Model output discussion - 20th Feb onwards

[Banbury]

Another variation form GFS after mid term I see

[fergieweather]

4 hours ago, Singularity said:

Yet even under that scenario it seems likely the middle of March will feature blocking focused just NW of the UK. This is something GloSea5 and EC-32 seem to have started to pick up very well indeed following the initial 'noticing' period (first signs in ensemble products) a week or so ago. 

The notion of troughing to E & heights to W was repeatedly signalled for March from as far back as Dec in GloSea5. What's noteworthy is how the model remains steadfast in maintaining northern blocking during early April too, with a conspicuous theme of below average temperatures continuing. Hopefully the subsequent signs of temperature recovery thereafter (incl in EC Seasonal Model, which has interesting dry anomalies then later spring/early summer) will become reality. 

Of course next winter we'll be doing this cold-or-not gig all again, but perhaps against a La Nina backdrop and easterly QBO...!

[JP1972]

6 hours ago, chris pawsey said:

Going down the depol office to get his name changed... or he's has a heart attack!! 

Big turnaround in the models over the last few days... the next few will be interesting! Still hope for coldies

Ironically you've changed the name of the Deed Poll office.

[Spah1]

Effects of the QBO include mixing of stratospheric ozone by the secondary circulation caused by the QBO, modification of monsoon precipitation, and an influence on stratospheric circulation in northern hemispherewinter (mediated partly by a change in the frequency of sudden stratospheric warmings). Westward phases of the QBO often coincide with more sudden stratospheric warmings, a weaker Atlantic jet stream and cold winters in Northern Europe and eastern USA whereas eastward phases of the QBO often coincide with mild winters in eastern USA and a strong Atlantic jet stream with mild, wet stormy winters in northern Europe (Ebdon 1975).

Really, mild and wet. 

Quote

 

[Radiating Dendrite]

5 hours ago, Spah1 said:

Effects of the QBO include mixing of stratospheric ozone by the secondary circulation caused by the QBO, modification of monsoon precipitation, and an influence on stratospheric circulation in northern hemispherewinter (mediated partly by a change in the frequency of sudden stratospheric warmings). Westward phases of the QBO often coincide with more sudden stratospheric warmings, a weaker Atlantic jet stream and cold winters in Northern Europe and eastern USA whereas eastward phases of the QBO often coincide with mild winters in eastern USA and a strong Atlantic jet stream with mild, wet stormy winters in northern Europe (Ebdon 1975).

Really, mild and wet. 

To be honest I would have thought a milder USA E. Coast would be a much more favourable proposition. The severe cold they have had in the last few years has just fired up the jetstream!

 

 

[IDO]

We have a repeat of the same synoptics next week, but with the uppers not as cold, 2m temps could be even higher if we can get the sun shining:

The GFS in week 2 looks like trying to repeat the pattern for the third time. Again the axis of cold remains E.Asia-W.US from D1 to D16 on the GFS so all we can expect from a PM flow is washed out uppers coming from the core cold to the NW. We need more HLB to reset where the cold upper pools are.

Other models and GEFS offer variations on the same theme next week though all have in common rather tame upper air temps and in March we will need better to get snow anywhere away from higher ground.

ECM and GFS at D7: 

Still no respite from a lobe of PV over to the NW so any Atlantic ridge will struggle to be anything other than a toppler, especially with no upstream meridional flow.

Looking at the CFS w3 and w4 there are no Scandi heights or Greenland heights so doubtful we will get any blocked pattern based on those charts:

That may be reflective of the MJO (Kelvin Wave) going quiet in the second week of March and ENSO background re-establishing.  Later in March maybe with the strat PV finally giving up the ghost further cold seeping south. However late March to early April Spring warmth is my main hope, not cold rain!

Edited February 27, 2016 by Paul
Removed off topic part of post

[knocker]

The GEFs 10-15 anomaly this morning is a duplicate of last night which of course isn't that surprising. Depending on how the surface HP to the west aligns it probably leaves room for systems to sneak around the HP circulation and bring periods of quite wintry weather but there remains the ever increasing hope of drier and quieter spells albeit if the temps might be a little depressed against the average.

[mountain shadow]

1 hour ago, Radiating Dendrite said:

To be honest I would have thought a milder USA E. Coast would be a much more favourable proposition. The severe cold they have had in the last few years has just fired up the jetstream!

