Model output discussion - 1st December onwards

[damianslaw]

I said expect lots of twists and turns from each model from one run to the next over the coming days. We are entering a transitional period as the northern hemisphere undergoes a significant shift from its Nov-Dec pattern, longer term the shift is ripe for cold conditions to invade the UK. In such times best to look at the trend taking shape rather than get bogged down with run to run variations.

[KyleHenry]

Chart below is outer FI but not beyond the realms of possibility due to upstream patterns and Tropospheric pulses ongoing.

Current WAA in process is the initial pattern change which creates the Kara High and allows -ve AO to evolve. 

In the meantime we must traverse through 10-14 days of +NAO and with that LP systems & more flooding.

If this next possible future WAA, is in the position shown,it will lead onto ridging up through Greenland and create -ve NAO.

Then we can talk Omega and easterly with confidence.

Keep the faith.

[kumquat]

Not sure why folk south and west of Shetlands are still chasing the phantom easterly. All models seem to be backing away from this (barring a few pertubations) while showing a slightly rugby-shaped ball of low heights pushing through the UK. There are signs further down the line of pressure rising to the North backing Northwest which could bring something colder, but I'm not hedging any bets on long-term teleconnections, be they or be they not in conjunction with El Nino or MJO signals or whatever else.

That the vortex (and associated colder air) will be pushed down to lower latitudes, yes I'm thinking it will. Pressure looks set to rise to some degree to our side of the pole and upstream aiding this, but, as usual, finding cold in this part of the world, inhibited as it is by latitude (especially those of us below 52 north - M4 corridor) and proximity to a large body of water (upstream) that has been constantly moderated by the AZ high to such a degree remains tentative.

Mid-Atlantic ridge looking like a possibility later on and we're just starting to see it in the models but as we are now, the next couple of weeks only bring damp, wet, windy and further compound the problems of flooding in the NW.

Last year it was the SW that bore the brunt and it's interesting to see how global weather patterns so influence us on the micro-scale when they become so repugnantly stagnant and relentless.

 

[Mucka]

It is till the outside bet to get cold and snow to low level England based on the all output tonight but certainly plausible.

If you are in the South you need to hope UKMO is leading the way and things can develop further on to give you a chance.

 

[damianslaw]

As others have alluded too, we should most likely be looking to the NW over the coming week for a cold injection, and then the NE.. rather than the east.

There are more and more increasing signals for heights to ridge north towards Greenland from the mid atlantic caused by an amplified flow taking shape thanks to developments over the arctic regions.

The most likely route to a much colder evolution is heights building from the azores northwards linking eventually with those robust heights to the NE - the jet sunk southwards.

The models are likely to play around with various scenarios over the coming days, but in time should stabilise somewhat to such possible trend.

[A.J]

1 hour ago, Sperrin said:

Rookie question; could someone briefly explain what a dam line is and how it relates to cold weather? Cheers.

certainly......if it's below the mid 520's, then it's dam! feeling a bit nippy outside, it'll snow for sure..........................or if it's above the mid 520's, then it's dam! bloody rain again, jeez, this country sucks for snow, why don't I emigrate to Alaska......

 

hope that helps! 

[Geordiesnow]

Do find it rather amusing now people are talking about look towards Greenland for a sign of the next cold shot because you know by the time this suppose WAA heads into Greenland and it doesnt turn out as expected, it will be, wait until the end of the month because something will happen by then so on and so forth. 

Of course I respect signals may point to that but for me, it does not interest me at themoment because as we know, the longer term is very much subject to change and I will never take a GFS FI run seriously so for now, we have to concentrate on the reality and there is potential however it does seem as it always has been in fairness that an easterly in the nearer shorter term does look long odds which is ashame really considering the blocking on offer and the strength of the cold pool, would be a wasted opportunity really. 

[nick sussex]

Latest NCEP thoughts re pattern over the ne USA, amplified solutions preferred which would support the UKMO output solution.

The area forecast for the Burlington VT area noted the differences between the models in the dig south of colder air. The GFS 12hrs run was not preferred, regardless of the later part of some of the operational outputs which move the snow/rain boundary further east if you want the UKMO to have a chance of verifying then you must have that upstream amplitude.

