Model output discussion - here comes the beast!

[kev238]

Well the theme from the 12z runs is to consolidate the idea that the low from the south late on Thursday and into Friday is a real possibility and that this will lead to a potential historic blizzard in some places whilst others might witness a sleety mess 

If I were in the West Country and places like Gloucestershire and Wiltshire I would be getting quite interested in the potential now 

[WalsallWeather123]

Milder air mixing in on ECM at T144 compared to the 0z run.

[Mike Poole]

The chart we want to see is the Friday T144 one, and here it is:

This doesn't look the best, to be honest. Not at all sure where this goes from here?

Edited February 24, 2018 by Mike Poole

[fromey]

1 minute ago, Bristle boy said:

It's dragging milder air up from the Med. Follow the isobars. Direct feed from East being cut off for some areas. The trend is glaringly obvious now imho.

Really?

[I remember Atlantic 252]

Hmm, not sure what to make of this? too far west I think, most snow in West, this location and E/NE/SE of it though should remain cold with SE'ly flow

[Ayrshire weather]

1 minute ago, Bristle boy said:

It's dragging milder air up from the Med. Follow the isobars. Direct feed from East being cut off for some areas. The trend is glaringly obvious now imho.

Sorry thats my fault still new to this think iv'e got this a but wrong mind u Scotland looks not to bad however most likely will change near time!

[ukpaul]

Well ECM looks like it wants to curtail anything next weekend by stalling west and instead set up a reload from the north east. A response to the second warming?

[terrier]

ecm looking good to me. Plenty of snow and cold right there. Everyone in the game here. North,east,south and west. 

[Weather-history]

2 minutes ago, mb018538 said:

ECM 120 is great, much less mild air mixed in than gfs! Winner!

Looks the other way around to me 

ECM                                                      GFS

 

[LRD]

1 minute ago, Daniel Smith said:

Not sure I agree

Less cold, yes. But SE winds ahead of the low will mean that it'd be an all snow event, even down to the coast.

That chart is ok of course but the trend of the movement of that low pressure is a really poor one today for longevity of the cold. Models wobbled this time last week about the spell even happening in the first place. I'm expecting this to be a blip but no dressing today's runs up. Bravo GFS for first spotting this trend for the too-round low getting too close to us

[Bristawl Si]

Just now, Weather-history said:

Looks the other way around to me 

ECM                                                      GFS

 

Ah....i thought i'd interpreted correctly

[mb018538]

No, because Friday is the crunch day everyone is referring to...

[Guest]

REASSURING THOSE WHO ARE WORRIED THAT THE COLD SPELL MIGHT END QUICKLY AND ALSO THOSE WHO MIGHT SUFFER GENUINE HARDSHIP

I was going to produce my Arctic profile report today but that will have to wait until tomorrow. I have skimmed through the last 30 pages on this MOD thread and there are still a lot of posters (and I imagine even more readers) who have various concerns. Some seem to think that the upcoming cold spell will be over barely before it has started while others have real concerns about how they and the vulnerable might cope if the country is buried in deep snow and normal life is interrupted. Well for a lifetime weather enthusiast who was one of those who experienced the 1962/63 winter (aged 10) and was snowed in at my parent's hotel halfway up Dartmoor for 5 days in the February 1978 blizzard, I feel that I'm qualified to report on both sides to all of this and I will try and tackle it in this post.

PART 1:  THE UPCOMING COLD SPELL - HOW COLD, HOW LONG, HOW SEVERE, HOW CERTAIN?

There is some ongoing concern at the GFS solution for week 2 which they have shown on many of their recent runs. To avoid repeating myself too much, I refer you to my post on page 64 of this thread:

https://www.netweather.tv/forum/topic/89388-model-output-discussion-here-comes-the-beast/?page=64&tab=comments#comment-3767360     Please read this if you haven't already as it will allay many fears.

