Model output discussion - 1st December onwards

[Captain Shortwave]

The current operational output is like a game of Russian roulette with the potential risk of some pretty catastrophic amounts of rain depending on where the low to our south west stalls with its associated fronts.

Day 6 rainfall prediction

The GFS obviously doesn't like the Welsh I guess..... The Midlands and parts of NW England also get it pretty badly too.

To be honest, a Bartlett set up is better than this 

Edited December 9, 2015 by Captain Shortwave

[Mucka]

Finally getting a little consistency in the output today for the medium term but it isn't what coldies would like to see unfortunately with most of the energy riding over the top of ridges rather than undercutting.

 

UKMO does offer a little hope further upstream though and certainly not a done deal yet by any means.

 

We really need these lows to disrupt further West and get some undercut if there is to be any chance of MLB or HLB further down the line.

 

Edited December 9, 2015 by Mucka

[IDO]

The big issue from this weekend is a stalling front over the UK from around T78 till T144. Where this lies will give large totals. It appears at the moment Wales will get another deluge, but hopefully the NW will avoid the worse:

Again after a few days cooler uppers for the north we get a quick return to very mild uppers: 

 

Even milder than the 06z run, which seemed unlikely at the time! GEM is not dissimilar.

Edited December 9, 2015 by IDO

[Gavin Hannah]

Well on the 12Z, colder air is making its way further into europe with a HP cell located over the eastern bloc.  Could lead to something more promissing down the road. t.186 showing an intense LP of the west coast which leads to more mixing of the air masses compared with the 06Z. No doubt bringing with it more rain.

Edited December 9, 2015 by Gavin Hannah

[Bullseye]

Alot of talk today , on Twitter at least, about MJO going into phase 7 late Dec/early Jan. Question is how much of an influence does this have on the models which is still FI at this stage? Phase 2/3 was showing only 3 days ago so quite a turnaround if it indeed comes out at Phase 7.

[Gavin Hannah]

1 minute ago, Bullseye said:

Alot of talk today , on Twitter at least, about MJO going into phase 7 late Dec/early Jan. Question is how much of an influence does this have on the models which is still FI at this stage? Phase 2/3 was showing only 3 days ago so quite a turnaround if it indeed comes out at Phase 7.

I'm not clued up on MJO phases.. would this be a benefit or a hindderance?

[AWD]

It will be interesting to note what (if any) impact the currently modelled warm 850hpa air mass a couple of posts above has on the tropospheric pressure patterns and eventually any impact it might have on the lower stratosphere.

Perhaps a warm 850hpa air mass well north into northern latitudes could help the troposphere penetrate into the lower stratosphere and help change the current highly posutive AO/NAO and thus change our surface weather pattern we are currently stuck with?

Or have I just wasted 3mins of my life posting drivel?

[Geordiesnow]

9 minutes ago, Captain Shortwave said:

The current operational output is like a game of Russian roulette with the potential risk of some pretty catastrophic amounts of rain depending on where the low to our south west stalls with its associated fronts.

Day 6 rainfall prediction

The GFS obviously doesn't like the Welsh I guess..... The Midlands and parts of NW England also get it pretty badly too.

To be honest, a Bartlett set up is better than this 

Looks like the main uncertainty for the weekend is just how far Northwards any belts of rain from the South will go, it does seem Scotland could remain in the colder air throughout. Interestingly, the Northern boundary of any rainfall could well have a wintry element, even at lower levels so one too keep an eye on. 

I do feel those PPN charts might be slightly exaggerated in respect of the rain going by the charts won't linger around for 24-36 hours unlike the last event but in any case any persistent heavy rainfall could well lead to more flooding issues unfortunately.

[Bullseye]

3 minutes ago, Gavin Hannah said:

I'm not clued up on MJO phases.. would this be a benefit or a hindderance?

I should have said seems to be phase 6 late December then phase 7 early Jan: https://twitter.com/EdValleeWx/status/674616771207438337

Phase 7 to January - 

[Man With Beard]

The behaviour of this rogue high to our north is far from certain - low pressure in the Atlantic isn't that far from undercutting it. Wouldn't go any further than T144 at the moment

[nick sussex]

As soon as the GFS phased that low with the upstream troughing it was game over. There is no middle ground with this type of set up. You either get the undercut or the death low phases with the troughing sending the energy over the top.

It then goes onto deliver a catastrophe for the European ski resorts and some extremely mild conditions, I seriously hope this doesn't verify as it will wipe out many of the lower ski resorts Christmas hopes.

A ghastly GFS operational run, to top it all it also delivers yet more rain to those areas currently suffering from the floods.

The UKMO isn't much better that phases the death low aswell and would likely deliver the same output if it went out further, thankfully it stops at T144hrs!

[Singularity]

 

Just to emphasise how dire the GFS 12z is for much of Wales and the middle swathe of England. Very nearly 72 hours of persistent, often heavy rain for many within those regions.

In terms of accumulations, here's up to the end of the weekend on the left, and to Tuesday evening on the right.

