Model Output Discussion - Spring Has Sprung

[Mike Poole]

GEM manages to bring in some rather surprisingly cold air country wide along with that low at T240:

[feb1991blizzard]

What a reversal!, wished we could just save it up as a phone a friend for next January.

[daz_4]

ECM warm from start to finish over Europe. February on track to be 7C above average in my backyard.

[feb1991blizzard]

That 12z run had the 10mb u-wind down at a shattering -28 m/s.

Edited February 23 by feb1991blizzard

[TillyS]

I’m off to Norway next week and I’m starting to get excited about this:

 

The signal for a Scandinavian High has been popping up on various GFS runs, although not consistently, but now it is an ECM signal too.

Needless to say, I’d be thrilled because whilst I should see some spectacular snow on the ground, a Scandi High would increase the possibilities for seeing the northern lights.

In terms of the effects on UK weather, there’s very little cold air wrapped around its eastern and southern flank but that might change:

[stodge]

Evening all

The rest of February looks to be set. Once the LP which crosses southern England into Sunday migrates to France on Monday (leaving a raw chilly day for the south east I suspect)  HP builds back and with postive re-alignment a couple of quieter days before the pattern repeats at the very end of the month as the Azores HP is aligned negatively allowing the trough to sink over the British Isles.

The start of March seems to have two options - I spoke last night about a clean phasing o energy from next week's LP and both GFS and ECM OP (and KMA) runs have this allowing a strong build of heights to the north east. Other models aren't so keen - those building the Scandinavian HP keep the core of the displaced PV over western Siberia so the air flow is more ESE or SE than pure E or NE. The coldest air dives over western Russia (-16 850s) but could still advect west by mid month.

The 10 HPA FI charts continue to show the PV in shreds - caution last night with hints the reversal might not be as drastic as some hoped. We'll have to see where we are today. 

The possibility of northern blocking won't help southern areas yearning for a drier spell as LP could  be close to or over southwestern areas.

[Mike Poole]

ECM clusters T192-T240:

Clusters 2 and 3 there doing their best to pull in an easterly under a Scandi high.  I think appearances might be a little deceptive, as I’m sceptical that there’s any cold there, so a toothless easterly is on the cards.  A northwesterly as cluster 5 might actually bring colder air.

T264+:

Longer term the Scandi high option in cluster 1 with 22 members is the preferred evolution.  Cluster 2 moves to an Atlantic ridge.  Not sure whether these evolutions are related to events in the strat, zonal winds on the 46 dayer trend to a slightly stronger reversal than yesterday, but seems a little soon to equate that with the Scandi high signal.

Edited February 23 by Mike Poole

[WYorksWeather]

Still looks like knife edge stuff as to whether the February CET record will go. A milder incursion around the last couple of days of the month could prove decisive, but equally some cold nights possible before that.

Beyond that, into early March, there's still far too much scatter to say anything with any certainty in my view. Possibly the only clear good news is that we look to get a solid rise in pressure into March. Mean now gets us to 1020mb.

Looking at March more generally - in winter we often tend to focus on the cold pool, but I also think it's interesting to look at the available warm pool. It's an incredible pattern for the time of year. The first chart is tonight's GFS 12z for the 10th March. The black outline in red is the +20C isotherm area. After that, we have the equivalent charts for 2023 and 2022.

2022 is perhaps closest to this year's chart, but the extent of the 20C isotherm is still far greater this year. It's really quite extraordinary to see. To make the point even more, here is the GFS for the 6th of April 2023, which is the earliest chart I could find from last year that looked similar! We're nearly a month ahead.

More local to us, it's also notable how little cold there is to our east. Even if we do get an easterly, it would need to drag the cold a long way west, and perhaps more south-west. There's nothing much to work with over central Europe, we need to go all the way to Russia or north to Scandinavia to find anything of note.

Interesting to watch this going forward, but it is a key factor. We need to be looking not just at the synoptic charts, but also the actual amounts of warmth or cold available.

