Model output discussion 25th Jan - The final third of winter beckons..

[Guest]

ARE WE SEEING A POSSIBLE DOUBLE EVENT UNFOLD HERE?

I am going to break with one of my golden rules, which is not to comment on detailed model output beyond week 1, to make a particular point. Let's make the "daring" assumption that most of the recent model "operational run" output is broadly on the right track. We are told by our "strat experts" that we may be seeing multiple warming events with the main impacts expected in the second half of February. It has come as something of a surprise that we have seen a "seemingly" big acceleration of the process. Could it be that the possible evolution to a very cold easterly is simply a precursor to the main event (in terms of a longer lasting cold spell - not necessarily the severity of the cold)?  The initial recent warming may be sufficient to build HP westwards into Scandinavia, interrupt the Atlantic flow, divert the Jet Stream even further south, with secondary or breakaway LPs diving south-east towards the Mediterranean with a classic undercut encouraging the cold pool (still over western Asia) to march westwards, with most or all of the UK benefiting from that cold air advection. This all occuring from around D9 to D12. Then as the easterly flow eases, we see the main impact of the possible SSW (or further warming) with HLB developing to our north-west from the Azores up to Greenland around mid-February. This greater HLB, assisted by the MJO moving through the favourable phases 7,8 and 1, producing a broad Arctic airstream. If this general sequence of pattern changes is anywhere near accurate, then this morning's GFS 6z output would seem to be reflecting this. Let's look at the D10 and D16 charts from the Feb.1st GFS 6z:

                       T+240                                                        T+240                                                      T+384                                                      T+384

       

CAUTION:

1. only a suggestion.

2. just one run from one model - we need far greater consensus and consistency in future output.

3. definitely FI.

Over to the strat experts to either shoot this to pieces or back it up!  

EDIT: Whilst preparing this post, I see that @Tamara has already provided an excellent update on the broad pattern changes and the potential pitfalls. Very encouraging that it is generally in line with what I say.

 

Edited February 1, 2017 by Guest

[weirpig]

The Opp at the moment is a cold outlier, Which i think most of us realised it would be.

[Stu_London]

The OP is on the cold side which is consistent with the last few runs and fits in with the SM theory that with easterlies, the operational leads the way and the ensembles catch up later.

What does encourage me is that there is a really tight cluster up to about day 5. If they were less clustered, it would in my opinion signal that the model is struggling to pick the correct pattern and would lower confidence.

 

 

[MKN]

With regards to this chart.  Have seen the models show this scenario more times than i can remember and often when the centre of high pressure is just to the north of the UK showing bitterly easterly winds the actual outcome tends to see the high shunted south due to to much energy going over the top and northern spain southern france italy etc all in the firing line instead.

Unless its shown at +48 or less i wouldnt give it much chance of happening. 

[Daniel*]

Has anything seen the NASA model it goes to infinity & beyond. It's the pinnacle for a coldie the ultimate cold synoptic/scenario potentially on offer. Daytime highs of -5C with heavy snow transferring from east to west across Southern England. 

brutal uppers bullseye! 

Edited February 1, 2017 by Daniel*

[Ali1977]

3 minutes ago, Daniel* said:

Has anything seen the NASA model it goes to infinity & beyond. It's the pinnacle for a coldie the ultimate cold synoptic. Daytime highs of -5C with heavy snow transferring from east to west across Southern England. 

brutal uppers bullseye! 

Ha, not sure on NASAs probability rates but I imagine not very high.  -18C upper though, that is crazy cold for the UK

[Arthur1882]

Fantastic charts, if the GFS 6z verifies it could be our snowiest period since 2010. But the Met Office don't seem very excited in their outlook to the 15th, talk of periods of cold with wintry showers possible in the notth, very underwhelming, don't the Met Office use their own model? because UKMO tells very different story to the update 

Remaining cautious till Met Office on board, but we could be on the brink of a once in a generation period of weather

[frosty ground]

Until we get some ensembles support we really are in the dark on this one.

[snowray]

9 minutes ago, Ali1977 said:

Ha, not sure on NASAs probability rates but I imagine not very high.  -18C upper though, that is crazy cold for the UK

-19c uppers clipping the London area, frost fairs start on the Thames as everything freezes over.

[bluearmy]

NASA should stick to beyond the strat !

more likely to see six weeks of ian browns zonality than -20 uppers over the North Sea !

EDIT: though the track of the upper heights cold pool is feasible

Edited February 1, 2017 by bluearmy

[radiohead]

20 minutes ago, Ali1977 said:

Ha, not sure on NASAs probability rates but I imagine not very high.  -18C upper though, that is crazy cold for the UK

Those very cold uppers are not very likely, but not impossible either.

 

1987 :

[snowray]

1 hour ago, Alexis said:

Look at the trends we've been seeing - low pressures not as quite as deep and swinging up towards Greenland. It was only a couple of days ago that we were looking at storm after storm slamming across us.

