OldMetMan
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Posts posted by OldMetMan
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You're the only one then!
I think most people are now suffering from model fatigue and just want a resolution to this so we can either throw our toys out of the pram or look forward to something a bit more interesting!
You'd think this modelling lark was rocket science given the inability of the models to just agree on an outcome at 144hrs!
The ECM is my favourite model but even thats getting on my nerves now! In terms of the ECM NOAA have gone with the earlier ECM ensemble mean/operational combo.
BASED ON THESE CONSIDERATIONS THE UPDATED PRELIM FCST WAS BASED ON
A SOLN CLOSE TO THE 00Z ECMWF ON DAYS 3-4 THU-FRI... WITH HALF
WEIGHTING OF THE 00Z ECMWF ENSEMBLE MEAN INCLUDED DAYS 5-7 SAT-MON
TO ACCOUNT FOR INCREASED DETAIL UNCERTAINTY BY THAT TIME. THE 12Z
GFS STILL DISPLAYS A PROGRESSIVE TENDENCY IN GENERAL WITH THE 12Z
GEFS MEAN HEDGING AT LEAST PARTIALLY AWAY FROM GFS IDEAS. OTHER
12Z SOLNS VARY TO SOME DEGREE BUT WITHOUT SUFFICIENT CONSENSUS TO
RECOMMEND MEANINGFUL CHANGES IN THE PRELIM FCST ASIDE FROM A
SLIGHTLY WEAKER TREND WITH THE SYSTEM CROSSING THE NORTHEAST EARLY
IN THE PERIOD.
However I'm not sure if they even included the ECM 12hrs in that discussion, they mentioned other 12hrs solutions but normally they single out the ECM.
Quite agree Nick, I am quite bewildered by the variety of model solutions.
Must be hard going for the "official" forecasters!
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Do you rally believe the ECM would give widespread snow? Uppers look v marginal to me away from highest ground. I expect the ECM to be a mild outlier and think the GFS 12z will be closer to the mark. If I lived on low ground south of Leeds I wouldn't be holding my breath for snow (in the next 5 Days) other than a snow shower on Fri
Hi Tim, I have seen such a pattern in the past, albeit rarely, produce snow, where there are LPs revolving with a broad and deep upper trough, but I really don't think such a pattern as the ECM shows will come about. I was just astonished at the ECM for coming up with such a solution!
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Well we're doing again aren't we getting the prozac out because of one run. :blink:
From a personal viewpoint and from over 40 years of weather watching experience I believe that this weekends progged cold /cooler spell is the start of a gradual transition to a real piece of winter as we go through february and only part one of the transition at that. We should remember from GP'S forecast that mid january would be our first window of opportunity not our only window of opportunity.
In reality if the models were to serve up and and verify on a 2 week cold and snowy spell with a northerly outbreak becoming an easterly one just about every cold/snow lover would be happy. I would point people in the direction of the winter of 77/78 when naff all happened until the last week of Jan for Scotland and the second and third weeks in Feb for the rest of us. but when it came it was certainly worth having waited nearly all winter for it.
With the waning PV coming under continuing and further attack pretty much anything beyond 144 on any of the models is little more than speculation. Such volatile condtions are going to mean rapid changes in output as varing ideas are picked up because of this I think we will find that when our piece of winter arrives it will do so at relatively short notice.
Well said Mcweather! We must be of a similar vintage - I became interested in weather in 1967!
I too remember Feb 1978 - 12 hours of continuous snow even on the Isle of Wight where I lived at the time.
Yesterday, I suggested the possibility of an abrupt upper wave amplification. Today it looks more like a gradual transition as you say, but I also agree that the coldness itself could arrive quite suddenly - I have seen such events in the past - but having just been rude about the latest ECM, I can't envisage quite such a rapid change as THAT shows!
It's all fascinating stuff!
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Hmm, I think the ECM has become demented judging by the 12Z! What HAVE we got? Arctic front activity? Sure looks like it.
Massive upper trough covering most of the N Atlantic and UK, and how about that intense HP over N Canada!
