Model Output Discussion 29th December - Into mid-Winter.

[Nick F]

8 minutes ago, Glacier Point said:

There is a view, one which I would endorse, that the RMM Indices are not capturing fully MJO activity. For example, right now, upper and mid tropospheric winds are flowing all the way across the West and Central Pacific all the way to the East African Coast. Likely convergence and convective activity around West Indian Ocean (MJO Phase 1).

Yes, I have been keeping tabs on Kyle MacRitichie's realtime MJO and 30 day CFS MJO forecasts - which have been propagating MJO out of COD, unlike the EC/GFS/JMA/UKMO, from phase 6 (today) through phase 7/8/1 later this month

Edited January 11, 2017 by Nick F

[Seasonality]

5 minutes ago, snowice said:

IN relation to the uppers shown by ECM and GFS if the Easterly comes.

There is three days snow forecast for Warsaw in Poland and by Wednesday next week day time temps are -10.

My point is heavy snow forecast for the weekend that should enhance the uppers next week as the event hasn't happened yet,

and  i do not believe the models account  for this.

 

There is a little snow forecast for Thursday, Friday and Saturday and a brief "warm" up consequently as a blip of warmer uppers come in from the west (maybe some sleet too). Thursday may see the heady heights of +2 degrees C reached during the day with +1 on Friday if you take the ECM output as read (I'm sure UK coldies would love to be afflicted with such a situation!). Then by Saturday sub zero again and cooling as colder uppers dig in from the euro trough and later the easterly influence increases the chill. The colder weather is not "caused" or enhanced by the brief milder and wetter conditions but as a result of the pattern that follows. What I'm trying to say is that you've spotted the correlation but the causation is something rather different. Rest assured the models account for this, but I'm with you in the statement that the uppers may well  improve.

[nick sussex]

1 minute ago, Nick F said:

Yes, I have been keeping tabs on Kyle MacRitichie's realtime MJO and 30 day CFS MJO forecasts - which have been propagating MJO out of COD, unlike the EC/GFS/JMA/UKMO, from phase 6 (today) through pahse 7/8/1 later this month

Its very hard to have a lot of confidence in these forecasts when they can't even agree where the true MJO signal is currently located. I read the research paper by MacRitchie and Roundy and they seemed to make a better case for not using the normal Wheeler and Hendon one as that had too much interference from other factors. I think the issue that's constantly causing probs is those cyclones and Rossby wave interference aswell as the complications surrounding Kelvin waves.

[Singularity]

16 minutes ago, nick sussex said:

Given Nick F's post this really calls into question the UKMO view which completely dismissed any MJO influence. How on earth they can make that call is beyond me. They should at least wait to see if the signal continued its movement out of the COD.

December 2015 into January 2016 there was an active MJO phase (eventually responsible for the colder spell mid-Jan but severely limited by the raging vortex) which the Met Office dismissed the chances of in the run-up to it kicking off. GEFS were by far the most keen with ECMF the least keen. We seem to be in a similar position this time, except back then the activity was 7-8-1 whereas this time it's 8-1 or 1-2.

So the MJO is, perhaps, the Met Office's Achilles Heel.

Over the past fortnight I've generally taken the approach that the models are repeatedly showing broad-scale patterns which correspond well to 6-7-8 MJO activity, therefore there's a good chance it's taking place, regardless of what many of the usual measures are showing.

[nick sussex]

3 minutes ago, Singularity said:

December 2015 into January 2016 there was an active MJO phase (eventually responsible for the colder spell mid-Jan but severely limited by the raging vortex) which the Met Office dismissed the chances of in the run-up to it kicking off. GEFS were by far the most keen with ECMF the least keen. We seem to be in a similar position this time, except back then the activity was 7-8-1 whereas this time it's 8-1 or 1-2.

So the MJO is, perhaps, the Met Office's Achilles Heel.

