Model Output Discussion - Spring Has Sprung

[KTtom]

 Johnp yes, checked out the 850' s when I saw that chart...shocked just how far the -5 isotherm is away from the UK ! Colours at 500hpa misleading .

Edited February 15 by KTtom

[WYorksWeather]

 Ladyofthestorm Well, meteorologically, winter will be over in two weeks, during which time there is virtually no support from any ensemble for anything sufficiently cold for wintry weather.

You're right that prospects for wintry weather do continue into early spring, but it's rare for any snow to stay around for very long unless you live halfway up a mountain and/or in the north of Scotland.

[Dennis]

a liitle fun into this: snowbomb

Edited February 15 by Dennis

[Ladyofthestorm]

Ok let's look at the ensembles . The first one for Scotland , west coast weather part of the UK because it's right in the firing line of the gulf stream .

Minus 5 uppers and consistently so . That's not mild. 

 

 

Next one to avoid the north of Scotland bias . South Yorkshire  again look at those minus 5 uppers . 

 

 

 

I definitely wouldn't throw in any towels  snow is great.  Ice is a pain in the neck. 

[WYorksWeather]

 Ladyofthestorm Not trying to start an argument here, but you've misrepresented what I said. I never said it was mild. I said temperatures would be near the seasonal norms or a little below, which is exactly what is shown when you then look at the 2m temperatures, which are showing daily means of around 5C, a little below average but not spectacularly so.

And at this stage in late winter and more so into early spring, the -5C 850hPa is not going to be cold enough for snow to accumulate and remain for any reasonable amount of time down to sea level. Which let's face it, is the benchmark most people are looking for.

Less than 24 hours of marginal accumulations of slushy snow which rapidly melted and turned back to rain is what we had at my location earlier this month. In that spell, the 850s were lower than on the GFS 12z charts, and of course occurring two or three weeks earlier. It'd be a rain only event for the overwhelming majority.

[Dennis]

see that HP rise below greenland

 

[stodge]

Evening all

The key event, while not yet in the reliable but supported across all models, is the HP withdrawing from Iberia west into mid-Atlantic which allows the trough to negatively align and offer a spell of PM-dominated unsettled conditions with potentially large amounts of rain (snow for higher ground) at the end of next week.

Exact positions of the trough are far from resolved but it would be quite a shock after this week's exceptionally mild conditions.

Beyond that, it may be the Atlantic pattern will quickly re-assert (GFS Control) or it may be an opening for a more meaningful mid-Atlantic ridge offering a transient N'ly which again would be a shock to the system for all though any snow would likely be limited to high ground (not perhaps in the far north of Scotland or the Highlands and Islands). Another option well touted in model FI is the continuation of negative alignment and a second LP moving NW-SE through the British Isles at month end.

Far too early to be thinking about March - the state of the 10 HPA vortex at the very end of FI on the GFS 12Z OP continues to suggest slower zonal wind speeds and opportunities for amplification which in March usually means northern blocking and a stand off between colder air to the north and east and warmer air from the south west.

[North-Easterly Blast]

 LadyofthestormI do not think that March 2010 was exactly cold after about the first ten days, and I do not think April was.

I do not recall much in the way of cold weather or snow, in March 2021 either, though April 2021 was a notably cold and frosty month, the coldest since 1986, and the first significantly below average April since 1989.  

 

[North-Easterly Blast]

 WYorksWeather In late winter and early spring, -5 850hpa's may produce snowfall to the higher elevations of the UK, but for low levels nothing more than short lived snow coverings and more likely a wintry mix of sleet and rain.

[Blessed Weather]

GEFS members have finally all made their mind up on this afternoon's 12z run with a SSW probability reaching 100%. But according to the Op run forecast it will be a 'blink and you'll miss it' 24 hour reversal with the mean zonal wind at 10hPa 60N dropping to 0 m/s at midday on the 18th, switching easterly (negative) at midnight by -2 m/s, but then back westerly again (+ 1 m/s) by midday on the 19th. Will this be the briefest technical reversal on record? The sPV remains  weak, taking until T384 to creep back up to + 9 m/s.