It seems a bit of stretch to say the least for such an amplified development to happen from T144 to T240 - a mere 4 days.. If such a pattern did, by some remote chance verify, the resulting actual weather would be interesting indeed - certainly cold enough for widespread snow - and such a trough would take some dislodging.
I await with great interest subsequent runs!
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Thanks OldMetMan that is one of the most informative posts I have seen in the model thread for quite a while...
My personal view is that the model output last wednesday indicated to me that a pattern change was on the way (by way of examples the GFS 00z of the time had almost all of the UK covered in snow which had not been seen up to that date, and it was from the East, in additon there was (and still is) very signfiicant spread in op and ensembles comparing all models), I believe the issue still yet to be resolved is the exact time of change.
With not very many years of model watching under my belt I am convinced that all of the models handle pattern change extremely badly, which is what I would expect given the low level of weather certainty we are able to achieve past 72 hours, and given the extremely difficult nature of modelling so many variables of which we do not completely understand the interaction of... Even though the modelling systems do not have defined bias, I think there is likely to be an inherent bias due to the nature of the inputs and our understanding of.
Thank you Buzzit. Yes I agree. In a way, I am glad that our current level of model sophistication is as it is, I like to see them get caught out from time to time, most notably by major pattern shifts as you mentioned.
I tend to be rather subjective in assessing the models as I will look at it in terms of how I have seen similar evolutions in the past. I know this is by no means a scientific approach exactly, but I have seen so many weather charts over the years, sometimes it works out!
Yes I too believe models, particularly the GFS, revert to what you could call an "average" circulation - a south-westerly flow in other words. There seems also to be particular points in a run sometimes where a model cannot decide between alternate future synoptic developments and then just reverts to the "average". Just an impression, I haven't a clue in mathmatical or physical terms how they work!
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Also, it is clear from all models that there is a strong signal for a block to our NE. But, there is great uncertainty as to when it will form, how strong it will be, and also how powerful the PV will be during this time. Until the block actually forms, model watching is going to be a pain.
Quite agree. The output beyond 120H is becoming increasingly erratic.The GFS still insists on basically keeping the mobile theme going in the medium- to long-term but for the medium term in particular, both the ECM and GFS just look plain wrong to me.
I'd agree that the shift from a SW to NW jet direction looks plausible up until around 120H, but beyond that we have the ECM and GFS developing new LP up near S Greenland and I think what happens after this is crucial and seems to be where the models are having trouble.
From a purely historical perspective, given the forecast situation at 120H, I would suggest that the new LP I mention above would more likely spiral down SE to join the low complex over Europe, introducing a NE flow as the Russian HP extends westward, possible linking to building HP in mid-Atlantic.For this to happen, there has to be a more decisive long wave amplification over the US and Canada. There are a few tentative signs of this happening now with the E Pacific showing increasing troughing and the jet energy heading on a more NE course in the mid-US, heading up into Canada. You can see this process happening on the WV satellite.
I keep banging on about the jet location and strength upstream from the UK and by creating a N Hemisphere animation of the last week or so, I can see there seem to be clear signs of long wave amplification, together with a gradual weakening of the polar jet into the NW US and Canada, and a stronger sub-tropical stream heading across Mexico and the southern States. All this suggests to me a gradual slowing down of the mid-latitude mobility across the US/Canada into the Atlantic, with most of the jet energy at sub-tropical latitudes. In other words, some mid-latitude blocking from the US to Europe in some form.
All conjecture I know but I sense an overall gradual transition to LP over the Mediterranean and HP building to the NE to NW.
We shall see how the models handle it within the next 2-3 days.
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It looks to me that the 18Z GFS is even weirder than the 12Z ECM. Beyond about 144H it seems to lose the plot and looks to be sending yet another powerful US jet in our direction beyond that time - with its common theme of zonality returning. And what happened to the LPs heading SE from S Greenland in the medium term?
Need to see the rest of the run yet though to see how it resolves.
Hmm, as I thought, the GFS just doesn't know what to do.
