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phil nw.
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Posts posted by phil nw.
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There looks to be an ongoing trend to ridge heights later in week 2 but as yet no sign of troughing getting underneath.
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Yes the Euro models at least keep the cold air around the UK as opposed to the American models which favour the Atlantic keeping it milder next week.
It looks like a pattern change is underway with height anomalies increasing further north.
It's a complicated picture,the Atlantic is slowing against signs of rising pressure further north and east.
We can do without a protracted standoff,but it will take some days before we know where the pieces will fall.
Let's hope it gets a move on though.
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The interest is around T168 where all the runs show the Atlantic jet buckling as it comes against the ridging developing through the Uk.
We see they all try to move to the start of an easterly but not quite getting there at that stage.I do like the ukmo run though it seems less progressive at that stage and we can see the cold from Scandinavia starting to move this way.
The low that has finally moved east towards Denmark more of a feature and is almost acting like a trigger for the easterly.
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It's easy to be downbeat i guess as many of us have been disappointed this Winter but I think we need to give modeling time to see if the pattern can develop further.The ensembles are showing a pattern change towards a-AO but any easterly does not suddenly appear.
The first stage with Euro/Uk ridging is often unexciting until the high moves further north and we can get a low heights underneath.We know there is no certainty but we can only hope this comes to something before it gets too late in the season.
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Yes good to see.The UK/Euro ridging is in the ensemble guidance.Its a wait and see if we can get this further north.
Easterlies are always more than one simple step and often fail as we know from bitter experience.
Still we have to start somewhere and this is more positive than the dross that has been on offer recently.
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An early glance at the gefs height anomalies out to T180 clearly shows a change to the current pattern to a more blocked outlook.
Atlantic trough cut off as the jet weakens and European/Uk ridging north towards the high latitudes.
It may take a while to get the cold from that but often this is a route to northerly blocking.
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Jff off the 12z GFS
Thursday 9am.Freezing levels and snow area.
Shows how steep and narrow the boundary is between the Arctic and sub;tropical air masses as they meet over the UK.Understandable why the pros always find it difficult to pin point the exact locations for snow in these scenarios.Just a small wriggle,timing or angle in the approaching fronts can shift the pattern a few miles north or south which cause modeling to change at short notice as we have seen recently.
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Just putting these here T72hrs
Even at this range there are subtle differences and by day 5 the raw UKMO looks to send the low east rather than north so this really is a messy scenario.We should hope we do get that low east eventually which does help to keep the cold air close by and return it south over the weekend.
It has to said none of the current outcomes are good for deep cold with gfs and ecm mixing the colder uppers out because of the low movement dragging the pattern north.We do have a better chance with the UKMO but even that isn't what we really wanted,it just keeps some cold around.
The underlying problem on the whole setup of course is the lack of blocking heights to our north.
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Comparing the T84 fax with gfs 06z we can see the fronts are further north on the gfs by Thursday 12z
The gfs has run 6hrs later of course but given this morning's met office warnings which fit the fax you would tend to favour their view based on their short range data.Having said that there is still room for a small change even now as we are looking at a wriggling set of fronts extending from a complex developing area of low pressure out in the Atlantic.
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The latest fax at T84 showing the progress of the cold front which looks like reaching the south coast later Wednesday and alongside the raw 850,s for that time.
A good visual of the long boundary separating the 2 airmasses from the Atlantic into Russia.
We can see the low complex and it's fronts lurking to the south west ready to head into the cold air in place over the UK. where some part of the country will see snowfall on the northern edge of this.
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I think it's becoming increasingly likely we will see an Atlantic high or strong ridge development ,once the trough heads east next week end.
Ensemble guidance is trending that way and this opens the door to the cold heading south.
What follows that will be interesting.
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Just a brief overview of the coming week or so as i deduce from current outputs.A messy pattern coming next week with lows moving in on a more southerly track for a short period bringing the possibility of a battleground across the UK and the possibility of snowfall on the northern(cold) side
First the present picture and we can see the effects of this mild westerly on much of Europe with the cold pushed way east and north.
The Iberian high again the bad smell that hangs around but later in the week he does get pushed south as the cold upper trough tries to make headway from the north so we see a battleground across the middle of the UK
ECM mean and last night's fax shows there is still a little wiggle room on the exact progress south on this but it looks like any snowfall is favoured north of the Trent as the front stalls before easing north again.
The next low to the south west is modeled to swing ne across Scotland by the end of next week so a slight warm up before we get the colder air returning from lee northerly as the whole low complex moves east.
The day 10 eps mean anomaly heights continue to show the lack of solid Arctic blocking which, apart from the brief early December GH,has been the theme so far this Winter.
Frustrating to see cold air lurking just to our north at times but no forcing from high latitude blocking to bring it further south.We have seen brief incursions of cold at times, especially for Scotland ,mainly from the movement of the jet tracking further south,but because of persistent mobility these are all too brief.This coming week is a good illustration of this.
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At the moment I am not too impressed with the models wrt sustained cold next week.
Some may get lucky with snow but it's all very marginal in such a mobile cyclonic setup.
No northern blocking to sustain a cold feed so the coldest temperatures will mix out under these conditions.
