Model output discussion - heading into 2018

[Man With Beard]

I wouldn't call the ECM op an outlier at T240, but it isn't in the biggest cluster. The top cluster, yet again, sees wintry potential as a NWly flow gets on the back of a trough that's got to our east. 

[blizzard81]

2 minutes ago, Man With Beard said:

I wouldn't call the ECM op an outlier at T240, but it isn't in the biggest cluster. The top cluster, yet again, sees wintry potential as a NWly flow gets on the back of a trough that's got to our east. 

Things are looking a little more positive for cold in the long run this morning. 

[comet]

1 hour ago, Tim Bland said:

Strange how weather.us and Windy etc seem to be showing the 00z ECM output? 

Ps 8-10cm so far here in Hertfordshire @ 100m ASL so ECM was much closer to the mark than most others. Euro4 was way out 

Looks closer to 5cm to me which is still probably double what we had roughly 11 miles south of you, although you do have that extra bit of elevation in Stevenage.

Back to the models and on the face of it they do look a lot, lot better this morning than they have done. Just a word of caution though the nw/se PM airflows quite often flatten out when enter the reliable timeframe. Not saying it will be the case this time but something to keep in mind. However a lot more to be optimistic about this morning that's for sure.

[bluearmy]

To me, the story of the eps in general is the return of the neg epo. Note the op at day 10 going into overdrive on that. 

[Bring Back The Beast]

25 minutes ago, bluearmy said:

To me, the story of the eps in general is the return of the neg epo. Note the op at day 10 going into overdrive on that. 

What are the implications of this for our side of the world?

[Catacol]

Morning all - I watched snow fall at 2am here which gave me a slight fuzzy feeling.... though none of it stuck. 

On the model watching front - a model of a different kind. The SOI - Southern Oscillation Index. For those that dont know it measures the relative pressure between Tahiti and Darwin and is a measurement usually of the strength of Nino or Nina. Values over +7 are reckoned to symbolise an active Nina phase and values below -7 an active Nino phase.

I'm puzzled by the values we are seeing. Index for December here:

https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/30daysoivalues/

According to this data we have been seeing a Nino style setup in the pressure relationship since December 11 after a spell of much more predictable Nina values. Both October and November averaged +10, which given our Nina profile is not surprising.

So why have we had 2 weeks of Nino values in December? Somewhere there is clearly some "noise" affecting the expected pattern. Anyone got any ideas? 

Latest Schiraldi plots with the handy ability to jump back up to 5 days to compare runs show that, once again, we have models failing to spot the correct GWO progression. Is this linked to the strange SOI values? Is there more energy lurking in the pacific than the swift decline of the MJO a week or so ago suggested? By hook or by crook there is a drive back across to a low amplitude phase 3 

and MJO forecasts in general are not holding it in the "circle of death" for long... which is a change from a few days ago

Overall conclusion? SOI index suggesting Nino-style forcing... added to Schiraldi plots pushing towards phase 3 rather than 1/2.... plus MJO re-emerging with some amplitude... added to the 23rd Dec graph from WDT on the 23rd showing frictional torques rising again (with MT expected to follow...) = a sense that the zonal spell may not last too much longer than the 2 week period I alluded to a few days ago. Back then 7th Jan was an easy time zone for minimum length of atlantic westerlies, and in my mind it could have run 1/2 weeks beyond this. However I think the timeline can be brought forward if this current data trend holds up. I think tentatively we can hope for a change of outlook by mid-Jan - at least in terms of some much better looking NWP output as we move towards Jan 15.

Just to be clear on what I mean by "better looking output" - my cards are firmly on the table. I am always looking for a high lat block - either over Greeny or Scandy. This is my definition of a setup for cold winter weather. Polar NW airstreams are quite possible in a zonal setup (eg last night and today) - worth being clear as to what benchmark we are actually using for forecasting success.

Overall therefore feeling a bit more optimistic this morning.

[Rocheydub]

1 hour ago, shotski said:

Just goes to show that you don’t have to always go chasing the hallowed Greeny, Scandi blocks. 

 But that’s very much depending where you live, NW’ly incursions deliver very little/nothing where I live, but that’s IMBYism at its finest! I don’t see anything in the outputs to get remotely excited about at all.

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

 

just had a look at fantasy land  its looking good  for the coldies ,we could get plenty  of  the white stuff!!

[knocker]

Now that I'm back in the land of the living and managed a glance at this morning's EPS output nothing really to alter my opinion based on last night's anomalies of remaining pretty unsettled for the next 14 days with temps varying around the average. Essentially the key player is the vortex lobe N. Canada with a flattish flow across North America and the negatively tilted trough Greenland/Scandinavia and thus still a strong upper westerly flow across the Atlantic. There may be a suggestion of the Azores HP taking closer order towards the end. Perhaps even supported by the clusters although I must admit I'm no great fan of those map projections.