Just a thought, one possible scenario beyond 120H or thereabouts is for the HP to build NE and for the long wave pattern to sharpen abruptly - upper trough building SE from Canada, upper ridge building N towards Iceland and the Norwegian Sea, upper trough extending S and SW from Europe. The net effect would clearly be some sort of easterly, which sort dependent on where the centre of HP centres itself.
See what the UKMet says later.
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Today's model output has some interesting potential, plus an amount of confusion beyond about 144H,
The general consensus of the current block breaking down, followed by a more mobile westerly turning northwesterly looks reasonable, with the European upper trough amplifying accompanied by a steady decrease in thickness values as progressively colder air spreads south.
Beyond that, a variety of possible outcomes are given depending on which model and run time you look at. The 12Z ECM looks particularly weird as it doesn't seem to know where to go beyond 144H with deepening LP coming SE from Iceland and then E - doesn't look right to me. More likely I would have thought successive LP moving SE over and to the W of the UK tend to deepen the European upper trough until eventually we end up with an easterly and rising pressure to the N and NE - I've seen that happen a few times. Given that we still are forecast to have that Russian HP not too far away, I would bet on an easterly.
The GFS sort of does the above over a longer time scale but with an unsettled LP interlude until the final few charts for the 12Z which have a tantalising glimpse of some really cold continental air moving into the UK.
I can't shake the feeling that upstream long wave features are going to suddenly amplify, with a more pronounced mid-atlantic ridge and a general slowing down of the polar jet. I keep looking for clues in satellite imagery but, apart from the E Pacific trough deepening, there is not enough to go on at the moment.
All in all I would say this is a difficult situation to call, not just in the medium- to long-term but even within the next few days, as there are still changes from run to run in the detail of the timing of the HP breakdown, which is pretty unusual. Interesting though!
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I'm finding the model progression over the last week fascinating.
Two things that are catching my eye still. The intense HP over Russia is still being forecast by all the main models, and has a potentially significant role to play if the ECM end-of-run pans out - linking to HP near the UK as LP pushes towards Greenland with the chance of cold air filtering SW towards us. It was this kind of development I had in mind yesterday to happen sooner but with more model consensus today for the current block to dissolve, seems we'll have to wait a bit longer.
The other is the continuing amplification of the upper trough in the E Pacific which I still think could have a significant downstream effect - a ridge/trough pairing that could allow for an upper ridge to the NW and N of the UK and a European trough extending SW..
The GFS seems to have kept to a fairly consistent theme up until around 120Z but seems to have gone off in various directions after that in its different runs but it basically once more carries on relentlessly with the mobile development, in stark contrast to the ECM.
Once again, I shall look to the UK Met charts for the longer term trends.
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It seems the GFS is keeping to the same idea at 18Z. Also, the UKMet is killing off the current HP by T120 and is fairly close to the GFS.
Whether it is within the spirit of this thread or not I am not sure, but I sometimes think that, rather than simply comparing the different model outputs and what they show, perhaps each should be more subject to a "reality check",if you like, in terms of whether a particular model's predicted synoptic development looks realistic. By this I mean, are the stages shown from T0 to T120 (the only fairly reliable time frame I think) look as if they could happen as predicted, given the present starting point.
For example, we currently have something of a meridional flow, ridge over the uk, flanked by upper troughs either side, so does it seem reasonable for this to be bulldozed aside as shown by the GFS particularly? Are there other signs, other than model changes with successive runs, that suggest the predicted outcome of a model will actually happen? I am always pointing to satellite imagery, water vapour specifically but not exclusively, as it often shows the upper wave pattern very clearly and how it's changing (national hurricane centre uses this a lot to determine what going on aloft and where it is heading).
I also think it helpful to review recent developments to see how we got to the present situation and whether the models carry through the recent development in a way that looks possible.
Of course, this approach does assume some knowledge and experience how synoptic patterns can and have developed, with the proviso of course that no 2 situations are identical.
Forgive me mods if I am being in any way off topic with these ideas, or if this does indeed get discussed much more than I am suggesting (I don't always have time to read through the many interesting threads here) but I do like to read posts where reasons are given for why a particular model solution may or may not verify (for example, the state of the stratosphere). There is so much data available to review when attempting to see where the weather is heading so why not use all of it?
