Model Output Discussion - 1st February Onwards 12z--->

[fergieweather]

 

The last ECM forecast had the MJO going into phase 8 at around the same strength as the statistical models however looking at its output its not really picking up the baton.

 

EC and MOGREPS both strongly signal the restablishment of dominant westerly-biased anticyclonic cell after the trickier/uncertain period Thurs-weekend. All in keeping with the key drivers....the (effectively stationary) Rossby wave out across eastern CONUS looks set to continue steering cyclonicity on more northerly track across the western North Atlantic, whilst warm advection ahead keeps reinforcing the ridging out west of the UK. Could take some time to budge that, albeit as noted earlier, both EC-M and GS5 agree on a shift to a zonal W-NW story into turn of month, with temperatures around average then.

[Hotspur62]

Looks like any potential cold spell after mid month looks unlikely if I have interpreted Ian Fergusson's above post correct . Still time for things to change but I had hoped for a Scandi High to develop after mid month but that is probably wishful thinking now and Met Office have been bang on the money this winter so well done to them and with the above comments from Ian have no reason to doubt them this time either. 

 

I wonder if the delightful Tamara is about as would be interested to see what her comments are and if her thoughts have changed since her last excellent post I read I think couple of days ago(btw fair play to her and Tom snow chasing yesterday-That is what I call dedication !!-See SE Regional Thread for details)

[fergieweather]

Looks like any potential cold spell after mid month looks unlikely if I have interpreted Ian Fergusson's above post correct . Still time for things to change but I had hoped for a Scandi High to develop after mid month

There's every possibility of disturbances running down the eastward flank of the high to usher-in phases of colder weather for at least the N and E of the UK. A variety of such outcomes appear in some of the 00z EC clusters, but all in transient fashion.

[Hotspur62]

There's every possibility of disturbances running down the eastward flank of the high to usher-in phases of colder weather for at least the N and E of the UK. A variety of such outcomes appear in some of the 00z EC clusters, but all in transient fashion.

"transient" being the key word unfortunately lol. A cold snap maybe, but the chances of a cold spell seem to be diminishing.

[winterof79]

"transient" being the key word unfortunately lol. A cold snap maybe, but the chances of a cold spell seem to be diminishing.

We are in a cold spell and quite a few have had transient falls of snow,some of which have dropped quite a few inches.The fact that more are a possibility is a plus and beats the pants off last winters feeble attempt.

A period of dry cool weather is to be expected in any winter and some will have fantastic hoar frosts while others cloud.I like the sound of systems running in from the n/nw.

[Weather Wizard]

A transient spell like 11th-14th Jan 1987 would be ok though 

[Nouska]

I think high pressure is likely to be close by but its just where exactly it sets up that's more uncertain. Further nw of course brings some colder potential for the UK.

 

It might be CC that the MJO may well be muted out somewhat, we'll know over the next few days because if somethings going to happen in the NWP then I'd expect it to show very soon.

 

The NWP output is not surprising given that two of the key drivers of weather signal high pressure cells in the vicinity of the UK.

 

The MJO wants to perform handbrake turns in phases seven and eight....

 

 

...and the ENSO composites for the warmer three/four sector are also high pressure dominant.

 

Edited February 6, 2015 by Nouska

[polar vortex]

The GFS has in my opinion trumped the Euro's again this time with the MJO signal. I would not be at all surprised to see a much more 

amplified pattern going forward from mid month onwards with the risk of some really potent Arctic outbreaks.

Having said this I would expect the models especially the GFS to be picking this up in its longer output. No reason what so ever to feel 

disheartened by the Meto update. Although they have been fairly good this winter they can and do get it wrong.

Below are the last 3 days OLR anomalies. Certainly looking quite impressive.

[Tamara]

The answer for the reluctance of the MJO to attain higher amplitude is because of the repeated low AAM base state of the atmosphere.

 

The story of the winter :-

 

Negative (easterly) tendency in the atmosphere fires up convection in the Western Hemisphere - and hence the MJO signal is at highest amplitude in its earlier phases. Progress of the convective wave is halted by the repeated Nina-esque re-cycling state of the atmosphere, which increases negative AAM tendency in the tropics (manifested as easterly trade winds) . This easterly momentum, pumps up the sub tropical anticyclones, such as the Azores High, to mid latitudes, while at the same time over Indonesia and the Philippines these fresh bursts of easterly trade winds re-fire strong convection which perpetuate restricting the higher amplitude phases of the MJO the 'wrong side' of the globe.

