Model Output Discussion - Spring Has Sprung

[Mike Poole]

ECM clusters, don’t really get going with cold potential until the extended T264+:

Cluster 1 has a very southerly jet with a trough in southern Europe, options here, and it has 19 members.  Cluster 2 looks wedge, I think the -NAO regime comes from the southern low pressure rather than high pressure further north with this setup.  It’s something I’ve commented on re the 46, the stronger signal seems to be for a trough in Europe to our southeast, rather than for a massive block to the northwest.

Clusters 3 and 4 flirt with ridging in the Atlantic, perhaps too close to the UK on the representative members shown in this instance.

[sebastiaan1973]

Well, the plume doesn't seem to indicate a cold period is coming soon. 

[feb1991blizzard]

sincerely hope we don't end up with an SSW that actually derails cold again.

[Mike Poole]

Much improved 46 tonight, as others have said.  Zonal winds at 10hPA interesting, this is quite a recent signal to put the brakes back on, there was a hint of it yesterday:

The MJO plot is fascinating as well, the actual track of it progresses nicely into Phase 7 (grey line) despite the model telling it that it has to then go round the houses back to 6 - will be interested to see what the eventual track through 7 actually looks like - and, more importantly, whether we make it into 8 at decent amplitude, which would, I expect, put the cat among the pigeons for an interesting second half of February.  

Edited January 29 by Mike Poole

[IDO]

D10 ECM charts are not helpful in setups like this, where wedges dictate the flow. The op at D7 is already an outlier:

The D10 op and mean show how the wedge changes the picture and is strictly JFF:

It's not impossible, but a wedge like this usually disappears 12 hours later.

[bluearmy]

  @feb1991blizzard sincerely hope we don't end up with an SSW that actually derails cold again.

still early days to see what route the lowering flow comes from 

there could be a mixture of slower flows due to displaced spv but also splits led from the trop if we do get the amplification in the ec46 

 

[Chesil View]

  @IDO Every once in a while an outlier is actually the trendsetter.  We await to see if more ens join in going forward.

[feb1991blizzard]

  @bluearmy

Must admit i haven't been following the strat as much as i usually do, i have believed there are enough other favouribles to override / repel, anyway, regardless of strat, EC46 still going as expected, solidifying the potent sustained cold spell, defined euro troughing now to add to persistent high lat blocking.

[feb1991blizzard]

 

These are charts that go with my previous post.

Edited January 29 by feb1991blizzard

[Rain All Night]

11 hours ago, RainAllNight said:

0z deterministic runs, Mon 29th to Mon 5th

I'd take the GEM solution for an extension of the dry weather... the UKMO is quite a sorry sight as you can see the cold air really wants to pay us a visit, but can't quite make it through our high pressure shield...

0z ensemble means, Mon 29th to Mon 12th

It looks like we could be heading for a period of cooler and more cyclonic weather in the second week of February as the high pressure to the south recedes.

12z deterministic runs, Tue 30th to Mon 5th

This afternoon we see very little difference in the model outputs over the UK until day 6. All agree on a mostly dry week for the southeastern half of the UK. The system running to our north on Wednesday PM will provide some rain for those further north.

12z ensemble means, Tue 30th to Mon 12th

What catches the eye here is the suggestion of a cooler, cyclonic spell of weather beginning around the 9th Feb (day 11). How long this might last is unclear. The high pressure to our southwest looks poised to return to our shores whenever it may feel like it.

The signal for the return of precipitation to the southeastern half of the country (Reading used as a proxy) does not become significant until around 8th Feb on the ECM ensemble, over a week away.

Edited January 29 by RainAllNight

[Spah1]

  @TEITS I can’t see it. You’ll have to get the crayons out and educate us amateurs

[Paul White.]

We have just seen the 46, strat and MJO all looking favourable in delivering a cold spell. Whether the UK is encapsulated within that is TBC.

Edited January 29 by Paul

[Rain All Night]

Where's this going? 

Edit: Not here 

Edit 2: It's certainly keen to keep that HP there though!

Edited January 29 by RainAllNight

[Battleground Snow]

I've been away the last couple of days, but watching from afar.

Not much has changed though, mid to late February has great potential. Mjo plus other Tele cons

Some strange posts complaining about the next 7 days which never had much potential, outside pm shots 

 

 

[Metwatch]

  @RainAllNight

Don't think it will make it here, high sinks into central Europe, brutal cold for eastern / south eastern Europe, reminds me of early January 2017 and the final week of January 2006.

More glad about how dry the run is with that high to our east for a quite a while, extremely welcome!

[Don]

28 minutes ago, Metwatch said:

Don't think it will make it here, high sinks into central Europe, brutal cold for eastern / south eastern Europe, reminds me of early January 2017 and the final week of January 2006.

That would not bode well for a cold mid to late month period.  Fortunately it's FI!