I tackled the issues head on. I'm not one to criticise a model if it doesn't show what I'd like it to. Despite all the advances with far greater accuracy in the shorter term output (up to around day 7 or so) which some do not seem to realise, all the models still have their deficiencies. GFS sometimes comes in for greater criticism than most, simply because they're brave enough to go much further into the extended period than the other main models. As I've often said, we should use the output in different ways. The D1 up to D5 (shorter for difficult to predict snowfall events) to focus on the micro details for our country. Around D5 to D10 to see the likely broader pattern for our neck of the woods and possible changes and updates. Then D10 to D16 to see the range of solutions and outcomes on the table in terms of the macro broad scale pattern and set up. In certain scenarios the longer term changes in (or continuation of) a particular pattern are much easier to predict than others such as with a prolonged summer heatwave. On the other hand, very short term forecasts can still be very tricky. Remember, the short-wave drama last December when even the "nowcasts" couldn't get the exact areas for who would get and who would miss out on the snow event? Each model has it's known biases, strengths and weaknesses. Two of the GFS nemeses are modelling the breakdown of a cold block and more generally modelling of a "pattern reversal" situation. Well we now have both and their frailties are already being exposed. The former is where the GFS is usually far too progressive and the latter is where GFS (and in fairness, other models too) cannot cope with an unusual set-up and tend to be be far too keen to return to the climatological norm. 

The Sudden Stratospheric Warming (SSW) Impacts:

We have just seen a record strength SSW. The northern hemisphere flow has already gone into full reversal. The associated HLB patterns have been established with, for once, the UK right in the firing line. All the cold in the Arctic (and there's still some available despite record low sea ice build up!) is spilling out towards the middle latitudes. There is a broad belt of HP stretching westwards and south-westwards from Siberia, Russia, Scandinavia and even towards Greenland. This is the classic pattern to establish a proper long fetch easterly. Exceptionally "deep" cold (very low surface and upper temperatures) air is surging westwards through Russia towards Europe, including the UK. This SSW event is even stronger than the pretty big event in March 2013 which brought us an unseasonable protracted very cold spell from March 10th to mid-April. This one is starting off about 2 weeks earlier. 

I was struck by one of the fax charts I saw this morning for Wednesday, Feb 28th:

    Met O Fax for T+120 for 1200 28.2.18                    UKMO T+96 for 0100  28.2.18                           UKMO T+120 for 1300 1.3.18

                          

I know that long fetch easterlies have been rare during the last 30 years or so but regular readers of my posts will know that I've experienced and commented on many of them when they were much more common during the 1960s to 1980s. I have seen flows all the way from Siberia all the way to the mid Atlantic but this one beats the lot. It reaches all the way to Newfoundland, 7,000 to 8,000 miles! This is the extent of the flow reversal - quite amazing. 

GFS vs the Other Big Models: 

Right, let's look at some of the evidence. This is in addition to what I said in my earlier post referred to above. The key period seems to be from around March 2nd onwards. So, I'll start off with those charts. I am deliberately using the GFS 0z (archived output) as this is then an exact match to the other models and the 6z is a slightly colder and more snowy solution. GFS may return to the less cold solution again on the next or a future run or they may fall more into line with the others. These are all T+144 charts for March 2nd 0100 with the pressure above and 850s below:

                          GFS                                                                     ECM                                                                   UKMO                                                              

                                      

                           GFS                                                                    ECM                                                                   UKMO                                                             

                                

Fairly similar charts but GFS have a slightly deeper LP pulling in rather less cold air from the south. They show the -4c, -2c and 0c 850s skirting the south coast. The other 3 have this warming gradient a fraction further south. Some have said that we needed all the deepest cold to hit us directly and not go too far south. I've said before that we needed some of it to go further south. Both the very low 850s (initially with sub -12c) and the surface cold are shown to drive well south into at least northern and central France. The deep cold European pool will become well entrenched and also cover the UK just prior to this approaching LP system. That is one deep and massive block of dense cold air in place. In early February last year we had an easterly but that was with almost entirely surface cold with only rather low 850s appearing very briefly. It was also a more mobile pattern with a stronger jet stream. Even so, the block was only broken down after quite a battle (very little snow). This is a completely different ball game with even deeper surface cold and almost record low 850s (please refer to my post on page 104 of this thread which compared the predicted 850s for this spell to the lowest values seen in most of our previous severe winters spells going back to 1879 with archived charts: https://www.netweather.tv/forum/topic/89388-model-output-discussion-here-comes-the-beast/?page=104&tab=comments#comment-3771172

