The hunt for cold - Model discussion (late November)

[frosty ground]

1 hour ago, Steve Murr said:

Im afraid thats not strictly true

If you have one long continuous jet stream then yes its hard to back the cold SW however when you have a jet streak which then moves through the residual flow of the High & low that is left in its wake will advect upper air SW due to the natural flow & wind allignment- its a slower process but if you look at 144 UKMO thats whats happening -

The jet is alligned NE SE across scandi not W > E

The cold air then filters SW around the base of the high-

 

Thanks for the detailed response.

[Spah1]

Huge differences on the 06 Z at 168hrs of the location of the low out west compared to the 0Z. 

[Summer Sun]

GFS 06z is bringing the low closer again by early next week 

06z

00z

[Weathizard]

Just now, Spah1 said:

Huge differences on the 06 Z at 168hrs of the location of the low out west compared to the 0Z. 

Indeed. This run is much more progressive, not in a good way! Heights are just not strong enough nor positioned correctly to disrupt the low enough.

Stuck in a middle ground as usual on our little island!

[Jonathan Rhodri Roberts]

33 minutes ago, bluearmy said:

On meteociel - ‘GFS para’

Is that going to completely take over from the GFS? If so that's a shame because only last year I think it was that they added 1hr timeframes to them which is far more detailed and very useful IMO, GFS Para doesn't when I looked at it recently only the original 3hr timeframes, a step backwards? 

[Ben Sainsbury]

3 minutes ago, Jonathan Rhodri Roberts said:

Is that going to completely take over from the GFS? If so that's a shame because only last year I think it was that they added 1hr timeframes to them which is far more detailed and very useful IMO, GFS Para doesn't when I looked at it recently only the original 3hr timeframes, a step backwards? 

Whilst 1hr timescales are useful you're right. Ultimately how successful a model is, is dependent on its verification stats (a judge of how accurate they are when modelling the weather) and currently the GFS Para is verifying better than the main GFS model hence why the Para is going to take over.

[mb018538]

6z is one for the bin. Low gets too close, mild SW'erlies return. No thanks.

[Seasonality]

4 minutes ago, mb018538 said:

6z is one for the bin. Low gets too close, mild SW'erlies return. No thanks.

All joking aside, wait for the Para/FV3, it is verifying better!

[Paul_1978]

11 minutes ago, mb018538 said:

6z is one for the bin. Low gets too close, mild SW'erlies return. No thanks.

It's not for the bin if it's right, which it could well be.

[Man With Beard]

ECM ensembles clusters D9

Emphasises the problems being caused by the Atlantic low coming up against the block to the NE - ridging could well spill in a number of directions. However, though a cold feed from the NE is just about possible, no clusters obviously scream significant cold this morning, the op cluster being the closest.

D13

In all honesty, ridging looks like it will be too far away either to the NW or NE to advect cold to the UK. Also, I detect a pulse of heights into C Europe in all clusters (like the GFS parallel has been showing), which would promote a SW influence. I'm not optimistic about cold chances around this time, therefore.

[Methuselah]

I don't know but, so long as the PV remains oddly misshapen, just about anything can happen - over a 2-3-week timescale?

[Paul]

31 minutes ago, Jonathan Rhodri Roberts said:

Is that going to completely take over from the GFS? If so that's a shame because only last year I think it was that they added 1hr timeframes to them which is far more detailed and very useful IMO, GFS Para doesn't when I looked at it recently only the original 3hr timeframes, a step backwards? 

That's just because it's the para, the one hour timeframes will still be in the upgraded operational as far as I'm aware.

[stodge]

10 minutes ago, Paul_1978 said:

It's not for the bin if it's right, which it could well be.

Oddly enough, I think it's a very good run.

Yes, there are no screaming NE'lies with -20 uppers heading toward us but the one thing the GFS 06Z OP isn't is raging zonality. It's unsettled and often cold condition to the north of the British isles and plenty of rain for all parts (which is badly needed).

Looking at the NH profile, the attempt to build the PV back over Greenland fails and the PV ends up right over the Pole which you don't see every day of the week.

It's a plausible scenario going into December and the possibility of heights rebuilding is clearly there.

Control and Parallel will no doubt look very different.

 

[nick sussex]

The GFS 06hrs  run starts okay and then unravels quickly as a phase tragedy sends all the energy ne wards .

The key timeframe is before the low to the west re intensifies, around T138hrs you’ll see one round of trough disruption that little low developing near Brittany , it tries to eject a second shortwave but fails this then moves nw absorbed into the main low . From that point there’s no way back.

These situations are poorly handled by models , especially the GFS which has a bias to take too much energy ne rather than split that.

So I’d not view this GFS run as indicating some definitive trend, we’ve been here many times with this type of set up. I wouldn’t cancel the ear muffs and scarves order just yet !

Edited November 20, 2018 by nick sussex

[Summer Sun]

The ECM weeklies have updated

This week as we know is chilly we know with temps below average for a fair few areas

Week 2 sees a change as the colder air shift east allowing temps to recover for western Europe

Week 3 sees the temps widely above average for western Europe including the UK and the colder air shifting further east

Week 4 see the temps ease back slightly but still remaining widely above average for western Europe

Edited November 20, 2018 by Summer Sun

[Methuselah]

11 minutes ago, stodge said:

Oddly enough, I think it's a very good run.