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Once again, the GFS 12Z brushes aside any potential HP blocking, while the ECM is still giving us a deepening upper trough with cold air creeping down at us from the NE.
I am finding it hard to see the synoptic reasoning of the GFS, and to some extent the ECM, given where we are at the moment. In the next few days, we seem likely to get a disrupting upper trough to our west, the upper ridge right over us and LP running NE around a growing large LP over N Canada and Greenland. Meanwhile, LP drops SE into E Europe whilst HP continues to intensify over N Russia.
In this situation, you would expect the NE moving LP heading towards Iceland to strengthen the upper ridge allowing the Russian HP to absorb our HP and start to spread very cold air SW towards us. It's quite a common scenario in my experience.Yet from around 96H to 120H both the ECM and GFS collapse the upper ridge and start bringing LP back down over the UK again, whereas only a few days ago, the GFS was insistent on keeping HP east of the UK, feeding coldish easterlies at us.
As I mentioned earlier, this seems to have everything to do with the strength and location of the polar jet coming out of the US, which, if it continues as it has for many days now, would indeed look likely to collapse any block.
I keep referring to the Water Vapour imagery and the E Pacific is clearly now showing an amplifying trough whilst the jet across the central US cannot seem to decide whether to remain in a split stream state or merge. I still think that most of the energy will head further SE with the polar jet itself weakening, allowing LP to be maintained over N Canada and even SE to off the US east coast, whilst the downstream flow becomes increasingly meridional, favouring the "Omega" block situation with an amplifying upper trough over Europe and the UK..
I think perhaps the UKMet might give us a better idea of post-96hr development later today - it's anyone's guess really whether the GFS will still stick to its story for the 18Z run!.
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All the models continue to tantalise with the promise of a significant change of pattern, although there is marked differences in how this is achieved.
One thing I notice all the models showing today is the presence of an intense HP over N Russia by about 120hrs. The upstream developments are a little difficult to fathom, as to which way they will go. The ECM is making more of the deep troughing over and to the E of us, which would favour an eventual pressure build westwards from the intense HP to the NE, as the trough amplifies. The GFS on the other hand is still keeping mobility going with no major blocking.
Further west the US has most of the jet energy across the mid-west but over the E Pacific there is increasing signs of a deeper trough developing, which would tend to amplify the downstream pattern. Alternatively, if this fails to materialise then we can expect the GFS to be nearer the mark in the long term with the polar jet still pushing LP NE out of the US and keeping pressure high over and to the west of the UK, cutting off any potential easterly from heading our way
I think we need to keep a close eye on US developments, especially the latitude and strength of the jet. I suspect that we may end up with a major trough off the US east coast, as the US jet heads on a more southerly track That would make the ECM the most likely outcome.
Either way, HP looks set to dominate our weather for some days. Interesting times ahead.
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Fascinating models today.
A mild/cold battle such as depicted by both the ECM and GFS we haven't seen in a while. Given the strength of the HP shown to develop, and the developing depth of cold over Russia, it would seem the cold would eventually win out.
Meanwhile, I still think the polar jet is shown as too strong and that most of the action will be to our SW rather than NW, but that remains to be seen. The crucial thing will be where the axis of the disrupting upper trough will be as this will determine the western extent of the initial cold air incursion, and thus any snowfall.
It will be very interesting to see whether the models show any sign of an extended cold spell by building HP towards Greenland.
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Today's runs continue to intrigue me with their comings and goings.
There's still a noticeable difference in the GFS and ECM in the mid-term and it's hard at this stage to see which is more likely to verify.
I think there is still a lot of uncertainty as to the strength and speed of the polar jet. The NCEP discussion yesterday mentioned that the models were suggesting a single jet developing across the US, from the current split flow. That would seem to be why the forecast block near the UK is fading with each run.
However, we still have 2 streams to the jet to our SW and NW and I think the models are banking on the US consolidated jet pushing E and for the southerly stream moving away.
