 - we will take all you’ve got of those !

ECM clusters T192-T240, big change since last couple of runs: Clusters 1 and 2 firmly Atlantic ridge, scandi trough and look very good for a UK cold plunge (total 23 members), cluster 1 slower to retract the Azores than cluster 2, so no surprise the op is in cluster 1. Cluster 4, also Atlantic ridge, but the high possibly a bit close the UK. Cluster 3 attempts heights into Scandi, I think this is a solution that is decreasing now in probability, and 5 has the block too far west. But nothing remotely zonal (for those of you still of that view) on any of them. Very promising as we move forward towards this chase proper…

That’s as may be, I was taking the earlier part of the run as read, and from T192 the evolution looks eminently sensible to me.

The eventual retraction of the Azores high to join the forming Atlantic ridge was obvious at T192 if you looked on NH view.

JMA at T240: To be honest this one just following on from a similar solution on the 0z run. My take on the 12z suite overall now is a slight increase in probability of the bulk shift of most of the PV to the eastern side which is very good news, ECM take suggested the Azores high might be sluggish to retreat but it seems it will have to realign with the Atlantic ridge in the end. All eyes on the clusters, I would expect to see much higher numbers showing the Atlantic ridge by T240, and beyond than the last couple of runs. By the way, with this kind of setup, with the vortex moving and all, it is really important to view the NH view not the Europe view, because it is much easier to see with the Azores, for example, what is driving its position.

Azores just slowing evolution a little, starting to move away by ECM T240 and the cold is on the way: Happy with this run. First one I think when we’ve had something really promising at day 10, not beyond. Still massive uncertainty, of course.

ECM T192, there was a run like this yesterday, one of the GFS runs, I think: Pushing the vortex to the eastern side but for how long?

I’m still of the mindset that it all hangs on the distribution of the trop vortex post day 10, i.e. what percentage of it ends up to our east, and what remains in the Canada region. To illustrate, here’s the ECM and GFS at T240, and the JMA at T264: ECM has more of it on the eastern side, retaining a lobe to the west, leaving a gap for a height rise into Greenland. GFS retains a much stronger lobe to the west so that option isn’t there going forward. JMA pushes more or less all the vortex east and I’d would have liked to see the next few frames of that one. Until this is sorted out, the blocking options remain on the table, alongside the Atlantic dominated options.

The sea level pressure contours over Greenland are problematic, because the surface is way higher than sea level and the model has to extrapolate what the sea level pressure would be. And they all seem to do it rather differently, JMA seems to be the worst at ridiculous ‘sea-level’ pressures over Greenland. So you need to look at the colours (Z500 height) and get first light blues then green and oranges in there to indicate proper heights over Greenland. As starting to show now on GFS T264:

For me, this is about what percentage of the trop PV ends up on the eastern side and what remains over Canada/USA. We want as much as possible over on the eastern side. But in today’s runs it has been quite variable this! Now the GFS 18z, T204, looks like a good solution with a healthy dose of WAA acting on the remaining PV lobe over Canada, should prove a good run this:

Yes, and neither are we at the day 7-10 timescale. Our speculation as we have discussed the pub run in the context of recent GFS runs is beyond that timeframe for now.

For me, that last one at T300 looks a bit forced, suggesting that the model has gone a bit wrong by this point, I think that if it has gone wrong it has erred on the side of keeping too much of a Canadian vortex lobe, from the earlier position, I would expect it to be weaker than this by now. So I would see this run as an upgrade, but with power to add in runs maybe tomorrow evening, but note it is all still outside 10 days so we only really have the GFS to go on, and ECM clusters/ensembles. But very happy with the runs today from a coldies perspective looking to get something out of January. See you all tomorrow .

T264: Next push could see more of the vortex pushed to the dark side

Pub run T192, think this is going to be a cracker, long draw WAA west of Greenland:

GFS 18z T168, what do people reckon, push into Greenland about T216? Much faster with relocating the vortex to our east. And it looks like the heights into Scandi at this time are aiding and abetting that move of the vortex. Not quite sure why, but it seems consistent on runs that have both.

Thanks for the reply. But actually I do agree that the relation goes both ways, which is why I assert that while the two vortexes seem to be doing different things, while that may mean the trop vortex has more latitude to split and move as forces down here dictate, also, I think that means there is much less chance of the trop precursor patterns for a SSW to take hold, which is why I have thought for some time now that there won’t be a SSW. At least in any timeframe where it could influence late winter. We will see…

Not had time to post earlier today, but I think it needs to be stressed that the period of interest is not within the 10 day period, so whatever dross is shown up to then is what it is. A subtle change in the extended clusters T264+ chart today: The majority cluster is still the Greenland high, the second and to some extent the third show the Atlantic ridge transferring to Scandi, while the fourth looks less promising. But - at this range, none of the charts have the blue border (+NAO) so while the destination remains unclear, on this model at least, zonal flow from the Atlantic seems unlikely. We are in the game for the latter third of January, I think. That’s no guarantee, but it is something to chase over the next week or two!

Seems stuck at T240, I’d guess not as far as the 12z run, but much less of the vortex left to our NW so is probably a better run for UK in the longer term.