Model Output Discussion - Cold spell ending - what next?

[Big Gally]

BFTE part 2 will do nicely 2018 please thankyou.

[Paul]

10 minutes ago, TillyS said:

It does indeed look serious and ought really to be taking more of our attention.

Although it can obviously be discussed in here too. There is a dedicated thread on the go for Sunday into Monday here

https://community.netweather.tv/topic/99787-possible-storm-isha/?do=getNewComment

[Daniel*]

37 minutes ago, Drifter said:

Many scandi highs of the past occurred during +ve NAO phase. 

Aye, I’ve always thought Feb 91 beasterly was one of greatest examples.

[bluearmy]

39 minutes ago, northwestsnow said:

Well im going to have a look at EC 46 regardless..

The model was seeing HP in our locale now we need to see if it can nudge the high north...

Slowest retrogression ever !

[Mike Poole]

All hell’s broken loose on the extended clusters, T264+:

It’s like the model’s got wind of something .

Even on clusters 4 and 5, which continue the +NAO regime, there are blocking attempts, but they don’t take hold.

Clusters 1 and 6 build a Scandi high, I imagine the different members will mean different outcomes for the UK here, but the general pattern is what is important this far out.

Clusters 2 and 3 show retrogression towards Greenland.

[bluearmy]

2 minutes ago, Mike Poole said:

All hell’s broken loose on the extended clusters, T264+:

It’s like the model’s got wind of something .

Even on clusters 4 and 5, which continue the +NAO regime, there are blocking attempts, but they don’t take hold.

Clusters 1 and 6 build a Scandi high, I imagine the different members will mean different outcomes for the UK here, but the general pattern is what is important this far out.

Clusters 2 and 3 show retrogression towards Greenland.

Reckon will take a few more suites to get a direction of travel. We could end up honing in on a scandi cluster and a mid/east Atlantic one. And I doubt we’d avoid a U.K. mlb cluster on most runs! 

[joggs]

45 minutes ago, northwestsnow said:

Well im going to have a look at EC 46 regardless..

The model was seeing HP in our locale now we need to see if it can nudge the high north...

Welcome back proper nw

[sebastiaan1973]

Windplume De Bilt this morning and evening. An significant increase memebers with easterly winds (control included). O= East. Controle = Control (blue line) 

[Daniel*]

Heathrow 12z EPS

 

12z EPS yesterday 

[pages]

 

I want cold and snow as much as anyone my young son constantly asking when is it going to snow enough to go on sledge.

But I just can't see us getting opportunity for at least 3 weeks.

I know MJO forecast is just that but it's not trending in a good direction.

A few days back ECM and GFS both had MJO reaching phase 7 at decent amplitude.

Now ECM has it barely reaching for phase 7 and heading for COD and GFS looks even worse diving into the COD from phase 6 and looking like it's going to cycle back to phase 5. 

 

 

 

 

[stodge]

30 minutes ago, TillyS said:

Not the ECM.

Without any northern blocking and those powerful SW winds up over the top, and warming Scandinavia, this is a recipe for a flattening of the high - kicking it out across northern Germany. If you watch it from T198, to T216, into T240 this is the process. Which is about the worst possible outcome for UK cold.

Far be it from me to say you're wrong but you could be wrong. So much depends on the orientation of any block.  An elongated block does allow colder, drier continental air to be advected from the south east over especially southern Britain (I'm in East London so shameless local plug).

There's also as always the possibility of fog and frost (what is termed on here faux cold) under an inversion so while I appreciate for snow fans this is all horrible for cold fans it offers some possibilities. Oddly enough, I wouldn't want to see the HP move too far NE as the shorter the sea distance for the airflow the less likely it is to be diluted by a passage across a relatively warm (even then) stretch of water.

[WYorksWeather]

ECM 12z broadly similar to GFS on temperatures - very mild from around 22nd-26th, then something nearer normal after that. Still the possibility of a daily record break during that very mild interlude.

[Rain All Night]

9 hours ago, RainAllNight said:

A summary of this morning's model runs.

Deterministic runs up to day 7 (Thu 25th)

The Monday (formerly Sunday) system now has less of a "dartboard" shape on these three models, and ECM has similarly re-imagined the Tuesday-into-Wednesday system. ECM still offers the most generous ridging after the second system has passed.

Ensemble means at days 10 & 13 (Sun 28th & Wed 31st)

These are a little better than last night's (see my quoted post for those). It looks like much of England should be dry next weekend, at least.

A summary of this afternoon's model runs.

