Model output discussion - 20th Feb onwards

[nick sussex]

30 minutes ago, feb1991blizzard said:

Apparently though according to latest UKMO thinking, it wont actually be the end of the Stratospheric vortex for the end of the winter, very surpising.

I think that's because we'll still be having the final warming during spring. The final is just part of the normal cycle of the seasons compared to this one due in a few days time which will be classed as a major SSW unless theres a major backtrack in the forecast which is unlikely.

[chris55]

ECM midterm looks like some hard frosts will about, some crisp mornings scraping the car, i do like a crisp cold morning

[feb1991blizzard]

23 minutes ago, nick sussex said:

I think that's because we'll still be having the final warming during spring. The final is just part of the normal cycle of the seasons compared to this one due in a few days time which will be classed as a major SSW unless theres a major backtrack in the forecast which is unlikely.

It is the normal cycle but you can have a final SSW around this time, the final warming can just be a gradual relaxation of the hold the Strat Vortex has on the trop or can be an abrupt reversal by a sudden huge rise in temp? even one In April might still be the driver of blocking?

[Summer Sun]

ECM, GFS and GEM all going for something milder tonight but its still 10 days away

ECM not quite so quick but still shows a south westerly flow

Edited March 1, 2016 by Summer Sun

[nick sussex]

9 minutes ago, feb1991blizzard said:

It is the normal cycle but you can have a final SSW around this time, the final warming can just be a gradual relaxation of the hold the Strat Vortex has on the trop or can be an abrupt reversal by a sudden huge rise in temp? even one In April might still be the driver of blocking?

Yes but the spring one rarely gets a mention and a major SSW one doesn't happen every year. And yes we often see wonderful blocking in April when its too late! Regardless the current SSW isn't showing a quick trop response which is a shame and it looks like we'll have to wait for that to have an effect.

[gottolovethisweather]

Now I'm getting slightly more excited than I have all through this Winter with regards to wintry precipitation prospects. Note my use of the word "wintry". Over the coming five days perhaps beyond hold almost daily nationwide wintry interest in terms of blizzards at elevation, snow, sleet and ice. Of course, the usual suspects should fare best but there are likely higher chances of brief periods of widespread wintriness this time around.

• Parts North and West in Scotland and Northern England down to Central regions i.e. the Pennines are almost guaranteed to see some lying snow with thawing by day for many a day to come. Thursday the driest day this week for them. An 80-90% chance of seeing snow falling and perhaps lying especially over higher ground.
•  
• Parts South and Southwest England can only hope for hilltop snow or overnight events, where snow chances are greater at such a time when parameters fall right. A 50-70% chance of seeing snow falling but only lying briefly at elevation
•  
• Parts due East might also get lucky for the white stuff over the coming days with tomorrow morning/early hours of Thursday holding their best chances in the near-term. I rate their chances of seeing snow falling at 70-80% with little hope of lying snow, other than at elevation.

 

I hope the above is of interest and my thoughts cover the first half of March in general and are taken from a number of sources from both in here and via some media forecasts. March will have a sting to it (note short-term strong wind potential courtesy of Storm Jake for instance). More especially I think it's safe to say that Spring warmth will be a long time in coming just yet.

 

Edited March 1, 2016 by gottolovethisweather

[KTtom]

Nothing for Wales then?!  gotolovethisweather?

Edited March 1, 2016 by KTtom

[knocker]

But I have a feeling this may only partially correct.

 

[phil nw.]

The next 3/4 days look probably as cold as anything we experienced nationwide through the Winter and a good chance many places will see at least some snow falling if not settling.

This maybe the last window of opportunity for such a widespread Arctic event as next week does look less cold as the Azores ridging starts to nose in cutting off the coldest feed for a while.

Overall although those polar +ve height anomalies look seductive the ens still show segments of the pv to our north -no real Arctic blocking showing yet. 

 

Just a continuation of our rather cold west/north westerly pattern out to the end of week 2.

Edited March 1, 2016 by phil nw.

[Guest]

This is a fuller report on some of my current thoughts pulling together and updating some of the analysis and comments from several of my earlier posts and taking account of some useful feedback from several other model thread posters. In part 1, I will start with the broader pattern and look at some of the main variables likely to have at least some impact on pattern changes during the next few weeks. In part 2 (to follow later tomorrow) I will then consider two colder scenarios and what would probably need to fall into place for them to verify and deliver. I will also state what I shall be looking for in the models. I will include plenty of links to charts, graphs and reports and I’ll try to set these out as clearly as possible. Where I refer to a particular source, if any one feels that there is a better or more reliable one please let me know – so that I can improve the quality of data input in any future posts. I am not a professional, I do not have any meteorological qualifications and do not have access to the more sophisticated computer models. I have read around the subject and taken a keen (some friends and family might say obsessive) interest in meteorology for 56 years (since age 7).