So, a likely technical SSW, a displaced sPV and ongoing weakness. Unfortunately current model output showing little sign of any favourable impact for the UK if it's notable cold you're after.

Source: http://www.weatheriscool.com/prod/ztemp_multilevels.html

[phil nw.]

A very unsettled and sometimes stormy outlook to come.

More deep lows and rain on the way up to month end as the jet strengthens again.This fired up by another surge of cold coming around the pole and down into the Canadian maritimes next week

It looks like a colder spell too with systems approaching from the north west so a change from the current tropical maritime air to polar maritime as the storm track is diverted by the regressing Azores high.

As usual though away from favoured locations the Atlantic will limit the possibilities of lying snow through the modification of the surface layers. 

We really need to see a direct Arctic flow from the north to bring more snow chances but we lack sufficient ridging out in the Atlantic to get a long fetch Northerly.

It's promising to be another disappointment to end this Winter unfortunately.

[Mike Poole]

 Blessed Weather ECM 46 (albeit of 0z data) actually still falls just short of reversal on the mean.  The difference between today’s zonal winds and 3 days ago laughable really.

Like January, it won’t make any difference if it is a technical SSW by the barest of margins (where’ve I heard that before?),  it isn’t going to be delivering any BFTE this year.  

Absolute codswallop from the models (all of them) re the strat evolution this year.  First the SSW that wasn’t (which did for winter in the view of many), then the January SSW which was watered down to a gnat’s fart, and now this equally pathetic fiasco!

Edited February 15 by Mike Poole

[Kirkcaldy Weather]

Leading onto my post above.

Some really nice showcasing of the MJO phase 6 feedback during February + El Ninò February's. 

Obviously going to the very extended outputs we're still waiting to see the next MJO progression which is currently too noisy between all models really and the behaviour of the North Atlantic Oscillation and PNA though there really isn't anything surprising here given recent teleconnective evolutions.

[January Snowstorm]

 phil nw. I guess every location is different but I haven't found the Winter particularly stormy or wet. Yes we have had quite a few named storms but none have been really severe, almost all just about met criteria. Going forward the models are agreeing on mainly mild/unsettled for next 10 days. Its been a winter to forget, but hey such is life, we have no control over it. 

[Uncertainty]

The ensembles are  keen on a euro low. Here’s the big 3 for the start of March 

EPS

Geps

Gefs

The GEFS is the least pronounced, but the other two have a 1010mb low over the se med. 

Like the scandi high, this feature is modelled  many times more than it actually manifests. However, the models have to get something right at some point so maybe this one might verify?

Getting Atlantic amplification has also been hard to come by recently. To really take advantage of the euro low we need the jet to sharpen in the Atlantic. There are members that do this across the suites but not enough to have any confidence. 
 

If I was looking at these charts, post ssw, in a ‘normal’ year I might be getting a little interested. But, given the incredible backtracks on favourable patterns (for cold) we have had all winter, it’s hard to think of anything other than ‘meh’. We are getting to the point where we need more extreme variants on the ar pattern  to force a countrywide snow event. Indeed, I feel a flip to a flatter, zonal pattern is far more likely than more amplification when it comes to verification. My reasoning is based on an unfavourable ssw, the mjo headed to the cod / warm phases and the ongoing high solar background. 

Very happy to be wrong or for an argument to be posited to the contrary. I’m afraid my ‘faith’ has dwindled to the point that I just don’t believe the models anymore when it comes to cold or blocking.

Saying all that, it would be ironic if, after all the winter disappointment, that spring itself started with a cold spell. It wouldn’t be the first time…

[Blessed Weather]

1 hour ago, Mike Poole said:

Absolute codswallop from the models (all of them) re the strat evolution this year.  First the SSW that wasn’t (which did for winter in the view of many), then the January SSW which was watered down to a gnat’s fart, and now this equally pathetic fiasco!