                GFS 2m temps T+144                                 GFS Jet Stream  T+144                                  GFS   Jet Stream  T+192                              GFS   Jet Stream  T+240  

                          

I actually believe that GFS is understating the surface cold but let's assume that the 0c to -4c temps are about right. Then we have that peculiar very small breakaway loop from the pretty strong west to east jet stream that is well to the south of us blowing through the Med and north Africa. The loop is already breaking up and weakening. I do not see it forming in the first place but if it does it would bring that LP a little closer but then it should stall with nothing to push it into the UK and everything in place to resist it. It should either fill up in situ, be displaced north-westwards or more likely be deflected away south-eastwards. In terms of the temperatures, I feel that there might be a little mixing but no more than that. The block should easily hold off this minor "bump" into it. In fact, the air ahead of it is so cold, that it is likely to mix into the LP circulation. In terms of any precipitation, this is much more likely to fall only as snow. It is possible that it might very temporarily turn a little sleety on the south coast and in the far south-west but even this would appear to unlikely (perhaps even a rare freezing rain or ice storm event). Again refer to my "why GFS is wrong" post for details of similar events in the epic winters of '46/'47 and '62/'63. There were numerous examples of successive LPs being unable to penetrate the block. If this event occurs (and these is some doubt if the LP will even get close to the UK), it is actually more likely to produce some very heavy snowfall and even some blizzard conditions. I won't over ramp it at this stage but I'm just a little bit excited for IMBY here in Exmouth. 

Moving on, the GFS charts show the jet stream back further south again 48 hours later which should drag the LP away south-eastwards anyway. Extraordinarily, GFS then repeat this process several more times later in this 0z run. Let's move on to the day 10 charts to see what they show. UKMO only go up to day 7 so I'll just show the 2 models now. These are T+240 charts for 0100 on March 5th:

                       GFS   T+240                                                ECM     T+240                                                GFS    T+240                                            ECM     T+240                                                   

 

                 

GFS continues to push LP around the UK and filter in some slightly less cold sir to the far south. ECM show that LP further to our south and east with most of the UK still under sub -8c 850s and even the far south-west still under sub -6s. I know that several other models are undecided over this outcome The GEFS ensembles mostly favour the operational run type solution but a good proportion are more in agreement with the ECM solution as are most of the ECM ens (not shown but plenty of references to them on the MOD earlier today). The 12z output is just rolling out as I write this but I will not comment on it now. I've made my points and they'll carry on applying right up to next weekend's "possible" event and beyond that but we'll see how things actually pan out.

Longevity? 

How we get through next weekend and into the following week may well be put into context. The SSW hasn't finished with us yet - far from it. There is a second warming (perhaps multiple events) going on. This is expected to reinforce the HLB and the cold block towards and beyond day 10. So even if we do see an easing of the cold (to any extent) this is likely to be very temporary indeed. Just as in March 2013, GFS kept underestimating the strength of the block and also the extent of further bouts of HLB patterns with continuing flow reversals. ECM have a much better handle on this. We can pick it up much more clearly by looking at their northern hemisphere charts from their 0z run:

                   ECM     T+168                                                ECM     T+240                                                ECM     T+168                                              ECM     T+240    

                       

At day 7 ECM  still have the easterly in place with the LP just to the south but unable to make any inroads into the cold block. Note that the 850s to our north-east have weakened a little but still with some sub -16s showing and the UK is once again under sub -8s, -10s and -12s - so still a little nippy!  Now, note by day 10 that the flow is re-orientating slightly to the north-east which is a perfect direction if sustained cold is your thing. More significantly, just look to our north-east and those 850s.  There is another lobe of sub -20s pushing directly towards us. In fact with the flow backed to the north-east these should have our name on it. Perhaps with sub -16s pushing across an even larger part of the country than the initial hit due this week. With the very cold air already in place, this will really top things up. There may well be one or two more top-ups to follow. I feel that this almost record breaking cold spell might last for much of March. It seems set to be even colder than March 2013 but may not be quite as long . 