Deterministic runs up to day 7 (Thu 25th)

The specifics of the string of nasty weather systems visiting us between Sunday and Wednesday are still undecided, and others will do a better job of discussing these than I can.

ECM again makes the most effort with the ridge at day 7. The ridges shown on these charts do not look like they would survive, but the ensemble means for day 10 below strongly suggest that there will be a further, more robust ridging attempt subsequently.

Ensemble means at days 10 & 13 (Sun 28th & Wed 31st)

These are a significant improvement on this morning's (see my quoted post above), so we have a promising trend emerging (for dry, and possibly also for cold).

We have one dissenter at day 13, but it's the weaker model.

Edited January 18 by RainAllNight

[BurwellWeatherWatch]

Certainly mega mild after this week, for a bit ... Would be tempting to get the BBQ out if it wasn't for the small matter of the gales.

A week down the track and it's really much harder to see what is going on. There is evidence for extremely different possible outcomes and I don't think there is any clear way forward, despite a few fairly opinionated-sounding posts on here tonight that may claim to know for certain.

I think some interest still in the pipeline for February and the fact that we are at such an unknown juncture and potential fork in the road makes it pretty interesting regardless of the outcome.

 

Edited January 18 by BurwellWeatherWatch

[WYorksWeather]

The Reading ECM meteogram also looks to have downgraded temperatures a little towards the end of the month. However, it doesn't at this stage look to be a pattern that is compatible with anything really cold in this period - just some hints that the wind might turn more towards a westerly or north-westerly rather than south-westerly, which moderates the temperatures somewhat. The wind probability diagrams on these charts are very useful.

Again, proper cold, if it comes, will come in February. I still believe that to be the case.

[Rain All Night]

1 hour ago, Anthony Burden said:

Evening all,The Atlantic surge might well be short lived charts beginning to firm up on high pressure within a week or so time frame in regards to positioning all fingers crossed for a east/northeast feed eventually.The important fact cutting of the Atlantic train gives hope in getting a cold feed to establish over the UK.

53 minutes ago, TillyS said:

They are not 'firming up' on this.

There is very little in the ECM to support it as the Atlantic is not in abeyance and any high pressure at T240 is just as likely to get flattened by the Atlantic. There isn’t any support from the UKMO out to T168. Even the GFS operational is out on a limb with the idea

I think the charts I've posted above suggest that it's reasonable for Anthony to say that the models are "beginning to firm up on high pressure".

[Singularity]

27 minutes ago, pages said:

 

I want cold and snow as much as anyone my young son constantly asking when is it going to snow enough to go on sledge.

But I just can't see us getting opportunity for at least 3 weeks.

I know MJO forecast is just that but it's not trending in a good direction.

A few days back ECM and GFS both had MJO reaching phase 7 at decent amplitude.

Now ECM has it barely reaching for phase 7 and heading for COD and GFS looks even worse diving into the COD from phase 6 and looking like it's going to cycle back to phase 5. 

 

 

 

 

Ah but here’s the thing - once you’re into Feb, with an El Niño-like (high AAM) background such as is expected next month, the Scandi high signal emerges with MJO phase 6, with 7 becoming the transitional one that’s part Scandi high, part -NAO.

So if the models lock onto predicting it to be slow moving in phase 6, I won’t be concerned about all this talk of highs to our N/NE being for nowt.

[Battleground Snow]

It is uncanny how the gfs does seem to pick up a pattern change first, and then the ecm gets interested a few runs later.

I thought the other day that we would accelerate towards to Scandinavian high solution in the final days of January, but then the gfs stepped back from this and made me look stupid, hopefully this isn't another false dawn.

Would like to see a hlb sooner rather than later if mjo does lose amplitude, although the other teleconnections may be enough on their own to sustain it  in February.

Edited January 18 by Battleground Snow

[ribster]

1 hour ago, TillyS said:

They are not 'firming up' on this.

There is very little in the ECM to support it as the Atlantic is not in abeyance and any high pressure at T240 is just as likely to get flattened by the Atlantic. There isn’t any support from the UKMO out to T168. Even the GFS operational is out on a limb with the idea, which anyway was out at T300 or so:

That doesn’t mean that the Atlantic won’t blow out. It might. And eventually it will. But please let’s not gild the lily. We have at least a week (could be a fortnight or more) of wild and mild according to the latest runs. By the time this hits at the end of this weekend, we’ll certainly know we’re back under the influence of Atlantic storms. It looks pretty serious:

 

It does indeed look serious and ought really to be taking more of our attention.

