Model Output Discussions 06z 04/11/16

[feb1991blizzard]

4 minutes ago, Frosty. said:

Well what a run for coldies, makes up for the last 2 Gfs 18z low res mild mush fests!

Severe frosts, ice days and snow

Yes, wave 2 now very evident in the mid stratosphere as well.

Edited November 22, 2016 by feb1991blizzard

[Mapantz]

The 18Z was worth an 850 GIF..

 

[Zakos]

Fantastic run from the 18z tonight.

Aside from the brilliant cold and snow prospects, 3 day snapshots of the run show completely blocked weather for the next 16 days.

Very encouraging that the atlantic is still failing to fire up, and the low heights over Iberia are refusing to budge

The trend in recent weeks has been to send energy south over the UK and towards Iberia.Charts like the above have been shown on a number of runs and I think this is what will happen, not the coldest scenario but certainly potential for snow.

The cold airflow may miss the UK, but the outlook is very blocked and stacked with potential for cold and snow

[DR(S)NO]

Well folks ..... The charts this evening are far more encouraging for the start of Winter....

In fact they are full of........

PO

[Nick F]

Despite the difference at the surface between 12z and 18z GFS beyond t+144, one thing they have in common is a similar upper pattern. I.e. split / bifuricated jet due to block near UK ... but eventually all energy goes into southern split branch, diving SE towards Iberia and Morocco, while the northern arm weakens. This weakening of the northern arm, in effect, allows cold air to start pouring south from the arctic toward the UK. So we have an upper low over Iberia and troughing over northern Scandi, ridge in between, then eventually the ridge is squeezed out and a large trough is carved out over much of northern and western Europe, as cold air pours down from the north.

Time for some diagrams again to illustrate the above pattern evolving using jet charts:

And ... if you are still in doubt that the pattern may bring riches in the coming few weeks, take a look at the NAO and AO forecasts, all keep negative. Also, despite zonal winds at 10 hPa showing signs of increasing at higher polar latitudes, the PV maybe strengthening a little, at least the core of the vortex is shifting toward Eurasia.

Also note, not any serious deep cold over N America either, it's all over Russia, Siberia and E Asia. So no huge temp gradient over NE N America to fuel a strong zonal jet and Atlantic storminess for the UK for weeks on end

Edited November 22, 2016 by Nick F

[Zakos]

Not entirely sure, but looks like the retrogression to Greenland/Hudson Bay is (finally) creeping into the reliable timeframe from the ECM/GFS means,these  charts are only 168+ hours out.

Looking at the day 10 means, looks like a lot rests on the block setting up in a favourable position, looks promising to me but risky with the atlantic door (potentially) open.. however potential then for frontal snowfall events as the atlantic pushes into cold air entrenched over the UK interesting times ahead.

 

Edited November 23, 2016 by Zakos

[Banbury]

Keep your feet on the ground folks the 18z is naff all N24 talked about ,

Yes the Control also flashes the Nly at us but that's well into FI

[Summer Sun]

 

[Banbury]

There's some good ones in the ENS

[booferking]

The UKMO 00z looks good at 144hr but its a case if not to take any model gospel until they figure out what going to happen upstream.

GFS 00z not looking as good from last nights runs but its what happens on eastern seaboard that will determining this.

Edited November 23, 2016 by booferking

[The PIT]

Frustrating 00 oz even the teasing in deep FI are unimpressive. A long settled spell coming up which is good news for those wanting to dry out. Otherwise not a lot happening.

[ArHu3]

 

EC big difference at +144h with yesterday's run

Edited November 23, 2016 by ArHu3

[knocker]

Today and the next couple of days.

Today sees the beginning of a much drier and quieter spell of weather which will be greatly appreciated in many areas. The Azores HP ridges in from the SW and with the upper low over Iberia we have the analyses as indicated in the 18z chart for Friday.

So today in N. Ireland and Scotland starts with quite a severe frost and remains cold, crisp and clear for the rest of the day. England and Wales mainly cloudy, perhaps brightening in some areas later, and any light rain confined to SE England which tracks north into East Anglia. A fairly marked latitudinal variation with the temps.

The GFS this morning and what the current interpretation is regarding the interplay of the energy emitted upstream and the cold/warm air HP/LP downstream.

Initially we have the upper low from NE North America combining with energy arriving from N. Canada to form a new low which is over the southern tip of Greenland by 12z Sunday. This maneuver has pushed the Azores ridge east and into an enclosed HP cell over N. Britain

It is from this position that the evolution tends to get a bit wobbly. This low fades but it has opened the door for energy transmission around another surge from the Azores for a trough to form in the eastern Atlantic which phases in with the Iberian low. Thus the formation of a new trough and we arrive at this position by Weds 00z

From here the trough tracks east and deconstructs, and it  all becomes very messy, so suffice it to say this translates to this surface analysis.

