weather eater
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Posts posted by weather eater
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In terms of the snow prospects over the next few days the BBC via the MO don't seem very keen on getting ahead of themselves, a very cautious one/two day at a time approach. Wise given the way that small synoptic changes will make a big difference between rain and snow, who gets it and who doesn't.
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I can't see a quick return to zonal, a MLB over the UK seems far more likely if the high topples than zonality at the moment. A lot depends on how the models are dealing with the lobe of the PV to our NW, we need it to stay west, if it does so or the longer it does so, then that makes a quick return to outright zonality pretty impossible. If we use the operationals over the last couple of days as an ensemble then the cold looks a good bet until this time next week at least. Thereafter is in the lap of the weather gods because there's an awful lot of synoptic evolving to get through before then and I expect the models to throw out some interesting possibilities over the next few days.
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Wow lots of changes really quite early on that demonstrate what absolute forecasters nightmare this could be. One thing for certain this is not looking like a standard northerly tippler and therefore it seems to me all bets are on the table including heights to our NW, however, a MLB over or close to the UK still looks the form horse for the end of next week.
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In the short term we have no upgrades or downgrades just standard modelling as they get to grips with the small details, this will keep changing right up to zero hour, although no doubt some will see things that way from an IMBY prospective
Overall and at long last this winter the UK is on the cusp of a decent cold spell but longer term there is much to resolve.
1. Will the high topple setting up a MLB over the UK This seems to be odds on at the moment.
2. Will it topple and let the Atlantic back in, not showing in the modelling at the moment except in the far reaches on the GFS and after a period of MLB. Certainly little sign of a topple and a straight return of the Atlantic, so I would put that as the least likely mid range plus evolution at this stage.
3. Can we keep the lobe of the PV far enough west to allow HLB to develop over Greenland, also, not showing as yet as the models seem keen to shift it east. but I would say slightly more likely than 2 at present although history would say otherwise.
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Westerly's a dead cert I was never sure and I'm even less so now, I keep using this word, evolution, in this sort of set-up small changes are having big impacts, let's just hope it's not a false dawn The runs over the next few days may make very interesting viewing.
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Being pedantic but likely suggests around 75% chance which in my book denotes a clear signal. Not certain granted
Maybe but clear signals change if they didn't do so then this thread would be consternation free, Clear signals have a habit of becoming unclear although I would allow its less so when it comes to the UK default pattern.. Still I'm not sure I would put it at 75% just yet and I suspect we will see some other options on display that don't back a return to a westerly regime, synoptic patterns are a constant evolution.
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It is interesting that fergieweather notes there is a clear signal for a return to a westerly regime- I hope this is noted.
Sort of but not exactly, likely is the word here.
"A gradual transition to a more mobile pattern across the Atlantic is likely to gradually take place, through may take until later next weekend to become fully established."
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Looks to me that part of the problem is the modelling of the lobe of the PV over Greenland, this morning's runs have it further north, only as we get into lower res does this start to drop down. I would not view any return to SWlys as set in stone, likely maybe but not a certainty at the stage.
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Completely understand why people think of back flips but you only get out what you put in. contrary to popular myth the models do not work from past experience only from pure maths based on the input data and that does not stand still, charts are effectively out of date before the number crunching begins so in truth I'm always amazed by how good they are. But it is frustrating when people expectation get raised by seeming model consistency.
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Actually I don't think that's true either, it's just we don't notice or when dealing with a large low pressure systems maybe several hundred miles across its going to hit us anyway despite any corrections north south east or west this on the other hand
was always a fine line to tread
As it stands the evolution will continue but I doubt whether that will mean it evolving back to something more favourable for a prolonged cold snap for a little while at lest. Still 6 weeks of winter still to come and early spring can deliver some potent snaps.
I would say the can be reliable up to 192 hours in a strong Westerly zonal pattern, throw in a hint of blocking and that drops to 72/96 hours.
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Anyone any Ideas what changed this reversal in fortunes?? What did the models get wrong or predict wrong??
Nothing they just did the maths based on the data they had at the time, I can't stress this enough you cannot rely on computer synoptic modelling post 120hrs sometimes less and to do so in regards cold and snow will result in tears almost every time.
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No back flip has occurred just the same old problem when viewing model output in that the evolution doesn't just stop or carry on in a theme that suits us, that's why stella charts at 120hrs plus and often less are of as much use a marzipan very stiff thing often used in the bedroom. what remains to be seen is how they will evolve from here but given the starting place and the lobe of the PV sitting over Greenland like an angry wasp it will be not to our liking for a while I think.
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I suspect not but this sort of thing has been tried before without success, people just don't bother with the other thread in just the same way as happens now. we have other threads for moans groans etc but people still use this one because it is the one where they know their post will get attention.
Has this very "popular" post been responded to by forum hosts or moderators? If it has , the response has been lost ( to me) in the jumble of the preceding posts to this post.
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Mmm I wouldn't be too confident on the return of a sustained period of zonality so to speak, a shift in the overall pattern is taking place and cold pools at this time of year are hard to dislodge.
Worth looking at the Jetstream profiles which still show split jet, energy northern arm much weaker than recently and with low heights over Europe every chance heights to the east will build in situ maintaining the split flow energy, which will be forced SE. Yes we are very likely to see more atlantic energy from the NW but not necessarily a locked in mild wet fest, more a rinse repeat episode.
I agree but I can see where he is coming from, lots of varied solutions in the near term all leading to a similar outcome rather dictated by the strength of the lobe of PV over southern Greenland. However just because the models can't see the way past that at the moment doesn't mean there isn't one.