We then have the SSTs to consider. Here we are at days 0, 5, 10 and 15 from the ECM, both the absolute values and anomaly view. Absolute SSTs are now bottoming out, and the anomaly view clearly shows that the warm SSTs near the Azores are not going anywhere any time soon.

   

Summary

In short, continued cold / near average and wet for the time being. Bit of a drying trend into March, possibly an early signal for warmth, but nothing too out of the ordinary really for the time of year.

Looking at a much broader scale though, the amount of warmth available this year is really quite something. If that does start to filter into parts of Europe, the risk increases that at some point we tap into it. Warmth is therefore very strongly favoured, though of course not guaranteed. I think it will be very tough to get any prolonged spells of below average temperatures for as long as the wider Northern Hemisphere temperature profile remains so warm.

 

 

[Rain All Night]

10 hours ago, Rain All Night said:

0z deterministic runs, Fri 23rd to Fri 1st (day 7)

0z ensemble means, Fri 23rd to Sat 9th (day 15)

Still a slow learning process. From 3rd March (day 9), the ensemble means tell us that a lot of member runs feature raised heights to our east, but the means remain too blurry to indicate what pattern might be setting up just yet, and by 7th March (day 13), the signal fades back to noise.

None of the ECM ensemble cluster representative members at day 10 convince me that a strong blocking pattern is emerging, but perhaps there could be some opportunities for drier weather ahead:

12z deterministic runs, Sat 24th to Fri 1st (day 7)

The models seem to be finding more amplification this afternoon (GEM excepted), which gives me some hope for drier times ahead.

12z ensemble means, Sat 24th to Sat 9th (day 15)

The ECM ensemble mean is nice to see, with a mean Atlantic shutdown from 3rd March through to the end of the run. The other two models look like they need a little more convincing, though the GEFS mean is still a good one (unless you're only interested in a cold outcome, which is not on the table in this timeframe).

Edited February 23 by Rain All Night

[WYorksWeather]

GFS 18z is increasing the amplification of the Azores high compared to the 12z at around day 5.

Here's the 12z at T+126 on the left, the 18z at T+120 on the right. It's subtle, but this detail means likely significantly milder conditions over the UK around this time.

Of course need to see where it sits in the ensemble, and how the rest of the run goes.

[ANYWEATHER]

At day ten, yes day ten, gfs and ecm singing the same tune ...! Perhaps a long dry spell coming up...

[WYorksWeather]

I hope this GFS 18z run ends up verifying. We get a great big block setting up over the UK from around day 11, which then stays to the end of the run. Probably feeling quite seasonal for early spring with fairly mild temperatures by day but still cold nights. And most importantly, it will be dry.

There is some ensemble support, but the mean remains fairly non-committal at this stage.

A significant dry spell is a possibility, but as the mean shows, certainly not all that likely yet. Fingers crossed though.

[kumquat]

Quote

"And most importantly, it will be dry."

 

Yep 18Z shows a good outlook in this respect from 192 onwards as the last part of the vortex forced into our direction shreds off south into Iberia - some rain for them and the start of some higher pressure for us. Possibly going into the next couple of weeks cooling from the east and then warming again from the SW - but please let us have some sun and not just the grey skies of late. (NW coast Africa/ out to Azores SSTs not withstanding)

Edited February 24 by kumquat

[Rain All Night]

Even more amplification being found now?

Edited February 24 by Rain All Night

[TillyS]

5 hours ago, WYorksWeather said:

I hope this GFS 18z run ends up verifying. We get a great big block setting up over the UK from around day 11, which then stays to the end of the run.

Vanished entirely on the 0z.

Even by GFS standards, it is very inconsistent at present.

[Lukesluckybunch]

Just when you think the ecm holds some promise..it turns out really

bad,that trough at day 7 doesn't undercut them heights building over Europe,I thought there was some chance of a easterly developing..instead we just end up chilly and wet

[Markus03]

High pressure might be coming but it won't get much cold. Even Scandinavia isn't going to be cold with some Easterlies. However it seems to come from the South East which for this time of year brings in mild air, unlike January.