PART 1 - THE BROADER PATTERN AND POSSIBLE IMPACTS

ENSO:

The El Nino Southern Oscillation is in a late mature phase. It is now getting to a record breaking event (certainly in the strongest three ever recorded). It was basin wide and remains strong in the central Pacific but has weakened significantly in the eastern Pacific in recent weeks. It is expected to weaken steadily during the next few months and some of the expert analysts are expecting it to move into a La Nina phase this Autumn and into next Winter. In our part of the world, El Ninos often produce mild first halves to our winters and colder second halves. The strongest events seem to produce some unexpected impacts and do not necessarily stick to the rules. I feel that the record warm December was largely caused by the El Nino and perhaps only slightly attributed to other factors, like global warming. January was far less mild and February saw some rather cold spells but nothing exceptional for lowland UK areas south of Northern England.

El Nino:  http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml

MJO:

The Madden-Julian Oscillation has now reached phase 8 at decent amplitude. There is considerable disagreement as to what happens next. Most models have shown it weakening during the next few days with some taking it quickly to “0” but some of these forecasts have improved again slightly today, keeping it in Phase 8 for longer. Some of the ECM ensembles are rather better. The NCEP/GEFS was the best, taking it through Phase 8 and on into Phase 1. The ensembles do this at various speeds and amplitudes. I still like Kyle MacRitchie’s MJO analysis and forecasts. When I last covered this topic (see my post on page 40 of this thread), I got some interesting feedback from fellow posters. Gael_Force (on page 40) pointed out that Kyle’s analysis is biased being based on the CFS (NCEP/GEFS) forecast. Nick Sussex (on page 41) felt that as Kyle modifies the input to make allowances for the effects, such as El Nino, which he does not think the others do, he still rates the results. Well, it looks like Nick is right. Kyle’s 30 day forecast updated today is much more bullish than the others – with all 4 of his ensemble members speeding it through Phases 8, 1, 2 and 3 quite quickly and 2 of them at high amplitude and 2 at moderate amplitude. Whether he is right or wrong, who knows? I shall keep including his charts for comparison for my future reports to see how well they verify compared to the others. I have a feeling that Kyle’s specialist atmospheric research into the southern oscillation conditions and the MJO and their relationship and impacts on mid latitude patterns may well come out ahead! We want Phases 7, 8 and 1 which are associated with northern blocking.

UKMO: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml

ECM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml

NCEP/GEFS: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml

Kyle MacRitchie:  http://www.kylemacritchie.com/real-time-maps/realtime-mjo/

SSW:

A Sudden Stratospheric Warming event is already well underway. Some predictions expect this to be a record event. Some say that the SSW back in early February was minor and finished quite quickly. Judah Cohen (see the same link as in AO below) feels that this is all a single event with multiple warmings within it. He is expecting the next peak within 2 weeks with further warmings going into April. It looks like this SSW will beat the previous records for both strength and longevity. I’ve picked out three GFS charts for today, 1 week and 2 weeks away. Just have a look at the Netweather strat charts and go through the whole run. It appears to be all over the place but it does reflect Judah’s “multiple warming events” expectation. I am sure that there are more comments on this on the strat thread.

GFS 1st March – today: http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=10&carte=1

GFS 8th March – 1 week: http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=168&mode=10&carte=1

GFS 15th March – 2 week: http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=336&mode=10&carte=1

AO:

The Arctic Oscillation is neutral but should be trending negative by this weekend and is expected to stay negative during next week and perhaps rather longer. The NOAA ensemble members show a variety of outcomes. Dr Judah Cohen is much more bullish and expects a strongly negative phase to last for the next few weeks and this would be consistent with HLB (reflected in the AO indices going negative) being re-enforced by the imminent stratospheric/tropospheric coupling.  