So what does all this waffle mean weather wise for the UK? From here until next week the latter will remain under the influence of high pressure centred to the north so dry with gentle zephyrs from the east until the HP starts to slide SE at the beginning of next week and the winds veer and pick up a tad. The exception may be the far south where the winds may be a little stronger. From the middle of next week the trough will make inroads and some wet, and maybe windy, weather will ensue.Temps could be quite chilly under the HP with perhaps even some freezing fog around but with little wind could be quite pleasant if the cloud is minimal. Good Sidney weather.

Edited November 23, 2016 by knocker

[Ali1977]

Looking good at 192 from the ECM, different to the 00 GFS though. Just need a little more westward movement of the high pressure and we'll be in a cold Northerly.

[knocker]

Just a had a quick look at the ecm. Key difference with the GFS is that it doesn't complete the formation of the trough as another surge NE from the Azores cuts off the jet from tracking SE. Better for the UK as we would hang on to the drier weather longer.

[northwestsnow]

Doesnt look very nice to me at 192, too much energy to the NW again...

[IDO]

GFS:

So UK HP establishes till around D6.

That UK HP cell is eased east from around D6 as the Azores High re-establishes.

The Azores HP fails to ridge till after D10 due to the proximity of a vortex close to the NE.

In the interim from around D8 we have signs of the N Pacific ridge creating an upstream wave (GEFS not as instructive yet).

This gives the amplification for the Azores to ridge in the Atlantic and on this run we get a 48 hour transient cold shot around D11-13.

The Pacific Ridge has toppled by D11 so upstream flattens again and the Atlantic ridge collapses.

The pattern then restarts with another mid-latitude high close to the UK.

The difference from now and D16 is that the PV is showing as more organised, though still not the normal December nightmare.

Looking at the GEFS D16 and there is a strong cluster mimicking the op run so a more believable run than last night's 12z. The differences in the GEFS relate to the forecast strength of the Pacific Ridge (D8) and that could go either way.

Conclusion: still no sign of the long term pattern getting a reset with no apparent strong driver to disrupt the status quo though the inevitable slow strengthening of the PV is now trending, though not to the extent where we should worry yet. On this run the UK gets one of those transient cold shots (d10 approx), but this is subject to change (eg GEM has us on the warm side of that ridge/trough & ECM in between). 

November looks like it will be a slightly below average month temp wise, CET -0.4c at present (21st) and surface temps look on the cool side under the high even though uppers are not too cold. Not a bad prelude to the upcoming Winter.

[Seasonality]

Gfs v Ecm at t240 from the 00z. Nothing settled yet. But Ecm has been more consistent with the evolution.

[bluearmy]

Looks like the ECM is following the ens route - that's good in one way because we know where we should end up but with a non progressive evolution, we have litttle idea if subtle changes will mean we end up looking at areas to our east or west receiving cold temps come verification whilst we don't. 

[northwestsnow]

Ecm 240 is interesting, on the one hand we have a pretty impressive euro high, on the other signs of some retrogression in the Atlantic, interesting stuff..

[That ECM]

Remarkable yet arguably boring for some. HP over or very near us for the whole run. It has the feel of being in aircraft waiting for a slot to land. Circling over the airfield and thinking, come on, I want to get going....

Edited November 23, 2016 by That ECM

[karlos1983]

In some respects this year is more frustrating model watching than last year, I mean at least we had a fairly good idea consistently of what might be happen in 5 -10 days time 

One thing we do know, the lack of an organised PV! So don't worry it's not nagative. 

Quite a majority of the members head sub zero later in the run. Let's hope that becomes a trend!

 

Edited November 23, 2016 by karlos1983

[ArHu3]

1 hour ago, northwestsnow said:

Doesnt look very nice to me at 192, too much energy to the NW again...

New ec looks good when it matters,  in the reliable range, see above how much today's +144h changed compared to yesterday's +168h 

[knocker]

Quite warms the cockles- or even Sidney's nuts

[Singularity]

Well, the swing by UKMO to support GFS with that low over Newfoundland at +144 hours is noteworthy.

If we could at least sort that out, attention can turn to getting enough amplification with the next trough-ridge combination to its west. GEM shows how things could still go very wrong (for the first week of Dec) even with the low at +144 being held up.

ECM is on track to win the 'most bizarre output of the week' award but that doesn't necessarily mean it's not got the broader idea right... namely that trough not being held up. 

 

In the end, we're chasing a cold blast for a time period at least a week ahead of when the signals really start to come together, so anything we achieve could be considered a bonus. Of course, that's extremely presumptuous regarding mid-Dec  which is risky behaviour I know!