 

 

Makes no difference as the permanent PV segment always sit between the US and us. It is this PV segment which drives our weather.

Below average temps for the foreseeable but not cold for snow for most.

[northwestsnow]

1 minute ago, knocker said:

The GEFs 10-15 anomaly this morning is a duplicate of last night which of course isn't that surprising. Depending on how the surface HP to the west aligns it probably leaves room for systems to sneak around the HP circulation and bring periods of quite wintry weather but there remains the ever increasing hope of drier and quieter spells albeit if the temps might be a little depressed against the average.

I'd prefer something drier moving forwards.The sun is gaining strength now knocks so should feel pleasant in the sunshine, even up here in the north west, imagine that!!!

[bluearmy]

8 hours ago, fergieweather said:

The notion of troughing to E & heights to W was repeatedly signalled for March from as far back as Dec in GloSea5. What's noteworthy is how the model remains steadfast in maintaining northern blocking during early April too, with a conspicuous theme of below average temperatures continuing. Hopefully the subsequent signs of temperature recovery thereafter (incl in EC Seasonal Model, which has interesting dry anomalies then later spring/early summer) will become reality. 

Of course next winter we'll be doing this cold-or-not gig all again, but perhaps against a La Nina backdrop and easterly QBO...!

 

GLOSEA-5 is fast becoming the premier seasonal model.  Has it had the same success over the past couple summers as it clearly has the winter periods?  perhaps it's better modelling of the strat makes it a better winter tool than summer??

[Banbury]

32 minutes ago, bluearmy said:

 

GLOSEA-5 is fast becoming the premier seasonal model.  Has it had the same success over the past couple summers as it clearly has the winter periods?  perhaps it's better modelling of the strat makes it a better winter tool than summer??

It's certainly been very consistent, maybe the one to follow- courtesy of Ian

Edited February 27, 2016 by Banbury

[Guest]

Following on from my post last Tuesday (on page 25 of this thread), I feel that things are now just starting to fall into place for a prolonged cold spell. So here is an update on my interpretation of the forthcoming pattern changes and what I shall be looking for in the models during the next few days.

I based my views in my last post around the excellent Arctic Oscillation report by Judah Cohen from the AER published on February 22nd. Here is the link again:

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

It is too early for an update from the AER but we can look at the changes to the key indicators that Judah referred to. 

 

The Arctic Oscillation:

The AO has already trended negative and the ensemble forecasts are for this to remain so in the foreseeable future – certainly the next 2 to 3 weeks and probably longer.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml

 

The Madden-Julian Oscillation:

I follow the excellent posts by Singularity (+ Nick Sussex and others), particularly in regards to the MJO and its likely impacts. I am pleased to see that we have gone through the blip by most of the models earlier this week when it seemed we might barely reach phase 8, with lower amplification before returning to zero. Now we have just reached phase 8 at decent amplification and likely to remain here for longer than previously indicated.

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

Some forecasts take us back to “0” quite quickly but there are some that now take us right through Phase 8 and into Phase 1 at good amplification at varying speeds.  An example of this is by Kyle MacRitchie (PhD in Atmospheric Science, USA).

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

The overall trend is very encouraging and we are likely to be in the right phases (8 then 1) for much of the next 6 weeks.

 

Other factors:

The El Nino continues to weaken in the eastern Pacific but remains strong in the central Pacific (no significant change since Judah’s report). The current stratospheric warming is gathering momentum and the latest output from the main models seems to indicate a major SSW by mid-March. Judah Cohen predicted a full stratospheric/tropospheric coupling starting around now, re-enforcing and prolonging the negative AO. He also predicted this weekend’s final injection of energy into the polar vortex. It seems that this is responsible for the short lived interruption in the colder pattern. So far it seems that Judah is spot on. He then expects the polar vortex to move down into Europe, a cold pool to develop there, low heights from the Arctic north of Scandinavia right down into central Europe, higher heights to our north-west and a long fetch north-easterly to become dominant. He then expects the Siberian high to spread westward by mid-March, maintaining the default north-easterly and strengthening the cold. I should remind you that he does add the caveat that this would be the likely impact in a mid-winter SSW event but he feels should still apply to a late winter-early Spring event.

