Model Output Discussions 18z 31/01/2016

[nick sussex]

1 minute ago, Singularity said:

True, I expected at least a bit more of a draw from Iceland but never mind. We'd be losing our minds over marginality under that scenario, relying on evaporative cooling as the winds fell lighter.

This would feel raw, but snowfall would be hard to come by given the lack of decent surface cold to draw across from the continent.

If we could get a better reach N of the ridge from the Atlantic +168 to +192... yep, here we go again! 

Yes its frustrating the synoptics look better than what they actually deliver. If the lows were further south initially then they wouldn't displace as much cold from mainland Europe and we might be able to pull something colder into the flow from the north and of course if the Azores ridge was more amplified. All ifs and buts at this stage, I'm sort of underwhelmed but also a bit more optimistic our MJO is the Obi Wan Kenobi to Princess Leia!

 

[snowray]

If the ever popular Euro slug was to move up over us be the end of the month I would think that temps in the high teens could be expected pretty widely. There have already been hints of this on some runs showing a nice plume of 12/14c uppers moving up from Spain.

[Purga]

One helluva preciptation spike on the ENS suite!

Otherwise the Op run was very much on the cold side in FI with the rest on the cool side of average.

[Banbury]

8 minutes ago, snowray said:

If the ever popular Euro slug was to move up over us be the end of the month I would think that temps in the high teens could be expected pretty widely. There have already been hints of this on some runs showing a nice plume of 12/14c uppers moving up from Spain.

And if a high was to ridge down from the Artic we would have Ice days......,,,,,,,,,,,,,Spring is some way off at the moment

Edited February 6, 2016 by Banbury

[snowray]

4 minutes ago, Banbury said:

And if a high was to ridge down from the Artic we would have Ice days......,,,,,,,,,,,,,Spring is some way off at the moment

Of course Bambury, although the charts have been showing a hell of a lot more of the Euro slug influencing our weather than any Northern block, have we had any kind of Northern block at all this winter, In can't remember even a transient one?

I personally am happy with either scenario, although if we do get some ice days, it would be cruel not to see some of the white stuff too. I think that some transient snow events are more likely, something akin to what is shown at around T72.

[Tamara]

 

The linked very long post on the MOD thread that started winter attempted to analyse and identify the likely problems that would be faced this winter synoptically in attaining a cold pattern.

The post suggested we would require phasing of very high atmospheric angular momentum simultaneous with constructive forcing coupling of tropical MJO activity in the Pacific to coincide with clean Eurasian troposphere>lower stratosphere disruption of the vortex and consequent step changing from a flat warm zonal +AO pattern of the first half of the season to attaining an -AO and amplified profile in the Atlantic thereafter (and perhaps better still lead to high latitude blocking if an SSW could be timely and occur favourably in terms of how the vortex might be split or displaced thereafter)

Notwithstanding that time has shown us clear absence of higher latitude blocking occurring through a full blown vortex disintegration, the start of winter suggestions of an amplified profile occurring through the combination of factors, as described above, coming together has proved true enough.  It did hallmark quite well some autumn and first part of winter discussions regarding sub and intra seasonal extra-tropical and tropical feedback factors (linked to ENSO) providing a link to a -AO occurring in July and then again in January

The mid winter period colder amplified phase in January occurred during a temporary period of disconnect between the upper/mid powerful west QBO vortex and what was a disrupted troposphere/stratosphere boundary. Courtesy of warm air advection into the pole supplied by the combination of a strongly positive (poleward directed) Global Wind Oscillation phase, and the amplification signal further augmented by Pacific rossby wave action courtesy of the January MJO phase imprinting the strong Nino base state, we were indeed able to turn a flat Euro High and Atlantic trough pattern into a converse Atlantic ridge and Euro trough pattern

However, the external stratospheric pathway in terms of the mid and upper vortex has proved every bit as problematic as underlined in the above highlighted post, and of course by most others who have contributed regularly to both the MOD and stratosphere threads throughout the season. 