But there is still a great deal of energy heading NE towards the southern US states from the Pacific, plus the powerful Pacific jet itself is showing signs of producing a deep low off the US west coast, setting up a downstream long wave amplification.
Personally, I think the southernmost Atlantic jet is more likely to be the stronger with the polar jet heading more NE and weakening. The net effect of this would clearly be to allow a stronger block to develop to our east.
I think that within a couple of days the situation will be clearer.
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Hi OMM
You asked/mentioned why models are now 'suddenly' picked this view/trend up, I have my views and indeed RJS predicted this....we're not there yet but huge improvement, but I go back to posts saying that the PV will be really hard to breakdown. Well if there are forces/influences timed not to break it down until approaching mid Jan, and we see it collapsing before our eye...is it really hard to break down? Or were there just no 'forces' at all into place to make any real atttempt until now and it never really was due to change until now? What I'm saying is take RJS theory, if it doesn't break down, move , split as aroungd his timings or of course GPs method then maybe yes its hard to breakdown.
Hi BFTP, thanks for that.
Today's models are even more interesting, GFS trying to return to zonality, the ECM sticking to its guns and setting up a cold blocking pattern. It's a little hard to fathom the differences, other than repeating the regular accusation that GFS defaults to a zonal flow.
I see what you are saying regarding the PV. The jet position and strength is clearly going to be critical if the model trend is to happen.
I've got a 200mb hemispheric chart that shows the current situation very nicely:
I was discussing jet locations yesterday and I think the current situation does favour a breakdown of the strong polar jet.
First, we have a split flow to our west. We need that at least if any easterly has any chance of developing.The most energy seems to be in the Pacific jet right now whilst the sub-tropical jet to our south is weakening and heading off E into S Europe and Asia. At the same time new energy is developing from the Caribbean and heading out into the Atlantic as well as the SE Pacific heading for Mexico and the Gulf.
Looking at the polar jet from the US to here, this has weakened quite a lot from what we have seen lately.
What I am trying to say in my roundabout way is that it looks to me as if we are seeing energy transference southwards with the main jet pushing eastwards to our south. The GFS is re-introducing the strong jet right at us again before any blocking can take hold and this doesn't look right given the current jet positioning. The ECM on the other hand looks more likely with a weaker polar jet to our NW.
Jet postions apart, with the current HP over us for a few days, the model development of a low plunging SE over E Europe and pulling in the extremely cold air from Siberia is a very reasonable prediction, one I have seen on many past occasions. With the very cold air comes the opportunity for intense HP to develop.
So, I think it all comes back to what I said at the beginning; jet position and strength and based on what I see in the current positioning, I would favour a block developing.
Of course, my reasoning could all be spurious! As always, I am happy to be corrected by those more knowledgeable about these technicalities!
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Very interesting to see 498dm thickness values moving into E Europe on todays' GFS end-of-run, must be the first time this winter. After weeks of persistent zonality it begs the question as to why it is now taking this trend. Such a scenario would quite probably drag very cold air towards us if it happened.
Interesting too is the ECM's HP over Scandinavia in 10 days, again something of a departure from previous days' runs.
I notice the early run of the GEM was suggesting a similar development.
Clearly a new trend is developing. The synoptic pattern up to 7 days looks quite reasonable for both the GFS and ECM; HP breaking down and LP moving in from the W, by which time it should be clearer if the deep cold air is starting to develop to our NE and E.
One current feature which I think might add some credibility to what the above model output is saying is what the WV imagery is showing. The sub-tropical jet that has been running at some speed across N Africa for weeks now appears to be fading, which suggests to me that the polar jet will move a lot further south in our longitude. At the same time, there is a lot of sub-tropical activity further W over the E Pacific and Caribbean. This might possibly mean a much greater long-wave amplitude - strong ridge over the E US with a deep and broad trough over much of the central and east Atlantic, with LP tracking much further south.
Meanwhile, a few quiet days make a welcome change - the model output give weak fronts within the HP so little chance of clearer air from the near continent to give any cold nights.