 NOAA:  http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif

JUDAH COHEN:  http://www.aer.com/science-research/climate-weather/arctic-oscillation

IMPACTS:

We have been repeatedly reminded all winter by the professionals and experts just how complex the current events are. Whilst all the events I have outlined above undoubtedly interact with each other, the challenge is to work out cause and effect and does one event help or hinder another. With a record breaking El Nino and a recording breaking SSW to come within 2 weeks I would call it more than challenging! Computer models rely on analogue data but how can they take account of events that have never come together so strongly before? The very broad picture would usually be easier to forecast and the Met Office with their sophisticated computers Glosea5, the EC-32 and others seem to have been ahead of the game. Even they seem to be admitting that it’s a real struggle right now.

The free-to-view models are all over the place from beyond 7 days with drastic swings from blocked to flatter patterns and back again. There seems to be more of a consensus in respect of this week’s and this weekend's colder spell (which may see some proper cold) but with the usual marginality and caution on any possible snow events but this is all within 5 to 7 days. The Met Office still appear to be going for it being pretty cold for much of the next 6 weeks. Last week I got very excited about Judah Cohen's weekly report from Feb 22nd (see my posts on pages 25 and 36 of this thread) but I was a little disappointed last night with a slight downgrade in his Feb 29th update (see my post on page 42). He expects strong blocking with northerlies and later easterlies very dominant and with the polar vortex swinging down into Europe, a cold pool to become established. Is it too late? I will cover this in part 2 of my post which I shall finish later tomorrow.

 

Edited March 8, 2016 by Guest
one link wasn't working - should be now

[stodge]

Evening all

Again, a few general comments on the evening's 12Z output. I won't say too much about any wintry prospects for tomorrow or over the weekend. GEM and NAVGEM keep the SE in or closest to the cold air for the longest and that's a continuing trend from last night.

Elsewhere, there is a growing divide into next week between those runs which return us to a milder more Atlantic-dominated regime (GFS OP and ECM) and those which move us toward the kind of blocking scenario Ian Fergusson was suggesting a few days ago. The latter, whether with the HP to the NW or North of the British Isles, has plenty of support in the GFS Ensemble Members but it's worrying the OP persistently keeps the Atlantic-dominated theme.

My thought on this is, as we have seen twice already this winter, the attack on the PV and the resulting amplification sends the trough down through the British Isles but, because there is no rise of heights to the NE, the Atlantic breaks back through as the PV re-builds and re-strengthens. The last re-strengthening was of shorter duration and I've seen it argued each renewal of the PV is shorter and weaker and provides the opportunity for another assault on the PV.

And yet we are now seeing a significant warming with a wind reversal - is the initial response to this a brief re-strengthening of the PV before its final dissolution or are the models not handling this new warming well and treating it more like the Wave 1 attacks we saw last month and in January ? Initially, the signal was that each disruption of the trough would provide an opportunity for the mid-Atlantic ridge to set up as the PV weakened but now it seems the PV is simply re-bounding so I'm more than a tad confused.

Are we to see a final brief spell of PV dominated zonality before the final weakening or are the models struggling with how quickly the warming propagates down ? 

[Singularity]

For what it's worth, I'm very suspicious of any suggestion from the models of heights setting up over Europe for more than a day or so.

I expect there will be a dramatic pull to the NW before mid-March. Such can be envisioned from the ECM 12z day 10 chart, what with that trough digging very sharply south in the North Atlantic and that shortwave low clearing east from Iceland. 

This does, however, assume that the MJO isn't going to fall as quiet as ECMF and UKME are projecting.

There may also be a sudden, dramatic impact from the expected SSW event in the stratosphere, but how soon is uncertain; it looks to be an event that splits the vortex, which typically propagates down very fast, but the split itself is looking poorly defined on the most recent GFS output, with a great imbalance between the two daughter vortices (one is far stronger than the other - though both are weak by strat. vortex standards).

[bobbydog]

well... GFS showing snow for almost everyone in the next few days-

even in the south! will it happen though?

lets hope so, us snow-starved southerners have been waiting a while.....

Edited March 1, 2016 by bobbydog

[knocker]

It looks quite likely once we get rid of this quite nasty forthcoming interlude that a few days of more settled weather is on the cards. Although not everyone is quite on the same page vis the orientation of the main players, Atlantic trough, ridge to west of the UK and trough dipping into southern Europe there is enough consensus to say the HP will be quite influential with mainly a north westerly flow, dry with little weather to speak of and temps remaining below average

There is no consensus in the 10-15 day period with NOAA keeping the ridge to the west thus retaining the NW flow whereas the GEFS and ecm tend to weaken it and nudge it east (particularly the ecm) and with the trough mid Atlantic taking more interest there is a backing of the upper flow to the W/SW and a subsequent rise in temps to around normal although more unsettled weather returning, particularly to the NW may well be another corollary. This has still to be resolved.