 

Therefore, each time the GWO cycle orbits through -AAM phases 1/2/3 it drives AAM tendency downwards, re-initialises the low angular Nina state of the atmosphere, and causes the MJO to lose amplitude in its eastwards progress and beat a retreat to where the convection has re-fired once more in the Western Hemisphere.

 

However, since mid January we have seen atmospheric tendency attempt to neutralise towards mirroring a neutral ENSO state and hence rather more in the direction of the underlying weak El Nino oceanic state (otherwise overridden this season)

 

The corresponding GWO Phases 3/4/5 to this more Nino like atmospheric signal have just orbited for the second time since Mid January and a second +MT has occurred.

 

The effects of these +MT's over East Asia are to help assist displacing the vortex to our side of the pole. We have also seen the advantage of this when the Pacific pattern has retrogressed because it has also enabled the MJO to progress rather further at higher amplitude in its cycle as the Nina signal has been, very temporarily, muted.

 

The GWO orbit however is returning us back once more to -AAM tendency state as the GWO orbits through Phase 0 towards and then through Phase 1.   

 

It is this fresh Nina atmospheric signal which is behind the MJO low amplitude forecasted phase state.

 

This signal, in beefing up the tropical signal, re-strengthens the sub tropical ridges, and hence overrides the -NAO potential of MJO Phase 8 because the default convection signal is re-initiated.

 

In truth, with the atmosphere in co-operative state with the ocean (El Nino) we would not currently be looking at a mid latitude high to follow the recent protracted amplification in the Atlantic - but a higher latitude block instead, and no doubt some kind of undercut.

 

It is in this way that the GWO orbit can give us a guide which way the weather patterns are likely to head. Nina like -AAM tendency does not support higher latitude blocking in the winter months. We are restricted to Atlantic amplifications whilst the GWO is in favourable amplification phasing.

 

This is exactly what we have seen so far.

 

However, assumed persistence of this regime into March will start to have different implications.

 

Shorter wavelengths under -AAM will become more and more conducive to cold air being expelled from the Arctic. Anticipation of increasing amplification through February (the trend has been responsive as suggested since Mid January) leading to better blocking prospects has been based on the atmospheric signal being more and more co-operative for longer and longer each time than we have started to see since the middle of January.

 

Traditionally this frequently happens in weak El Nino winters and is why they often feature 'end-loaded' winters for cold blocking.

 

This one is trying hard not to follow the script. However, with two GWO orbits into higher angular momentum territory in the second half of the winter supporting a favourable displacement of the vortex, it wouldn't take too much of a further atmospheric change of signal to lead to much better amplification potential than the seeming nothingness of a string of mid latitude ridges eating up remaining valuable time.

 

That higher amplitude MJO would be the trigger to improve the holding pattern. Some of the reasons though have been given in this post as to why this is proving stubborn to achieve through this season.

 

Late Edit: pm was sent to polar vortex

Edited February 7, 2015 by Tamara

[Hotspur62]

We are in a cold spell and quite a few have had transient falls of snow,some of which have dropped quite a few inches.The fact that more are a possibility is a plus and beats the pants off last winters feeble attempt.

A period of dry cool weather is to be expected in any winter and some will have fantastic hoar frosts while others cloud.I like the sound of systems running in from the n/nw.

Don't get me wrong as you say this winter has been a massive improvement on last winter and without sounding too much imby some in the South have still not seen a flake in nearly 2 years. I appreciate that those in NW Britain have fared much better and good luck to you(At least some of UK have had decent snowfall this winter lol)

 

I reiterate I think the Models have performed pretty well this winter, esp the GFS and I cannot remember once where they have shown decent heights in the right places for cold as a trend so in that respect the current coldish spell we have had this last 9-10 days could be seen as a bonus if you like.Im think the problem was we have been spoilt a bit in previous years so the last 2 winters have been big disappointments in terms of snowfall.

 

As you say, the next best thing is frost and I look forward to hopefully pleasant late winter days after morning frosts which what the models indicate as a possibility in the next 10-12 days.

[Captain Shortwave]

Day 6 charts

 

GFS

 

UKMO

 

Both models show a renewed push of heights from the Azores reinvigorating the high present over the UK in into central/northern Europe.