[Purga]

Knife edge stuff - lol

[WYorksWeather]

So, key point to make first is on timing. The best way to understand what's going on is to use the summer as an analogue. he hottest part of the summer is from around mid-July to mid-August, and that's usually when we'd expect to have a major heatwave if we get one. Of course, it can happen outside of that period, but that is core high summer. The period around it, so the meteorological summer as a whole, still has good chances for hot weather, but somewhat less so in late August and quite a lot less so in early June. Beyond that you have the extended warm season, from May to September, which can deliver heatwaves under the right circumstances, but it's not something you'd expect - more warm than hot, on a good day.

So, by analogy, we are currently in mid-winter, which runs from mid-January to mid-February. Our absolute chance of a major cold spell in this period is still quite low given CC (not going to debate that here!). Relatively speaking though, it is still our best chance. We then have a somewhat lower chance of cold in the second half of February, a significantly lower chance in December, and some chance, but not something you'd bet on, from November to March. So, in terms of chances, we'd ideally like something to land before mid-February, or failing that, at least still in the meteorological winter. Beyond that, our chances rapidly diminish with each passing week, just as there is an enormous difference between mid-August and mid-September.

So, the question is, how is it looking?

Looking at prospects for the south first, the ECM 12z largely says no to anything cold. GFS is a maybe, if you squint at it, just enough support to drag the mean below average. But again, looking at it compared to what we'd expect to seriously deliver, where you'd want runs getting down to -10C and very few mild ones, it's not really very inspiring.

For northern England, chances are a bit better. ECM still doesn't look very inspiring but GFS gets the mean down to -5C, and there are enough colder runs to make the signal a bit more robust, albeit still well beyond the reliable in terms of timeframe.

All in all though, it looks like the south is probably out of luck for the first half of February, and the north is probably on a bit of a knife edge. I imagine that as always, hills, and parts of lowland Scotland, will still do well.

You can also see this on the ECM meteogram - using Reading, the south has very slim pickings, with equal chances of north-westerly, westerly and south-westerly winds, and that only at day 14, before which it is pretty much mild all the way. Newcastle looks colder in absolute terms but in relative terms actually stays milder throughout. You're probably looking more at Scotland if the ECM is right, and even there will probably take some altitude to get anything wintry in the next 14 days if these charts are anywhere near right.

So, beyond that, we're very much reliant on teleconnections, which yes, do look positive. However, we've been here before, and an amenable large-scale pattern does not guarantee UK cold, let alone the tougher task of getting cold into the south. Throwing in the long range models, the CFSv2 now looks a bit better for weeks 2-4, getting the cold into Scotland week 2, and then only slightly milder than average weeks 3 and 4, which suggests possible milder episodes balanced with colder ones.

You can see that even in weeks 3 and 4, completely scrubbing the heights to our south proves difficult. In week 3 we have a mid-latitude block ridging up to Greenland and down to Iberia, so not quite what we need. Even in week 4, though the positive anomaly over Iberia is gone and the high is a little further north, it's still more of an Iceland / Northern Scotland high than a Greenland high.

So, my current view of where things are at:

• Mild south-westerlies will prevail across most of the country for the next 10-14 days
• From around the 10th onwards, the chance of colder spells increases
• Temperatures for the UK as a whole for the second third of February drop back to around average
• Below average in the north and above average in the south
• Chance of a more prolonged and widespread cold spell is low

And overall, I now expect that based on a mild, or possibly very mild first 10 days of February, it is overwhelmingly likely that February 2024 will be yet another above-average month, at least relative to 1961-1990.

[northwestsnow]

Another dreadful set of 00z runs.

Hoping EC keeps the faith.

[Gadje]

  @WYorksWeather

Well I'm not so glass half empty. These ensembles are trending colder as the charts you posted show. How cold? well we will need to wait and see.

GFS Thursday - Saturday - Monday

Still dropping and a growing cluster at -5 to -10 . Oh and that is London in the far South

 

 

 

[bluearmy]

10 hours ago, bluearmy said:

  @feb1991blizzard sincerely hope we don't end up with an SSW that actually derails cold again.

still early days to see what route the lowering flow comes from 

there could be a mixture of slower flows due to displaced spv but also splits led from the trop if we do get the amplification in the ec46 

@feb1991blizzard  the gfs op end of the run has stretched the spv and will no doubt soon go on to split it (axis Siberia to n Canada) 

seems to be a very quick upwelling from the Alaskan and nw scandi ridges thrown up in the trop around day 14/15.  if it is trop led then it’s irrelevant at this range.  It’s effectively down to timing on several levels.  not much we can deduce from it. you’d assume the 46 will garner a few more members on its 00z run. 

[bluearmy]

  @northwestsnow was very little support for the wedge solution yesterday. Even the fi NH profile is on another street this morning.  Ec has made a bit of a mess upstream with the east American trough. That doesn’t mean the other models were a lot better but they certainly werent as wrong as ec op has been on it 

probably why the eps haven’t been of much interest 

[Drifter]

Well this mornings runs are a kick in the nuts. Back to hibernation…

[Gowon]

  @Drifter I'm actually getting a lot of work done.

[winterof79]