Model Output Discussion - Spring Has Sprung

[Lukesluckybunch]

And there you go..gem gives us some day 10 joy!getting boring now!

[Cheshire Freeze]

 Ali1977 I’ve seen the Arpege as errant as other models 

[Battleground Snow]

Arome 12z, defo slight shift south on all the models today, just about time for another 50 mile shunt south by t0

 

[Man With Beard]

Bit further ahead ... a really interesting chart here from the ECM ensembles 00Z, which shows virtual non-existence of westerly winds for London after about D8 until D15:

[Lukesluckybunch]

Just now, Battleground Snow said:

Arome 12z, defo slight shift south on all the models today, just about time for another 50 mile shunt south by t0

 

dusting as far south Oxfordshire!

[sheikhy]

 Ali1977 well gfs has gone further south so maybe its the global models playin catch up with the arpege?!!!

[Lukesluckybunch]

Ukmo extended..looks quite poor..but uppers are cold next week!

[Ice Day]

UKMO at 168 giving hints about a Scandi pressure rise at 168 as well

ECM showed something similar at day 9 this morning

The GEM finished like this at 240

How this affects the UK on the ground is up for question, but the pathway forward is at least a little clearer now.

[E17boy]

I don’t think until Thursdays drama clears we will have a clearer’s picture of what will happen going forward all seems to be mush mash right now. Nothing can be said for definite. 

[Singularity]

Some extraordinary scenarios for what goes on this weekend. The GEM 12z has helped me make more sense of what's causing so many difficulties:

Between Sat & Mon, the low that's just off NW Scotland in the left-hand chart travels all the way to Iceland on this particular run. Such a large movement in that direction is rarely seen. It appears to be the result of the mean Atlantic trough position retrogressing exactly when the low over the UK is being disrupted. If it wasn't for that, a lot more of the low would head southeast and we'd arrive an an easterly both quicker and with colder air in play.

Between Mon & Wed, there is another westward retrogression to the mean Atlantic trough position. This is a crucial step that GFS has really been struggling to lock onto (very on-off for several runs now). So begins what looks likely to be a 'slow burner' type cold spell should we actually see any very cold airmass arrive at our shores sometime.

So, I believe we're experiencing a case where the process that encourages highs to build across northern Europe generally is arriving at just the wrong moment from the perspective of those seeking a quick descent into notably cold, snow-inclined UK weather.

That being said, I'm not yet convinced that the ratio of northwest to southeast movement of parts of the low will be quite as high as the 12z GEM & GFS runs depict. On the other hand, it's hard to see enough of a change now to take us all the way back to the quick easterly pathway.

[Cold Winter Night]

 Ice Day

Exactly.

They have in common that around 168h they show simulatneously developing heights over the UK and over Western Russia, which then connect towards 240h to form a larger NE High.
GEM 240h really is a massive 1060 hPa beast.

GFS -of course- the odd one out, but to me it looks strange again with the distribution of ridges and troughs around 240h.

[Ali1977]

Ok I think I’m going to discount the Arpege completely, the METO really insist it’s rain south of Birmingham on their latest forecast video and they will have the best info!! Chase on again

Edited February 6 by Ali1977

[Drifter]

The Alpine Ski destinations will be praying the GFS 12z is wrong with the holidays coming up. GEM is the more plausible route in my opinion. 

[Singularity]

Talk about finely balanced! Probably a stalemate outcome on this UKM run, with the low swinging into the one just north of the Azores serving to stall it.

A messy picture overall, as with so many forecast model runs of late. Bottom line is, they are, as usual, struggling to resolve how a slowing of the Atlantic polar jet will play out.

Even the GFS 12z slows the jet considerably for 13th-17th Feb, which makes what it does with the Atlantic lows look pretty daft if you ask me.

[Harveyslugger]

 Ali1977 but remember met office did get the last snow event wrong:)when they thought the most likely scenario was midlands then they got that wrong.then they said most likely southern england.they got that wrong and it basically missed the country entirely

[Ali1977]

 Harveyslugger this is true - but at what times at was that? I think that was around 4/5 days out 

[IDO]

 Ice Day

The problem with a Siberian High is that the cold has do loop around the high and takes forever to get the main cold close to the UK:

  

Some of the cold may break off for a cold pool, but then we have to hope it is signposted the UK. The above shows the progress of the very cold uppers over 4 days and to get to the UK, it may take another 4 days...a long time weather-wise.

But, I am not even sure this is the correct longer term solution. The models remain fluid, and we may have to wait until the end of the week before we get a grip on post D5.GFS 12z shows how the Arctic high and Alaskan heights can block off good Atlantic/Europe cold. 

 

[Mcconnor8]

 Drifter

The absence of any cold uppers across the whole of Europe on this GFS run is quite outstanding albeit into FI.

[Frosty.]

I think , essentially, unfortunately, the gfs has performed well  recently and the other models have been dragged towards it.               ( including exeter )...but quite frankly, i don't care, i'm not scared... This winter, for the most part, for the majority of the u k has been a joke...roll on spring already, to be sure, it hasn't felt like winter much since dec 1st .... Please correct me if i'm wrong? 

[Harveyslugger]

 Ali1977 the midlands scenario was 4-5 days out.but literally a day or 2 out they thought it was still going to give southern England a snow event 

[bluearmy]

The 12z gfs op has a strat split solution (as opposed to displacement). With most split runs leaving a w Atlantic segment, we see the risks again of a split ssw 

note the atmosphere looks pretty well coupled bottom to top, it’s hard to see where the drive is coming from although the reversal comes from the top so we’ll say it’s strat led but very quick response down through to the trop 

[phil nw.]

Jff off the 12z GFS

Thursday 9am.Freezing levels and snow area.

 

Shows how steep and narrow the boundary is between the Arctic and sub;tropical air masses as they meet over the UK.Understandable why the pros always find it difficult to pin point the exact locations for snow in these scenarios.Just a small wriggle,timing or angle in the approaching fronts can shift the pattern a few miles north or south which cause modeling to change at short notice as we have seen recently.

[Stephen W]

I’m more interested in the potential for more sustained cold synoptics for the second half of Feb. A transient snow event this week is of little interest. GFS 12z operational has totally flipped and we end up in a mild south westerly next week with quite a powerful stream of lows running to the north and north west of the UK. That’s quite a change and would be difficult to shift! UKMO/GEM/GFS looking similar at 120hrs and to my untrained eye those synoptics don’t look great for cold thereafter although GEM does go on to build a continental feed albeit underwhelming.

i appreciate that these are just one set of deterministic runs so we await the ensembles but the potential for cold to develop during second half of February seems to be waning despite the favourable background signals being discussed.   In fact, I wouldn’t be surprised to end up with more of the same, exceptional mild temps on face value of this evenings output, next week has that possibility (again!)

This winter is a bust for my locale and I’ve pretty much given up on anything materialising now. 

[Singularity]

3 minutes ago, IDO said:

The problem with a Siberian High is that the cold has do loop around the high and takes forever to get the main cold close to the UK

Indeed. I believe getting a deep cool of cold air to our shores will require the retrogression toward Greenland type scenario (not of the entire high, mind - instead we tend to see part of the high do that, with a low cutting through and instigating transport of deep cold air from near or within Siberia).

[ANYWEATHER]

17 minutes ago, Harveyslugger said:

but remember met office did get the last snow event wrong:)when they thought the most likely scenario was midlands then they got that wrong.then they said most likely southern england.they got that wrong and it basically missed the country entirely

Forecasting snow in this country often goes down to the wire, and even with All,  the technology we have its still a headache to forecast