Over the past fortnight I've generally taken the approach that the models are repeatedly showing broad-scale patterns which correspond well to 6-7-8 MJO activity, therefore there's a good chance it's taking place, regardless of what many of the usual measures are showing.

Yes I remember that but what really surprised me yesterday was that on the day the forecasts were showing movement of the MJO and NCEP thought there would be a strengthening of the MJO the UKMO come out and dismiss it out of hand citing the EPS as not being interested when the ECM also agrees on movement. Even if its a lowish amplitude signal they still can't be sure it won't have some effect and they basically said no influence on the NH pattern for the next 25 days!

[pyrotech]

1 minute ago, Iceaxecrampon said:

Class.

How marginal has this turned out...! - coupled with near coastal position non event on the cards.

Even Cumbria is dry.... 

Will see.

That does not show Cumbria as dry

That shows Cumbria as not in a warning area, Warnings are done on two objectives

The risk and likelihood

It shows that snowfall in Cumbria for that time is lower risk and with it the effect on snowfall effect on people and infrastructure.

Its also subject to change as slight alterations in wind direction can change the warnings even as late as hour before.

Precipitation from showers is likely to be dying as it moves southwards towards that region but as looking at the models that by no means a certainty as if winds moved slightly more west convection from North sea would enhance them 

[Singularity]

36 minutes ago, nick sussex said:

I'd happily accept the JMA at T84hrs, its 06hrs run is more amplified than the GFS.

So of the 3 global models this morning with 06hrs outputs all have increased the upstream amplification. We have one good model the GFS, one not so good the JMA and one only to be viewed in desperate times the NAVGEM also increasing that amplitude, that's only upto T66hrs so far but  better than its 00hrs output.

It seems the models are still having a problem with that area around Iceland, until this is resolved we won't know our starting point for how vertical any ridging might be to the n/ne.

Two quote notifications from me this morning, times are busy 

Yes good trends there, and when it comes down to it the whole area S. Greenland to Iceland is a troublesome one for the models due to the frigid air and high ice sheet of the Greenland landmass which can result in steep thermal gradients coming and going in very short spaces of time, and the potential for localised modification of airmasses by cold pooling across Iceland that could tip the balance between a shortwave low developing or not.

When lows are trundling by to the south of these places we see less chaotic model output, as disturbances don't tend to develop on the northern flanks.

A major trough passing to the north of Iceland is not something we see every day - hence these 'Murr Sausage' type Scandi Highs are few and far between. Very interesting to see how it all pans out in the end.

[Singularity]

5 minutes ago, nick sussex said:

Yes I remember that but what really surprised me yesterday was that on the day the forecasts were showing movement of the MJO and NCEP thought there would be a strengthening of the MJO the UKMO come out and dismiss it out of hand citing the EPS as not being interested when the ECM also agrees on movement. Even if its a lowish amplitude signal they still can't be sure it won't have some effect and they basically said no influence on the NH pattern for the next 25 days!

Three notifications now 

I agree it seems very strange on this occasion - as if they are looking at a different version of the ECM ensembles somehow!

Indentically, we'd all be jumping for joy if the MJO followed the EC monthly going into Feb:

This is similar to the update of a week ago, but with more of a loop through phase 1.

Phase 7-8 in Feb is basically BOOM time.

 

Prepare your prayers! 

[Alexis]

7 minutes ago, pyrotech said:

That does not show Cumbria as dry

That shows Cumbria as not in a warning area, Warnings are done on two objectives

The risk and likelihood

It shows that snowfall in Cumbria for that time is lower risk and with it the effect on snowfall effect on people and infrastructure.

Its also subject to change as slight alterations in wind direction can change the warnings even as late as hour before.

Precipitation from showers is likely to be dying as it moves southwards towards that region but as looking at the models that by no means a certainty as if winds moved slightly more west convection from North sea would enhance them 

But that just means the risk is that it will be more likely dry than not?

[Troubleatmill]

13 minutes ago, Iceaxecrampon said:

Class.

How marginal has this turned out...! - coupled with near coastal position non event on the cards.

Even Cumbria is dry.... 

Will see.

Right through you and me in Penwortham, I think we will just miss out again, took tomorrow off to go up Wetherlam too! 

Ensembles are a big improvement going forward though, far more are picking up a colder feed as we go into next week, most promising set we have seen I think, up to now (apart from the one GFS run yesterday) the GEFS ensembles were steadfast with high pressure further south and a milder Atlantic influence.

 

Good signs

 

[warrenb]

ECM ensembles good, latest meto 15 day outlook is good (which uses the Meto ensemble), JMA is good,  That is all I need.

And a Meto level 3 cold weather alert. It is coming together nicely

Edited January 11, 2017 by warrenb

[Iceaxecrampon]

16 minutes ago, pyrotech said:

That does not show Cumbria as dry

That shows Cumbria as not in a warning area, Warnings are done on two objectives

The risk and likelihood

It shows that snowfall in Cumbria for that time is lower risk and with it the effect on snowfall effect on people and infrastructure.

Its also subject to change as slight alterations in wind direction can change the warnings even as late as hour before.

Precipitation from showers is likely to be dying as it moves southwards towards that region but as looking at the models that by no means a certainty as if winds moved slightly more west convection from North sea would enhance them 

Thanks - yes I agree looking at it from your point of view.

It's just my perception through experience of what is considered "dry" 

[Seasonality]

ECM meteogram not showing snow for London tomorrow... Which way will it go?

 

[Nick F]

47 minutes ago, nick sussex said:

Its very hard to have a lot of confidence in these forecasts when they can't even agree where the true MJO signal is currently located. I read the research paper by MacRitchie and Roundy and they seemed to make a better case for not using the normal Wheeler and Hendon one as that had too much interference from other factors. I think the issue that's constantly causing probs is those cyclones and Rossby wave interference aswell as the complications surrounding Kelvin waves.

There are various ways of gauging MJO activity, other than using the more easier to understand RMM plots. tropical and ex-tropical interactions can be seen through the magnitude of the upper winds and the waves in them, as GP suggests, as shown on plot below:

Found at: http://mikeventrice.weebly.com/tropical-waves.html

Also the velocity potential (CHI-200) charts can show the propagation of the MJO, if you know how to read them, but charts below do show eastward propagation of an MJO wave

https://ncics.org/portfolio/monitor/mjo/

So the RMM plots we are used to don't always pick up the MJO activity well, as they may not filter out other modes, such as Kelvin and Rossby waves.

 

Edited January 11, 2017 by Nick F

[Nouska]

23 minutes ago, Singularity said:

I agree it seems very strange on this occasion - as if they are looking at a different version of the ECM ensembles somehow!

Ian talked about no influence in the next twenty five days - perhaps, allowing lag time, they only see the amplification in phase 7-8 as being significant thereafter. IO is a high pressure set up over the BI, just more of the same as we are seeing. Different matter altogether with six/seven in the forecast.

@Tamara was talking about a February 2012 similarity - the MJO for the period - look at the amplification going into six/seven.

[nick sussex]

2 minutes ago, Nick F said:

There are various ways of gauging MJO activity, other than using the more easier to understand RMM plots. tropical and ex-tropical interactions can be seen through the magnitude of the upper winds and the waves in them, as GP suggests, as shown on plot below:

Found at: http://mikeventrice.weebly.com/tropical-waves.html

Also the velocity potential (CHI-200) charts can show the propagation of the MJO, if you know how to read them, but charts below do show eastward propagation of an MJO wave

https://ncics.org/portfolio/monitor/mjo/

So the RMM plots we are used to do always pick up the MJO activity well, as they may not filter out other modes, such as Kelvin and Rossby waves.

 

Thanks, yes I've looked at the velocity potential on that site  but you'd think with all this modelling and 24 hour data they should have come up with by now a way of incorporating that into a more accurate RMM measure. If the normal forecasts suggest the MJO is in one place at time of initialization but the VP shows it in another then surely this calls into question the starting data fed into those forecasts.

[Man With Beard]

ECM ensembles London

Are we getting somewhere here? The "GFS" mild blip for 15/16th seems to have made it into the ECM servers now. But straight back into the freezer afterwards. Not unlike the op, and not unlike the GFS (though it takes a bit longer to get there).

With most ops now on the same page for 17th onwards, are we getting to the place where we can confidently call a "slack" easterly, at least for the southern half of the UK?

And a note for the future - we'd be unlucky not to get a snowy breakdown from a January easterly...

[Tim Bland]

You couldn't make it up!  Just as we start to accept our fate of a slack easterly with little snow the Meto jump on board and give a risk of snow all next week in the East!

Perhaps ECM this morning was a rougue run and it will go back to the previous runs later?  GFS will hopefully stay on track and stick with it.  I expect Mogreps and other Meto models are really going with the easterly now as they seem very confident.  I also worry though that they are a day behind the models with their updates ?

[Man With Beard]

Just now, Tim Bland said:

You couldn't make it up!  Just as we start to accept our fate of a slack easterly with little snow the Meto jump on board and give a risk of snow all next week in the East!

Perhaps ECM this morning was a rougue run and it will go back to the previous runs later?  GFS will hopefully stay on track and stick with it.  I expect Mogreps and other Meto models are really going with the easterly now as they seem very confident.  I also worry though that they are a day behind the models with their updates ?

I suppose even a slack easterly may still produce coastal showers if the temperature gradient is sufficient?

[West is Best]

1 hour ago, nick sussex said:

Thanks that's very nice of you. In terms of easterlies , I sometimes wonder why we're so fixated on them, a lot of the times they're drab snow grain affairs but when they're good they are so much better than any northerly toppler or PM flow.

I think its because they have become part of weather folklore in here and they can deliver non slushy snow and often can be a pre-cursor to a more extended spell if theres a signal for retrogression towards Greenland.

Yep like February 1986: bone dry awful. No snow, just horrible dry cold until the breakdown snow on March 01st.

[nick sussex]

2 minutes ago, West is Best said:

Yep like February 1986: bone dry awful. No snow, just horrible dry cold until the breakdown snow on March 01st.

You have a better memory than me! lol But I've seen plenty of dull tedious easterlies with the sum total of a few snow grains blowing around in the wind. Its hard to know what will happen with this one, it really depends on low pressure over southern Europe and the depth of cold available for the UK. Its somewhat ironic that the UKMO come out with their more interesting type easterly forecast today, I hope they haven't jinxed things now!

[pyrotech]

1 hour ago, Iceaxecrampon said:

Thanks - yes I agree looking at it from your point of view.

It's just my perception through experience of what is considered "dry" 

Here is something for our friends in North West (Cumbria)

Like models show snow is likely, but not with potential of disruption in the South

That potential in the south also comes with possibility of a no event so seems you have the safer option

Edited January 11, 2017 by pyrotech

[winterof79]

A fast evolving and highly fluid period of weather has begun

Edited January 11, 2017 by winterof79

[ukpaul]

27 minutes ago, pyrotech said:

Here is something for our friends in North West (Cumbria)

Like models show snow is likely, but not with potential of disruption in the South

That potential in the south also comes with possibility of a no event so seems you have the safer option

Neither of the metoffice warnings or the above chart are showing the extent of snow potential. The spine of the Pennines has, for example, kept a number of hours of heavy snow symbols throughout the morning, despite any chopping and changing as the forecast adapts to the reality.

[Scandinavian High.]

Cold weather ahead this is looking interesting most members going cold and I'm likeing the meto update to staying cold east and south east with snow showers.