The southern half of the area with 100+ mm has only 10-20 mm up to the end of Saturday, so that's a sizeable slice of the UK seeing near 80-100 mm in the space of 48 hours, with higher totals for high ground. Madness.

 

Finally for now, here's the 10-day total, which shows 319 mm over high ground in NW Wales. If that verified somewhere in the region would surely be close to 500 mm for the month with a third of it still to come. For context, the average rainfall in Southern England for a whole year is around 700 mm (+ or - 100 depending on where exactly you look). Obviously the mountains of Wales have a much higher average for the year, but still...

Edited December 9, 2015 by Singularity
Added 10-day total and remarks.

[Methuselah]

So, the GFS and UKMO are both phasing LPs...But what happens if the weather chooses not to follow orders?

[Nouska]

34 minutes ago, Bullseye said:

I should have said seems to be phase 6 late December then phase 7 early Jan: https://twitter.com/EdValleeWx/status/674616771207438337

Phase 7 to January - 

I don't know where these composites came from but they are definitely not appropriate for current climatology - they show pattern for ENSO neutral when we are currently in one of the strongest ever positive phases of ENSO.

Too much disagreement in the short term to even be looking at what is likely by January.

[nick sussex]

1 minute ago, Ed Stone said:

So, the GFS and UKMO are both phasing LPs...But what happens if the weather chooses not to follow orders?

It would take a miracle of Biblical proportions to avoid that phasing given the timeframes, everything that can go wrong does because the upstream pattern amplifies at the worst moment.  Unless the ECM plays Santa tonight and delivers some hope then it looks pretty dire.

[Bullseye]

1 minute ago, Nouska said:

I don't know where these composites came from but they are definitely not appropriate for current climatology - they show pattern for ENSO neutral when we are currently in one of the strongest ever positive phases of ENSO.

Too much disagreement in the short term to even be looking at what is likely by January.

I didn't realise these where for neutral state, apologies. As for the category for this EN that is up for discussion. And at end of the day, don't see the problem with looking further ahead to late Dec/Jan as that is why the GFS and ECM give us this chance. 

 

 

[SMU]

Afternoon -

A dreadful past 72 hours of weather modelling signalling yet more mild weather - & sadly the much anticipated pattern change is just a mere distant memory -

as mentioned above by some - the immediate focus again turns to a band of significant rainfall setting up at the weekend - sods law could be that if it jogs a little further north than planned then the same areas that were recently pounded could get the same again...

rough & barron times if your a snow lover ....

[gottolovethisweather]

2 hours ago, Singularity said:

 

Just to emphasise how dire the GFS 12z is for much of Wales and the middle swathe of England. Very nearly 72 hours of persistent, often heavy rain for many within those regions.

In terms of accumulations, here's up to the end of the weekend on the left, and to Tuesday evening on the right.

The southern half of the area with 100+ mm has only 10-20 mm up to the end of Saturday, so that's a sizeable slice of the UK seeing near 80-100 mm in the space of 48 hours, with higher totals for high ground. Madness.

 

Finally for now, here's the 10-day total, which shows 319 mm over high ground in NW Wales. If that verified somewhere in the region would surely be close to 500 mm for the month with a third of it still to come. For context, the average rainfall in Southern England for a whole year is around 700 mm (+ or - 100 depending on where exactly you look). Obviously the mountains of Wales have a much higher average for the year, but still...

Agreed, there has to be some concern over the forthcoming weekend's newsworthy event. I have seen this event being discussed on current BBC media forecasts but uncertainty remains as to where and how much is in reality likely to fall at this range and quite rightly they're being very cautious. As Capel Curig in Snowdonia has received over a meter of rain during the space of 44 days another 200mm wouldn't be great news for that part of the UK, for sure. Also, should the latter stages of the GFS 12z came about, Spring like temperatures would seemingly be possible on a couple of days in the run up before Christmas and before that, further deluges and windstorms amongst some drier periods. The Cuckoos might well be on their way back from Africa at this rate too. Any chance the GFS operational is off on one beyond its' D5/D6 timeframes, YES 100% sure it is. SUMMATS UP THOUGH METHINKS! 

Edited December 9, 2015 by gottolovethisweather

[gottolovethisweather]

1 hour ago, Captain Shortwave said:

The current operational output is like a game of Russian roulette with the potential risk of some pretty catastrophic amounts of rain depending on where the low to our south west stalls with its associated fronts.

Day 6 rainfall prediction

The GFS obviously doesn't like the Welsh I guess..... The Midlands and parts of NW England also get it pretty badly too.

To be honest, a Bartlett set up is better than this 

Alternatively, we could have a more benign Winter like last year with just a touch of snow here and there, I'd take that now. Currently, it feels like a re-run of 2013/14 Winter wants take a grip of us whilst effecting differing parts of the UK this time around. At least, some hope of longer lasting drier periods as well, which didn't occur for weeks upon end back in 2013/14.

