Model output discussion-mid Autumn and beyond

[bluearmy]

9 minutes ago, The PIT said:

You are talking about February I'll give you a tip forget about it. Trust me I saved you a millions.

Knocker enlighten me what is there to be afraid off . To me it looks like if there is a block we are too far west for any effect here. Different story for Europe.

 

I’m not talking about feb - I’m contradicting TWO re jan 

[knocker]

After some mid term amplification due to upstream shenanigans the ext mean quickly reverts to zonal flow in the ext period

[knocker]

Following on from the short range with the gfs and the battle continues to rage between the energy exiting the eastern seaboard and the amplifying subtropical high zones starting with a brief flurry from the latter at T144.

But for this run this would appear to be the last desperate flurry before the pressure from the west wears them down

[knocker]

The ecm is a tad more successful than the gfs in sustaining north west ridging of the high pressure for a while. But this does allow the colder air to slide south a tad closer to the UK

And just impinge by the end of the run

Critical period between T144>168

[knocker]

And after the little burst mid term the ecm continues to de-amplify in the ext period

[Radiating Dendrite]

I'm enjoying the settled weather at the moment.

The SSW is still being touted as the second coming in the madness thread but I just see a continuation of the pattern we have seen so far this winter - a lack of heights to the north with these continuing to sustain over Iberia and occasionally ridging North over the UK or to our East.

[knocker]

Merely an observation but 130kts at 500mbs south of the Newfoundland trough is really quite impressive

 

[knocker]

The energy flows in and out of North america towards the end of the ecm det. run and the eastern Atlantic at same time.

[knocker]

Every indication at the moment that the above is the beginning of the process of eroding the ridge

[SLEETY]

More the lack of data as not so many planes fly over the Xmas period I think. Mega runs starting again soon, keep the faith, the big freeze is incoming

[knocker]

According to the gfs the intensification of the high cell is short lived as can be seen if we with run the evolution on three days from T120

[knocker]

The ecm is, predictable, in not such a rush to erode the high cell. So in the process of the energy attacking the mid run amplification of the ridge it manages to isolate a high cell to the north which facilitates the removal of the warm airmas to be replaced by some cold pooling as it slips south. Thus some widespread frost, perhaps some freezing fog, towards the end of the run before the energy slowly gains the upper hand

Of course this is a long way from a done deal

 

 

[northwestsnow]

1 hour ago, knocker said:

The ecm is, predictable, in not such a rush to erode the high cell. So in the process of the energy attacking the mid run amplification of the ridge it manages to isolate a high cell to the north which facilitates the removal of the warm airmas to be replaced by some cold pooling as it slips south. Thus some widespread frost, perhaps some freezing fog, towards the end of the run before the energy slowly gains the upper hand

Of course this is a long way from a done deal

 

 

Quite right , EC det is indeed very cold by day 7 onwards,i might even get chance to don the new scarf and gloves- perish the thought!!

[knocker]

The EPS mean still looking at the erosion of the ridge medium term

[phil nw.]

Yes still nothing out of the ordinary to get the juices flowing in the ens.

Some differences yes in the movement of the high before it moves away but essentially modeling continues with a +NAO outlook.

First the differences reflecting in the 2m temperature graph for London showing both ops are at the extreme end of their ens.suites.The GFS going warmer still and wetter whilst the ECM op brings in some colder air and drier before losing the high a little later from another Atlantic push.

The means at day 10

I think within that pattern some incursions of polar maritime air are likely so once the high moves off temperatures look like varying around the norm.

 

[knocker]

I have to say my juices are flowing quite well

[phil nw.]

11 minutes ago, knocker said:

I have to say my juices are flowing quite well

Indeed the mid-Winter warmth on a gentle Atlantic drift

Nice for some i guess.

[knocker]

Still a lot of energy in them there hills according to the gfs

[Singularity]

Posting here so it has more time to air before further posts take things onto the next page.

 

 

Looking at these non-lagged composites for ENSO+ MJO phase 5 in Dec and 6 in Jan, I can see where the more mobile spell for the UK with increasing 'cold zonality' flavour is coming from that's been depicted by one or two recent GFS runs, given what it's doing with the MJO during the coming fortnight. Most of the GFS and even GEFS runs, though, have instead remained very flat with a distinct lack of poleward ridging that the phase 6 composite shows, and these seem to have no reasonable basis when looking at tropical forcing. Even a flushing down of zonal winds by the SSW (ahead of the reversal) shouldn't have a strong enough impact to override the MJO forcing so much.

ECM is so much less amplified and quick through P5-6 that this is likely the reason why it's managing to keep more ridging in place across the UK in the 7-10 day period. I've a strong suspicion, though, that it's making too little of the MJO through phases 6 and 7. However, movement of the GWO through P5 may allow for the ridging to find more of a foothold for a time anyway, so a colder shot into the SE is still plausible.

If we take half of the GEFS amplitude and all of the MJO propagation speed, we get a sequence that supports a trough of some form moving through the UK by the late stages of next week and then a big ridge building well north out west then northwest of the UK while the trough drops south/southeast into Europe by the late stages of the week after. However, the GWO moving through P6 complicates matters as we could see the ridge putting up too much of a fight for such a straightforward transition. Perhaps it could disrupt and slide into Europe instead... many possibilities here!

Either way, once the MJO is in P7 there is the potential to do us wonders mid-Jan - but only if you're a fan of cold weather of course!

Edited December 27, 2018 by Singularity

[knocker]

At T144 the ecm is virtually identical to the midnight run as the energy gets to grips with the recent amplification of the ridge with a resulting in a high cell to the north containing some colder air.

This then sinks south with the cold pool over the UK resulting in a severe frost Friday morning in the -5-6C range as a ball park. But the precise orientation of this important as a fraction further east and the UK stays in the warmer air

Edited December 27, 2018 by knocker

[Polar Maritime]

A few posts have been hidden, Please use the pm function for anything other than Model Discussion in here.

Onwards and upwards..

[MattStoke]

I’m guessing the GFS didn’t move towards the mighty ICON after all, seeing as no-one is posting about it this morning.

[Methuselah]

7 minutes ago, MattStoke said:

I’m guessing the GFS didn’t move towards the mighty ICON after all, seeing as no-one is posting about it this morning.

Seemingly not, Matt...But if one subtracts the GFS's well-known eastward bias, we should be in the freezer at T+138...Nailded!

Edited December 28, 2018 by Ed Stone

[phil nw.]

1 hour ago, Ed Stone said:

Seemingly not, Matt...But if one subtracts the GFS's well-known eastward bias, we should be in the freezer at T+138...Nailded!

Actually days 4-7 are worth a second glance as that cold plunge down through Scandinavia could well bring the UK into a mini cold snap.

The 3 at day 5,slight differences with, not surprisingly the GFS, further east.When looking at the London ens we can see this reflected in the 2m temp.graph

Maybe 3/4 days of dry,crisp weather with hopefully brighter skies.

We can see how close at day 4 we were to a decent pattern ie regression developing-UKMO

 

Just to much forcing from that Canadian lobe to hold the ridging at higher latitude and we get the edge of the cold plunge with the high settling over us.

 

[phil nw.]

Just looking a little further on to day 7 and comparing the ens means of the GFS/GFS(p) and ECM 

The GFS showing it's flatter bias on the UK ridging even in the ens.suite against the other 2.This tendency is often pointed out when viewing the operative runs where this bias is more apparent having not been smoothed out like the means.

It is good to see this show up as it's something to be aware of especially in later gefs by which time the progressive nature of this model can be multiplied further.We often see westward corrections or a less flatter option nearer the time.