Think you've misquoted Anthony...

[blizzard81]

The most crucial part of this winter is upon us. There is significant potential at around day 7. Because the models are out of their comfort zone aka 'amplification' in the area of north west Europe, I feel we could see some quite mouth watering synoptics appearing in the next 24 hours. 

[northwestsnow]

GFS like a dog with a bone here.. 

[blizzard81]

Just now, northwestsnow said:

GFS like a dog with a bone here.

Gfs really is gunning for 47.

[Catacol]

And so the cold snap ends. Snap rather than a spell - 9/10 for the depth and quality of the cold (I loved the frost free dry cold and then the intense frost that broke the fuel flap on my car!) and I daresay 9/10 for many in Scotland or parts of the NW who love snow. The NW probably viewed a scandy trough dropping in with a sense of "been here before" - and then low and behold the trough developed a curious westerly and many parts cashed in. The wonderful variability of the weather. But the overall 9/10 has to lose 3 points for the shorter than expected duration, and then a further point for the failed channel runner and anything for the south. Those in the east (like me) would probably knock a further 1 off for the absence of any north sea activity. Lands as a sort of 4 or 5/10 for me.

We have been unlucky with events in the strat this season, no doubt about that. First the SSW that failed at the start of the month that could have done much to cement a cold month (and was probably a key factor in suggestions from the MetO) and then a second warming that split the vortex but has turned into a reflection type of warming, where wave forcing bounces off the strat back towards the trop and helps reinforce default westerlies. Laid out nicely in Amy Butler's recent blog. And frankly a frustration....but one we have to live with. Coincides with IO MJO phases and the lagged impacts the elastic band of AAM being at the wrong end of the "ping" have ensured. Hey presto - cold out very fast, violently mobile atlantic arrives. The weather may be chaotic, but it is also broadly predictable once drivers lock in.

And that broad predictability is what lends significant wintry optimism going forward. First of all, the ebb and flow of momentum that is the GWO.

Look at the patterns here. Note that prior to our December snap and again prior to our January snap we saw a rising orbit take hold. This graphical representation of global windflows gives a strong indication as to whether the atmosphere is predisposed to encourage blocking, and to see the next orbit kick in we need a rising momentum profile.

And here it is. This has been sluggish - I thought the gun had been fired a few days ago...but it appears now that 16 Jan was the moment we hit the starting button. Frictional torque distinctly positive

Mountain torque generally positive also

and this produces the awaited beginning of the next surge in momentum illustrated by a positive tendency now in play

This will accelerate, not least because the MJO is coming back to where snow lovers want it - phases 6/7/8/1 broadly speaking

So. We watch and wait with anticipation given GLAAM has remained positive overall and we are in a back loaded Nino context. The atlantic will fizz for the 5 days or so I have flagged before as the likely window, and then we will gradually see the effects of the forcings listed above impact on NWP. There are signs already, as expected catching the eye around 26/27/28 Jan. Note ridging towards Scandy on the EPS for the end of the week

quite pronounced by the end of the weekend

Someone earlier said there was little sign of such developments, and used GEFS 850s as the tool to evidence it. Worst possible source of evidence for extended forecasting possible. Don't get swayed by such stuff.

Disappointing to see the intense cold depart so soon, frustrating that the strat has refused to play ball so far, but winter a long way from done and the mild I suspect will be an interlude rather than a pattern starter. I still see February as blocked and have faith in the recent Glosea, JMA, CMC and other long range models that see a -AO overall. Plenty of time still to roll those dice again and get lucky.

 

 

Edited January 18 by Catacol

[Ice Day]

GFS day 10 - 12z vs 18z

  

I'm enjoying the consistency

[Eagle Eye]

Quite often transitioning phases of ENSO or similar spark a significant change and the +VE IOD collapse is no different. Amplified MJO going into phase 6-7 soon and that could well have a significant response by mid February here. For now, the best we're looking at is the rising GLAAM and phase 5 ish response. However, the +VE IOD collapse has aided the potential for a larger MJO-GLAAM tropical and subtropical forcing for that mid-month ish potential. Wouldn't be surprised if we saw a long lasting Scandi high signal with the +VE NAO meaning nothing with the late Winter MJO 6-7 response signal and high GLAAM, that vortex is pesky to shift but not impossible to block. Scandi high being one of the better blockers I can think of other than a Scandi-Iceland dipole which I think occurred pre-minor SSW last Winter which was coming out of a -VE IOD phase.

 

Edited January 18 by Eagle Eye