[Chris W]

Looking at the GFS I don't think I've ever seen the polar front jet so far south - it's almost over Spain! Polar maritime air sure is getting very involved in our weather (I'm visiting the UK until Jan 8). There is potential whatever the temperatures for some very severe winds in the next week or two.

[stodge]

3 minutes ago, knocker said:

Now that I'm back in the land of the living and managed a glance at this morning's EPS output nothing really to alter my opinion based on last night's anomalies of remaining pretty unsettled for the next 14 days with temps varying around the average. Essentially the key player is the vortex lobe N. Canada with a flattish flow across North America and the negatively tilted trough Greenland/Scandinavia and thus still a strong upper westerly flow across the Atlantic. There may be a suggestion of the Azores HP taking closer order towards the end. Perhaps even supported by the clusters although I must admit I'm no great fan of those map projections.

Both GFS and ECM have tried to send the Azores HP NE and turn the trough to a positive tilt consistently and persistently in FI but it's not amounted to anything so far. The models have tried to dig the trough to the west of the British Isles but if anything the reality has dug the trough into Europe leaving the trough negatively aligned and more PM air in charge. Why this has happened I don't know but I wonder if it relates to the overall pattern of the PV.

The lifting of heights into Europe could be a precursor to a pattern change leaving Europe more anti-cyclonic - that was being posited from early in the New Year but remains the preserve of a minority of members at the edge of FI.

For those wanting cold (which I know includes you), the pattern is indicative of something we've not seen for a while and is rather different than hoping against hope for a Greenland or Scandinavian block and a 7-10 day severe spell followed by a thaw as the block breaks down. A PM-based set up (aka cold zonality to its friend) can deliver persistent snow almost anywhere though areas with altitude further north will always do better in that regard. The problem with the southerly tracking jet for those of us in the south will be wind and rain as I'm sure you are already well aware.

[Faronstream]

Looks extremely horrible in all weather models last days, not even a single day with -10 in 850 hpa so no proper cold is on the way. The most weird thing is that the polar vortex is not even that strong this season and still we are stuck in mild air anyway

[Chris W]

18 minutes ago, stodge said:

Both GFS and ECM have tried to send the Azores HP NE and turn the trough to a positive tilt consistently and persistently in FI but it's not amounted to anything so far. The models have tried to dig the trough to the west of the British Isles but if anything the reality has dug the trough into Europe leaving the trough negatively aligned and more PM air in charge. Why this has happened I don't know but I wonder if it relates to the overall pattern of the PV.

The lifting of heights into Europe could be a precursor to a pattern change leaving Europe more anti-cyclonic - that was being posited from early in the New Year but remains the preserve of a minority of members at the edge of FI.

For those wanting cold (which I know includes you), the pattern is indicative of something we've not seen for a while and is rather different than hoping against hope for a Greenland or Scandinavian block and a 7-10 day severe spell followed by a thaw as the block breaks down. A PM-based set up (aka cold zonality to its friend) can deliver persistent snow almost anywhere though areas with altitude further north will always do better in that regard. The problem with the southerly tracking jet for those of us in the south will be wind and rain as I'm sure you are already well aware.

Excellent post stodge, to me this is extremely interesting modelling and at the same time extremely interesting weather. Beats anticyclonic or mild gloom any day!

[northwestsnow]

2 hours ago, bluearmy said:

localised though Tim - ten miles down the road at similar altitude barely a dusting has stuck 

tough to make a forecast and I think Exeter referencing this difference likely was pretty accurate. 

Eps firming up on troughing into Europe by day 10 - awaiting extended 

Exeter having nothing to do with that- now saying jan likely milder than avg and and colder interludes shortlived!!

[snowbunting]

13 minutes ago, Faronstream said:

Looks extremely horrible in all weather models last days, not even a single day with -10 in 850 hpa so no proper cold is on the way. The most weird thing is that the polar vortex is not even that strong this season and still we are stuck in mild air anyway

-10 values are a rarity on the UK and are usually associated with a direct Nly blast or beast from the East

 

[karyo]

2 minutes ago, snowbunting said:

-10 values are a rarity on the UK and are usually associated with a direct Nly blast or beast from the East

 

He is in Sweden though where those values should be easily achievable.

[booferking]

8 minutes ago, northwestsnow said:

Exeter having nothing to do with that- now saying jan likely milder than avg and and colder interludes shortlived!!

They to flip as much as the models all winter we've seen the jet stay south and it looks like staying that way.

[Snowy Hibbo]

1 hour ago, Catacol said:

Morning all - I watched snow fall at 2am here which gave me a slight fuzzy feeling.... though none of it stuck. 

On the model watching front - a model of a different kind. The SOI - Southern Oscillation Index. For those that dont know it measures the relative pressure between Tahiti and Darwin and is a measurement usually of the strength of Nino or Nina. Values over +7 are reckoned to symbolise an active Nina phase and values below -7 an active Nino phase.

