Model output discussion - 20th Feb onwards

[nick sussex]

2 minutes ago, Greenland1080 said:

Indeed Nick that high WAA is only going one way an that's up to the pole with a tanking negative AO combining with colder conditions as we head into mid March an Easter...Looking forward to some falling snow for my Easter bbq 

Lol! Yes I'm bringing  the Christmas decorations out again for Easter! Its a long way off but you never know, its not unusual go from some warm March conditions to a big change back to winter. We may aswell do it in style with a chunk of the PV over Scandi and the -15 850 hitting the UK!

[stodge]

Evening all

A chance for me to have a look at the 12Z output again this evening and it's strange - having been "away" for a couple of days it seems my thoughts of a cold, warm, cold, warm spring are being reflected widely in the output.

1) GEM and GFS OP almost identical tonight with the HP building over the British Isles and then moving north.

2) We have a nasty little rain event midweek coming and while it won't be snow, it won't be pleasant either especially in the South and a relatively mundane transition from cold to mild/warm now looks a little bit less so. 

3) It does seem we will have a short "false spring" over next weekend and while ECM is quick to take the HP due north, that is seen on other models with JMA heading to a classic Scandinavian HP event. A lot og LRFs touted February as a possible anticyclonic month but it looks like March will win that race as there's very little rain after midweek for much of England in particular.

4) The GFS Ensembles at T+240 are overwhelmingly anticyclonic but the position and orientation of the HP is hugely variable so a long way to go on this.

[Nick F]

Amazing how persistent the signal has been in the extended range from GFS and ECM for a deep cold pool to advance west across Russia and the Barents/Kara Seas towards /into Europe from mid-month. It's almost like an unstoppable train.

It remains to be seen for a good few runs yet whether high pressure progged near or over the UK mid-month will then position favourably to allow the cold pool to continue west over the UK, to give us a cold Easter, but better odds on a white Easter somewhere in the UK.

Edited March 6, 2016 by Nick F

[TomDav]

1 hour ago, knocker said:

Oh and I'm not spotting very cold air anywhere close.

Based on ensemble mean at 360 hrs, averaged over 5 days?

[Daniel*]

Out in beyond but you can draw similarities to how the great winter of 1947 evolved. 

[Frosty.]

I like that cold plunge through Scandinavia late on the Ecm 12z, it looks very potent with -15 / -20 T850's...

High pressure is on the way I'm pleased to say, after months of Atlantic driven dross!

[fergieweather]

6 minutes ago, Daniel* said:

Out in beyond but you can draw similarities to how the great winter of 1947 evolved. 

Particularly post-21st, no ensembles can yet be considered trustworthy/representative guides, for now. No model will yet adequately synthesise SSW impacts (but they will often lean more towards climatology and give a skewed impression). As for exactly what the SSW impacts may be... unknown. But a greater propensity for blocking, certainly (that does NOT necessarily = colder than average), and perhaps greater than ENS presently indicate. 

[knocker]

NOAA this evening predictable get's rid of the Atlantic trough but the 8-14 keeps the HP ridging north towards the Pole and thus the UK still in the circulation of the surface high. (and yes I realise it's the weekend)

Now the ext EPS 10-15 (which I can't post) does exactly the same with the trough away over in eastern Europe. but  It does edge LP further west if you look at the individual days at the end of the run but not the main trough so the flow becomes N of W right at the end of the period with the HP ridging south of Greenland.

 

[TomDav]

My first attempt at GEFS cluster analysis and therefore have no idea of the accuracy. Shows 850mb temp anomalies at 384 hrs

[Singularity]

Good to finally locate that ECM 12z run, it has not uploaded on most sites this evening.

It's as I have been expecting to see really - the idea of a block N/NE of the UK with a long-fetch easterly setting up between the UK and central Asia, supported by the reverse zonality in the stratosphere.

I have just allowed myself to spend a moment contemplating what an airmass with 850's lower than -10*C would achieve in terms of instability when crossing a North Sea that will probably be at around +7 to +8*C by the third week of March. This makes up one half of the potential impacts from such an event, the other half being the sudden plunge in temperatures giving recently/newborn wildlife some trouble. Somewhat concerning is how easily such a setup could then persist for a week or more, given that it will be during what is typically among the least mobile times of the year (with the highest incidence of easterlies in climatology).

It probably is a case of what we end up with as a result of SSW forcing, we keep for a fair while. To me it seems that an unstable easterly for the southern half (or two-thirds, perhaps) of the UK, with HP across the N of the UK, has pretty similar odds to a stable easterly or anticyclonic flow for most, with HP across central parts of the UK. A persistently cyclonic outcome (trough stalled over the UK) has a lower chance given the displacement south of the vortex remnants, but is still a notable contender. This being based more on intuition/theory than ensemble analysis.

[knocker]

10 minutes ago, Singularity said:

Good to finally locate that ECM 12z run, it has not uploaded on most sites this evening.

It's as I have been expecting to see really - the idea of a block N/NE of the UK with a long-fetch easterly setting up between the UK and central Asia, supported by the reverse zonality in the stratosphere.

 

Sorry but I'm a bit puzzled where you find a long-fetch easterly setting up from the ecm 12z. Just taking the last day in the run. And the block come to that.

Edited March 6, 2016 by knocker

[Frosty.]

The Ecm 12z ensemble mean is rock solid anticyclonic from the end of the coming week onwards, we have cross model support now for the most settled spell for several months and it will be a very pleasant change from all the wind, rain and mud which summed up the winter..I'm sure most on here will welcome a fine early spring spell!

[Nouska]

The ECM control certainly produces winds from an easterly quadrant in the 11 to 15 day time frame. 

