Model Output Discussion - Spring Has Sprung

[Ladyofthestorm]

Hi all

I was reading Nick's very interesting article about a final stratospheric warming relatively soon. 

When I googled on Google Scholar I actually stumbled across the article in Nature. 

 

Stratospheric Final Warmings fall into two categories with different evolution over the course of the year

WWW.NATURE.COM

---

The transition of the northern stratospheric circulation from winter to summer comes in two flavours, a smooth late one governed by radiation or an...

 

It does make enlightening reading .

Early/ Mid  March  final ( sudden ) earnings are quite rare. I stumbled a good analogue date of a final early-ish warming in  late Feb 2008. 

 Spring arrived late that year ( my first year on Skye) , but dry sunny and bitterly cold NLy right through to May. 

I would not bet against a dry cold/ cool spring in 2024.   

 

[minus10]

Well clear signal for the scandi high this morning...gfs,ecm and gem 0z

..even in the means..

..problem is the previous hoped for drier picture not looking so secure now as with this pattern throughs are moving ese around the block with potential for more unsettled and cool weather..

...rain spikes keep appearing later in the runs..

...Pressure ens not indicative of longer periods of dry settled weather either..although significant uncertainty later on as you would expect...

...lets just hope it is not going to be miserable March...

 

[Man With Beard]

 minus10 No surprise to me. I'm getting to the stage where I'm considering March to be my main winter month!

February has brought close to zero snow even falling from the sky in the past 20 years on the south coast, apart from the last couple of days in 2018.

March probably sees snow falling 1 in 2 years here, and 3 good coverings since 2013.

The frustration, of course, is that although we often get excellent synoptics in March, they'd be so much more wintry in January! Dare I say there's been many a year recently where the March synoptics rivalled January 1947 or 1963 synoptics in terms of wintry potential (2013 stands out), but the depth of cold of course was capped by the increase in solar strength and daylight hours!

[Met4Cast]

Despite a few interesting looking det runs the means are generally against the idea of anything cold/snowy. 

In fact, could end up being quite mild with southerly winds taking hold!

[Mike Poole]

 Met4Cast Means at that range possibly hiding some quite different options within a theme of a block to the north somewhere.

Extended ECM clusters T264+ show this quite nicely:

For the UK, all depends on where the block is and how it is angled.  Cluster 1 (17 members) looks potentially quite cold.  Cluster 2 (16 members) looks quite settled.  The other two clusters have weaker high pressure with the UK remaining unsettled, cluster 4 in particular being mild.

[phil nw.]

A pattern often seen in early Spring where we start to see blocking appearing further north as the vortex weakens.

On this occasion a decent Scandinavian high looks quite possible but not oriented favourably to get the cold from further east.

We need the cut back of the jet under the block for anything of cold interest especially this late in the season.

As it is we may end up with a milder south east or southerly flow with the UK in between the block and the Atlantic.

[MJB]

Chilly flow from the ECM .................240 h though 

 

[Rain All Night]

15 hours ago, Rain All Night said:

12z deterministic runs, Wed 28th to Tue 5th (day 7)

12z ensemble means, Wed 28th to Wed 13th (day 15)

Earlier on I'd take the GEFS as it looks drier, but later on, we've got a new signal - the demise of the block to our east, and in the case of the GEFS, a significant flattening of the heights profile. ECM and GEM prefer to hint that the heights may be moving over to our west side.

Bonus

The mean zonal winds bottom out at around -18m/s on around 10th March (day 12) on this morning's EC46. That's certainly much more significant than the previous two reversals.

0z/6z ensemble means, Wed 28th to Thu 14th (day 15)

The main question for now remains, will we see some dry days from 6th March, or will the Atlantic trough stay too close?

0z deterministic runs, Wed 6th (day 7)

Edited February 28 by Rain All Night

[Ali1977]

Friday into Saturday still getting more and more wintery looking each run 

[winterof79]

Before we are all persuaded it may become warm mid March i prefer to look a little shorter ahead.

Flow from E/SE ,don't follow isobars ,and cool to say the least.

Possibility of Greeny high too.All options on table after final warming

Edited February 28 by winterof79

[winterof79]

Interest for the Midlands North Friday am into Sat

[danm]

 

[feb1991blizzard]

could be a cracker this, if the cold pool decides to take more of a fancy to the Atlantic troughing rather than siberian vortex segment.

[Mike Poole]

GEM 12z is up for a full on March cold spell by day 10:

Incoming!

I’ve been watching this possibility for a couple of days now, it’s been there on the ECM clusters, not favourite, but it is in the mix, and now on this GEM op run.