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And the Gem has gone for the easterly, maybe it's right maybe it's wrong doesn't matter what is important that its wise not to look too far ahead, not to get carried away and not get despondent about synoptic patterns that may never happen.
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The 12z GFS looks poor with a large mild sector on the western edge...... If you think the GFS is good because of a weak easterly that will only bring low cloud and snizzle then fine.... otherwise why is it great
Because if you look at its earlier frames you can see the possibility for the synoptic pattern to develop in a much better way. Do not look at model runs in a literal fashion as they will change increasingly post zero hour the 18z will be different and the 00z and so on, models are displaying evolution not creation.
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Potential at 132..
But given how different the 12z is to the 06z by just 92hrs on a hemispherical level, you may as well be hanging teabags outside to predict the weather. Never known a year for the models to be such utter tripe at any type of predicting.
GFS Upgrade can go in the bin as far as I'm concerned, models are useless.
Models are likely to stay useless in regards our tiny plot for many years to come, its like doing any sum, if the start numbers keep changing you will get different answers every time and can somebody tell my dog I don't want sexy time with him.
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120hrs about as far as I want to go as so many small corrections early on make a nonsense of looking further. On saying that I feel that while it's more of a mixed bag in the short term, thereafter there are positive signs of the possibility of the PV lifting away from Greenland giving a better chance of blocking and a subsequent easterly. A blimey it's hard to type with the head of a large dog on your shoulder.
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Moved across this year from the peak district back east where I belong so haven't had much time for NW this year and honestly not much inclination given the weather so far this winter, it has not energised me much. However I do feel compelled to post as yet again I see the same mistakes and circular arguments that happen in the model thread every year, arguments that contribute to my lack of desire to take part. It still seems that many of the contributors in the model thread are rather apt to forget that climate is dynamic from its basic building blocks all the way up, it does not sit still and that is what makes it so hard to model. Subsequently the modelling is going to get progressively poorer from zero hour, every run every day, they are mathematical models that have to deal with the problem that the starting numbers keep changing. This is why ensembles are run in an attempt to factor this in but they also have limitations. The reason for this is that we simply do not have the ability to see many of the tiny processes that occur, butterfly wings is the phrase we use but it's much more complex than that and thus the starting numbers are likely to wrong even before the computer does the calculation.
So many posters (even some really quite knowledgeable ones) on this thread see a run they like and expect it to come close to fruition, for those that do I can assure you that you will almost always be disappointed, factor in our tiny Island and you are on a hiding to nothing. It's no wonder that one of the most sensible posters on here John Holmes uses the 500mb anomaly charts as a guide, while they may appear to be a bit vague they nevertheless offer good guidance for those that understand them. Ever notice he is rarely surprised and never appears disappointed, never ramps either. I always read his posts even though they may not appear to be as dramatic as some whom get a lot of likes and kudos and besides you only have to be positive about the prospects for cold and snow to do that and that is not to say before I get jumped on, that getting a lot of likes makes the poster untrustworthy.
Downgrades, upgrades it's a pointless way of looking at things and why worry none of it stands still. We will have some kind of cold snap and I shall enjoy what we get and keep watching with interest where the evolution will go next, who knows it may turn out to be more than a snap.
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Oh I certainly don't get excited about it either Mr frost, in fact I hate it but it is very noteworthy nonetheless and the ECM follows suit a couple of dryer days and then more rain, Thursday into Friday, has anyone got any spare timber I'm thinking of building an ark.
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Well the 12z has toned down Thursday’s system somewhat but both the GFS and the UKMO look wet, breezy with a train of low pressure systems bearing down on the UK for the foreseeable. An unneeded watery disaster as if we haven’t already had plenty of that already, I don’t think I can remember a winter quite like it and I’ve seen a few.
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Another excellent post from Tamara the reading and learning seems to be paying dividends. The 06z certainly should ring some alarm bells let’s hope the 12s tell a different story, if nothing else the 06z demonstrates why the METO are usually reticent about predictions more than two or three days ahead.
I see Japan has managed a drop of the white stuff. http://www.bbc.co.uk/news/world-asia-26222457
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So quiet in here it’s unbelievable, I guess the penny has dropped, not only is there no sign of any cold but the Atlantic doesn’t seem willing to give up either. While systems will be less intense than they were, they will still nevertheless be pretty vigorous, wet and frequent, no real end in sight for the zonal train.
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Might I suggest an alternative way to look at the models this morning, forget the hunt for cold it may or may not happen I don’t think an answer can be deduced from the current modelling. The real story is for less wet weather after this weekend and with the possibility that HP may become more of an influence as we move into week two, given the state of affairs and that alone would be some cheer for soggy Britain.
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Model Output Discussion - 23rd Jan - 12z onwards
in Forecast Model Discussion
Posted · Edited by weather eater
Never bothered with the GEFS myself preferring to make a judgement on an ensemble in my head of recent operationals. The operational runs are just that for a good reason, they are the best guess the model can make based on the data. The ensembles are tweaked data presumably to a preset set of parameters. To my mind I start getting twitchy when the operationals start jumping around or when there is a wide spread of opinions across model output, at least across the big three anyway. At this point of time we have as good a consensus across the model spread for the next week as you are likely to see. I remain cautiously optimistic and my interested is now in relation to the models is what happens Tues Wed and onwards next week. For the next few days the regional threads and what's out of the window will be my focus, I would say lamp post watching except we don't have one, maybe if I'm lucky making tea and coffee for benighted travellers stuck in their cars.