PART 2:  COPING WITH MASSIVE DISRUPTION AND DOING OUR BIT TO HELP EACH OTHER OUT AND PROTECT THE VULNERABLE

This leads me into a very serious part of my post. I know that many of us on the winter model thread love the cold and the snow and many also like extreme weather events. If this bitterly cold spell lives up to many of the predictions and I believe it will, then I fear that things will go beyond excitement and turn to worry and severe hardship for some.  We can do nothing about the weather but we can do something about how most of us can prepare for it and cope with it. Many of the younger generation will not have witnessed anything like what we may well be facing. If you have been on a skiing holiday (especially to the Alps this winter) you will have seen some very deep snow. This can be dangerous (with avalanche risks) but most of the time one can enjoy the wonderful conditions. Those resorts and many other very snow locations are completely prepared for regular heavy snowfalls but this is very different here and we can never be properly prepared. Indeed, should we be investing in very expensive snow clearing equipment which needs to be properly stored and maintained and perhaps only used once every 20 years? Some will always pose those questions and criticise the authorities, especially if their own lives are impacted in any way.

What Type of Disruption Might We Face?  

We know how a few inches of snow can bring roads, rail and airports to a standstill. How might we cope with one to two feet of it? Almost all roads will be closed for long periods, public transport will be seriously disrupted with endless cancellations. Being so cold, much of any snowfall is likely to be the dry, powdery type. In most countries this is much easier to deal with. They just blow it away. We hardly have any snow blowers (perhaps one or two at Heathrow?). We tend to salt roads all the time or use a de-icing substance for lower temperatures. Really we should use snow ploughs to clear it with little or no advanced salting and gritting.  All the salt does is partially thaw the snow which then re-freezes into huge icy patches which get compacted down and are far more difficult to clear. Most of our snow is wet snow with a high moisture content and then salt does do its job well.

With much of the road and rail network at a standstill, supplies of food, fuel and other essentials will be seriously disrupted, as will the emergency services. We may well see power outages. Snow can bring down cables and bury electricity sub stations. Demand for electricity will be at record levels and supplies may have to be rationed with set period power cuts except for hospitals, retirement and nursing homes and certain other essential services. The majority of schools would be closed except those used as refuge shelters. Businesses will be seriously impacted. If we do lose power, then there will be no computers, internet and no NetWeather viewing. Some of us will have burst pipes. This and any later rapid thaw can lead to severe flooding especially if the ground is frozen to quite a depth with nowhere for the water to go. 

Am I Being Melodramatic?

Perhaps I am but if these severe conditions take hold we need to be as best prepared as we can be. What i said above is just a small part of it. The major impact and concern would be on our actual lives. The vulnerable people might be in real danger. Severe winter spells always see a spike in the mortality rates. Any elderly, frail or ill people might really struggle to cope. If we are told not to drive unless it's an emergency then please heed those warnings. Accidents and abandoned vehicles can block the roads and prevent the vital emergency services from getting through, perhaps with the loss of life. Many of us are not prepared to drive in deep snow and icy conditions anyway. How many of us have winter tyres and snow chains?

What Can We Do To Cope With All This?

Back in 1962/63 I lived in north London. I was nearly 10 but I remember it all incredibly well. After the 48 hour snowfall that started on Boxing Day and then followed by a huge blizzard 2 to 3 days later we had over 2 foot of level snow and immense drifts to clear. Huge numbers got outside and cleared their paths and then the pavements and other's paths and helped to dig out shops etc. There are many archived pictures of snow pilled up over 3 to 4 feet high along the curbs and gutters but the roads and footpaths were usable most of the time. In fact many schools remained open - it is more a "health and safety" matter that so many are closed these days even following quite minor disruption. Many people walked to work but then most of our jobs were much more local to where we lived. We need to be prepared. Yes we should stock up on vital supplies but it will be plain selfish to hoard too much unless you'll be prepared to share some of it with others. Food, heating fuel, blankets and clearing equipment and materials (shovels and salt) might be on your shopping lists. I already have a set of foot snow chains which attach to one's shoes to prevent slipping over. They'll quickly sell out. 