 

Pattern Changes, Impacts and What to Look for in the Models:

The rest of this post is my interpretation of likely pattern changes based on Judah’s report and their impact.  As is often stated, most of the models take quite some time to factor in the full impact of negative AO and MJO influences. As Singularity said yesterday, it is quite unusual to see the MJO at good amplification in phases 7, 8 and 1 coinciding with a strongly negative AO. I agree with him that this will challenge the models. In fact, factoring in the state of the EL Nino and SSW as well, it is doubtful that any close analogues are available! The overall impact could be far greater than has been shown so far.

I would suggest that there will be much greater amplification than is currently stated. The NOAA anomaly charts, which John Holmes and others do an excellent job in posting and analysing, during the last week or so, have trended towards forecasting stronger North Atlantic ridging and some HLB, now in both the shorter and medium term outputs. They have gone from a dominant north-westerly flow with frequent Polar maritime incursions to a rather more north-north-westerly flow with several Arctic incursions. I believe that the “veering” trend will continue further! It will go in the direction indicated by Judah Cohen with lower heights in Europe and stronger HLB to the north-west and north and later on to the north-east. “If” this happens, then things would turn decidedly cold, especially so for early to mid-March.  

So far the models like GFS, ECM, UKMO, GEM, NAVGEM and JMA have started factoring in the short-term changes up to around T+144. This was to forecast last week’s cold spell, downgrade it to a “rather cold” spell, show a temporary less cold interlude mid-week (around Tuesday/Wednesday) and then trending colder again later in the week and into next weekend. Then the divergence starts. The models that go to 10 days and beyond show varying degrees of cold but apart from GEM (which is more consistently cold) none of them really show prolonged north-easterlies or a substantial cold pool building in Europe. If Judah is right, we should start seeing much colder charts within a few days. I will be looking for much stronger HLB by this time next week. A veering of the flow through north to north-east and little or no westerly interruptions with a weak jet, ”not” a series of quite deep low pressures pushing through (albeit mostly colder ones). 

Looking further ahead, I will be looking for Judah’s prediction of the westward push of the Siberian high, helping to maintain the default north-easterly flow and feed in even colder air and lower uppers. This will help counteract the usual seasonal warm up.  Although we rarely get this type of pattern set-up, once it does become established, it tends to be long lasting and takes a lot to shift it. March 2013 is an example of this. I am not saying that we will match that famous cold spell but we may get quite close to it. As I said in my last post, the airstream may be quite a dry one but there would be reasonable potential for some wintry precipitation and with uppers probably in the -6c to -10c region for prolonged periods we “might” see one or two significant snow events. It is also possible that we see many dry days with extensive stratus cloud and very low daytime temperatures (perhaps 1c to 4c).

As I believe that the models will struggle initially with these pattern changes due to a distinct lack of analogue input being available, I would expect many of the operational and control runs to be at the colder end of the ensembles. This would reflect the “human expertise” needed to make the appropriate adjustments.

Finally, I must stress that all this is only my personal opinion which largely depends on Judah Cohen’s predictions coming to fruition. As always, much can go wrong. I just wanted to provide an indication of what is possible and what to look out for during the next 2 weeks.

Edited February 27, 2016 by Guest
grammatical - missing word(s)

[Polar Maritime]

The GFS 6z ups the snow risk for Wednesday as a front pushes in from the N/W, After the milder blip Mon/Tues.

Edited February 27, 2016 by Polar Maritime

[MR EXTREMES]

cold air is being mixed out far to much and still no true northern blocking this morning from all the models the ecm and gem still have deeper lower 850s bottled up to our nw but slight signs of deeper cold to our ne.

but as the fairly deep lows slide from the nw  in a se direction its picking up lesser cold 850s and constantly mixing out the colder uppers.

we still do not have a true sustained Greenland high or sustained straight northerly arctic air although I suspect arctic air will be drawn in but quickly gets mixed out.

its crazy knife edge stuff and the models are climbing down from recent runs slightly but this could be a direct response to how the mjo is playing out.

but theres no doubt the Scottish ski resorts are not going to complain although some of the lows projected to swing down from the north west look pretty active wet cold to the south colder further north but not really extreme and low level snowfall not so much an issue yet.

but I feel theres lots more changes to come infact its very possible that the quick climb downs from the models could very quickly upgrade.

my concern is not seeing a sustain arctic or Siberian air source,

and although around Greenland its very very cold the air from the nw has a long sea track and is not sustained either so I feel its pretty much more of the same as the last few days or week or so!

some up north could have suprises but at this moment cold wet and windy for the majority of the uk.

but I most certainly would not dispute that in reality none of the charts into fi this morning are really the holy grail.

but I also would not dispute upgrades this evening or in the coming days..