This might carve out a ridge in between the UK low at T120hrs and the shortwave following on, even if the outputs don't want to take that UK low se'wards and want to pull this nw with shortwave energy heading se we might see a trigger shortwave running east a bit like the GEM output.

That was close to delivering that deep cold pool further west just the Atlantic low was a bit close but theres still room for changes.

Bear in mind that the amplitude upstream allows the PV to split in northern Greenland and helps to allow the ridge extension from the Russian block in that area.

Anyway I'm rambling now so will bid you all a goodnight and we'll see what happens in the morning.

[Mucka]

Another marginal improvement from GFS (out to 120 at least - don't look at FI if you value your sanity) but is it really likely that low would run under the block with little or no disruption?

 

Oddly enough after the discussion last night about GFS being more progressive it is actually less progressive than UKMO - here are the 72h comparisons this morning, note UKMO has the first low further East.

 

UKMO 120/144. 

The low stalls and disrupts SE which prevents cold uppers getting across us from the NE but if the upstream pattern was conducive could actually still be quite good. It does look likely that any initial cold is going to be held too far NE at the moment but still big changes in the NH if not immediately for the UK.

 

GEM keeping the faith, good snow chances, especially for the Midlands and North on that one

 

And continues into FI with blocking tot he North and low pressure disrupting across the S of the UK as the cold air sinks further and further South so most places would see some snow at some stage if only this were the outcome.

 

While GFS stays exceptionally wet unfortunately. (If GFS were a person it would be one of those people that interrupts and finishes all your best stories when you are halfway through telling other people)

 

I'm not going to say bin it but that low around 120+ doesn't look right at all.

Edited December 30, 2015 by Mucka

[northwestsnow]

Gfs is an abomination for an already soggy country this morning, this Atlantic is just ridiculous. There is next to no chance of any blocking influencing our weather until something changes towards Greenland, sooner rather than later.im off to the moaning thread, probably stay there for a while.

[cheshire snow]

To sum up this morning GFS Wet,Stormy,and  probably more flooding,and way out into FI Temperatures back up to 14c

C.S

[Cheshire Freeze]

12 minutes ago, cheshire snow said:

To sum up this morning GFS Wet,Stormy,and  probably more flooding,and way out into FI Temperatures back up to 14c

C.S

We're in serious trouble if that GFS run comes off. It's really quite concerning now, the amount of water that has fallen and could fall if the GFS has it anywhere near nailed. That low around the 4th of Jan on the 0z GFS looks nasty and would dump another couple of inches widely.

[Mucka]

GFS is a shocker but I really wouldn't pay much attention to FI, especially off a single run from one model. There is wide scatter out to 144 among GFS ensembles. let alone FI.

Also there is well signalled build of high pressure from the SW either over the UK or in the Atlantic toward mid month.

 

Edited December 30, 2015 by Mucka

[kumquat]

It's not just the one run though, is it Mucka? Most runs across most models show devastating rainfall up out until way past 144. The pattern isn't going SE. It's bringing it across the country.

[knocker]

The next week is looking grim. First we have to get Frank out of the way and there is still plenty of wind and rain to come

http://earth.nullschool.net/#current/wind/surface/level/orthographic=-0.76,58.94,819/loc=-4.182,33.029

And then there looks like more systems later in the week witha couple of depressions skirting the UK next weekend before another intense low the beginning of next week. Hopefully this is subject to revision.

 

[Liam J]

Even the UKMO isn't looking quite as good, most of the UK in W/NW flow on the 00z instead of SE'ly and that low winding up in the Atlantic doesn't look great. Things not looking good and very worrying for already flood stricken regions. 

[northwestsnow]

9 minutes ago, knocker said:

The next week is looking grim. First we have to get Frank out of the way and there is still plenty of wind and rain to come

http://earth.nullschool.net/#current/wind/surface/level/orthographic=-0.76,58.94,819/loc=-4.182,33.029

And then there looks like more systems later in the week witha couple of depressions skirting the UK next weekend before another intense low the beginning of next week. Hopefully this is subject to revision.

 

No getting away from it.

