Model output discussion - 7th January onwards

[Ali1977]

Cherry picking but imagine if we can get this Perb outcome by next Fri.

[seabreeze86]

GFS p still refuses to slide that low, doesn't look to have any support which is good.

[Roger J Smith]

I am estimating a mean CET of -2.5 from day 9 to day 16 from the 12z charts (realizing this is speculative but that's what those charts would produce), certainly cold enough for snow by about the 22nd to 24th with the northeast winds. As the run ends, another Atlantic assault is mounting what looks like a high-energy slider, that could be interesting to monitor as it moves into range of later model runs. 

It was encouraging to see the GEM losing its zonal theme from the previous runs, and joining the consensus. 

As to what we consider reliable, I think when there is broad model consensus past day six, it's a lot easier to feel at least reasonable optimism (or pessimism) for an outcome than if you have a wide range or two camps. Also, with these arctic outbreak scenarios, I recall last February we were tracking a strong high moving very slowly across the polar region towards Franz Josef Land and that was inspiring confidence because there was a real feature in play, that had to end up somewhere, as opposed to scenarios where developments have to take place days from now.

This signal for much colder weather has been sustained now for about a week and is no longer being moved back every day or two, so that also begins to build confidence. There is such a thing as cold moving forward in model timetables too, we've seen that happen once or twice in the past ten years. 

The thing to remember about polar weather patterns is that distances from one longitude to another are very small and 20 degrees north of 80 N is, well, 80 N on the far side of the north pole. Some feature retrogressing through Siberia into Russia could take an age, but if it's moving from north of Wrangel Island and the other Siberian islands, it can appear very quickly north of Scandinavia. 

I'm thinking retrograde because the first half of February should see a peak in retrograde motion this winter, according to my research, and some analogue years include very deep cold in late January into February. If we can get this pattern to develop and begin a retrograde when high pressure is in northern Scandinavia, then a cold pattern could lock in for weeks. 

[MattStoke]

3 hours ago, Sweatyman said:

those forecasts are always hopeless. Keep that chart and show us again later !

I was talking about the downward trend in temperatures and upward trend in risk of wintry conditions. Not the specifics...

I am aware of the limitations of automated forecasts. Thanks.

Edited January 11, 2019 by MattStoke

[bluearmy]

2 minutes ago, seabreeze86 said:

GFS p still refuses to slide that low, doesn't look to have any support which is good.

Not to be discounted .....single eps cluster on that 8/10 day period tells me that many variables abound .....we sort of know where we’re headed but no one knows the actual route .........

 

[fujita5]

6 minutes ago, Ali1977 said:

Cherry picking but imagine if we can get this Perb outcome by next Fri.

That's a beauty.  Most of the trop PV to our NE, heights looking to link up over Greenland.  We'd start having to measure snow in feet!

Just one perb of one run.  Let's not get too carried away

 

 

[iceman1991]

6 minutes ago, Roger J Smith said:

I am estimating a mean CET of -2.5 from day 9 to day 16 from the 12z charts (realizing this is speculative but that's what those charts would produce), certainly cold enough for snow by about the 22nd to 24th with the northeast winds. As the run ends, another Atlantic assault is mounting what looks like a high-energy slider, that could be interesting to monitor as it moves into range of later model runs. 

It was encouraging to see the GEM losing its zonal theme from the previous runs, and joining the consensus. 

As to what we consider reliable, I think when there is broad model consensus past day six, it's a lot easier to feel at least reasonable optimism (or pessimism) for an outcome than if you have a wide range or two camps. Also, with these arctic outbreak scenarios, I recall last February we were tracking a strong high moving very slowly across the polar region towards Franz Josef Land and that was inspiring confidence because there was a real feature in play, that had to end up somewhere, as opposed to scenarios where developments have to take place days from now.

This signal for much colder weather has been sustained now for about a week and is no longer being moved back every day or two, so that also begins to build confidence. There is such a thing as cold moving forward in model timetables too, we've seen that happen once or twice in the past ten years. 

The thing to remember about polar weather patterns is that distances from one longitude to another are very small and 20 degrees north of 80 N is, well, 80 N on the far side of the north pole. Some feature retrogressing through Siberia into Russia could take an age, but if it's moving from north of Wrangel Island and the other Siberian islands, it can appear very quickly north of Scandinavia. 

I'm thinking retrograde because the first half of February should see a peak in retrograde motion this winter, according to my research, and some analogue years include very deep cold in late January into February. If we can get this pattern to develop and begin a retrograde when high pressure is in northern Scandinavia, then a cold pattern could lock in for weeks. 

Is that a ramp roger

[Ali1977]

A less impressive set of ENS but still v good with some books, over to the ECM. Would love to see a proper slider 

[Snow Grain]

13 minutes ago, Ali1977 said:

Cherry picking but imagine if we can get this Perb outcome by next Fri.

Looks good on paper, but in reality would give rain/sleet in the south with daytime temperatures around 6 degrees.  Snow up north though.  I’m waiting for the real deal from the east!

[edinburgh_1992]

GEFS is pretty painful to look at... especially for those in the north. Just shows how the evolution is anything but certain. 

On the other hand, excellent gfs12 run. GFS P12 also shows potential, that LP at T204 looks like it could sink into Europe and pull plenty of cold air in with it

[pdiddy]

2 minutes ago, edinburgh_1992 said:

GEFS is pretty painful to look at... especially for those in the north. Just shows how the evolution is anything but certain. 

On the other hand, excellent gfs12 run. GFS P12 also shows potential, that LP at T204 looks like it could sink into Europe and pull plenty of cold air in with it

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&lat=55.9533&lon=-3.1883&ville=Londres

I'm not in any pain with this at all.