The reasonable expectation in January was that mid/upper vortex disturbance would occur in the form of sustaining vortex displacement over Scandinavia and nearby Europe in such a way that the substantial cold pool that gathered just to our east and north east during the Atlantic amplified spell would not be shifted far eastwards, if at all - and withstand the (well anticipated)  resurgence of the upstream jet through the closing third of January.

This chart shows the healthy cold pool developed close by to our east and north at mid month, last month, and hints at how a better holding position might have made a considerable difference to our later winter pattern.

It has proved, as we know, not possible for the upper/mid vortex and the troposphere/stratosphere boundary to stay decoupled for long enough.  

Various factors conspired to very poor timing in occurring and undermining this, and made the difference between a previously expected temporary westerly phase before return to Atlantic amplification, and what we have seen instead in terms of a further sustained westerly vortex onslaught :

Tendency of AAM turning negative from very high values (and hence poleward amplification potential fading to sustain ridging) in tandem with return of tropical activity to the Indian Ocean at just the same time that the entire vortex strata layers re-coupled and tightened in strength. Net effect to enhance and then sustain polar westerly momentum and consequently dislodge the cold pool to our east and north east far too easily. In this way, the Siberian High growth and feedback was made redundant, instead of the possibilities of an adjustment process and then the cold backing properly west through renewed heights to our NW. There was in fact a brief period when the extended ensembles actually signposted this development before stratospheric developments scuppered the possibility

This tightening of the vortex throughout its strata layers ironically occurring ahead of  the mid/upper warming of the vortex we are now seeing come in to focus and which rather cruelly (for cold weather hopes) favours Greenland displacement rather than Scandinavia/Siberian.

However, its not just about the stratosphere. This basin wide Nino event is highly complex and is featuring an abnormally warm Indian Ocean (IO) which has occurred as a highly unusual aspect of usual Nino phases, and has provided lagged periods of destructive feedback interference that have periodically nullified the typical amplification feedbacks we see under Nino's - and these destructive feedbacks have occurred early in the Winter and now also after mid winter timed just when the vortex was undergoing another re-strengthening (prior to an upper warming that has favoured the wrong side of the pole anyway!)

The Global Wind Oscillation depicts clearly the lower atmospheric angular momentum orbit phases within the Nino high base state - in November and then through the last third of January.

Both these lower phases caused through MJO IO destructive interference of the base Nino AAM state, and both coincide with assisting further strengthening wQBO polar vortex westerly phases. The first in November, being the new seasonal deepening cold representative of the VI period (vortex intensification) and the second one the re-tightening of the vortex in the last couple of weeks following the mid season decoupled upper/mid stratosphere with the troposphere and lower stratosphere boundary layer.

We also note the very high amplitude phase in earlier January which was associated with the one amplified and colder period of weather we have seen this winter. This representative of when the MJO was closely coupled with the Nino forcing in the Pacific and when the troposphere/stratosphere boundary was decoupled from the cold and stable mid upper layers.

Back to the present: With the upper stratosphere warming favouring the Alaskan ridge (yet again!) and with upper vorticity sustained close to Greenland, this means that downstream we see enhanced gradient and spawned very deep low pressure as cold air ejects from the Canadian Arctic into the Atlantic. This extra jet energy makes the task of forthcoming upturning AAM and next phase tropical coupling in the Pacific as the MJO heads east re-boosting amplification in the Atlantic much harder than it previously appeared prior to the renewed uptick in the polar vortex.  

It could be credibly argued that the much more amplified and colder trend anticipated through February would have been better served through the continued uncomplicated decoupled trop>strat feedbacks we saw during January being able to resume through this month.  The much derided Jan/Feb 83 template held credibility in terms of a progression of the Jan pattern re-occuring in Feb in anticipation of further AAM uptick and next round of MJO Pacific amplitude coupling with the Nino base state. Much as discussed earlier in the post.

Instead, upper vortex disturbance has pushed colder mid and upper layers the stratosphere layers towards the troposphere, and then,because the warming is not a major SSW we do not see the sort of complete vortex disintegration which would have made the chances of vorticity remaining over Greenland much less, if never possible to be guaranteed. A favourable fall of the cards would have taken advantage of renewed poleward AAM and eastward moving MJO amplification rossby waves in February.