The ironic thing is the day meto mrf goes cold, the models trend, wet, and windy, and, well, nowhere near cold.

 

[Mucka]

22 minutes ago, kumquat said:

It's not just the one run though, is it Mucka? Most runs across most models show devastating rainfall up out until way past 144. The pattern isn't going SE. It's bringing it across the country.

It is only one run and one model as far as the storm day 6 is concerned but I guess ECM did model the trough to move over the UK in FI last night.

It doesn't look great at the moment but ECM and UKMO still offer hope out to 144 and GFS as expected is out on its own by this time.

Edited December 30, 2015 by Mucka

[kumquat]

4 minutes ago, Mucka said:

It is only one run and one model as far as the storm day 6 is concerned but I guess ECM did model the trough to move over the UK in FI last night.

It doesn't look great at the moment but ECM and UKMO still offer hope out to 144 and GFS as expected is out on its own by this time.

If there's anything to strawclutch (I know you're not doing this mucka) the crazy warm winds tonight moving south to north. One would expect to pump up the Scandi High. This just isn't usual behaviour. There's something a bit alien about this.

[Weather-history]

5 minutes ago, kumquat said:

 One would expect to pump up the Scandi High.

Here lies the problem for me. It isn't really a Scandi high. The centre of the high is too far north and east. The centre of high is near Murmansk when it needs to be the Baltic Sea. It is only having a finger tips reach for the UK.

[Mucka]

1 minute ago, kumquat said:

If there's anything to strawclutch (I know you're not doing this mucka) the crazy warm winds tonight moving south to north. One would expect to pump up the Scandi High. This just isn't usual behaviour. There's something a bit alien about this.

I'm just trying to stay positive, I accept the output isn't going the way we would like and always said colder was the more unlikely option but at the same time I don't feel this over yet and ECM does at least give some snow chances for a short while, more especially for the N and E. If we can just get the cold air further West then the lows will disrupt more and the knock on effect would deliver something more like GEM. Yeah it's a long shot but my Dad used to always roll a double to get out of jail in Monopoly.

[Timmytour]

 I think the day of joy and day of gloom cycle is a common theme in these kind of situations.  i imagine many good spells in the past would have been preceded by such spells in the past with such close scrutiny of every run of every model. In fact it's a sense of being in this cycle that gives me cause for optimism that the cold weather will eventually prevail, and I fully expect the hunt for cold to be re-invigorated as the day wears on

However  at the same time I take my hat off to chief" cold hunt saboteur" Knocker.... he's been mostly relentless in his view, taken from his reading of the models than his preference imo, that the cold is not coming, sometimes flying in the face of some resounding optimistic readings of model runs.  I sometimes think that, much as it can be easy to criticise the ability of anomaly charts to pick up on changing trends, anyone with a particular interest in calling what the weather will be, invariably will have a higher rate of success in predicting it by using them.

What's driving my current optimism is only a gut feel about my perception of the current volatility in the day to day model runs.  But tbh if i wanted a reputation for being accurate rather than wanting my wishes to come true, I know i could do worse than follow Knocker!

[knocker]

Looking at the GEFS anomalies this morning doesn't hold out much hope in the short term but later an indication of positive height rises to the W/SW which is also what the EC32 is indicating around that time.

[shaky]

Woke up looking ath the posts here and youd think the atlantic has barrelled through and the scandi high has been blown apart!!absolutely ridiculous!!!so i thought i would check the models and to my eyes ecm looks better than it did yesterday same time and ukmo is not bad either!!gfs is obviously known to go crazy with deep lows so that 144 hour chart will probably not look like that come closer to the time!!heights look better to our north this morning aswell!!

[West is Best]

30 minutes ago, kumquat said:

If there's anything to strawclutch (I know you're not doing this mucka) the crazy warm winds tonight moving south to north. One would expect to pump up the Scandi High. This just isn't usual behaviour. There's something a bit alien about this.

Yes and the west to east progression of Frank's fronts has been slower than expected even 12 hours ago, suggesting an underplay of the Scandinavian high already.

In these situations it's good to keep an eye on all three models. The GFS always over pumps the Atlantic.