I'm puzzled by the values we are seeing. Index for December here:

https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/30daysoivalues/

According to this data we have been seeing a Nino style setup in the pressure relationship since December 11 after a spell of much more predictable Nina values. Both October and November averaged +10, which given our Nina profile is not surprising.

So why have we had 2 weeks of Nino values in December? Somewhere there is clearly some "noise" affecting the expected pattern. Anyone got any ideas? 

Latest Schiraldi plots with the handy ability to jump back up to 5 days to compare runs show that, once again, we have models failing to spot the correct GWO progression. Is this linked to the strange SOI values? Is there more energy lurking in the pacific than the swift decline of the MJO a week or so ago suggested? By hook or by crook there is a drive back across to a low amplitude phase 3 

and MJO forecasts in general are not holding it in the "circle of death" for long... which is a change from a few days ago

Overall conclusion? SOI index suggesting Nino-style forcing... added to Schiraldi plots pushing towards phase 3 rather than 1/2.... plus MJO re-emerging with some amplitude... added to the 23rd Dec graph from WDT on the 23rd showing frictional torques rising again (with MT expected to follow...) = a sense that the zonal spell may not last too much longer than the 2 week period I alluded to a few days ago. Back then 7th Jan was an easy time zone for minimum length of atlantic westerlies, and in my mind it could have run 1/2 weeks beyond this. However I think the timeline can be brought forward if this current data trend holds up. I think tentatively we can hope for a change of outlook by mid-Jan - at least in terms of some much better looking NWP output as we move towards Jan 15.

Just to be clear on what I mean by "better looking output" - my cards are firmly on the table. I am always looking for a high lat block - either over Greeny or Scandy. This is my definition of a setup for cold winter weather. Polar NW airstreams are quite possible in a zonal setup (eg last night and today) - worth being clear as to what benchmark we are actually using for forecasting success.

Overall therefore feeling a bit more optimistic this morning.

There is often noise with the SOI, but not for the period that the SOI has been negative for. That would be a signal. Probably associated with the MJO Phase 8 signal, and the tropical forcing that has occurred on the North Pacific. Has/is helping the +PNA event in North America, so Ninoesque for Europe I think and the ramifications the +PNA event entails on the other side of the Atlantic....

 

[frosty ground]

18 minutes ago, northwestsnow said:

Exeter having nothing to do with that- now saying jan likely milder than avg and and colder interludes shortlived!!

Probably best to stop taking the LRF as gospel along with the Extended EPS they change and evolve all the time.... 

[tight isobar]

6z london ens...options a-plenty.

This could be by winters end(as things stand)-go down as on of the snowiest for many a-year from polar martime airflow.

There looks many options for further incursions where snowfall may take centre stage.....

Notable cold 'perhaps' not.

 

Edited December 27, 2017 by tight isobar

[northwestsnow]

17 minutes ago, frosty ground said:

Probably best to stop taking the LRF as gospel along with the Extended EPS they change and evolve all the time.... 

True FG

[phil nw.]

Day 10 eps clusters and mean are not bad for a decent cold shot from the n or nw

The largest cluster favouring the jet going south of the UK again with a decent euro trough-polar nw pattern.Mean uppers -2 to -5c depending on location south to north.Signs of a bit of Atlantic ridging out west  so would expect quite a cold nw flow in that setup.

Not the ideal pattern for coldies with a wavering rather than a meridonal jet.No +ve polar heights so transient periods of cold rather than anything more than day or 3 but  as long as the Azores high stays out in the Atlantic rather than set up shop over C.Europe the jet is unlikely to tilt towards a mild sw-ne angle.

[Man With Beard]

2 hours ago, knocker said:

Now that I'm back in the land of the living and managed a glance at this morning's EPS output nothing really to alter my opinion based on last night's anomalies of remaining pretty unsettled for the next 14 days with temps varying around the average. Essentially the key player is the vortex lobe N. Canada with a flattish flow across North America and the negatively tilted trough Greenland/Scandinavia and thus still a strong upper westerly flow across the Atlantic. There may be a suggestion of the Azores HP taking closer order towards the end. Perhaps even supported by the clusters although I must admit I'm no great fan of those map projections.

What don't you like about the clusters? (genuine question as a bit of critical evaluation will help us all in using them in the right way)

I pretty much agree with your assessment although I think this morning's ens is the first time that Azores High has looked more convincing in its intent to reach the UK, so "more runs needed". 

Beforethat point, though, I think the mean charts taken at face value do hide the alternations between short colder pulses and milder pulses in the first ten days of January.

Edited December 27, 2017 by Man With Beard

[chris55]

ECM day 10 not without some wintry interest going forward

I get a feeling that within the broadly west to east flow a wedge of high pressure here or there could well deliver some colder shots and potential snowfalls.

[Polar Maritime]

The GFS as others have put shows a very strong signal for Pm shots from the N/W, With deep low pressure sytems sweeping South at times bringing cold wintry conditions with gales for some. A very mobile outlook ahead which should make for some interesting model viewing.