Its turned out to be a case of all or nothing. Either a continued disconnect of the trop/lower strat with the upper strat, or a full blown SSW would have been preferred. Not something in between which has left us with the worst of all worlds in terms of any seasonal cold weather that resembles proper winter.

Not wanting to sound negative here, but simply realistic hopefully as usual. In the prevailing circumstances, it might be harder to achieve the amplified pattern we saw in January, let alone the better Feb 83 scenario credibly envisaged prior to the unfavourable vortex developments. A more southerly adjusted storm track may shift some colder air southwards for the north of the UK from time to time. But without the definitive amplification mechanisms seen in Jan being able to manage their potential, and which had been expected to increase their influence this month, it is going to be hard to get any meaningful and lasting country-wide cold air advection southwards before further lows flatten the pattern out..

We will see how the next week or two plays out in terms of tropical forcing expectations, re-floated AAM and stratospheric forecasts, but in the circumstances as they are instead of how they appeared around mid January, and with further rain and problematic gales on the doorstep.

The complexities of the bigger picture (that have made this season hard in its second part to get right even though the first part was straightforward enough) continue to be of great interest and have provided yet another positive learning curve  I would readily admit though that adjusted expectations mean that an end to this rather horrid and unpleasant 'winter' cannot come soon enough.

Edited February 6, 2016 by Tamara

[wishingforsnow]

A great summary from Tamara. The winter so far has been 95% horrible and what most people are looking for now in model trends is dry weather as opposed to snow. Basically we have had the worst possible luck in regards to how this winter has played out in that we are literally clutching at the last possible straw in the MJO to give the UK colder conditions. The UK could have had some colder and more settled weather by now had it not been for Hurricane Alex and the unfavourable strat warming but unfortunately luck wasn't on our side. If the MJO doesn't work out either then I think that's really it and roll on Spring and more so Summer which hopefully can make up for the horrible weather we have had to endure so far as surely 4 months of predominantely rain and gales cannot continue for much longer- that would be a stretch even for the UK imo and people would go absolutely crazy. Hopefully it will balance out in the end  There is always light at the end of the tunnel; recently Summer 2014 after the similarly horrid winter.

Edited February 6, 2016 by wishingforsnow

[Abyss]

56 minutes ago, wishingforsnow said:

A great summary from Tamara. The winter so far has been 95% horrible and what most people are looking for now in model trends is dry weather as opposed to snow. Basically we have had the worst possible luck in regards to how this winter has played out in that we are literally clutching at the last possible straw in the MJO to give the UK colder conditions. The UK could have had some colder and more settled weather by now had it not been for Hurricane Alex and the unfavourable strat warming but unfortunately luck wasn't on our side. If the MJO doesn't work out either then I think that's really it and roll on Spring and more so Summer which hopefully can make up for the horrible weather we have had to endure so far as surely 4 months of predominantely rain and gales cannot continue for much longer- that would be a stretch even for the UK imo and people would go absolutely crazy. Hopefully it will balance out in the end  There is always light at the end of the tunnel; recently Summer 2014 after the similarly horrid winter.

All I've heard all Winter long is a cold spell is dependable on a SSW in the second half of winter and now apparently it was a hindrance. That's why I don't buy in to long range forecasts no matter what signs etc are showing. As you said yourself the implications the hurricane had and no one could have foreseen that happening therefore LRF are a waste of time IMO. 90% of time we'll have wind and rain in Winter its our climate.  Hindsight is a great thing looking back at what made things go wrong but in reality it was only a guess to begin with.

Edited February 6, 2016 by Abyss

[wishingforsnow]

8 minutes ago, Abyss said:

All I've heard all Winter long is a cold spell is dependable on a SSW in the second half of winter and now apparently it was a hindrance. That's why I don't buy in to long range forecasts no matter what signs etc are showing. As you said yourself the implications the hurricane had and no one could have foreseen that happening therefore LRF are a waste of time IMO. 90% of time we'll have wind and rain in Winter its our climate.  Hindsight is a great thing looking back at what made things go wrong but in reality it was only a guess to begin with.

It could have helped had it not been simply a displacement with an unfavourable position for the UK.