I can only see the trend continuing. Watch that 955 low at 180h filling more and more over the next few runs and the block to the east strengthening.

I think your right Alexis, think some of those Atlantic lows are OTT and could well be toned down in the next 24hrs. Surely one or both of these bad boys will likely be downgraded.

[ACCOUNT DELETED]

Hi everybody, I'm trying to understand how the ensembles graphs work. 

I know about the 20 different runs/scenarios they produce. I'm guessing the red line is the average from all 20 ensembles, blue is obviously control which is what we see shown on the main charts, but can somebody tell me what exactly does the white line "GFS Run" indicate please?

[bluearmy]

1 minute ago, DJ RY said:

Hi everybody, I'm trying to understand how the ensembles graphs work. 

I know about the 20 different runs/scenarios they produce. I'm guessing the red line is the average from all 20 ensembles, blue is obviously control which is what we see shown on the main charts, but can somebody tell me what exactly does the white line "GFS Run" indicate please?

It's the operational!

[Panayiotis]

1 minute ago, DJ RY said:

Hi everybody, I'm trying to understand how the ensembles graphs work. 

I know about the 20 different runs/scenarios they produce. I'm guessing the red line is the average from all 20 ensembles, blue is obviously control which is what we see shown on the main charts, but can somebody tell me what exactly does the white line "GFS Run" indicate please?

The white line is the operational GFS run- when we all talk about the GFS it's typically to do with the operational (OP). It can be viewed on meteociel by clicking the GFS EUROPE tab on the left side of the page. 

[EastAnglian]

Blue is the control run for the ENS I think or at least that is how I have been trying to make sense of it. The red is as you say the mean. I believe the white is the Operation run (the one we seen every six hours) Please feel free to correct me if I am wrong.

[Tim Bland]

perhaps we are missing some potential snow interest in the short term?! 

He mentions in other tweets that Meto current view is for dry cold mid Feb and a full SSW possible late Feb. 

[frosty ground]

1 minute ago, Tim Bland said:

perhaps we are missing some potential snow interest in the short term?! 

He mentions in other tweets that Meto current view is for dry cold mid Feb and a full SSW possible late Feb. 

I mentioned yesterday that day 5 (now day 4) could surprise us with slack conditions below freezing uppers and any heavy precipitation. The output has changed a bit since then but clearly the UKM see some potential   

[ACCOUNT DELETED]

12 minutes ago, bluearmy said:

It's the operational!

Thank you, much appreciated.

[ACCOUNT DELETED]

10 minutes ago, Panayiotis said:

The white line is the operational GFS run- when we all talk about the GFS it's typically to do with the operational (OP). It can be viewed on meteociel by clicking the GFS EUROPE tab on the left side of the page. 

Thank you, much appreciated.

[ACCOUNT DELETED]

10 minutes ago, EastAnglian said:

Blue is the control run for the ENS I think or at least that is how I have been trying to make sense of it. The red is as you say the mean. I believe the white is the Operation run (the one we seen every six hours) Please feel free to correct me if I am wrong.

Thank you, much appreciated.

[winterof79]

44 minutes ago, Arthur1882 said:

Fantastic charts, if the GFS 6z verifies it could be our snowiest period since 2010. But the Met Office don't seem very excited in their outlook to the 15th, talk of periods of cold with wintry showers possible in the notth, very underwhelming, don't the Met Office use their own model? because UKMO tells very different story to the update 

Remaining cautious till Met Office on board, but we could be on the brink of a once in a generation period of weather

Yes if you were born after 2010

[mb018538]

The MetO quite rightly won't put any emphasis on a cold outbreak - why would they? At the moment the percentages favour it not being snowy and bitter. Just sets them up for a big fall if they start promising Armageddon and it doesn't surface. Now, if Nathan Rao worked for the Met.....can you imagine their extended outlooks?!

'BITTER COLD AND NORTH POLE SIBERIAN CANADIAN POLAR VORTEX JET STREAM TO SMASH UK WITH -25c TEMPERATURES AND POLAR BEAR ATTACK'

[Nouska]

This mornings ECM 360 hour ensemble mean still looking good - sees the Scandinavian high pressure still present at a good latitude,  Atlantic kept at bay and indications of very southerly jet stream. The mean 850 temps not very low but do not need to be with a continental feed. 

Probabilities for T850 < -8C coming in from the east, starting to make an appearance.

 

[Fozfoster]

20 minutes ago, mb018538 said:

The MetO quite rightly won't put any emphasis on a cold outbreak - why would they? At the moment the percentages favour it not being snowy and bitter. Just sets them up for a big fall if they start promising Armageddon and it doesn't surface. Now, if Nathan Rao worked for the Met.....can you imagine their extended outlooks?!

'BITTER COLD AND NORTH POLE SIBERIAN CANADIAN POLAR VORTEX JET STREAM TO SMASH UK WITH -25c TEMPERATURES AND POLAR BEAR ATTACK'

Do you work for the Express?