kold weather

Still plenty of options from the GFS 06z ensembles, even as soon as 120hrs the shape and ridging of the Azores high is noticeably different from run to run and that obviously has a big impact down the line. I'd say there is probably a slighter tighter grouping than previous runs (in that we are losing the very mild solutions of recent suites) and there are only a few runs that look bleak. There are conversely a few that go ballistic and create a very sustained cold and snowy spell. Also worth noting very few completely blow away the set-up and quite a few could very easily fall into the sustained cold pattern with a slightly weaker PV lobe. Good set of ensembles overall. Now just get that stupid ECM onside on the 12z please and for once can we have some stronger consistency from the models just to give the nerves a rest!

Just looking through the 00z ECM ensemble individual runs and they are...ok...most do still have a decent cold shot but most also force the flow back to a more westerly direction by 2-4th Feb. A fair amount do at least attempt a second ridge up which probably would re-introduce colder air later, but if ECM enesembles yesterday were a 9/10, these are probably a 7/10. Good enough and possibly still quite snowy, but not as sustained. Less variety of solutions as well than the GFS ensembles I note. PS, the control run 06z GFS looks quite close to what many of those ECM ensembles do by the way!

Not really, but the 00z GFS para was decent as you say, maybe not quite as impressive as the 06z GFS in terms of pattern but on the right line. 06z control run is cold but the whole thing topples down pretty quickly under pressure from the PV lobe and so the Azores high eventually comes back in again. Another possibility if that PV lobe does exert too much pressure on the whole thing, though not without further potential further down the line in the form of repeat NW/N efforts.

Control run shows us why the Russian high was such a big aid on the op run. Still a fine run in its own right but Azores high topples very quickly in front of another attack from a cutoff low coming form the PV over Canada.

Well that is a certain bank from the GFS 06z! PV huffs and puffs on this run but doesn't get very far until right towards the end of the run due to a good formation of upper high this run. PS, IDO the Arctic set-up is still a nice and total mess I see in forecasting terms!

Conversely it also helps to stop the PV forcing the whole lot SE and toppling the Azores high into Europe, so I think whilst I understand what your saying, its a net positive feature on this run as the cold is already in place.

Well this is certainly turning into another boom run from the GFS. Because the upper high builds in strongly enough from both sides, the upper low can't go anywhere and the PV runs out of steam and splits a small upper low southwards towards the UK. This allows the flow to go more pure easterly as well as opening up another snow chance. Small macro differences have led to a huge weather difference between the models this morning...I wonder what type of set-up the ensembles/para will reflect today...

Interesting squeeze job going on with the upper low over Europe with upper ridging building over the Nw and NE, means the upper low is going to stuck where it is and with the PV trying to force its way eastwards, could see something of a scandi high type set-up establish this run later on. Hopefully this run gets abit more support from its ensembles, only 3/4 went with this type of solution on the 00z run. Night and day difference in potential from the 00z ECM and this 06z GFS for sure, even though on a global scale there isn't *that* much of a difference (main difference being the LP track is different, much shallower approach and there being a small area of upper low where the GFS has a building upper high.

The trend for the PV re-establishing in a big way over E.Canada is still there on the 06z GFS, but if we can get the cold far enough south before that happens we should be ok for a while yet. IF we weren't to get the Azores high amplified enough beforehand, then that spells big problems...bt no such issues from the 06z GFS.

Perhaps, but if you get something in that position with the general SE trend that should only help to promote the surface azores to ridge in. Really this is a good 06z GFS, much needed after a very messy ensemble suite from the GFS and abit of a dogs dinner of a ECM (though, once again its not terrible for everyone...)

That is fine, the LP in that area should head SE and introduce the colder air and ridging from the Azores high behind it. Its good! Bluearmy, that is why I'm too fussed about the ECM as it is at the moment, just thought worth mentioning there is a notable shift for the negative over both the Arctic, the state of the NWE PV and less digging of the trough on the 00z suite in general and its not a trend I want to see continued!

Maybe, but that is where the 00z ECM would head for certain. (maybe I have overanalysed that chart a little ) Anyway, the ECM is not infallible and so we move on! 06z GFS looking a little more amplified this run upstream and as I said in a previous post, we don't need great amounts of cold pooling to do the job, just enough.

I;m not feeling anywhere near as downbeat (yet!) over this one, as we do have cold opportunities still and there is still ample time for a movement of those LPs into one more favourable for snow, as this set-up won't rely on having that deep of a cold pool, so more flexibility here. Tim, it maybe worth a watch, then again the GFS did a poor job with the set-up on Monday night so may need to look at other models for support.

Yeah that's what I'm worried about, because whilst good for Scotland, its a pants set-up further south and with that PV lobe on the move again I can't see any mechanism to shunt the cold south of where it is. The only thing I see is HP building towards Europe with there being a weak upper low to our north and the cutoff low heading south sand a strong push from the west with a new PV lobe moving towards NE Canada...and that equals game-over again.

Yeah, still pretty volatile modelling out there and ther ehave been shifts. Still when the ECM latches onto something like it seems to have done (this is now like the 4th run with the same broad trend) and the other models start to move towards it in small steps, I start to become very suspect. Still plenty enough to keep an eye on though and not to become overly despondent, yet. Also at last we are seeing some cold intrustions now which is better than the first half of this winter, so that is positive regardless of whether its snowy or not.

They are still ok, but they are definitely a large step back from the great 12z ensembles of yesterday, and you all know where the slippery slide leads to, we've already seen it just last week...

Well this morning 00z abit of a letdown it has to be said. Still leaves options open but we have reverted back again to the NW-SE jet which is suggestive of marginal snow events. Some would do well, some would leave this winter with 0cms in such a pattern (me! Think I missed the chance yesterday), but hard to say how it would fall just yet and may end being a messy situation Models should be treated carefully, lots of volatility still, both good and bad.

GFS ensembles are a complete mess again. One big trend (and not for the best unfrotunatly) is to refuse the PV again in a position where it makes any major ridging like the 18z GFS very difficult. If anything the GFS has become entrenched in that position on the 18z GFS suite. Still plenty of cold runs, and some very cold, but there are a few that make a real mess of the northern blocking and revert back +VE AO/NAO pattern pretty sharply. Unrealistically quickly if you ask me. EDIT- GFS ensembles has got form for being way too quick to shift these sorts of set-ups as well...

There is considerable differences in the GFS ensembles even at 96hrs, indeed I'd say a slight majority now have a slight easterly influence by 120hrs. Nothing too extreme but could be a snowy set-up for a time for the SE as that low sinks southwards.

Right, wonderful run, lets see what the GFS ensembles produce and the para GFS, would be nice to get them to also go a similar way, even if not as extreme.

Ah well, just have to cope with the marginality that is -15C won't we!! Needless to say the 2nd is VERY cold, maxes on that run were -2/3C. Indeed most days are barely above 0C, several don't even make that.

AO going quite positive again and PV reforming quite rapidly near Greenland again by 348hrs. That is no certainty and its quite possible that we get another reload of the pattern instead of the flattening out upstream. Still no complaints from me, that's a cracking run!

ICE DAY, that high shouldn't be going any further south than it is for a little while afterwards as the forcing to move it any further is still quite far west.

FWIW those 850hpa temps are pretty comparable to the Feb/Mar 18 cold. I'd suspect that is at the extreme end of what is possible in this pattern, certainly maxing out what we have on this run for sure!

Great run. Could be even more interesting down the line again, maybe an attack from the NW followed by another pressure rise towards Greenland a the PV lobe moves up and out.