[gottolovethisweather]

1 hour ago, Weathizard said:

Bank

 

Edit: absolute stonker sypnotically this

All I can say is, should that come off, Happy Birthday gottolovethisweather. Intriguingly, such charts have been replicated on several recent occasions at that timeframe of late, hmmm. Could it?

Edited January 11, 2019 by gottolovethisweather

[Kirkcaldy Weather]

5 minutes ago, Ali1977 said:

A less impressive set of ENS but still v good with some books, over to the ECM. Would love to see a proper slider 

If these are less impressive I cant wait for the more impressive charts to appear  

Just now, edinburgh_1992 said:

GEFS is pretty painful to look at... especially for those in the north. Just shows how the evolution is anything but certain. 

On the other hand, excellent gfs12 run. GFS P12 also shows potential, that LP at T204 looks like it could sink into Europe and pull plenty of cold air in with it

 the GEFS are fine and the ones that perhaps are less cold over the UK are more about focusing on the bigger picture - blocking which many look primed for 

        

[feb1991blizzard]

2 hours ago, bluearmy said:

What’s the maximum number of trigger lows you can have within a five day period  ??????

On the GFS - 100

[gottolovethisweather]

1 hour ago, Easton Luna Boys said:

I'm not sure we'll see any comment from the experts over the weekend on the BBC forecasts. If the likes of Paul Hudson mentioned something tonight on Look North I'd be astonished. That should tell you all you need to know in forecast confidence >144, especially without cross model agreement. Tis the holy trinity of forecasting. 

Snow is being mentioned in the media forecasts, in the mid to longer-range. Moreover, they quote it as "wintry weather", quite rightly so given it's at the realms of FI and the surface-level specifics (will it, won't it snow) are guesswork at that range right now. The fact they are giving mention of it hints to me, that the beginning of FI (where model divergence is rife and spreads are all over the place) is around about next Friday, so D6 or D7. All to play for beyond this timeframe as well but the first snowfalls will come through next week for a few of us and then hopefully the snow risk will increase further still into FI. 

Edited January 11, 2019 by gottolovethisweather

[Roger J Smith]

Not a ramp, just a reading.

If you run the 850 mb temp loop on the GFS (at a high speed) you will get a good sense of how the colder air builds up in waves from a position north of Iceland, occasionally the source region comes into view, and it's clearly the Canadian arctic islands to northeast Siberia sending some super-chilled air across the pole. But running that animation also underscores the fact that this cold spell is generally pushing down through North Sea into central Europe with the odd twist of cold injections from Scandinavia joining up, and also that the Atlantic keeps trying to interact with weak injections of warmth (= moisture). That's fine as long as these don't manifest as liquid precip. But it would not inspire much confidence that southwest Ireland will get into the colder air very often, so a battleground scenario with sliders across Ireland into southwest England is implied. That works well for a lot of people interested in this outcome. 

[Tim Bland]

Whilst the GFSp looks nice the Conditions on the ground are a bit dull unfortunately 

[chris55]

25 minutes ago, bluearmy said:

we sort of know where we’re headed but no one knows the actual route .........

 

Sorry blue, cropped your reply there, but it’s a good quote.

Most models/ensembles now on board with colder conditions one way or another. Looking good with the polar front digging well south and cold potentially coming from the north - east and even the west/north west!

still lots to pay out in term of details but overall it seems we are slowly heading into a much colder pattern.

 

[nick sussex]

25 minutes ago, Ali1977 said:

A less impressive set of ENS but still v good with some books, over to the ECM. Would love to see a proper slider 

You shouldn’t worry too much if the first low doesn’t slide . It’s not an essential part of the evolution between day 6 and 7.

As long as it clears se into mainland central Europe . It might just be a bit too developed and a bit too far east and displace any cold before the cold moves back sw wards as low pressure clears to the se.

The main thing is the high displaces nw and then we see the PV lobe over Canada get pulled nw, this will allow the high after to topple towards Scandi supported by low pressure to the se.

It maybe there would be further attempts at a slider low . 

Edited January 11, 2019 by nick sussex

[WhiteFox]

17 minutes ago, pdiddy said:

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&lat=55.9533&lon=-3.1883&ville=Londres

I'm not in any pain with this at all.

Look good to me. Mean is sub -5 from 19th. Note that op run still on its own on 23rd, but if 18z continues the theme of possible sub -10 temps then expect some other members to start joining the club.

[chionomaniac]

Here’s hoping that a Wedge from the West leads to a Beast from the East on this ECM run. Would finish the working week off nicely. The usual swings this week but a good weeks model watching and now the pattern is a lot closer to the reliable. Next week we will have to watch shorter term for the slider show, and FI watching longer term, for the blocking show.

[markw2680]

25 minutes ago, Snow Grain said:

Looks good on paper, but in reality would give rain/sleet in the south with daytime temperatures around 6 degrees.  Snow up north though.  I’m waiting for the real deal from the east!

Blimey if it’s 6c in January with a chart like that then I think our winters will well and truly be over. 

[Radiating Dendrite]

1 hour ago, Easton Luna Boys said:

I'm not sure we'll see any comment from the experts over the weekend on the BBC forecasts. If the likes of Paul Hudson mentioned something tonight on Look North I'd be astonished. That should tell you all you need to know in forecast confidence >144, especially without cross model agreement. Tis the holy trinity of forecasting. 

Yes - I am aware. 

Since when did local weather forecast a week away. All I was saying is that it is getting closer.

[Stormeh]

Para ends like this...

I think my wife is going to leave me, she said I spend more time on this forum than with her 

 

[bluearmy]

Is this gfsp beginning the run of fi ops showing the greeny ridge that the long rangers have been pointing at to end jan ???