Mike Poole

ECM T96 v UKMO: Notice the two lows to the southwest, one thing I’m increasingly starting to notice is that UKMO is reluctant to develop deep lows here, ECM a bit more, and GFS over the top. I’m convinced that in this region, massively affecting the UK, the UKMO has it right.

ECM T72 v UKMO UKMO more diffuse over the pattern in the UK actually, otherwise similar across the piste.

That’s confidence for you!! Hope ECM delivers the same, every chance, we’ve got past the issue a few days ago ECM was having trouble with, now the GFS is struggling. Now that we’ve got past the troublesome low story, it would be well worth watching developments on NH view for reasons @chris55 notes above.

Hmm, dry easterly, I’m not sure but if an easterly is going to be dry, it is dry from the outset as the high pressure isn’t far enough north to start with. That’s not the ballpark we are in, and I would be surprised if the jet running so far south it is bone dry is an issue for the foreseeable.

Well, I think there has indeed been some narrowing of the uncertainty envelope in the 6 day outlook, here’s GFS, GEM and UKMO at T144: Well wow! UKMO is sensational! And this one has maybe sniffed out a longer run of cold than the 5-7 days we might have been expecting from runs so far, pity it doesn’t go out to T384!! GEM is also excellent. GFS is an improvement on the 6z, but is less to be trusted in these UK scenarios we know this, it tends to blow up lows rather than let them slide. Yes, before anyone asks, it did well in some earlier setups this winter, but the area of interest then was off the east USA to Greenland, which is an area it does well, and better than the UKMO and ECM. But for this, I don’t rate it.

Absolutely right, and that is a big difference between the 12z T132 and 6z T138 on GFS, here: And why this run is much better.

GFS out to T90, compare 6z T96: Much better on the upstream lows disrupting, looks much more like a slider, they won’t blow up like they did on the 6z, I would suggest...

As the 12z ICON starts to roll, maybe worth a brief summary of where we’ve come to over the last 24 hours. Cross model agreement on the cold easterly development since last night’s GFS 18z. What’s at stake now is the size of the uncertainty envelope next week, and the chances for snow. I think GFS 6z showed the northern extent to which systems might push into the cold, but, to me, at least, I think it could have been overblowing the lows on that run. I’d like to see this northern extent reduced in the 12z suite, and expect it to do so. Snow looks certain to come from convective showers from the east coast; for midlands and south, from depressions abutting cold air or channel lows - these will take a while to pin down so plenty to look out for.

Very good mean that. It was by far the most likely option that the GFS would capitulate to the UKMO and ECM (and some of the others) but you don’t know for sure until you see it. I think though, that as far as the best guess across models, it has put a kink in the easterly flow that will affect the south, not from cold air, that will go round, but re the strong easterly, until the kink is flattened. But good runs tonight, actually good runs all day bar the earlier GFS and occasional ICON! Tomorrow we will find out a better take on the cold evolution, and start the snow where and when question....

GFS pub run T156: Think I’m just going to listen to music, drink beer and watch this beauty unfold...

GFS T126: That low is still there in the SE, but the uppers are good for snow anyway. So - snow. Much improved this run. Until we see the low out of the way we won’t get the long draw easterly into the south. On the plus, I think the snow is in earlier than other recent runs. But the main point is the GFS has dropped the nightmare solution that cut off the whole of the south from the cold.

I presume you mean on the computer screen not literally!

GFS 18z T66 v 12z T72: Iberian low is weaker, just like ICON at this point. This one is going to be better, I think.

I can’t!

Hi KW, I was thinking more of the longer term evolution than snow at this point!! You can see the difference at T114, T120 on 12z for comparison: Our problem low is already on its way and trough disruption on the next one and it will go under. Good run, wish we could see it further.

ICON T84 compared to 12z T90, the UK low a bit deeper, the Iberia one a little less deep, I think this is positive change:

Interesting question and very pertinent to the current situation. The models do the best they can with the physics, but there biases because all models are approximations. This does seem to manifest in overplaying the northern extent when lows and weather fronts come up against cold air in our location, so they do tend to correct south in the last couple of days. We are not there yet. There is genuine uncertainty about the behaviour of the 3 lows that are causing the headaches. Once we have a pattern the models are agreed on, it may correct south 50-100 miles at most in the last couple of days, not more, because we are close to those last couple of days now anyway. I can’t recall many scenarios where the differences at T72 are causing such widely different outcomes....on to the pub run

ECM T192 and we’re home and hosed. That low took a bit of time to stop messing things up for the far SE, but it has done now, and maybe this might correct south nearer the time anyway. Excellent.

ECM T144, think this will now go on to be very good

Yep this run is good enough. I think I’m getting model fatigue! Still would like that correction though. IMBY!!

ECM T120, pulling away to east, but a little further north than I’d like: The next low is clearly going under so should be OK

Yes, but it doesn’t look anywhere near as influential as the GFS run.

ECM T96, somewhere between UKMO and GEM, I reckon here:

ECM T72 compared to the others:

UKMO T144, that low should now slide and go south of the majority of the country so a good run, similar to this morning.