Mike Poole

Yep, and shame it only goes to T120, there’s only so much you can glean from such a run.

ICON 18z T120, compared to 12z T126: Looks sharper with the ridge but blows up the low N Scotland a bit more. Worry is that might push it a bit further west. Any road, on with the pub run...

Feel I’ve been swimming against the tide a bit tonight, but hey ho! The way I see things from the model output only is this. Starting with the ECM mean at T240: The yellow arrow is the advection of cold in our direction around the arctic high, the red is the omega block into Greenland, whether it becomes a cut off Greenland high is still up for grabs, the black circle is the problem area. ECM op at same time: There is no clean path for the cold to reach us in the black circle, it is messy. Because there is nothing driving the weather strongly in this region, out of reach of both the arctic high and Greenland ridge which has now gone too far west on this run. A look at the spread same time: There is some uncertainty associated with the black circle region but I would like to see more here. Plenty of uncertainty to our west and north, this is what we need to see resolved to determine the actual outcome: All of which leads to temperatures in the black circle region on the mean rather poor and not what might be expected. But that is what the models are saying, the situation in the strat is still ongoing and there is plenty more uncertainty outside of the ensemble means still in my opinion, so everything is still very much on the table, that’s just my view on what we’ve seen on the 12s. All the best, Mike.

With the arctic high, I presume you mean? Ideally yes, but this run looks quite a long way from that at the moment.

ECM T192: Like the GEM, for me at the moment this is setting up shop too far west to get the real cold to our shores quickly.

ECM T168, clean ridge, really strong, the question is can the cold air get far enough south to the UK on this one? Other models have struggled this afternoon, let’s see...

ECM T144, looks like this run could go well:

I’m not sure since the upgrade, it seems to verify quite well now as 3rd best model most of the time, but that is on heights not 850 temperatures.

The GEM looks fine from a pattern perspective but, very little cold air, at T240 anyway: Obviously the pattern would be conducive to advecting the deep cold towards us to an extent unknown, but that would be longer term, for now it is too far west.

Awesome mean at T228, closed off on the mean is big time. As @Allseasons-si notes above: Some work to do on the uppers but they will follow, they can’t not do with this set up.

GFS // T282: And look at what is practically on the doorstep. WHITES in the new upstream.

GFS 18z // T210, improving picture but can we just get enough from the remnants of the arctic high (red circle), in conjunction with the Greenland ridge to force the cold south enough?

A ghostly spectre has graced the GFS 18z at T234:

GFS // at T156 This looks like a very good run coming up. Edit T174, nope it has phased the lows, may come good again in FI though...

Where did that come from? LOL! So much going on at the moment that you cant keep your eye on all timescales and models at once!

In living memory the only time we got the -20 close was this, I think: March 2018 came close though. Good chance to beat it this year though, because the synoptics to deliver a bitterly cold NE long draw feed are *possible*.

Yes, I’m happy with todays runs, and given a ‘prior’ direction of travel due to the SSW, I have increasing confidence in a cold spell. Interesting what you say about the time of year, too. At this time of year any significant snow is not going to melt quickly, and lying snow just bakes (wrong word!) the cold in further, so yes it could be a prolonged spell. But we have to get the pattern confirmed in the first place before thinking too much about that.

Hey, you’d take this at T240 for a mean chart!!!

This is what can happen with a SSW sometimes, if the ultimate destination is not governed by what is going on at the surface, but by shenanigans higher up in the atmosphere, then you tend to see this with the op runs. Trouble is we can only estimate what the fallout from the SSW will mean, but then it will start to show more consistently in the output as the downwelling of the pattern progresses - looks like being about 20th Jan, so I reckon in 3 days time the main op runs should have a good idea.

I think the GFS run was written off by some far too soon, see my comment at T168, locally poor, but NH decent, and now T270:

ECM very good pattern at T192, but uppers not that cold over UK, slower rise of Greenland ridge than GFS, but much better evolution local to the UK. Should be a great last 2 charts.

GFS 12z looks decent enough to me at T168, indeed better than 6z, potential for the Greenland ridge to link with the arctic high even, which could unlock the whole freezing lot, just not yet is all given local conditions:

The big win of GFS over ECM and UKMO in December was about trop stuff, the SSW hadn’t happened then, now I’m not so sure, things are a bit more 3 dimensional!! So you would look to ECM, GFS // to have the best handle on it, UKMO too, but it only goes to T144. I think it is very uncertain but if you have a decent prior (Bayesian term) in your mind of where this is going, I wouldn’t be too worried about today’s output.

Surprised to see you compare a T222 op run with an ensemble mean? Models are a total mess today. I wouldn’t believe any of them.

GFS 18z is a decent run, here T204, the red line follows the 1025 mb contour, and gives a chance to move the cold towards us as per the arrow.