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The "block" in the Atlantic looks narrow though, and probably what you might call flimsy. Surely the secondary depression to the left would just smash through this and take us back to square one?
If the upper wave pattern does start to amplify as the ECM suggests, then the trough off the US coast would dig progressively further SE and pressure would buildin mid-Atlantic, probably over Greenland as well. Meanwhile, the same sort of amplification to the European trough would drag much colder air SW towards the UK.
Much depends on whether the meridionality persists, which it has shown a great reluctance to do so lately. If it doesn't, then yes it's likely the LPs will start pushing through towards us once again.
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Given the disparity between the 12Z ECM, which is still showing a much more meridional flow at 240Z, and the GFS still keeping to its zonal story, as an adjunct to the models, Water Vapour imagery provides a very clear picture of the current evolution of the long wave pattern. It is clear that amplification is happening both in the E Pacific and off the US east coast. Also, there is sub-tropical involvement going on, in the Atlantic as a small cut-off trundles westwards over the Canaries towards the jet which is almost to the Caribbean, and in the E Pacific as a tropical disturbance is moving N towards to mid-latitude westerlies off the Californian coast. Both these I have seen happen before quite well in advance of a major long wave amplification.
North Atlantic:
http://www.ssd.noaa.gov/goes/east/natl/flash-wv.html
North-east Pacific:
http://www.ssd.noaa.gov/goes/west/nepac/flash-wv.html
The ECM seems clearly to have picked up on this possibility. I would hope that the GFS will detect it very soon if it's likely to happen.
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It is always interesting and informative to read your posts Old Met Man. Your comments about the upper trough over southern europe historically being a precursor to arctic outbreaks over the UK is something I have noticed as an amateur over the years. As you say there could be some interetsing developments.
I think the mistake that many are making is that they are viewing each operational run of the GFS as gospel. Personally when it comes to the GFS. I tend to view it as we are told to view the later stages of its ensembles namely as a trend spotter. Regardless of any mild looking operationals the fact is that it keeps on coming up with more and more cold options from run to run compared to say a week ago or even a few days ago and it is this trend that needs to watched. The main thing that the entirety of the gfs product is telling us is that a change is coming. Which is likely to be a change to colder conditions and is also likely to come roundabout mid month which pretty much ties in with GP's thoughts in his winter forecasts.
Thank you Mcweather. I agree about the models, the latest 12Z GFS seems even more a case of, as Shunter puts it, "Default to Zonal". It's as if it cannot pick up anything beyond about 4-5 days that would suggest an alternative development pattern.
Yes, the extent of cold air coverage to our north is increasing with each run, but that could simply be a function of the increasing cold that develops anyway as we progress through January - I don't know if any such variable is programmed, or could be programmed into the GFS model.
I think the 12Z ECM might give a clearer picture of longer term trends. Interestingly, the GEM model, which I sometimes take a look at is in pretty good agreement with the 00Z ECM at 9-10 days. I don't often look at the GEM, it seems to be even more prone to predict zonal than the GFS.
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The models continue to keep the Atlantic LP train running.The meridional development I suggested the other day doesn't look likely - at least not yet.
Some interesting differences between the ECM and GFS in the longer term. The GFS continues to keep the zonality, with HP close to the south of the UK but the end of the ECM run shows some interesting possibilites, with a pattern that favours Arctic air sweeping south.That scenario looks more realistic, with that particular placement of HP, which would retrogress.
That development of strong HP nearby beyond 5 days does look reasonable for both these models, given that the upper trough over S Europe appears to be amplifying up until then. But that same upper trough has often existed historically soon before an arctic outbreak has occurred over the UK.
It is interesting to note that Water Vapour imagery is showing an increasing southward push of the jet, both in the E Pacific and the SE US over recent days and I think the models are depicting this trend to some extent. The problem seems to be that they seem reluctant to maintain any meridionality and just keep the mobility going.
It is worth remembering that most major cold outbreaks in the past have arisen following HP near or over the UK as the models are predicting
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Happy New Year folks!