Maybe this is just the taster for something better beyond mid month but for now the current output is all a bit underwhelming until those Northern heights appear.
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Yes ECM gets the cold south a bit later than gfs/ukmo but essentially the same trend.The lack of northern heights means we are subject to these micro changes and in this case it takes a little longer for the any upstream mini ridge to force the next low on a more southerly track.
Just noticeable that there appears to be no development of any heights further north after the initial cold gets in so the colder uppers look like being modified later on,so maybe a cold snap rather than anything long lasting based on gefs.
Disappointing if this turns out to be the case.
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Well the waiting for another cold spell looks like bearing fruit.A fascinating watch next week as we monitor the track of the cold/mild boundary gradually fighting it's way south.
Snow is likely as low pressure slides in against the Arctic plunge if this setup does verify.
Actually although we rely on wedges to get the cold here this cyclonic pattern does bring more chances of different areas seeing snowfall as the front ripples south-compared to a GH which often brings a dry northerly away from the far north and windward coasts.
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Just coming over the horizon of nwp in week 2 is a pattern change now,from mild to something colder.
Still early days but enough of a change in the 500 anomalies to take notice.
The concern currently is the lack of amplification in the Atlantic pattern so any cold from the north will struggle to get far enough south to cover the whole of the UK..
This of course may well change as we go further on.The lowering of heights to the south and increasing heights to the north west shown in the ensemble means and clusters is a good sign and the essential first stage to a colder set up.
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I haven't posted much recently as the modeling continues to remain uninspiring in the short term.
There are some signs of a pattern change in week 2 with height anomalies appearing in the Atlantic in the ensembles but the Euro heights remain stubbornly present, maybe a little move west with time.
Zonal winds remain relatively strong at 10hPa but lower down there is a forecasted weakening and depending on some help from the mjo may provide something colder as we head beyond day 10.
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Difficult to see an end to the mobility yet.
Signs of the main spv heading towards the Siberian side later but the 500 pattern continues to keep a small section towards Canada.
Some interludes of colder westerly winds as the lows pass across but it is still essentially a waiting game for a pattern change towards any notable cold spell.
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If we are to get another cold spell it is odds on now that we are looking well into February based on all nwp outputs.
My hope is that the recent brief ssw will downwell and along with mjo moving out of the warmer phases will shake the pattern up.
It is all about the time lag though and this change is over the horizon of current modeling.
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Just now, bluearmy said:
I wouldn’t disagree Phil but seeing as we get to see the cross sectional that goes with op run, we may as well have a gander
Indeed why not
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4 minutes ago, bluearmy said:
It could be a downwelling wave from the warming at the end dec into Jan. three to four weeks wouldn’t be outside the expected range. The cross sectional of the atmosphere later may show how the weaker flow comes about through the run.
Looking on the 3d profile on Stratoserve the spv looked in good order after the bottom split reforms.This is of course from previous runs.I didn't see any sign of downwelling waves on those Nick.
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15 minutes ago, feb1991blizzard said:Not sure if it does happen it will be strat lead, its more likely from trop lead tropical forcing in the pacific.
Yes I think so feb.The split today quickly reforms hence the collapse of our block later this week.
It looks like any Scandinavian heights will come from the expected mjo movement and momentum increases.
Good to see Gfs is starting to pick this up.
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It is quite notable how quickly we change the pattern over the coming weekend as the Atlantic moves in.
For now we are in the cold Arctic airmass with night frosts,some freezing days and snow showers about ,the conditions more severe further north as usual in this northerly setup.
Looking at current conditions and the 500hPa pattern for Europe pretty much gives the picture this week.Cold everywhere in Europe away from the far south west.
Then a complete switch around looks to be established by early next week
A return of the westerlies and switch to a +NAO/AO setup as the block collapses and we see a replenishment of cross polar -ve anomalies across the Arctic.
For many of us that won't see any snow this week is ,too me,is still the preferred conditions with blue skies and crisp sunshine allowing the ground to dry out.
Next week back to mild and some damp days but if milder weather is sought then this will be your thing with double figure daytime temperatures back on the menu.
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46 minutes ago, nick sussex said:
So the bitter irony and one we’ve seen before is the strat warming turns up and messes up the blocking by moving the PV .
It’s bit like heads you lose tails you lose !
From what I could see from the recent Strat.charts Nick we have a split up to mid levels in the next 3/4 days.
It looks like a bottom up warming but unfortunately it doesn't last and the 2 sectors quickly reform.
This was forecasted days ago and the milder turn at the end of next week has also been in the ensembles for a few days.
The breakdown looks to be a day or two quicker than expected though.
The main disappointment for myself and many others I guess is the less likely protracted breakdown giving a snow event before mild wins.
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Model Output Discussion - Spring Has Sprung
in Forecast Model Discussion
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I share the frustrations.
We are heading for a notable -AO indicating an even weaker pv but still we can't get the cold here.
The Atlantic pattern still remains unfavorable with the influential ridging again from the sub tropical/Iberian area often thwarting the southerly extent of cold.
I can't remember a Winter with so many obstacles that seem to crop up from promising background signals.