Edited December 9, 2015 by gottolovethisweather

[gottolovethisweather]

39 minutes ago, nick sussex said:

As soon as the GFS phased that low with the upstream troughing it was game over. There is no middle ground with this type of set up. You either get the undercut or the death low phases with the troughing sending the energy over the top.

It then goes onto deliver a catastrophe for the European ski resorts and some extremely mild conditions, I seriously hope this doesn't verify as it will wipe out many of the lower ski resorts Christmas hopes.

A ghastly GFS operational run, to top it all it also delivers yet more rain to those areas currently suffering from the floods.

The UKMO isn't much better that phases the death low aswell and would likely deliver the same output if it went out further, thankfully it stops at T144hrs!

Sounds like the script of the Star Wars film to me Nick, especially as I think I need one of your diagrams to understand the point of your post. Either way, the gist is for us coldies to forget cold Winter synoptics for a while. 

 

Edited December 9, 2015 by gottolovethisweather

[The PIT]

Well Saturday and Sunday is still uncertain according to the forecast I've seen. Since this weekend it's gone from very mild for most of England to rather cold for Northern England then mild again then back to rather cold again.  GFS doesn't want to push the system north while UK Fax run shows the front pushing through steadily. Rainfall amounts and position have varied as well.

At the moment I would wait until tomorrow evening which hopefully will indicate the more likely outcome.

[Mucka]

16 minutes ago, nick sussex said:

It would take a miracle of Biblical proportions to avoid that phasing given the timeframes, everything that can go wrong does because the upstream pattern amplifies at the worst moment.  Unless the ECM plays Santa tonight and delivers some hope then it looks pretty dire.

 

It certainly does and the ensembles don't offer any cheer either. The last 24h have seen a big swing away from cold prospects, say from 65/35& against keeping the pattern amplified and a cold shot to 95/5%

Unless the output does a quick about turn it is going to be a long slog just tog et some dry settled conditions let alone cold and in the short to medium things look pretty dire re rainfall and there doesn't look to be anything dry in FI after these transient ridged are flattened out with the jet returning North. The Azores/Euro high is proving to be very resilient to a Southerly jet.

Finally the MetO are now going for mild and unsettled through the Christmas period so hard to to find any silver lining at all except the output until the lsat 24 h has been all over the place so still the slim chance of the models changing course again, However if the output remains the same through tomorrow I think it may be a good time to take a break from the search for cold again and concentrate on hoping for something less dreadfully wet.

[nick sussex]

Just now, gottolovethisweather said:

Sounds like the script of the Star Wars film to me Nick, especially as I think I need one of your diagrams to understand the point of your post. Either way, the gist is for us coldies to forget cold Winter synoptics for a while. 

I always become more melodramatic when faced with these types of outputs! lol The death low is circled red! The mothership is in black. As soon as the death low gets attached to the mothership its game over.

Even without the phasing its a hard slog to keep any colder conditions but with it is akin to climbing Mount Everest without crampons.

Its doubly frustrating because the jet does dig quite far south and amplifies the mothership trough later but once that phases with the death low the energy spills all ne.

 

[Captain Shortwave]

7 minutes ago, Mucka said:

 

It certainly does and the ensembles don't offer any cheer either. The last 24h have seen a big swing away from cold prospects, say from 65/35& against keeping the pattern amplified and a cold shot to 95/5%

Unless the output does a quick about turn it is going to be a long slog just tog et some dry settled conditions let alone cold and in the short to medium things look pretty dire re rainfall and there doesn't look to be anything dry in FI after these transient ridged are flattened out with the jet returning North. The Azores/Euro high is proving to be very resilient to a Southerly jet.

Finally the MetO are now going for mild and unsettled through the Christmas period so hard to to find any silver lining at all except the output until the lsat 24 h has been all over the place so still the slim chance of the models changing course again, However if the output remains the same through tomorrow I think it may be a good time to take a break from the search for cold again and concentrate on hoping for something less dreadfully wet.

The GEFs keep the slug entrenched until around the 23rd, then there seems to be signs of a pattern change with low heights forming over the eastern Seaboard which may entice something cooler to develop for the UK.

Perhaps seeing an Atlantic ridge/Scandi trough form just in time for Christmas. It is very far away though.

December so far is trying its hardest to go into the hall of infamy with the likes of the winter of 88/89 and 2013/14.

Edited December 9, 2015 by Captain Shortwave

[Cheese Rice]

I think what some people seem to be missing that it may not be the rainfall totals but the snowfall amounts that would make the headlines.

 

The fronts as they push north are rapidly turning to snow...

 

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2015120912/nmmuk-42-72-0.png?09-18 

 

 

Th NMM only goes out to 72 hr but when you run the sequence the freezing levels are quickly dropping as the band pushes north 

 

http://modeles.meteociel.fr/modeles/wrfnmm/runs/2015120912/nmmuk-37-72-0.png?09-18 

 

The 850's are around -2 and the lows buffet against the cold air 

 

 

Potential for some significant snowfall indeed, especially as the GFS suggests the fronts will struggle to make it past N.England