Mike Poole

Well on the clusters at that key T120-T168 time window, there are two, one where the low sticks around in some form in the vicinity of the UK, and one where it doesn’t. 33-18 in favour of the low sticking: This is so important for the UK, it isn’t really worth looking any further until this is resolved.

Must be true then Edit, but seriously it probably is coming from the east or northeast, it is just for a small island like ours the details do matter and that is why the conversation we’ve just had over the last 10 pages or so matters.

It isn’t as clear cut as that, depends what is causing the snow, if it is frontal snow, then yes that might be true near the coast, but if it is convective snow off an easterly, you’d ideally want the sea as warm as possible and the upper (T850) temperature as cold as possible to generate convection.

Certainly is Nick! I was not expecting that the run would suddenly dump the connection with the arctic high at T168 and build heights over Greenland and even west of it, instead. So it looks like a completely new evolution, and may therefore fall by the wayside in due course, but it is interesting. At least ECM is consistent in being inconsistent!

ECM T192, and now it has gone so far from what we’ve been seeing from the other models, need to check the T850s too: Marginal for the south only, with plenty waiting in the wings!

Weird, I tend to use my brain!

ECM T168...be honest, who saw that!

It probably will now, as it shouldn’t phase with the upstream one.

Absolutely, touch and go! T144 and it is still not certain, looks messy though:

ECM T120, I think we might be OK just, the weak ridge should push the low away slowly now. Won’t know for sure til the T144...on it goes.

ECM T96 compared to UKMO: Edit, what we need to see on the next one is a gap opening to join the high, its on UKMO already, here illustrated where it isn’t on the ECM 0z T120: (12 hr time difference).

GFS // T120: This looks to be clearing the low without any issues, and good alignment for advection of cold air from the NE with arctic high and atlantic high engaging nicely. Good run this will be, I think.

Yes, I’ve noticed that the means have tended to do this - suggests to me that the higher resolution of the ops runs is going to be needed to resolve this properly at such a short range. I would view all the op runs as a super-ensemble here and for the moment the GEM/ECM 0z solution seems to be a bit of an outlier, but that could still change over the next day or so.

It is vile, worse than 0z ECM, here T138: Thing is, that envelope of uncertainty I spoke of earlier obviously does include this evolution, we just hope it doesn’t happen. This may be the one bad model this set of runs, and the ECM may show better, just the way the cookie crumbles.

GFS T198, what a time to get the link with the arctic high, excellent alignment and pressure not too high over UK. Cold in place and on tap to reload. What’s not to like?

UKMO, GFS and ICON at T144: I don’t see this as models flipping between runs, it is more there is an envelope of uncertainty that we have in our minds, and what changes things is when a model shows something outside of it - like the ECM 0z, for me. All runs so far on the 12z suite are within the uncertainty envelope I have in my mind, so that is all good. The UKMO is not as good as this morning but it is still fine, the GFS looks good and so does the ICON. On to the GEM, GFS // and ECM.

Your question was originally about the GFS // i think? Well the same T0 data initialisation issues apply, no change there. But the vertical resolution increase would likely give it an advantage during a SSW as that’s where the important things are occurring. So, at the moment, I would definitely rate the // over the GFS op run. But come spring and summer, I expect it will be equally good/bad as the op as the strat doesn’t impact our weather then.

That’s a big question. What is wrong with the GFS? As I’ve some of my beer left, and nothing else to do, I will try to answer. The GFS has had several upgrades recently in terms of model resolution, vertical or horizontal, and none seem to have given it a gain over the GEM, let alone the UKMO and ECM. I don’t think it is the model, I think it is the procedure / algorithm for calculating the position at T0. Data is collected at various times and in various places, and the model needs to get the best possible understanding of the whole atmosphere at T0 for the forecast calculation. And that is a very difficult mathematical problem, called the ‘inverse problem’, determining what T0 conditions would have best come from the observed data at different times. The UKMO and ECM tackle this using state of the art maths (called 4DVar) but GFS fudges it a bit, so it doesn’t do it as well. It is a chaotic system, so if your initial data is a bit rubbish, no amount of extra model resolution will sort that. Ironically, this might be the reason why ECM is wobbling a bit. We’re lacking flight data at the moment, which is time varying, the kind of thing the 4DVar is designed to cope with - data at different times, it may be that the current data available to to model initiation doesn’t benefit the ECM as much. Just my take on it, of course, and happy to be corrected.

The parallel GFS has much higher vertical resolution than the op GFS. This may not matter much most of the year, but it does matter now, why? Because the SSW on 5/1/21 is a major player in this and will be for at least a month yet, so the higher resolution in the strat is definitely an asset to the new version.

Had to crack open another beer for the // pub run! T372: The gift that goes on giving. Phase 1, get the cold pool in via optimum alignment of Atlantic ridge and Arctic high. Tick. Phase 2, establish a blocking high in a more or less perfect position to get maximum draw from that cold pool. Tick. Phase 3, just keep it coming. Tick. And while keeping the high pressure far enough away that snow can happen. What a run!

One more from me, T342: May end up a wee bit north but whose counting at that range, T850s: That purple thing could be licking Nicola Sturgeon’s backside.

GFS pub run // T300: Just WOW!!! Goodnight everyone! See you for the upgrades on the 0z suite...not!

Yes. It is as well to remember that in an uncertain situation that this most certainly is, prospects can go up as well as down! Am I trying to sell a stock market investment or something,

GFS pub run // going all in on Greenland high at T228:

GFS pub run // has the balls to go with it at T192!