[Midlands Ice Age]

13 minutes ago, Singularity said:

Okay... might take until +192 with the W. Atlantic feature.

Interesting how the individual disturbances within messy trough at +144 again refuse to merge into a single storm system. The southern arm of the jet is just too enticing... so we end up with another angry looking low heading for southern UK. Thanks, ECM *sarcasm alert*.

Edit:

I saw it first!

OK Sing....

We'll let you keep it in your back garden. Please!

[hooch5]

I would like to say that the positive input from the more experienced and educated forum contributors has made this winter an absolute pleasure to be a part of, I know its been hugely frustrating, but you cannot hurl abuse at these guys just because we have missed out.

Its all about learning for me and since 2013 I have always read all comments on this forum, some have been down right rude, but the majority thankfully are superb.

A chance for me to say thank you for taking the time and effort to post, (I will try to post more model related this year with accompanying charts etc)

[nick sussex]

24 minutes ago, Abyss said:

All I've heard all Winter long is a cold spell is dependable on a SSW in the second half of winter and now apparently it was a hindrance. That's why I don't buy in to long range forecasts no matter what signs etc are showing. As you said yourself the implications the hurricane had and no one could have foreseen that happening therefore LRF are a waste of time IMO. 90% of time we'll have wind and rain in Winter its our climate.  Hindsight is a great thing looking back at what made things go wrong but in reality it was only a guess to begin with.

I'm not sure why this hurricane Alex has taken on this level of importance. It did not scupper any cold, it caused some model uncertainty for a few days but that's all.

In terms of any SSW it depends whether you're talking of a major or minor one. The latter has often been a hindrance because it bounces the PV around often to places that are not favourable to the UK. If we had seen a major one then it might have given a better window but again its still a lottery!

This is the problem when expectations on one synoptic saviour to salvage another crxp UK winter go pearshaped. Amidst all the attention on the strat the only major teleconnection that's delivered anything remotely interesting was the MJO and then all the pre-drama to that was caused by yes you guessed it another strat warming which stopped any ridging in the Atlantic from getting further north because these warmings cause an initial PV surge and increase in zonal winds.

Unless you have a weak PV then these warmings are only worth the pain if they actually deliver a major SSW otherwise IMO they're not worth the drama.

My view of the strat and all its mood swings and countless caveats as to its impact for western Europe is akin to being invited to a meal at a 3 Star Michelin restaurant and then arriving to find out it was a big joke and you're actually dining at Pizza Hut!

I'm bored of the strat and all its caveats, how many times have we seen oh a big warming coming but then oh no its not the one we wanted, or it was in the wrong place or sent the PV in the wrong direction. Has one synoptic ever garnered so much attention and delivered so little.

Anyway that's my strat moan over for another winter!

Edited February 6, 2016 by nick sussex

[Abyss]

6 minutes ago, nick sussex said:

I'm not sure why this hurricane Alex has taken on this level of importance. It did not scupper any cold, it caused some model uncertainty for a few days but that's all.

 

I didn't say it scuppered cold Nick. Apparently it was unprecedented for such mild air to be pushed deep in to Arctic that's all I read here anyway and that had serious knock on effects to any LRF which didn't foresee that happening. That's my whole point, one small thing can happen and changes how the rest of dominoes will fall. Can't say it didn't matter to what happened after that long term as the immediate small term changes lead to big changes down the line. 

Edited February 6, 2016 by Abyss

[feb1991blizzard]

7 minutes ago, nick sussex said:

I'm not sure why this hurricane Alex has taken on this level of importance. It did not scupper any cold, it caused some model uncertainty for a few days but that's all.

In terms of any SSW it depends whether you're talking of a major or minor one. The latter has often been a hindrance because it bounces the PV around often to places that are not favourable to the UK. If we had seen a major one then it might have given a better window but again its still a lottery!

This is the problem when expectations on one synoptic saviour to salvage another crxp UK winter go pearshaped. Amidst all the attention on the strat the only major teleconnection that's delivered anything remotely interesting was the MJO and then all the pre-drama to that was caused by yes you guessed it another strat warming which stopped any ridging in the Atlantic from getting further north because these warmings cause an initial PV surge and increase in zonal winds.