 

Edited February 27, 2016 by emotional rollercoaster

[Banbury]

Well into FI GFS drops the idea of HP sitting over us

[feb1991blizzard]

1 hour ago, bluearmy said:

 

GLOSEA-5 is fast becoming the premier seasonal model.  Has it had the same success over the past couple summers as it clearly has the winter periods?  perhaps it's better modelling of the strat makes it a better winter tool than summer??

I'm glad someone else has noticed this, its not just FAST BECOMING the premier seasonal model though, it has been since its upgrade from GLOSE4 in my opinion, the final test for me is in the next month, can it pick out a spell of sustained blocking at the 3 month range or more?  people might not remember the accuracy if indeed that's what occurs because its unlikely to yield bitter cold but neither did the model suggest that.

[Nick F]

The tropospheric polar vortex to the NW continues bounce back and forth across Greenland then back to north of Canada on the model output. When it pushes east across Greenland a fragment of the PV breaks away SE towards Europe into the European mean trough and we see this repeatedly happen. We see it early next week, then later in the week and again early the following week.

As the trop PV retreats back to N Canada it corresponds with an amplified wave moving downstream from N America  in the upper flow, which allows the Atlantic ridge to build N and NE across Iceland and Greenland as that fragment of the PV drops into Europe. Then the PV is, before too long, pushing back east into Greenland again with the process repeating. 

So we see fragmented rather than sustained cold pools sliding across the UK over the coming days, which usually end up more moderated at the surface than GFS predicts 4 days+ ahead, so it's hard to predict if there will be any meaningful snowfall away from higher ground in the north without a sustained cold flow. After the mild blip early next week, it does look to remain chilly, but I remain doubtful there'll be much if any lowland snow away from Scotland for now unless we get a sustained cold flow at the surface and not just aloft.

Heading into March and with lack of sufficient surface cold unless we get a more blocked set up with continuous cold feed, we will be reliant on nights and early mornings for snow chances in lowland Britain IMO.

Edited February 27, 2016 by Nick F

[nick sussex]

Not sure what the GFS was doing in its last few runs before starting to backtrack on its 06hrs run. It was getting flatter and flatter upstream.

Overall the models point to below average temps for the next few weeks but not well below which is whats needed to deliver for the UK.

I can say from experience here in this part of France at this time of year that the set up of that low anchored over Iberia with a ne/e flow is normally a shoe in for snow even to lower ground, whats transpired is a few flakes mixed in with the rain although the Pyrenees are getting a lot of new snow.

Its like someones hovered up all the available cold for Europe and left a few scraps! Not saying theres no snow likely in the forecast for the UK but at this late stage you really need a strong block holding on for long enough to tap more favourable upper air.

Looking back through February the synoptics have overall been okay, theres been many chances with on the face of it good wintry synoptics but the depth of cold hasn't been there.

Not trying to be too downbeat here because with the set up something might pop up snow wise, again we're talking generally marginal away from higher ground.

And with the MJO still continuing to move through the phases theres still a chance something colder might show up.

 

[phil nw.]

Well whatever happens longer term as a result of MJO/EN and the likely demise of the pv later in March,is it all going to be too late for anyone still hoping for a late snow event?

Certainly the ens graph continues below average until mid-month

but the current projected pattern of north westerlies may not be cold enough,especially further south.We do need to see a more direct flow from any deeper cold pool to the north/north east and the current day 10 ens means remain unconvincing in that regard.

 

If we are to see blocking further north and a colder north or north easterly it really need to show sooner rather than later in March for a final chance of Winter.

I think soon many folks will be thinking enough let's see some Spring sunshine and dry weather,even if it proves to be rather cold.

[mountain shadow]

Phil

The latest GFS 6z shows cracking Greenland blocking with winds from the North East, unfortunately, the -10 850 is North of Scandanavia, incredible for early March surely?

As others have alluded to, great synoptics but no bitter cold to tap into.