Unlike a few I just cannot see any real sign of even producing a transient northerly at the moment (though there have been very cold outliers within the ECM and GFS ensembles). Both the GFS and UKMO would suggest that high pressure would continue to dominate for at least another 3-5 days which would take us to around 10 days already. 

Whilst things can change, I think high pressure will sit around the UK for probably 2 weeks before it breaks down beyond the 20th February from increasing low heights to our north west trying to sink south east again into Europe, how unsettled or cold is still up for debate but given these are signals from the longer range models then this could easily disappear.

 

GFS at day 8

High pressure well and truly in charge

Edited February 6, 2015 by Captain shortwave

[Ali1977]

I know it's only Feb, however I think any meaningful cold may have passed us by this year, unless of course we repeat March 2013. This was a once in a life time event however, so not sure that will happen.

With this pattern looking stubborn till end of Feb I fail to see any country wide low level snow as an option....So with that, I for one am hoping for an early spring, and hoping for some proper winter next year.

[warrenb]

I think we have the block of all blocks here. It is not for moving.

[igloo]

the chances are if we have HP over us for at least the next fortnight it will at some stage land in a more favorable position in any case it looks a good time to do some outdoor jobs around my garden my shed badly needs painted and guttering cleaned

Edited February 6, 2015 by igloo

[EML Network]

Is this what they call home grown cold ? 

 

What a bleak and boring outlook

 

[Cloud 10]

ECM versus GFS at 168 hrs.

 

ecm..  gfs..

 

 

@confused.com

[Winter Cold]

Well a big change on ECM tonight. No sooner does Fergie suggest a possible low next weekend then it throws this out! Been no sign up until now on any output I dont think? Amazing

 

[TEITS]

Whilst the ECM  is rolling out I want to highlight the GEFS control.

 

 

Before anyone says I am merely highlighting the chart below towards all those posts saying "Winter is over", "No chance of snow anymore for low lying areas"!!

 

 

 

Just add how the ECM differs with regards to the low pressure in the Atlantic between +120 & +168 shows our outlook is far from certain. The ECM has this tracking SE into the Med, other models NE into Scandi!

Edited February 6, 2015 by TEITS

[Mucka]

Well a big change on ECM tonight. No sooner does Fergie suggest a possible low next weekend then it throws this out! Been no sign up until now on any output I dont think? Amazing

 

 

 

I don't want to put words in Fergies mouth but I don't think this is what he had in mind, more a glancing blow from a shallow trough rather than a low diving South through the UK and into the continent.

I think this is an extreme solution in that regard but Fergie can correct me if I misinterpreted his post and I'm going off memory.

 

Regardless it has very little support and looks like yet another ECM Op misstep of which there have been many this winter.

We will know tomorrow if there is anything more to it.

Edited February 6, 2015 by Mucka

[seaside 60]

ECM versus GFS at 168 hrs.

 

ecm..ECM1-168.gif  gfs..gfs-0-168.png

 

 

@confused.com

HOw different are those two models, quite impressive really.

I think we all know which one is more realistic...

[chris55]

That ECM is a classic example of how runs out beyond 144 are never ever set in stone.

 

 

Not really sure how this may effect the UKs chances of a late winter cold-mageddon we are all (most) on the look out for, but with the GEFS throwing out all sorts and this big swing from the ECM det, whos knows what's round he corner!!!

[TEITS]

I don't want to put words in Fergies mouth but I don't think this is what he had in mind, more a glancing blow from a shallow trough rather than a low diving South through the UK and into the continent.

I think this is an extreme solution in that regard but Fergie can correct me if I misinterpreted his post and I'm going off memory.

 

Regardless it has very little support and looks like yet another ECM Op misstep of which there have been many this winter.

We will know tomorrow if there is anything more to it.

I think you will find the low ends up just being centred E of Ibiza.

 

In my experience when you have one model sending a LP into the Med and other models sending this NE towards Iceland/Scandi then maybe none of the model output can be trusted and the outlook becomes rather uncertain.

[polar vortex]

The answer for the reluctance of the MJO to attain higher amplitude is because of the repeated low AAM base state of the atmosphere.

 

The story of the winter :-

 

Negative (easterly) tendency in the atmosphere fires up convection in the Western Hemisphere - and hence the MJO signal is at highest amplitude in its earlier phases. Progress of the convective wave is halted by the repeated Nina-esque re-cycling state of the atmosphere, which increases negative AAM tendency in the tropics (manifested as easterly trade winds) . This easterly momentum, pumps up the sub tropical anticyclones, such as the Azores High, to mid latitudes, while at the same time over Indonesia and the Philippines these fresh bursts of easterly trade winds re-fire strong convection which perpetuate restricting the higher amplitude phases of the MJO the 'wrong side' of the globe.