[Dennis]

Good weekend everyone

morning temps

[winterof79]

Next weekend firming up to be quite cold for some UKMO 168z

Could well be snow.Depends on Scandi influence and if we get a tilt on systems moving forward

ECM 168 and 192z

[johnholmes]

As you can see from the ECMWF, a 'cold' plunge is predicted on its latest, indeed its last couple of outputs, but no deep cold. It shows below zero C for the 850 mb  temperature for the whole country but the -5 C only briefly clips the far north. With an upper low over the UK one would imagine that it could be quite showery so, perhaps, at last the Scottish ski resorts may do well?

[northwestsnow]

As March approaches my attention turns to something dry at least.

Little sign of that on the 00z runs.EC if anything deteriates by day 10 ..

Another winter passes by with hardly any snow or cold to speak of even up here at 300m ASL.

Those Atlantic ssts will need watching as we head towards Autumn  ,im blaming the warm seas for the almost relentless rains since November ,locally at least..

Edited February 24 by northwestsnow

[minus10]

Dramatic difference in ecm0z and gfs6z day 10...

..whats going on??

[WYorksWeather]

 TillyS

The good news though is that there is support being maintained in the ensembles for a dry spell moving forward. It's not yet a very strong signal, and the GFS 06z was again on the more amplified side with the Azores high, but it is a trend we want to see from the perspective of dry weather. I'm not too bothered about another cold spell and see no point chasing it, so the GFS 06z solution with some early warm sunshine and cool, clear nights will do fine for me.

We still need to see that signal strengthen more before it will be very convincing, but at least the option is on the table.

[Rain All Night]

16 hours ago, Rain All Night said:

12z deterministic runs, Sat 24th to Fri 1st (day 7)

The models seem to be finding more amplification this afternoon (GEM excepted), which gives me some hope for drier times ahead.

12z ensemble means, Sat 24th to Sat 9th (day 15)

The ECM ensemble mean is nice to see, with a mean Atlantic shutdown from 3rd March through to the end of the run. The other two models look like they need a little more convincing, though the GEFS mean is still a good one (unless you're only interested in a cold outcome, which is not on the table in this timeframe).

0z/6z deterministic runs, Sat 24th to Sat 2nd (day 7)

Am I to be encouraged by the amplification, or concerned that the trough at the turn of the month may be getting trapped over the UK?

0z/6z ensemble means, Sat 24th to Sun 10th (day 15)

This morning's means start to diverge quite early (2nd Mar, day 7) as the little trough drops over the UK. ECM, which not quite as impressive as yesterday's 12z, still offers hope of high pressure subsequently in a protective role for the UK, as does the GEFS.

Edited February 24 by Rain All Night

[Jordan S]

On 21/02/2024 at 11:28, Jordan S said:

 

Gfs showed a big adjustment to Sundays low pressure system at short timeframe this morning with the orientation and location over the North Atlantic,  has brought the low slightly north as expected so Sunday is looking wet again for many southern areas of England and Wales, hill snow for Wales likely. Not a certainty and could remain to our south but unlikely I think.

previous update..

This morning’s..

The persistence of the rain and orientation of the fronts over southern UK on this Gfs update reminds me somewhat of storm Alex a few years ago October 1st 2020 I think, though unlikely to be anywhere near as wet as during that system.

Rainfall totals look to be around 10-20mm widely, locally a bit more, but a small chance of around 50mm widely and around 80mm locally, local snow accumulation on hills of Wales a possibility.

 

Looking at this low for tomorrow again quick, those higher totals are a small possibility for far southeast England and far southwest England. Those 10-20mm rainfall totals fairly widespread elsewhere over southern England. 

Lower chance now though of hill snow for southern Wales from this precipitation, this area is where the northern boundary of the rain will probably be and this applies for the south Midlands and southern part of east Anglia, this was evident from previous post.

The rain looks set to linger into Monday now though too in the southeast of England.