[Anthony Burden]

Evening all,charts beginning to show a cold easterly from northern blocking after a rather cold changeable period,GEM may be a bit extreme at 240 hrs but the writing looks to be on the wall for a cold march due to major SSW,possibly a below CET with spring on hold.

 

[Cambrian]

The end to another week marked by another cold trough dropping down from the north over the UK and Ireland, 12z GFS op, 0-78h. These are the 500mb temperature and heights charts. Nice to look at.

Last week’s colder snap flattered to deceive in many ways. The impressive looking 528 dam thicknesses only delivered for the tops. I must admit that I saw more scope in it for snow than transpired. 

This one will perhaps prove more interesting in the event as there is a low pressure system with its own circulation that forms at the base of the trough. The trajectory of arrival is more sharply NW-SE so there is slightly colder air wrapped up in it, with heights as low as 512-520 gpm, and there is also more organised precipitation.

This time there is a keen ridge building behind the low, which serves to cut it off from the trough at least for a while, until it merges west with the base of the next incarnation of the Greenland longwave. 

The models have struggled all week with the rate at which the low gets warmed out, with a trend over the last few days toward keeping it that bit colder for longer. @Ali1977 has been picking up on this firming up over the last few days. 

In any case, there’s certainly plenty of weather around on Friday into Saturday in particular, at 36-78h, as the low pivots its way through Ireland and the UK and spins out a secondary system to France. 

 

It’s made more interesting by the system arriving during nighttime hours and the relatively slack circulation as it grinds to a halt possibly aiding some evaporative cooling at times with the heavy and sustained precipitation, so maybe the first couple of days of spring this year might well have a decidedly wintry feel. 

Very likely my last post of the winter! I have greatly enjoyed it, though it seems that the models we study are possibly on as steep a learning curve as we are. 

[winterof79]

Hello Greeny

[Met4Cast]

Absolutely no support for the GEM det unfortunately, seems to have gone off on one and then some.

[Cloud 10]

ECM 144 hrs with a substantial cold pool heading around the eastern flank of the scandi high.

 

[Empire Of Snow]

As it stands, anyone's expecting a decent warmup with dry weather in early Spring it's likely to be dissapointed. The scenarios are either wet and breezy (normal temps but chilly under windy weather) or cold/very cold dry/showery. That said, any potential shift of the Azores high over us will likely bring very cold, snowy weather in Eastern Europe. 

[raz.org.rain]

 Empire Of Snow but there has been a pretty consistent theme for something warmer and drier going into March, just not abnormally so. Generally there's been no strong signal for anything other that slightly above average.

[Empire Of Snow]

 raz.org.rain , maybe temporarily for 24-36h? I can't say this is a consistent theme though. The Canadian PV has a strong Easterly/Southeasterly flow enabling the Atlantic. I think we'll have a clearer picture by the end of Sunday. I don't rule out ofc a major event of very cold weather in southeastern Europe as they're due for one this winter and March has historically delivered there. If this happens, yes it means a more prolonged very mild and dry weather for us. 

 

Edited February 28 by Empire Of Snow

[Scandinavian High.]

I’m back from my hibernation something wintery could be on the way for spring is winter finally on the way .

[WYorksWeather]

A fairly consistent theme for temperatures sticking close to average after a cool-ish spell in the first few days of March. Not much support for anything overly cold or especially springlike. Pressure charts do look a bit better though - more support for drier weather. The mean is a little deceptive as one or two ensembles with very low pressure are dragging the mean down.

[stodge]

 Met4Cast You really are a party pooper aren't you?

I thought this deserved another airing - yes, I know it won't verify etc, etc.

On a more serious level, still a lot of uncertainty about next week - the more immediate concern would be yet more rainfall early next week as a quite vigorous LP approaches from the south west re-enforced with the energy from the coming weekend's LP as it deflects back west.

We could be looking at a standoff next week between the residual Atlantic trough to the west and heights to the east which would leave the British Isles in a mild or very mild S'ly feed. The question though is whether, as per JMA, the trough will be close enough to keep the British Isles unsettled with periodic secondary LP in the flow. OTOH, 12Z ECM OP has the Scandinavian HP in charge by this time next week while 12Z GFS OP has a couple of very mild days before the Atlantic LP disrupts south as heights build from Scandinavia to Greenland.

At the moment, a lot of options are on the table (as you'd expect). One of the problems with this winter has been what is perceived as the persistent "failure" of the models to accurately predict what happens. My honest view is until it comes within T+96 you simply can't rely on it. 

Looking at the 10 HPA chart from GFS OP, it looks a sorry vortex by mid month with the next big warming coming from Europe - I'd assume a European warming would push the PV over to North America  leaving the possibility of heights over Scandinavia but with residual energy over western Siberia, I just wonder if we might see the block over us. All speculation at this time of course.