Yes, there are no screaming NE'lies with -20 uppers heading toward us but the one thing the GFS 06Z OP isn't is raging zonality. It's unsettled and often cold condition to the north of the British isles and plenty of rain for all parts (which is badly needed).

Looking at the NH profile, the attempt to build the PV back over Greenland fails and the PV ends up right over the Pole which you don't see every day of the week.

It's a plausible scenario going into December and the possibility of heights rebuilding is clearly there.

Control and Parallel will no doubt look very different.

Seems like it's only me and thee, stodge!

[nick sussex]

To explain a bit more about the trough disruption.

You can see here on the GFS 06hrs run T150 hrs chart.

The two circled red features are shortwaves, one you can see near Brittany, the other just to the east of the main low.

 

The latter is the main issue at this point, it fails to eject se from the main low and then runs nw and absorbed into the main low, this helps the eastwards momentum and takes the energy ne wards. Trough disruption is always a difficult area for the models because its basically a balancing act and if the model is out just a bit then the forward projections are greatly effected.

[carinthian]

4 hours ago, carinthian said:

Morning all , another spell of snow arrived overnight. Think there is a bit more than 10cm accumulated snow in the village. Current temp -7C. Quick view at this mornings models and looks like an improvement from last nights regarding the hunt for cold, especially from ECM latest run. However, the pick again is the UKMO which has shown consistency in its runs out to 144t and that's to hold the colder scenario over much of your part of the world with the flow still backing. Will get an update from the forecast team over here later this morning regarding their further thoughts ( see above post ) for you guys and hopefully some pictures of the very welcome snowfall in these parts. All snow guns working as well for piste preparation that is now well under way. Time for my daily bacon and eggs, Yorkshire tea, which I bring back from blighty in great supplies. Continental tea, crap!

C

 

Thought I would add this photo for lovers of snow. This is what Katschberg looks like when conditions are perfect. A long way from that at the moment as the mountains are hidden by low cloud but at least we have some snowfall in place , about 15cm. Long nights, short days, the ideal time for a cold spell to start ? Currently the synoptics look good during this last 3rd of November and its not even the start of winter. Certainly a major shift this last week in much of Europe, from unusual warmth to much colder conditions thanks to a strong Arctic high. Will it last I ask into the first week of winter ? The answer from our experts is 60/40 in favour. They think the GFS runs are far to progressive to push the cold block now in formation. They think some attack will be inevitable from the Atlantic , however, their single model still holds a strong Arctic ridge out to 10 days and then period  10 -15 day longer term charts indicate a build of pressure around Scandinavia with lower heights into Europe. Milder air seems likely to make an attempt into SW Britain for a while but any troughs/lows likely to disrupt as they meet the colder block developing to the NE , but that's a long way off. In short to medium term the UK  stays on the cold side.

Edited November 20, 2018 by carinthian

[Summer Sun]

GFS P now has the low a bit closer to the UK like the main GFS

GFS P

GFS

[swfc]

The lack of posts even after gfs parallel kind of sums things up so far today.Id agree ukmo looks ok even with fairly weak heighths to the northwest.The atlantic could be stirring and forcing things but that's beyond my pay band .

[bluearmy]

I’m not a lover of discounting the ens in the. 7/12 day period ..... it rarely produces anything other than disappointment when those ens have been fairly consistent in the mean without any obvious binary outcome being played out, run after run ...

however, this set up is one of those times when the ens could well be incorrect - but it’s doubtful that they are totally incorrect upstream ...... we aren’t getting to the point in the next two days where the behaviour of the Atlantic low will have to come into some cross model agreement between ec op and ukgm ..... resolution by thursdays noon runs I reckon - currently 70/30 in favour of the Atlantic imo but without re inforcements from upstream, that low will fill and not over run the block - there is a balance whereby the low is strong enough to drive WAA against the block but not strong enough to sink the block - that merely strengthens the block in situ .

its interesting ...... meto update will also be of note shortly as it will give us an idea how much the latest 46 is in line with mogreps .... just taking the 46 at face value would mean the wording should change 

 

[mountain shadow]

4 minutes ago, bluearmy said:

 

its interesting ...... meto update will also be of note shortly as it will give us an idea how much the latest 46 is in line with mogreps .... just taking the 46 at face value would mean the wording should change 

 

It hasn't. Still going for colder than average with only infrequent Atlantic incursions. 

[Man With Beard]

Just revisiting this UKMO chart - it's a stones-throw from being sensational

Just need to get that Atlantic low to disrupt with perfect timing to undercut the high.

Seen it happen but with the weight of ens guidance opposed to this, I'd only give it a 20% chance right now.

[BlueHedgehog074]

8 minutes ago, Man With Beard said:

Just revisiting this UKMO chart - it's a stones-throw from being sensational

Just need to get that Atlantic low to disrupt with perfect timing to undercut the high.

Seen it happen but with the weight of ens guidance opposed to this, I'd only give it a 20% chance right now.

We should all probably go into the Atlantic and stamp on that Low Pressure system in the models. Maybe then, it’ll become flat enough to slide neatly under the block and draw in lots of cold air from the East/North-East. 

[Bruegelian]

21 minutes ago, DiagonalRedLine said:

We should all probably go into the Atlantic and stamp on that Low Pressure system in the models. Maybe then, it’ll become flat enough to slide neatly under the block and draw in lots of cold air from the East/North-East. 

 Oh my childhood fantasies.....