[Scotland/Alba weather discussion - Jan 2021 onwards]

Just now, aggy said:

Eh it’s raining

Whoops You must be just on the edge of marginal - going by Wundermap the last places left east of Glasgow with a dewpoint over 0C are right on the Forth, and Cumbernauld seems to be around 1.5/0.3 or so.

[Scotland/Alba weather discussion - Jan 2021 onwards]

Not the prettiest but I do enjoy when the pattern is so weird it 'breaks' the models and ends up churning out stuff like this:

A nice 1000hPa low over the Algerian desert

[Scotland/Alba weather discussion - Jan 2021 onwards]

Some actual, real life, weather to report - it is in fact snowing here. The radar isn't showing it (of course, HC) and it's very light, but might be worth checking the lamp post since there seems to be a couple of line of, albeit probably snizzly, snow showing up on a sort of Clackmannan Bridge-M80-East Dunbartonshire and a Lauder-Lanark-EK sort of line too

[Scotland/Alba weather discussion - Jan 2021 onwards]

It does involve a bit of a break from cold uppers (but still probably widespread ice days at the surface), but the GFS pub run is coming up with a reload easterly:

It's not ideal yet, but if it keeps going the way it has been I'm not sure there'll be much of a break in proceedings by the end of the week...

[Scotland/Alba weather discussion - Jan 2021 onwards]

9 minutes ago, JoeShmoe said:

How we looking here LS? Or is it going north and south of Edinburgh do you think? Guess a lot will be radar watching ... 

Really hard to get a feel for this one to be honest, I think you'll end up with at least a wee bit because it does seem like the wind direction will change a couple of times, and the convergence lines seem likely to shift about as well which always helps with keeping the snow distribution relatively even (and deep, and crisp etc.).

[Scotland/Alba weather discussion - Jan 2021 onwards]

10 minutes ago, Michael Kaii said:

Could anyone help me. Was wondering with the model charts for what does it mean for Bo'ness I’m on the fourth and the last time we got an beast from the east we done well. So how does this one upcoming do for us

I'd think probably pretty well to be honest, but I'd think anywhere on the Forth estuary especially towards Falkirk/Bo'ness should be looking at at least a couple of inches. If some of the runs this evening come off though, could well be getting close to the totals from previous big easterlies by the end of the week.

[Scotland/Alba weather discussion - Jan 2021 onwards]

11 minutes ago, MAXcrazystorm said:

i got around 20cm i think to the SE of Perth, not as much as Fife and the central belt though....

I think it was around 40-45cm or so in Freuchie, it's still my profile picture February 2018 was decent here too, I think we topped 30cm but it was a wee bit less certainly than December 2010.

[Scotland/Alba weather discussion - Jan 2021 onwards]

1 minute ago, Penicuikblizzard said:

The red warning day was a SSE flow I take it there must’ve been convergence troughs in the forth that day/night as even Edinburgh had a lot of snow ???

Maybe due to the uppers being lower during the bfte

From what I recall there were a few troughs coming through, and the intensity was so strong that it didn't really matter about the topography so much:

- this is from 1.30pm on the 28th February

[Scotland/Alba weather discussion - Jan 2021 onwards]

2 minutes ago, Glaswegianblizzard said:

I bet they don’t bother with marginal set ups.

It's very boom or bust there from what my Dutch friend says, basically no hills of any note so you either get buried from something like this or just nothing at all for the winter

[Scotland/Alba weather discussion - Jan 2021 onwards]

Blob, incoming:

UKV has a bit of a wider net for snow showers up to +54, still incredibly good for Fife and Perthshire but a few more showers heading on the southern stream too:

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

28 minutes ago, Ruzzi said:

My nerves are still shattered at the thought of missing out on the streamers, I'm not worried about westward extent, but I can't help but think I'll miss the worst of the convective snow due to being just that wee bit too far south. I think the northern most parts of lanarkshire will fair ok, Kilsyth for example and then it looks a given that Angus, Perth and parts of Fife will be dumped on. 

Reasons to remain hopeful but with the cracking updates from @LomondSnowstorm

I reckon Tuesday evening into Wednesday will be my best chance but we shall see. Stranger things have happened I guess. 

