Model Output Discussion 29th December - Into mid-Winter.

[Nick F]

2 hours ago, Ali1977 said:

Not all doom and gloom though, we have a SSW or near as damn it about to happen which will help break up the PV and create some form of NH blocking, now we just need some luck that it helps us out by being in the right place. 

This block to our East has never been on the METOs radar to giving us anything properly cold, just a nagging S'Easterly which is now a little boring although plenty of frosts compared to the last few years.

The current strat warming is not forecast to break up the strat PV, merely displace it over towards northern Europe. A displaced PV, particularly over to our side of the N Hemisphere, doesn't particularly favour HLB to our NW/N/NE for now. As you can see from the Berlin geopotential and temperature charts for the strat. quite a zonal gradient feeding down in the lower reaches over the Atlantic which is surely driving Atlantic lows towards us, but a slow process thanks to the block to our east.

However, if the wave 1 warming keeps up, we could see a SSW as we head through Feb, particularly with help from the MJO which is propagating over western hemisphere now, so we may see enough reversal downwelling eventually to affect the trop to increase the chances of HLB. But don't expect a quick trop response from the current strat warming IMHO.

With regards to the current trop modelling, still a weak ridge signal extending NW from Scandi day 10 on the 00z EPS z500 mean, though this morning's ECM high res has backed away from showing a decent ridge to our north, GFS never really keen on the idea as still not on the 06z. Looks increasingly stormy period from day 7, as the jet digs south.

One last chilly day tomorrow, could be one of the coldest days of the winter too, with temps struggling much above freezing as we import colder and drier air from the SE off a cold continent, then turning less cold and increasingly unsettled over the weekend.

 

Edited January 25, 2017 by Nick F

[Turnedoutniceagain]

50 minutes ago, mb018538 said:

The 6z is another wind and rain fest, with some fairly deep low pressure systems moving across. On to the 12z.

 

Good news. High pressure has dominated for so long, local reservoirs are at Summer levels. The breakdown can't come quick enough.

[stodge]

Afternoon all

Well, I have to confess I'm looking forward to my lunch of humble pie with oeuf sur visage to follow.

The block has proved more resilient than I thought earlier in the week (and the models indicated).

A final chilly hurrah but the current models seem to indicate the Atlantic coming through over the weekend and then, as I expected, settling in for a 10-14 day spell.

Straws in the wind - the last few days of model watching have seen big changes from day to day so this may not be a done deal quite yet and the long fetch SW'lies promised especially on GFS earlier in the week have been replaced by a more perturbed outlook as the jet oscillates further south next week.

There are colder members in the GEFS but not too many in FI.

There's been talk about the lack of an SSW - the 10 HPA temperatures in FI are down around -68c. Last year they were still -84c or below going into February.

The PV will be much weaker and IF there is a second assault in February, so much the better. We shouldn't be surprised if the first result of an Eurasian warming is to displace the PV to the Canadian side - this is what happens.

Oddly enough, we may see February, usually a colder and drier month turning out more unsettled and stormy than January which is traditionally the more disturbed month.

Still plenty of February and early March to come for cold/snow fans so no need to feel too disheartened at this stage and as others have said, some rain may well be welcome. 

[Ali1977]

The SSW seems to have gathered some pace with ECMWF now predicted a pretty big one which will most certainly have effects on the PV, and NH blocking has a very good chance of occuring. The trop fallout of this is a few weeks away and won't be modelled yet so don't expect a sudden swing to blocked EPS or GEFS charts - and then if it does it may not be Europe that benifit - however a very good sign for mid to late Feb.  Remember the earlier we see this happening the better, if like me we want some UK wide big freeze type conditions that is.

Edited January 25, 2017 by Ali1977

[Jimmyh]

5 hours ago, mb018538 said:

Maybe our definitions of blocked are different!

I'd say the set up as it has been, and even today would still be blocked:



No Atlantic train of lows, amplified meridional jet.

Now fast forward 10 days:



Atlantic full of low pressure once again, strong zonal W-E jet running across the Atlantic.

 

Sorry but the last chart as I am seeing it shows Zonal winds yes but look at the trajectory NW-SE this is nothing like what has been in the past before. I remember back in 113/14 looking at the outlook and seeing 4 low pressure systems lined up waiting to hit us. Zonal yes, wind storms???? I can't see it on any charts. plus it is not a straight jet above it is kinked....

All to play for in my eyes.

[Summer Sun]

 

[Richard Fisher]

6 minutes ago, Summer Sun said:

 

GFS trumps ECM again? I would be interested to here whether Steve Murr is still backing the ECM today.

[warrenb]

13 minutes ago, Richard Fisher said:

GFS trumps ECM again? I would be interested to here whether Steve Murr is still backing the ECM today.

To hazard  guess, because it verifies better, is higher resolution and has a better ensemble suite, apart from that, I have no idea.

[helen47]

14 minutes ago, Richard Fisher said:

GFS trumps ECM again? I would be interested to here whether Steve Murr is still backing the ECM today.

Nothing has trumped anything yet it has not happend yet could all change on the 12z

[Tim Bland]

Even this mornings ECM doesn't back the run yesterday which Steve Murr said would definitively be correct! 