I'm watching the 18Z GFS unfold and the situation depicted beyond 96hrs seems to be developing the N blast more than previous runs, albeit a bit too far east for the UK to get the coldest air. The whole development seems entirely reasonable given the European trough digging right down to Greece.
Yet again, the GFS is keeping things mobile after this brief Arctic blast but I question this. The Canadian cold pool has been in its present location for some time, with a powerful jet and baroclinic zone spawning LP after LP. I suggest that the deepening LP that distorts the flow from 96hrs has the potential to pull the cold pool much further SE towards Newfoundland and then still further SE into the W Atlantic, and set up a meridional flow.
From an historical perspective such a development is quite common and has led to several days' very cold Arctic air.
However, the ECM is backing the GFS up and is keeping it mobile with pressure high over the S of the UK so I think the next few runs will show more clearly whether such a development is likely to happen.
As an aside, the Water Vapour imagery in recent days has shown the gradual progression of the US jet southwards. We'll see.
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Hope everyone had a good Christmas.
I've picked up a couple of things from today's runs. First, the GFS is taking the jet further S after Wednesday's intense LP, with pressure much lower across the UK. Beyond that, the model reverts to the familiar SW zonal flow but with LP running further S before then, it brings the possibility of cold air breaking through.
The other thing I noticed was HP once again being forecast to start building over W Russia by the GFS. That, combined with the more southerly jet, again suggests a possibility of colder air breaking through.
Still no sign yet of any major long wave amplification.
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I think it's a shame that so many equate interesting weather only with snow and cold. Personally, after over 4 decades of being interested in weather, I can find interest in many different weather types. For example, today we had a very vigorous cold front, with heavy rain and squalls (wouldn't be surprised if someone somewhere had a tornado, or at least a funnel cloud), a temperature drop of 4C in around an hour, and the Atlantic is continuing to feed in further active LP.
What I can't stand is the grey, murky, slack anticyclonic muck we can get in winter, cold, miserable and sunless. Such conditions can go on for days - at least it's not like that.
Having said all that, in my younger days I eagerly awaited snow and can remember the amazing 1962/63 winter where, even on the Isle of Wight where I lived at the time, we had snow drifts on our lawn from December to March!
It hardly needs saying ,but it is wise not to set too much store by anything the models say beyond 5 days so it's not necessary to become despondant if they keep repeating the same pattern in the extended time frame. Looking at the latest model output, there is a consensus on the development of a vigorous LP around 28th, but I don't think they handle what happens very well thereafter. Yes, we still have a pretty intense jet out of the US but it looks more likely to me that a more meridional wave pattern will develop as the upper trough in mid-Atlantic amplifies.
I think we still need to watch for a pressure build over E Europe in the coming days - it's the absence of any blocking there that I think is keeping the model output mobile.
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Yes, it is a classic Bartlett from the era that we have all lived through and know so well.
Possible though that it may not last, unlike in those winters, as I suspect the models are wrestling with a struggle to change the pattern, which in itself of course may flatten again.
The trend has been maintained in the 12Z GFS, and the 12Z ECM, with cold air coming south and HP to the NW, so despite the time distance, it's a distinct possibility I think, and one that I can recall happening in the past (for instance the end of December 1970).
Yes, it's all a matter of whether the mobility will take over again and simply displace the HP and cut off any possible polar air incursion, taking us back more or less where we started. If the Omega block did stick (I like that expression!), then how it would affect the uk would obviously depend on where the axis of the upper ridge lies; it would need to be around 20-30W to allow the cold air to get anywhere near us.
My own view on how upper long waves increase in amplitude is that it might only need a deep LP say to engage a particular upper trough, and thus increase its amplitude, for the process to ripple downstream, with corresponding high amplitude ridge, then trough and so on. This is what the models seem to be trying to deal with so it could go either way really.
Model Discussion - 16th January
in Forecast Model Discussion
Posted
Thank you Weath20, I appreciate it. I expect some would argue that the reasons I give aren't exactly scientific at times. I am always willing to hear from those far more knowledgeable than me if I am talking nonsense!!