 

 

Edited March 1, 2016 by knocker

[winterof79]

Could be a fair bit of the white stuff to the North of that front on Friday

[Eskimo]

Not a lot going on Friday if we look at the GFS. Snow reserved for mainly the highest ground. 

[Captain Shortwave]

1 hour ago, Singularity said:

For what it's worth, I'm very suspicious of any suggestion from the models of heights setting up over Europe for more than a day or so.

I expect there will be a dramatic pull to the NW before mid-March. Such can be envisioned from the ECM 12z day 10 chart, what with that trough digging very sharply south in the North Atlantic and that shortwave low clearing east from Iceland. 

This does, however, assume that the MJO isn't going to fall as quiet as ECMF and UKME are projecting.

There may also be a sudden, dramatic impact from the expected SSW event in the stratosphere, but how soon is uncertain; it looks to be an event that splits the vortex, which typically propagates down very fast, but the split itself is looking poorly defined on the most recent GFS output, with a great imbalance between the two daughter vortices (one is far stronger than the other - though both are weak by strat. vortex standards).

Ties in with the GFS ens to be honest.

      

It should turn drier and eventually a little milder by the 10th before we see a swing back to cooler and more unsettled conditions by mid month with another Atlantic ridge and a trough develops through Europe and the UK. Seems plausible to day 10 given the models wanting to cut the cold flow off around day 8 with the Azores ridge moving in if a little unconvincing for any prolonged spell of Euro heights, for example low heights over southern Europe should persist throughout the 16 day period even if the signal wanes for a time as higher heights move towards the UK.

Edited March 1, 2016 by Captain Shortwave

[Banbury]

I think most would happy to see this, not all settling but falling would be nice at least

[Banbury]

Fridays wintry set up

Subject to change and no doubt will

[Weegaz]

Snow showers are currently affecting parts of Ireland as precipitation moves eastwards. Net Weather Radar will allow people to track progress if they haven't used it before.

The charts for Friday looking good for Northerly areas again

[Frank Trough]

6 hours ago, johnholmes said:

Nothing in the anomaly charts to suggest what MWB infers, see links below

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

well, perhaps they're wrong? the azores ridge is going to be a player next week - to ignore it is folly. How much influence it has remains to be seen but the anomoly charts alone won't dictate that.  Your faith in them is troubling.

[Man With Beard]

23 minutes ago, Certain kind of fool said:

 

well, perhaps they're wrong? the azores ridge is going to be a player next week - to ignore it is folly. How much influence it has remains to be seen but the anomoly charts alone won't dictate that.  Your faith in them is troubling.

To be fair to John, he's simply calling a spade a spade - the Azores High will not sit over the UK by D10 (probably!) - I don't think he's saying there won't be any influence at all - we got crossed wires earlier. I believe the NOAA 8-14 trends even further this way tonight - but still a slight NW flow toward the UK so perhaps a stalemate between winter and spring coming up?

Must just comment on 18Z GFS - not seen so much snow forecast by this model at just T18, normally it's disappeared by this time - are many of us about to see our first flakes of the year?

Edited March 1, 2016 by Man With Beard

[Jonan92]

Some heights rising next to Scandinavia by 192h is the main difference in the 18z. Maybe the first signs of the SSW?

[Timmytour]

1 hour ago, Certain kind of fool said:

 

well, perhaps they're wrong? the azores ridge is going to be a player next week - to ignore it is folly. How much influence it has remains to be seen but the anomoly charts alone won't dictate that.  Your faith in them is troubling.

Personally I've seen JH hit the jackpot with his calls too many times to ever dismiss his thoughts....I've learned not to get excited by great looking charts if his interpretation of the anomaly charts don't back them up....and likewise if he senses something changing for the better in them (by which I mean cold and snow potential), then I allow my hopes to get up

[swilliam]

53 minutes ago, Timmytour said:

Personally I've seen JH hit the jackpot with his calls too many times to ever dismiss his thoughts....I've learned not to get excited by great looking charts if his interpretation of the anomaly charts don't back them up....and likewise if he senses something changing for the better in them (by which I mean cold and snow potential), then I allow my hopes to get up

Well the GEFS anomalies still showing the same thing with a blocked scenario

 

10 days

 

15 days

Seems odd that the ops keeping showing the flat option with AH ridging NE.

 

Not that cold though

but dry - could be quite pleasant