Sometime in the next day or two I'd like to discuss the bit in bold with you and @Met4Cast please Mike. That'll be best done over in the Winter Post Mortem thread, so I'll do a post and tag you both, but basically, from the info I can find, the Canadian warming and subsequent minor warming around the 4th Jan gave us a negative NAM and some terrific charts and it was the second SSW (major) on Jan 17th that screwed things? It'll be interesting to exchange some views with you both.

[Rain All Night]

11 hours ago, Rain All Night said:

0z deterministic runs, Thu 15th to Thu 22nd (day 7)

ECM still wants to bring in the big purple blob a little more gradually than the other models do.

0z ensemble means, Thu 15th to Fri 1st (day 15)

It's now the ECM that's most keen on showing us a glancing mean northwesterly flow between a ridge to the west and a trough to the east on 26th Feb, whereas for ages that had been the GFS's signature.

The high pressure signal out to our west unfortunately doesn't linger as much at the end of these runs as it did on the 12z runs yesterday.

12z deterministic runs, Fri 16th to Thu 22nd (day 7)

I suppose we want to cheer on the model showing the most interesting-looking storm now..?

12z ensemble means, Fri 16th to Fri 1st (day 15)

ECM now has the mean trough over the UK from the 22nd through to the 26th, which is a lovely prospect. And it brings it back over us by the turn of the month, although at least it leaves the mean surface low pressure on our eastern side, the slightly more interesting side. All three models show the Atlantic high pressure signal peaking around the 27th, but even at that point it isn't looking especially impressive.

[Uncertainty]

18z has a cold northerly, an impressive euro trough and a possible build of heights over the top.

[Boro Snow]

The Cold Northerly has 850s at -4c for the majority, nothing but cold rain for most 

[WYorksWeather]

ECM 12z mean is out - looks mostly cold(ish) cyclonic beyond the 23rd. 

Surface level meteogram for Reading is below. Interestingly actually even more bullish than I was suggesting earlier on temperatures. Daytime highs near the 20-year average, night-time lows actually a little above right to the end. Frankly, nothing to see here if it's snow you're after.

Of course if you go further north, possibly a different story, temperatures dipping below average around 23rd-27th. Still looks pretty marginal for snow, and not really that far below average, so I still really don't see anything to get that excited over though.

When we say that it's time to write winter off, the point I think for most people is getting a decent amount of snow to stick around for a while. Something like a good 5-10cm or more of snow that persists for a few days, say, and down to low levels across a large area of the country.

The fact of the matter is, that's a tall order these days even in mid-winter. The peak chance is probably the period from early January to mid-February, analogous to the summer period from early July to mid-August. As you pass mid-February, the chance of a notably cold and snowy spell decreases. It does so rapidly with every passing week, and by the middle of March is virtually gone across lowland areas.

I love snow just as most of our regular posters do here. But I'm also able to look at this objectively. And the following facts are indisputable. CC means that spring is, for all intents and purposes, coming on average at least a couple of weeks earlier than it did 30-40 years ago.

Also, from mid-February, the increasing strength of the sun begins to overpower the still-cooling SSTs, and mean temperatures are back on the rise, and the decline in SSTs looks like halting by month's end this year. There are very few ensemble members that support the sort of cold that would be needed for a significant snowy spell later this month, and after that we're into early March, so the bar in terms of 850s needed only gets tougher to clear. And if we look at the extended range models, for what little use they are, they've not got a robust cold signal for early March of the kind that would be needed either.

In short, there's nothing in the modelling at the moment to change my decision to suspend cold chasing. If we see a mean 850s chart down to around -6C or below, preferably -8C or below, within the day 7-10 range, at that point my interest would be reignited. But we're not even close to that.

[feb1991blizzard]

Actually quite a nice displacement SSW showing.

[Dennis]

Good friday all

Icon 0z and UKMO 

 

Edited February 16 by Dennis

[Dennis]

lets see that end of the month

[Dennis]

EC0z late febr

[Dennis]

EC forsees a more blocking sign late febr