[JamesL]

To be fair to Steve he said 99%, so I guess he covered himself by the 1% He may of course still be correct but sadly it's looking less likely now 

Eyes down for the 12z's now and we maybe slightly closer to resolving those small height rises to the north and the undercutting low scenarios 

[Seasonality]

3 minutes ago, Tim Bland said:

Even this mornings ECM doesn't back the run yesterday which Steve Murr said would definitively be correct! 

Steve Murr is very knowledgeable but he isn't infallible, even the Met Office with their supercomputers aren't infallible. Respect to Steve for the high stakes bet by placing all his chips on one number... And we still don't know for certain whether it will pay off or not

[frosty ground]

Energy digging slightly further south east on this run...... 
 

[booferking]

Guys i dont think this is the bash @Steve Murr thread  he is only human and the supercomputers might not even have it right yet. Back to the 12z and ironically the GFS looks better than uk model @96hr and thats not saying much.

Edited January 25, 2017 by booferking

[Blizzardof82]

People being a bit harsh on Steve Murr, at least he has the balls to try and read and predict what may happen from his viewpoint rather than just posting what charts show.

[Day 10]

The high certainly is putting up a fight, comparing yesterday's GFS 12z with today's. The jet isn't exactly blasting through the UK either! This ain't a done deal yet.

[Day 10]

Differences again at 120, this time the GFS looks better than the UKMO! Pointless going past 120 really as things keep changing.

[Singularity]

 

Less of a residual low by Scotland and the shortwave SW of Iceland held back west more. Relatively small adjustments that make a fair bit of difference to the extend of height rises across the UK during the following day or so.

 

Enough to keep the UK in chilly air throughout Monday away from the far S and SW.

 

This may take until it's at +72 or even +60 hours to resolve. Curiously the H-W observed MJO dropped suddenly today in the face of all the model projections - even  GFS - which may have triggered a sudden step-down in upstream amplification. Question is, how legit is the signal? Based on the form of the winter so far, perhaps not very. It's just among the quickest, easiest ways to track changes in what the models are seeing. Looking at upper wind plots suggests to my admittedly only partially-trained eye that if anything the MJO is divided between the west Pacific and west Africa, with a the H-W plot averaging this out to an artificial position in the western Indian Ocean. Even so it seems something has unexpectedly weakened or more likely interfered with the MJO signal today.

[Alexis]

1 hour ago, Summer Sun said:

 

I see their own forecasts are going for exceptionally mild in 10 days. Not that that can have any bearing on an objective ECM graph but just saying

[blizzard81]

11 minutes ago, Singularity said:

 

Less of a residual low by Scotland and the shortwave SW of Iceland held back west more. Relatively small adjustments that make a fair bit of difference to the extend of height rises across the UK during the following day or so.

 

Enough to keep the UK in chilly air throughout Monday away from the far S and SW.

 

This may take until it's at +72 or even +60 hours to resolve. Curiously the H-W observed MJO dropped suddenly today in the face of all the model projections - even  GFS - which may have triggered a sudden step-down in upstream amplification. Question is, how legit is the signal? Based on the form of the winter so far, perhaps not very. It's just among the quickest, easiest ways to track changes in what the models are seeing. Looking at upper wind plots suggests to my admittedly only partially-trained eye that if anything the MJO is divided between the west Pacific and west Africa, with a the H-W plot averaging this out to an artificial position in the western Indian Ocean. Even so it seems something has unexpectedly weakened or more likely interfered with the MJO signal today.

The question is,  what would unexpectedly weaken or interfere with the mjo signal?

[Singularity]

@blizzard81 I'm not sure to be honest, hopefully someone will have an answer or suggestions.

 

Doing a bit of straw-clutching, the 12z ARPEGE on the right peaks the Atlantic low sooner and further west, which improves the changes that there will be time for a secondary low to break away and slide SE before the next push from the westerlies arrives.

Not convinced we'll have enough tropospheric forcing to escape what the stratospheric forcing (displaced vortex) wants to make happen, though.

If we do see the displaced vortex influencing our patterns then reinforcements to the warming that displace the vortex yet further - right down into W. Eurasia - will be needed, ideally in combination with an active MJO propagating to the Pacific, to help break free from the mild and wet regime. GFS/GEFS currently lacks both of these so little wonder the longer-term output has been so dire of late.

[northwestsnow]

Goodness me the 12z are abysmal for coldies no wonder the thread is quiet!

GFS wants to introduce the PV from hell as we head into Feb and as much as i dont want to buy it....

UKMO doesnt look like offering anything in the way of alternative progression at 144.

Just thinking aloud here but i really hope we dont see northen blocking come March/April,that just rubs ( un-used) salt into the wounds..

[lassie23]

Looks like a two week spell of mediocre winter weather for the UK, probably not a raging Atlantic storm fest but something in between.

[Polar Maritime]

I thought it was the Steve Murr thread for a moment! Can we please continue with constructive Model discussion. And also a reminder that there is also a model ramp/moan thread open for general chit-chat. And a Winter thread open for hopes/thoughts.

Thanks.

Edited January 25, 2017 by Polar Maritime

[Mucka]

Looks like we coldies got trolled by ECM yet again.

Back to the strat warming and ensembles, which at least show an increased possibility of blocking 2nd week of Feb.