The GFS has completely dropped its widespread snow event for next weekend too.

[knocker]

16 minutes ago, phil nw. said:

Well whatever happens longer term as a result of MJO/EN and the likely demise of the pv later in March,is it all going to be too late for anyone still hoping for a late snow event?

Certainly the ens graph continues below average until mid-month

but the current projected pattern of north westerlies may not be cold enough,especially further south.We do need to see a more direct flow from any deeper cold pool to the north/north east and the current day 10 ens means remain unconvincing in that regard.

 

If we are to see blocking further north and a colder north or north easterly it really need to show sooner rather than later in March for a final chance of Winter.

I think soon many folks will be thinking enough let's see some Spring sunshine and dry weather,even if it proves to be rather cold.

And this morning's EPS 10-15 anomaly does little to alter this view rather in fact strengthens it, as indeed do all of the anomalies, Following on from the 6-10 it moves the Atlantic ridge east to just west of the UK accompanied by a similar movement east of the trough. Thus reinforcing the NW flow with temps a little below normal.

[SLEETY]

39 minutes ago, mountain shadow said:

Phil

The latest GFS 6z shows cracking Greenland blocking with winds from the North East, unfortunately, the -10 850 is North of Scandanavia, incredible for early March surely?

As others have alluded to, great synoptics but no bitter cold to tap into.

The GFS has completely dropped its widespread snow event for next weekend too.

yes what is the reason behind the air not getting that cold,the unusual warm in the Artic this Winter??

 

[phil nw.]

50 minutes ago, mountain shadow said:

Phil

The latest GFS 6z shows cracking Greenland blocking with winds from the North East, unfortunately, the -10 850 is North of Scandanavia, incredible for early March surely?

As others have alluded to, great synoptics but no bitter cold to tap into.

The GFS has completely dropped its widespread snow event for next weekend too.

That pronounced ridge at the end of the run ms would be fine in mid-Winter sure.Now though that blocking is still not far enough north to eject that cold cleanly to the UK.Of course by mid-March we are up against it as the cold pool is already shrinking.

Edited February 27, 2016 by phil nw.

[Gowon]

1 hour ago, Nick F said:

The tropospheric polar vortex to the NW continues bounce back and forth across Greenland then back to north of Canada on the model output. When it pushes east across Greenland a fragment of the PV breaks away SE towards Europe into the European mean trough and we see this repeatedly happen. We see it early next week, then later in the week and again early the following week.

As the trop PV retreats back to N Canada it corresponds with an amplified wave moving downstream from N America  in the upper flow, which allows the Atlantic ridge to build N and NE across Iceland and Greenland as that fragment of the PV drops into Europe. Then the PV is, before too long, pushing back east into Greenland again with the process repeating. 

So we see fragmented rather than sustained cold pools sliding across the UK over the coming days, which usually end up more moderated at the surface than GFS predicts 4 days+ ahead, so it's hard to predict if there will be any meaningful snowfall away from higher ground in the north without a sustained cold flow. After the mild blip early next week, it does look to remain chilly, but I remain doubtful there'll be much if any lowland snow away from Scotland for now unless we get a sustained cold flow at the surface and not just aloft.

Heading into March and with lack of sufficient surface cold unless we get a more blocked set up with continuous cold feed, we will be reliant on nights and early mornings for snow chances in lowland Britain IMO.

That has been the main issue.. Low heights just doesn't want to leave that vicinity, either that or we get shortwaves forming around south Greenland/Iceland or Norway that scuppers any chance to get proper cold south or deep cold coming West from eastern Europe. 

I used to be a bit sceptical of this, but it's got to be the result of global warming causing the tropospheric vortex to get stronger? I'm sure someone not too long ago posted an anomaly chart of the Atlantic low pressure over the years and it was clear to see how it has got more dominant..or am I chatting rubbish? 

[IDO]

52 minutes ago, mountain shadow said:

Phil

The latest GFS 6z shows cracking Greenland blocking with winds from the North East, unfortunately, the -10 850 is North of Scandanavia, incredible for early March surely?

As others have alluded to, great synoptics but no bitter cold to tap into.

The GFS has completely dropped its widespread snow event for next weekend too.

And of course it's one run; it's the 06z, so worthless after D7; has no support from its mean and an outlier in FI:

: