Model output discussion - 16th Nov onwards

[BornFromTheVoid]

image.png.

Could someone please take the time to explain this chart to me. I have tried looking around the forum and learning area to find out how to read the chart but I am struggling. I copied the photo from some other post if someone could shed some light that would be greatly appreciated thanks

 

Hi Scott,

 

That image shows a phase chart of the MJO on the top (Madden Julian Oscillation). This is an area of convection that travels around the topics. On the chart, the different sections with the numbers represent what phase/location the MJO is in, while the closer to the edge of the box it gets, the stronger the convection is. Where the MJO is located in the tropics can have knock on effects which influence the weather in the mid-latitudes. That chart shows that it's currently in phase 3, in the Indian Ocean and weak/moderate strength.

 

The bottom image is a composite anomaly chart for 500hPa. This takes all other dates when there was an El Nino (3.4 0.5C+) and a phase 3 MJO at the same time, then sees what the average pattern is like at the 500hPa level. This is useful for showing the large scale pattern over the northern hemisphere, with the blues/purples being troughs (lower pressure, unsettled) and the yellows and greens showing the opposite.

[mountain shadow]

image.png.

Could someone please take the time to explain this chart to me. I have tried looking around the forum and learning area to find out how to read the chart but I am struggling. I copied the photo from some other post if someone could shed some light that would be greatly appreciated thanks

 

The best phase of the MJO which might point towards colder weather here, are high ampltude phases 8 and 1. But I believe that tropical convention in those areas during an El Nino is rare.

[phil nw.]

It's fair to say whilst we continue with those low heights over Greenland driving the pattern for us then we can't expect prolonged deep cold.

We can however see short lived shots of colder polar air behind passing lows which will likely see some snowfall for upland areas further north.

If the jet comes further south then the chances of brief snowfall further south increase.

Maybe some night frosts during transient high pressure when winds fall light and cloud breaks.

 

This seems to be a typical early Winter outlook for the UK so no surprises-yet.

 

Just a few other thoughts from me now.

It's nice to see those cold charts on some op runs at later timeframes but i always bear in mind what the ensemble suites are trending.

It does save some frustration when any let downs come later.

That is why John H,myself and many others, some who have been on here a long time,refer to the ensemble outputs for the upper air patterns.

They are not perfect but up to 2 weeks give a good idea where the main areas of troughing and ridging will likely be.

 

By all means let's discuss all outputs-yes even FI charts if they excite- but always with a sense of realism in mind.

Edited November 27, 2015 by phil nw.

[phil nw.]

Ok guys let's keep on topic now and get back to discussing model outputs.

Ta.

[nick sussex]

Not too much of a surprise to see the GFS back away from the Scandi high. Without the ECM/UKMO giving support for the key T144hrs timeframe upstream it was always a long shot.

 

The ECM ensembles do show a lot more scatter after day ten and there is a cluster of wind direction solutions that do take this round to between se and ne. These likely amplify the upstream troughing and then ridge the Azores high ne so something similar to the GFS's earlier Scandi high trend.

 

So although the consensus seems to be a more mobile outlook still a small chance of high pressure near the UK or towards Scandi.

[bluearmy]

From a coldies perspective, Very much liking the 00z gefsp NH profile through the final frames

Let's hope this model is the way forward!

[Nick F]

Looking at the 00z EPS H500 mean out to day 15 on Weatherbell, it appears to retract the H500 vortex away from Greenland to be more centred over East Siberia by day 15 (12th Dec), so perhaps allowing more in the way of mid-latitude high pressure cells to set up across Atlantic/NW Europe. Big Aleutian low anomaly and high pressure anomaly over central/east Canada would suggest some strong poleward wave activity in this region too.

[Scott M]

Thanks guys appreciate giving me the info sorry for going off topic About the question

[mcweather]

Ian is simply commenting on what some of the models at the met office are showing, and what the forecasters there are currently briefing. Like any other set of models, or indeed any other forecasting organisation, they don't have the monopoly on being correct, or the holy grail to 100% accurate forecasts, and don't pretend to either. So yes, respect it, take it onboard and appreciate the fact that Ian is being kind enough to share some additional insight, but it would be daft to disregard other models, forecasters etc solely off the back of it.

 

On this occasion what's being suggested is not much different to what virtually every other model is pointing at anyway, but when it boils down to it, it's model output which may or may not come to fruition.

 

 

Indeed Paul. We are  lucky to have Fergies input on Meto thinking

 

I think what has compounded the current situation is that just a  very very short while ago we were being told

that there were tentative signs of high pressure anomalies developing to our northwest and that EC 30 dayer was suggesting negative temps anomalies in the run up to xmas

then as if by magic the GFS throws out charts for mid December showing just how that could happen

 

Then quick as you like that is off the cards. Perhaps suggesting that the Met office medium /long range tool flips about as much as the GFS FI does all of which brings us back to the Caveat that all medium and longrange models( including the Meto)  should come with namely take them with a huge pinch of salt.

Edited November 27, 2015 by mcweather

[Mucka]

Not too much of a surprise to see the GFS back away from the Scandi high. Without the ECM/UKMO giving support for the key T144hrs timeframe upstream it was always a long shot.

 

The ECM ensembles do show a lot more scatter after day ten and there is a cluster of wind direction solutions that do take this round to between se and ne. These likely amplify the upstream troughing and then ridge the Azores high ne so something similar to the GFS's earlier Scandi high trend.

 

So although the consensus seems to be a more mobile outlook still a small chance of high pressure near the UK or towards Scandi.

 

Here are ECM London ensembles

 

 

Clearly the Op had little support after day 8 and large scatter with some colder runs appearing week 2 of Dec.

The fact no ECM Op has had any interest in a Scandi high is obviously a big negative for cold lovers and also GFS ensembles have shown little interest in supporting the Op beyond some control runs.

 

However if we are being optimistic the 06z GFS is just one run and the Op may have been previously picking up details that the ensembles are too low res to pick out, especially since the signal is 8 days+ range and at least eCM ensembles have improved somewhat even if there is obviously no strong cold signal as yet.

 

On balance, and taking into account Fergie's comments, a Scandi high looks fairly unlikely at this time but there is still a little hope.

I certainly wouldn't be surprised to see the GFS 12z go back to trying to build Scandi high and the ECM be much more amplified this evening even if the eventual outcome is not what we want.

[fergieweather]

Indeed Paul. We are  lucky to have Fergies input on Meto thinking

 

I think what has compounded the current situation is that just a  very very short while ago we were being told

that there were tentative signs of high pressure anomalies developing to our northwest and that EC 30 dayer was suggesting negative temps anomalies in the run up to xmas

then as if by magic the GFS throws out charts for mid December showing just how that could happen

 

Then quick as you like that is off the cards. Perhaps suggesting that the Met office medium /long range tool flips about as much as the GFS FI does all of which brings us back to the Caveat that all medium and longrange models( including the Meto)  should come with namely take them with a huge pinch of salt.

 

Quick clarification - 

 - GloSea hasn't lost signal - instead, the balance of output means it's currently not a favoured outcome. So there's no 'flip' - just a shift in emphasis. That's standard fare, and further complications looking ahead into e.g. early Jan (stratospherically) really make any deterministic prognosis pointless at this range.

 - EC Monthly has never shown any -ve temp anomaly by Christmas in any bi-weekly run I've seen (unless someone saw otherwise). Last evening's run shows a gradually diminishing +ve temp anomaly into mid-December, becoming indistinguishable from climatology by later Dec. Equally, it favours a broadly W to NW flow by then, with (somewhat weakened but still pronounced) low height anomalies to the north of the UK and +ve precip anomalies in the west (a recurrent signal all Nov-Dec!!). Meanwhile, over some recent runs, GloSea has toyed with the opposite (blocked) outcome by later December, but this currently finds no parallel (a very small minority of stamps aside) in latest EC suite and is now outnumbered anyway by zonal members.. but there's still some key uncertainty there. Meanwhile, the GFS ideas of last night (re that Scandinavian blocking) weren't considered a likely outcome (as effectively no EC ENS support yesterday, nor in 00z output). Nonetheless, it sticking with the notion for 3 runs was eye-catching, for sake of it's continuity.

 

Modifications in emphasis and even total u-turns in model output (even at near-term) are standard woes in our world and we will see plenty of this sort of stuff through the coming season. 

[mcweather]

Quick clarification -

- GloSea hasn't lost signal - instead, the balance of output means it's currently not a favoured outcome. So there's no 'flip' - just a shift in emphasis. That's standard fare, and further complications looking ahead into e.g. early Jan (stratospherically) really make any deterministic prognosis pointless at this range.

- EC Monthly has never shown any -ve temp anomaly by Christmas in any bi-weekly run I've seen (unless someone saw otherwise). Last evening's run shows a gradually diminishing +ve temp anomaly into mid-December, becoming indistinguishable from climatology by later Dec. Equally, it favours a broadly W to NW flow by then, with (somewhat weakened but still pronounced) low height anomalies to the north of the UK and +ve precip anomalies in the west (a recurrent signal all Nov-Dec!!). Meanwhile, over some recent runs, GloSea has toyed with the opposite (blocked) outcome by later December, but this currently finds no parallel (a very small minority of stamps aside) in latest EC suite and is now outnumbered anyway by zonal members.. but there's still some key uncertainty there. Meanwhile, the GFS ideas of last night (re that Scandinavian blocking) weren't considered a likely outcome (as effectively no EC ENS support yesterday, nor in 00z output). Nonetheless, it sticking with the notion for 3 runs was eye-catching, for sake of it's continuity.

Modifications in emphasis and even total u-turns in model output (even at near-term) are standard woes in our world and we will see plenty of this sort of stuff through the coming season.

Many thanks for the clarification. Good to see that the tentative GloSea positive pressure anomalies to the northwest have not been lost, even if they are not 'currently' the favoured outcome.

As I said in my post the fact that GFS longer range started to show how we might get there seemed to put a bit of meat on those ,tentative' bones. I fully appreciate that at that sort of range nuance and flux play an even greater part in trying to find a path through all the conflicting signals and background noise. Hence my comment about caveats.

Your input is always greatly appreciated.

Edited November 27, 2015 by Polar Maritime
To remove post from quote.

[northwestsnow]

GFS shows more in the way of High pressure around the UK in the coming weeks.

If it can't snow hopefully it will dry out a bit.

[Singularity]

Perhaps GloSea5 has a tendency that's common among long range modelling, which is to bring about changes in the stratosphere in response to events in the troposphere too rapidly - this being a result of the assumptions/simplifications that have to be made in order to avoid unreasonable computation and power requirements.

 

This is just me thinking off the top of my head, mind, and relates to the well kept secret of verification statistics for that model!

 

 

The GFS 12z is very similar to the 06z really, even at +384 which is a bit unusual really. That theme could be summed up as a pattern that features more amplification and jet meridionality than might be expected given an El Nino background, but not enough to bring about any high (or mid-high e.g. centered over the Baltic Sea) latitude blocking. The polar view, though, is a lot more intriguing as the mean planetary wave distribution behaves well in terms of generating wave breaks into the stratosphere. The Aleutian Low/Canadian High combination mentioned by Nick F earlier today should be well supported by the El Nino basic state. As for low heights over Siberia - that I'm not so sure about. It's quite a departure from the vast blocking high that dominates during the short to medium range but may be a part of Cohen's feedback cycle - I'm not sure though as I need to find time to have a quick read through his papers again!.

Edited November 27, 2015 by Singularity

[gottolovethisweather]

Bar a milder blip during a couple of days within the next seven, courtesy of mild sectors within passage surface features, the outlook remains as currently expected for some time now. That is somewhat average Temps by day, minimal chances of frost by night with some brief spells of wintriness over the far North. D7 is still the timeframe by which things look set to change to somewhat more settled weather, at least for 4 days countrywide maybe longer.

 

All in all, two days on, things remain on track as per my previous post I'd say.

 

https://forum.netweather.tv/topic/84434-model-output-discussion-16th-nov-onwards/?p=3291242

 

Eyes down for any differences to this scenario in the ECM and UKMO runs beyond D7. December and Meteorological Winter will only be four days old by then and my best advice is to SIT BACK and enjoy the rollercoaster ride ahead of us. Butterflies will have hibernated but the butterfly effects will remain as we attempt to decipher those day to day predictions of our global climate. Do not get too hung up on the details and simply enjoy the ride. 

 

Take care now.

Edited November 27, 2015 by gottolovethisweather

[bluearmy]

Incidentally, a sceuro rather than Scandi ridge driving a southerly into the arctic to our North is no bad thing re trop/strat for further down the line.

[northwestsnow]

Incidentally, a sceuro rather than Scandi ridge driving a southerly into the arctic to our North is no bad thing re trop/strat for further down the line.

Well we need to start somewhere Blue, the PV already looks very angry .Hopefully some WAA up towards the Arctic will assist in breaking it down, or displacing it.

[Methuselah]

Please guys, is there any chance of returning to the topic? If you want to discuss possible WAAs, there are threads for doing just that...

[bluearmy]

Well we need to start somewhere Blue, the PV already looks very angry .Hopefully some WAA up towards the Arctic will assist in breaking it down, or displacing it.

And yet the extended gefs(p) members offer plenty of options where the vortex doesn't look in the least bit angry and scary.

[Geordiesnow]

Although there is a spell of windy weather, its a tad dissapointing we Havant quite got the deep low I would like too see and the models that have to an extent have been hinting at(albeit never directly fully on the UK)

 

That said, some interesting convective weather coming up, especially on Sunday as I feel the air will be that bit colder again and the winds a touch stronger at the same time.

 

As we head into next week, its a situation of where will the waving weather front which divides the mild and cold air will end up, does look like milder air will win to all parts by Tuesday(perhaps albeit briefly)

[Cloud 10]

And yet the extended gefs(p) members offer plenty of options where the vortex doesn't look in the least bit angry and scary.

 

"vanilla" GEFS has some long range interest this evening.

 

Edited November 27, 2015 by Cloud 10

[January Snowstorm]

One thing standing out for me is how cold Iceland is this year. Usually in a westerly flow such as now the uppers over Iceland would fluctuates more than they are doing.

I've a sneaky feeling Northwesterly's will be quite potent as we move on into Winter proper

[mountain shadow]

"vanilla" GEFS has some long range interest this evening.

 

gensnh-21-5-360.png

At face value that looks good with above average height anomalies to the West, however I would say the height anomalies are not high enough and indicative of NW zonal pattern but not wintry apart from Northern mountains.

[Costa Del Fal]

One thing standing out for me is how cold Iceland is this year. Usually in a westerly flow such as now the uppers over Iceland would fluctuates more than they are doing.

I've a sneaky feeling Northwesterly's will be quite potent as we move on into Winter proper

Do you think so? The Atlantic cold pool now is starting to look quite patchy in nature. There is quite a noticeable amount of positive anomalies surrounding our shores and throughout the Atlantic. Still some localised very cold spots but is the cold pool further disintegrating I wonder now? http://www.ospo.noaa.gov/data/sst/anomaly/2015/anomnight.11.26.2015.gif

[Ravelin]

Well the models seems to diverge fairly early on, sometime after t120, with perhaps the UKMO, GFS and GEM bearing the decent similarity at t144 below, with ECM much flatter across the Atlantic.

GFS & GEM still not a million miles apart by t240.