On 21/02/2024 at 11:28, Jordan S said:

Outlook for very early days of March mostly hasn’t changed though in terms of the weather conditions the UK and northwestern Europe will probably experience, (relatively cold and wet at times with snow on hills over northern UK possible) but synoptically a lot may have for 1st-3rd march,  a sluggish moving series of low pressure systems surrounding northwest Europe and UK looks to be the genuine consensus atm with wind direction potentially very variable for a time with an easterly component but switching west/northwest regardless a few days into March with heights to our west and northwest likely more prevalent than average keeping lows on a more southerly track compared to average, this last part similar to last outlook post.

Confidence of cyclonic and fairly cold conditions for UK for first couple of days of March continues to be high.

I’ve quoted the post I made 2 updates ago just above as opposed to the one quoted from the 16th in previous post as although they are both overall the same expected conditions for the UK, the “sluggish” area of low pressures aspect is proving to be more likely than the quicker pace northwesterly flow that I quoted on Thursday. 

Putting in a bit more detail, we see snow is a possibility for this time period in showers/longer spells of wet weather for northern high ground, especially as little features potentially spin up in an overall “sluggish” series of lows over the UK, slight emphasis that wasn’t picked up on previously is for higher pressure to our east helping the slow down of lows 1st-3rd march. Overall though largely unchanged from above quoted post of mine.

As for that more likely than not drier and possible much milder spell afterwards in the south..

On 21/02/2024 at 11:28, Jordan S said:

My previous post stating along the lines of a more likely than not transition to drier and much milder weather for southern and southeastern areas temporarily towards end of first week of March curtesy of southerly tracking lows stagnating over mid Atlantic with heights building to south and southeast, still could take place, I don’t think the scenario likelihood has dropped enough for me to not be as confident of this as a possibility but the additional possibility is also there for the slow moving areas of high and low pressure systems that are expected, to possibly align themselves in a way that keeps not only less mild conditions over the UK throughout the whole of early March and very unsettled conditions in western and northern areas, but possibly very wet in the south too, with exceptionally wet weather over parts of northwest Europe a possibility, with the tendency for weather fronts to get stuck over northwest/west Europe interspersed with heavy showers in intermittent northwest airstreams.
 

Either scenario seems plausible atm, whether the wettest conditions would efffect UK or areas to our south remains to be seen but a lengthy dry high pressure dominated period showing no sign of returning before mid March, if this changes you can be sure I’ll mention it, although there will be drier interludes obviously and in early March the direct sunlight without wind can have a fairly warm feel to it, so hopefully some decent sunny spells either side of rain bearing fronts, showers, wintry showers (north).

I wouldn't say much has changed from this..both scenarios on offer there though could occur back to back..

So beyond 3rd, increasing chance of those drier and milder temps for southern uk temporarily with higher pressure more likely than not making an appearance to our south/southeast, though it’s important to note given the models themselves are undecided, I wouldn’t want to sound certain of this but still confident. 60-75% chance would be a good estimate.

 

Western and more especially northwestern areas of the UK again more likely to remain unsettled at the same time 3rd-8th and possibly less cold, but still with temperatures around average to slightly colder than average in places in the northwest..

high to our southeast or actually now even east probably easing away from the UK by the end of this period, heralding more nationwide unsettled and average/slightly colder than average conditions beyond the drier interlude in the south (if it indeed takes place).. this renewed unsettled spell widely still looking more likely overall post 7th-8th March since my previous post first suggesting the possibility, with synoptics suggestive of slow moving lows in the vicinity of the UK and Western Europe, in addition to add in all of this of further chances of snow on high ground further north, especially for Scotland, though on balance less unsettled and longer drier spells here than over southern/southwestern UK later in the date period just mentioned above, this seems the most probable outcome right now, with very wet weather more likely than average for southern/southwestern areas and indeed Western Europe. 
 

If this set up does take place there would be a chance of warmer air clipping eastern and southeastern areas in a southerly flow.

Drier nationwide by mid March? Subtle hints this may be the case, though as for temperatures, could go either way with these blocking highs, which look to be a feature still by then. Very mild or slightly colder than average weather both equally as likely at the moment.