The thing that is letting me keep the faith is the synoptic chart for the day of the Red weather warning in 2018.... A clear south of east draw from the continent albeit with a stronger flow, so many a surprise may materialise but my nerves would be far reduced if that flow just crept a bit more north of east to raise the prospects for the central belt a bit more. 

Here is the synoptic chart for the day of the red weather warning for anyone else that's jittery

 

Not sure if this is a consolation or not, but I did dig up the EURO4 for the day before the red warning:

 

and the reality (well for the day after that, although most of the snow did fall on the red warning day further west from what I recall):

It wasn't too bad to be honest in distribution, but certainly underestimated depths and extent too (the map doesn't have depths for Cumbernauld for example which was completely buried).

 

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

5 minutes ago, metallikat34 said:

Question for you and really anyone in the group. Any papers on the dynamics of snow streamers off the North Sea?

This is a good question, and something I'd quite fancy writing myself in future if no one else has by then

There are some on specific events, this for example (although it's basically just a Met Office description)

https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/wea.3469?casa_token=nGUomhVbnCwAAAAA%3A2Kx4wRRQlyXPGLEhzqnFgf6SZIQ4BxOOPV2_8UYL5K4ExquP9TrNkw5qpWEIv-0mIPmn1W9C5GBMru4

But I'm sure I've read more substantive papers somewhere ( @lorenzo?). Most of our knowledge of this is really based on experience of following this with a sprinkling of theory but I would be very interested to read more on this actually.

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

2 minutes ago, Ruzzi - 188m asl said:

My nerves are still shattered at the thought of missing out on the streamers, I'm not worried about westward extent, but I can't help but think I'll miss the worst of the convective snow due to being just that wee bit too far south. I think the northern most parts of lanarkshire will fair ok, Kilsyth for example and then it looks a given that Angus, Perth and parts of Fife will be dumped on. 

Reasons to remain hopeful but with the cracking updates from @LomondSnowstorm

I reckon Tuesday evening into Wednesday will be my best chance but we shall see. Stranger things have happened I guess. 

The thing that is letting me keep the faith is the synoptic chart for the day of the Red weather warning in 2018.... A clear south of east draw from the continent albeit with a stronger flow, so many a surprise may materialise but my nerves would be far reduced if that flow just crept a bit more north of east to raise the prospects for the central belt a bit more. 

Here is the synoptic chart for the day of the red weather warning for anyone else that's jittery

 

I'm with you on this - as modelled the gradient north to south across North Lanarkshire is pretty stark to the point where Coatbridge and Caldercruix are both right on the edge of it. I do think it'll be a bit less cut and dry than that given how much the bands move north/south but we'll see what happens. I will definitely be taking full advantage of the local authority plus 5 mile for exercise rule if it does work out like modelled though

[Scotland/Alba weather discussion - Jan 2021 onwards]

10 minutes ago, Hairy Celt said:

You're ignoring the fact that the radar is claptrap for many places.

True, it hasn't exactly been the best over the last few days for a lot of us, but whatever it is did at least move in a vaguely coherent way so you never know

The road surface at Uddingston and Sanquhar are 'moist' (oo-er?) which is the closest I can get to a proper on the ground verification

[Scotland/Alba weather discussion - Jan 2021 onwards]

3 minutes ago, snowlessayr said:

if I can get any snow I will be pleased, looks more likely next weekend. ECM has some decent snow as a front struggles to get here. 

not expecting any showers here so I can hopefully get a nice suprise. Anyone wanna make a bold prediction that I will see snow? 

I reckon you'll see, at least a few flakes

Seriously though I do think the models might be underestimating the westward extent of the showers. Take the current radar for example - the UKV initialised 6 hours ago has this:

And yet the radar shows:

a) much more extensive precipitation up the east coast than modelled and b) there's a moderate shower already past the M74.