How Can We help Each Other?

Once we've taken care of our loved ones , families and friends we need to see how we can help those in real need. The Dunkirk spirit comes to mind. Beyond snow clearing duties, we should form small groups and organise ourselves. We need to ensure that everyone in our neighbourhood is accounted for. Check up on the elderly, those living on their own and the frail and vulnerable. Ensure that they have sufficient food and warmth and if possible, cater for any specific needs. In this insulated modern technological world we now live in, with instant communication we can easily feel protected in our own little bubbles. There is much that divides the nation (like Brexi)) but this would be a time to put all our differences aside and pull together.

Many will learn a lot if some of these dramatic events unfold. I accept that isolated parts, frail people and livestock are in far greater danger. I always believe in making the best out of any situation. The weather will do what it wants to and I will enjoy it all but I'm also aware that some may need a lot of help. 

I'll be be back with my Arctic report tomorrow.

 

[Djdazzle]

So those who were rubbishing GFS earlier today may have been a bit premature. If this trend continues we could be in SW’lys next weekend.

[ICE COLD]

ECM 168 oh dear . Not what I we want 

[mulzy]

A poor ECM it must be said - by day 7 a swathe of southern England in positive uppers.

[Guest]

ECM has really put the cat among the pigeons this evening. No doubt it'll be one of the warmest options in it's suite but a worrying trend all the same.

Thank goodness we've got a historic cold spell preceding it! 

[DR(S)NO]

2 minutes ago, LRD said:

That chart is ok of course but the trend of the movement of that low pressure is a really poor one today for longevity of the cold. Models wobbled this time last week about the spell even happening in the first place. I'm expecting this to be a blip but no dressing today's runs up. Bravo GFS for first spotting this trend for the too-round low getting too close to us

Hi LRD

Hope im not being too stupid here.... but how can we congratulate the GFS for spotting a trend of something that’s almost a week away and may not happen?

 

[Summer Sun]

t168 less cold air moving north clear trend at present can't be ignored

 

[kold weather]

2 minutes ago, Djdazzle said:

So those who were rubbishing GFS earlier today may have been a bit premature. If this trend continues we could be in SW’lys next weekend.

Its ironic because its far more agressive with bringing up the milder air than the 12z GFS earlier, the run people were saying was wrong.

The key remains how far west the LP comes up, the further west and the bigger the drag of milder air from the south will be.

Sure does look like a trend now...then again at one point we had a trend for the easterly to go into Europe....

Edited February 24, 2018 by kold weather

[Jason M]

26 minutes ago, danm said:

 

GFS not looking such a ridiculous model now . 

Does it mean that a warm up from the south is nailed on? Answer is clearly no, but it should be a reminder not to discount any output!!

Anyway, off to the regionals as the next few days still look exciting  

[Paceyboy]

I dont know about anyone else but id have much preferred a longer period of deep cold convective weather on a brisk easterley than it to be all over by saturday with a blizzard. I think for this we would require at least a 300 mile shift of fridays low south. Disappointing we could have been seeing ice days from wednesday through sunday. And yes i wanted the best for this spell as it just does not come around often.

 

Edited February 24, 2018 by Paceyboy

[davehsug]

3 minutes ago, LRD said:

That chart is ok of course but the trend of the movement of that low pressure is a really poor one today for longevity of the cold. Models wobbled this time last week about the spell even happening in the first place. I'm expecting this to be a blip but no dressing today's runs up. Bravo GFS for first spotting this trend for the too-round low getting too close to us

Bravo to a model for spotting something, in a weeks time, which probably won't happen anyway? 

[Guest]

2 minutes ago, Djdazzle said:

So those who were rubbishing GFS earlier today may have been a bit premature. If this trend continues we could be in SW’lys next weekend.

I think you're being just as premature. This won't be resolved for days - think how much data has got to come before next Thursday!

[Bristawl Si]

IF it happens, as GFS was hinting at yesterday, and kinda confirmed by Ecm this eve, then it's a massive turnaround from last few days' output. 2 weeks of severe cold?! Hmm......