Unless you have a weak PV then these warmings are only worth the pain if they actually deliver a major SSW otherwise IMO they're not worth the drama.

It all depends on the type of warming, if its a wave 2 split type with complete reversal, even if it doesn't have immediate implications, its very likely at some point during the rest of winter / spring we would get potent cold.

[Frost HoIIow]

5 minutes ago, feb1991blizzard said:

It all depends on the type of warming, if its a wave 2 split type with complete reversal, even if it doesn't have immediate implications, its very likely at some point during the rest of winter / spring we would get potent cold.

Hopefully. March 2013 was a rare event & I think anything close to that would be a monumental success after this awful "Winter"

[wishingforsnow]

8 minutes ago, feb1991blizzard said:

It all depends on the type of warming, if its a wave 2 split type with complete reversal, even if it doesn't have immediate implications, its very likely at some point during the rest of winter / spring we would get potent cold.

Personally I think our next best chance for potent cold is early Spring, tying in with Ian Pennell's thoughts, should the warming be as you described.

Edited February 6, 2016 by wishingforsnow

[winterof79]

If anyone can show me other than mild/normal conditions for the foreseeable I will gladly take it on board

Snow is not an issue this coming week according to the present output. Only the usual forecast based  upon one GFS output in 24 hrs.

 

Edited February 6, 2016 by winterof79

[nick sussex]

7 minutes ago, feb1991blizzard said:

It all depends on the type of warming, if its a wave 2 split type with complete reversal, even if it doesn't have immediate implications, its very likely at some point during the rest of winter / spring we would get potent cold.

Yes but we haven't seen the much vaunted major SSW which hit the buffers. The only remotely interesting spell for the UK which wasn't upto much but still better than the rest of the winter was that spell in January which was helped on its way by the MJO.  Unfortunately the PV has been relentless and together with the El Nino has made it an uphill struggle.

At this point I think our last hope is on the MJO gaining more amplitude and getting into a favourable phase.

[The Enforcer]

2 hours ago, snowray said:

Mildest Northerly I have ever seen in February, Just about sums up this Winter!

Looks like more of a no-therley to me, similar to the one in mid-January.

[Nouska]

30 minutes ago, Abyss said:

I didn't say it scuppered cold Nick. Apparently it was unprecedented for such mild air to be pushed deep in to Arctic that's all I read here anyway and that had serious knock on effects to any LRF which didn't foresee that happening. That's my whole point, one small thing can happen and changes how the rest of dominoes will fall. Can't say it didn't matter to what happened after that long term as the immediate small term changes lead to big changes down the line. 

Are you perhaps thinking of storm Frank rather than hurricane Alex. The warm moist air from Alex was mixed in a low pressure exiting Canada and gave a temporary bit of oomph to the flow. Storm Frank's warm air advection went right up to the pole, bringing record high temps in that region and giving birth to the persistent Kara sea positive heights.

Frank on Hogmanay 2015. 

[snowray]

Maybe some interest there again on the 18z for this Tuesday.

[nick sussex]

More changes from the GFS. The detail for later next week is difficult to pin down because of the changing view of shortwaves running into the UK.

Something might pop up in terms of snow but as to where difficult to say. That area south of Greenland seems to be an area the models continue to struggle with.

Edited February 6, 2016 by nick sussex

[Mair Snaw]

well thats me watching "the day after tomorrow for the 100th time this winter.... now this is some model watching..... so far this winter ive been on the be patient side but the last 24hrs ive really begun to feel like thats it and we are done until next winter.... model watching has been the hardest thing ever this season and i just cant think that we will see anything to get real cold and ice days for us now..... sorry winter 2015/16 you have given nothing other than rain warmth and wind for many.... ive had 2 snow falls and thats less than what i saw in 13/14 so just goes to show how bad this winter has really been... i will keep an eye on this thread over the next few weeks and months but then i will go seek out my wife and kids for a few months before coming back here in September to see how the build up to next winter is looking...

[snowray]

And then this...Am I seeing things, two potential snow events next week? Some nice charts there.

[wishingforsnow]

Well what do we have here? Snow events in the South? 

Edited February 6, 2016 by wishingforsnow