     

This doesn't lead to anything exceptional in surface temperatures for SW Holland but would probably produce plenty of convective snow showers if it made it over the North sea.

Edit to add the MSLP spread for the ECM at +168 - plenty of ensemble divergence in the key areas.

Edited March 6, 2016 by Nouska

[Singularity]

 

The SSW has hit the 18z GFS like a powerful drink, and for a while there it went a bit crazy!

Could be the first of many wild looking runs as the total breakdown of the usual westerly regime takes effect. The above is one of the long-winded, 'two bites of the apple needed' outcomes that could occur - with the trans-continental easterly taking until the end of the run to really get its act together.

Interesting to see how LP near the Azores could affect things - though it's so much stronger on this run compared to the past few that it's level of influence has to be viewed with some suspicion.

More notable in the earlier stages is how much further north HP is for the weekend;

12z:   18z: 

That's more so than the 12z ECM and UKMO runs were and by quite a distance. It makes the difference between isolated and widespread frosts overnight, and pegs the day temps back in the low-teens as well. The 00z runs could be significant in this respect and of course it affects how easily low heights are able to ride over the top of the high going forward.

[sorepaw1]

Haven't seen any charts or model data for 2 days ...currently  snowing here quite heavy 5cm And showers forecast all night.untill 11am Monday. 

Anyhow what a turn around looking at the 18z in my neck of the woods March can be the worst winter month for drifting snow on higher routes near me.

I would be interested to see the18z this Friday coming.if All stays similar. 

I think there's going to be some pleasant surprises for cold lovers.

Please don't confuse this post as a ramp.

And I will be looking forward to seeing a mild or warm spring  and summer.

[knocker]

The GFS this morning has a wet and windy day on Weds before giving way the HP at the end of the week which remains influential for much of the run although towards the end some more systems begin to move in from the Atlantic. Temps rising to above average and may even touch 16C.

Sidney got a bit carried away by the run I'm afraid

The GEFS anomalies this morning are still retrogressing the HP in the later stages with the European trough also moved west over the UK. This veers the upper flow NW and rather supports the det. take of more unsettled weather in the later stages with temps much nearer average.

 

Edited March 7, 2016 by knocker

[knocker]

The ecm has a slightly different take. Also wet and windy on Weds before HP becomes the main player but at the end of the run it builds the HP north and NE bringing colder temps to the eastern half of the UK. So at T240 there is HP to the NE, LP near the Black Sea and the Atlantic nudging in from the west.

[Alexis]

Cold continental air on the doorstep at 240h on the ECM. Would be typical if it actually verified for once!

[Frosty.]

The Gfs 00z turns into a peach of a run from the weekend onwards through next week with pleasantly warm anticyclonic conditions and temperatures into the mid teens celsius, I actually think the gfs is undercooking the max temps for Friday because bbc weather say somewhere in the east and south could reach 16c on Friday..well, we never had a winter but it looks like we will have a nice spell of early spring weather soon!

[Singularity]

That ECM run makes more intuitive sense to me than GFS' idea of a large trough forcing its way over our blocking high, via the Arctic.

Yet both models are still pretty slow to send the AO downward so it can't be discounted. I know a similar thing preceded the cold period in Dec 2010, though that was with the low squeezing across Greenland as a shallow feature and then deepening rapidly as it dropped sharply south to Scandinavia. Room for that sort of thing as well I suppose!

I'll ponder this more later - for now I've forecasts to be finalising.

[knocker]

17 minutes ago, Singularity said:

That ECM run makes more intuitive sense to me than GFS' idea of a large trough forcing its way over our blocking high, via the Arctic.

Yet both models are still pretty slow to send the AO downward so it can't be discounted. I know a similar thing preceded the cold period in Dec 2010, though that was with the low squeezing across Greenland as a shallow feature and then deepening rapidly as it dropped sharply south to Scandinavia. Room for that sort of thing as well I suppose!

I'll ponder this more later - for now I've forecasts to be finalising.

It's not forcing it's way over the blocking high; it has the whole upper pattern retrogressing. A similar idea was being mooted by last nights ext EPS so we await this mornings.

As a matter of interest is your forecast available in the public domain?

Edited March 7, 2016 by knocker

[Timmytour]

The current set up, with the models looking to deliver us a dry and perhaps nice mid month period before hinting that the cold may return is fascinating in its comparison to the winter/early spring  of 1924/25  

The mean CET for those months got progressively lower between December and March, the only time other than 2012-13  when it has done so, but the mildness associated with the former put it on much more of a potential par with the current set up.

If the FI cold the models are hinting at comes in for the second half of the month, we could well see this again.  It might not do anything for the colddies down south, but it's worth remembering that, on the 1st April 1925, Edinburgh woke up to 15cm of lying snow!

[Frosty.]

The Ecm 00z op also shows high pressure becoming the dominant feature of our weather from the weekend onwards with temperatures rising above average for a time, some very pleasant days with sunny spells but it does turn colder from the east by the middle of next week.

[El ninyaknow]

41 minutes ago, Singularity said:

That ECM run makes more intuitive sense to me than GFS' idea of a large trough forcing its way over our blocking high, via the Arctic.

Yet both models are still pretty slow to send the AO downward so it can't be discounted. I know a similar thing preceded the cold period in Dec 2010, though that was with the low squeezing across Greenland as a shallow feature and then deepening rapidly as it dropped sharply south to Scandinavia. Room for that sort of thing as well I suppose!

I'll ponder this more later - for now I've forecasts to be finalising.

you still manage to find time for this even between forecasts! :-P

[Frosty.]

The GEFS 00z mean becomes emphatically anticyclonic from the weekend until almost the end of next week. A very spring like spell is on the way to all parts of the uk.