 

Therefore, each time the GWO cycle orbits through -AAM phases 1/2/3 it drives AAM tendency downwards, re-initialises the low angular Nina state of the atmosphere, and causes the MJO to lose amplitude in its eastwards progress and beat a retreat to where the convection has re-fired once more in the Western Hemisphere.

 

However, since mid January we have seen atmospheric tendency attempt to neutralise towards mirroring a neutral ENSO state and hence rather more in the direction of the underlying weak El Nino oceanic state (otherwise overridden this season)

 

The corresponding GWO Phases 3/4/5 to this more Nino like atmospheric signal have just orbited for the second time since Mid January and a second +MT has occurred.

 

The effects of these +MT's over East Asia are to help assist displacing the vortex to our side of the pole. We have also seen the advantage of this when the Pacific pattern has retrogressed because it has also enabled the MJO to progress rather further at higher amplitude in its cycle as the Nina signal has been, very temporarily, muted.

 

The GWO orbit however is returning us back once more to -AAM tendency state as the GWO orbits through Phase 0 towards and then through Phase 1.   

 

It is this fresh Nina atmospheric signal which is behind the MJO low amplitude forecasted phase state.

 

This signal, in beefing up the tropical signal, re-strengthens the sub tropical ridges, and hence overrides the -NAO potential of MJO Phase 8 because the default convection signal is re-initiated.

 

In truth, with the atmosphere in co-operative state with the ocean (El Nino) we would not currently be looking at a mid latitude high to follow the recent protracted amplification in the Atlantic - but a higher latitude block instead, and no doubt some kind of undercut.

 

It is in this way that the GWO orbit can give us a guide which way the weather patterns are likely to head. Nina like -AAM tendency does not support higher latitude blocking in the winter months. We are restricted to Atlantic amplifications whilst the GWO is in favourable amplification phasing.

 

This is exactly what we have seen so far.

 

However, assumed persistence of this regime into March will start to have different implications.

 

Shorter wavelengths under -AAM will become more and more conducive to cold air being expelled from the Arctic. Anticipation of increasing amplification through February (the trend has been responsive as suggested since Mid January) leading to better blocking prospects has been based on the atmospheric signal being more and more co-operative for longer and longer each time than we have started to see since the middle of January.

 

Traditionally this frequently happens in weak El Nino winters and is why they often feature 'end-loaded' winters for cold blocking.

 

This one is trying hard not to follow the script. However, with two GWO orbits into higher angular momentum territory in the second half of the winter supporting a favourable displacement of the vortex, it wouldn't take too much of a further atmospheric change of signal to lead to much better amplification potential than the seeming nothingness of a string of mid latitude ridges eating up remaining valuable time.

 

That higher amplitude MJO would be the trigger to improve the holding pattern. Some of the reasons though have been given in this post as to why this is proving stubborn to achieve through this season.

Not sure this is the reason at all.At the present time we have strong westerly wind burst near the date line with strong convection. Easterly trade winds are weaker than they have been plus you can see quite easily on the synoptic models

the amplification over western north America and into the Arctic on the opposite side of the pole.

Stratospheric forcings are probably very much involved but with what I believe will be a increasingly strong MJO signal this may help to override the lower strat signals and we see a tropospheric response perhaps into the lower strat.

Overall I remain very optimistic for the last 8 or 9 days of the month.

Edited February 6, 2015 by polar vortex

[chris55]

I don't want to put words in Fergies mouth but I don't think this is what he had in mind, more a glancing blow from a shallow trough rather than a low diving South through the UK and into the continent.

I think this is an extreme solution in that regard but Fergie can correct me if I misinterpreted his post and I'm going off memory.

 

Regardless it has very little support and looks like yet another ECM Op misstep of which there have been many this winter.

We will know tomorrow if there is anything more to it.

 

 

He mentioned the uncertainty re Lows passing over the UK towards Friday on the Points West forecast just now.

[chris55]

HOw different are those two models, quite impressive really.

I think we all know which one is more realistic...

 

 

I don't?? But thats more to highlight the uncertainty, than giving either model bias.