Once you factor in the low dewpoints and I don't think you can really rule out a covering anywhere over the next 4 days. Not promising anything, but if you can get a shower through on this flow:

I wouldn't rule anything out

[Scotland/Alba weather discussion - Jan 2021 onwards]

The UKV seems to be starting to pick up on these convergence lines and, bloody hell some of these 3 hourly totals are impressive:

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

Just now, aggy said:

When’s that precipitation for LS

Sorry I forget they don't timestamp the ECMWF precip charts! Tuesday 6am-midday

[Scotland/Alba weather discussion - Jan 2021 onwards]

ECM has a bit more of a northerly tlit to the flow Tuesday, although also a bit of a kink which might stop it getting so far west later on Tuesday:

This is probably the highlight of the run precipitation wise but there's again enough about throughout, especially further east, to give a lot of hope:

[Scotland/Alba weather discussion - Jan 2021 onwards]

The NMM seems to be modelling the current situation pretty well as far as dewpoints go (freezing north of Dundee and on higher ground, 1-2C elsewhere). Find the freezing level, subtract an hour for Central European Time and this is when, roughly, you should expect the 'easterly proper' to begin:

[Scotland/Alba weather discussion - Jan 2021 onwards]

28 minutes ago, CatchMyDrift said:

@LomondSnowstorm you're on a full-scale rampede today it's good to see, if I was still in Scotland I'd be very excited.

Do you think any possible convergence zones just happen at random due to the weather pattern or will they be defined by the convergence zones which the landmass dictates? As we know in this type of flow the Forth will create its own convergence so does this then dictate all the other streamers up and down the east coast? I remember at the BFTE that I had my own fairly consistent streamer making landfall just south of Berwick and it seemed to coincide with a much stronger Forth streamer.

I guess it's a bit of both, you can end up briefly with these convergence zones in places you wouldn't expect but if it's near to a topographical line it'll probably end up there anyway because of where the showers die out/ keep going due to the topography, if that makes sense. The Tay-Clyde streamer that we saw once or twice (I think that was 2009/10, maybe?) isn't really an obvious streamer but equally if the wind direction is ENE or a bit north of that you will probably get one then.

I can't say I'm that familiar with behaviour like this (where it's like a wave propagating perpendicular to the flow) but it is very aethestically pleasing to see:

 

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

One thing to watch - if we do manage to keep things going through to Wednesday night, the -40C (threshold for polar low formation and the like) 500hPa temperatures start coming into the North Sea:

[Scotland/Alba weather discussion - Jan 2021 onwards]

The GEM puts the convergence line a bit further north and buries Perth - not easy to pin down exactly where this will end up even by looking at the isobars but I do think we're starting to see the signs of more substantial organised snow through Monday and Tuesday:

Wednesday again looking nice, this time with a proper ENErly flow:

No sign of an end on the GEM either really, snow still piling in from the North Sea on Friday morning:

[Scotland/Alba weather discussion - Jan 2021 onwards]

Looking a bit further out - the UKMO is gorgeous for Tuesday, with such a long fetch you could start to see showers merging and totals piling up:

An extension of the easterly proper into Wednesday is starting to firm up, certainly for eastern areas, with a slightly weaker flow but still due east and if anything even colder uppers coming in:

Thursday is the first sign of the Atlantic making inroads, but still very cold and very very close to an undercut especially on the UKMO:

 

 

[Scotland/Alba weather discussion - Jan 2021 onwards]

Reasonable consensus now between the GFS and UKMO on Monday - some nice relatively parallel isobars with 1020hPa running Aberdeen to Skye and 1015hPa near the Galloway coast:

As a result we see this convergence line moving in later on Monday across central Scotland:

ICON flags up that sort of idea too(bear in mind this is hourly precipitation):

The next bit is dependent on the timing of the low undercutting but I'm happy with how things are looking this afternoon.

We can see the GFS does move it a bit further north but basically has this convergence line sitting around the latitude of Loch Tay to South Lanarkshire (and all the way down the east coast), from Monday morning through to Tuesday lunchtime:

[Scotland/Alba weather discussion - Jan 2021 onwards]

I've noticed a bit of a northward trend on the isobars in the North Sea since last night on the UKV:

from:

to:

 

Hard to compare because there aren't like for like precipitation total charts (it goes from 3 hour to one hour resolution the further out you go) but likely a positive trend as far as convection and the angle of attack goes for more central areas through Monday e.g.:

I had previously noticed a general 'sagging' of the flow up to now which, while not uniformly terrible, probably wasn't the best thing, but good to see that trend being reversed.