Model Output Discussion - 31/10/2014 and Beyond

[Nick F]

No great changes overnight from the models that should lead to any concerns. Day 7-8, the Scandi/E Europe +ve height area has shifted towards Iceland/Greenland on EC, GFS and GEM while Atlantic troughing starts to progress east across western Europe, this allows an easterly flow to develop across the UK over the weekend continuing into next week as lows undercut the UK rather than stall to the W and SW, though GFS 2m temps don't look particularly cold, rather average as it happens.

 

By day 10, this morning's GFS op and parallel run have a weaker and smaller block over Greenland/Iceland which unfortunately fails to supress the PF jet south enough to stop depressions from tracking NE across the UK beyond day 10. But ECM has a more robust block to the N and NW. GEM similar, though deep cold pool drops down into NE Europe alot quicker.

 

All models seem to favour a deeper more organised cold vortex over E Canada by day 10, this powering up a strong jet out into the NW Altantic, we just need to see the Greenland/Iceland block develop sufficiently strong enough to supress this strong jet south away from the UK!

 

We may have to wait until Dec until everything eventually falls into place to drive the arctic deep cold towards the UK, but the building blocks are still falling into the right places for this to happen.

Edited November 10, 2014 by Nick F

[SteveB]

A wet and mild week ahead especially for the West of the Country, the East may escape the rain until the end of the week

 

 

But still plenty to keep positive about if your looking for cold.

 

Snow cover is looking amazing  https://forum.netweather.tv/topic/81111-snow-and-ice-in-the-northern-hemisphere-autumnwinter-2014/page-30#entry3067179

 

Stat forecast is looking  good  https://forum.netweather.tv/topic/81567-stratosphere-temperature-watch-20142015/page-

15#entry3067149

 

And we have the OPI  forecast today to look forward to https://forum.netweather.tv/topic/81494-october-pattern-index-opi-monitoring-winter-season-2014-2015/page-63#entry3067154

 

So plenty to keep us all interested  in while waiting for the snow to arrive 

[johnholmes]

Picking up from the post by Nick F above and the anomaly charts have been pretty consistent in predicting the pattern shown in the links below. About 4-5 days ago when they began to show the idea of this extended trough into Europe with +ve heights and ridging north of this, see below

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

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

 

Monday/Tuesday for EC-GFS and the following day for NOAA, so good consistency here which gives a high probability of it actually developing. Just what detail will transpire from this basic upper air pattern is yet to be decided but perhaps not the deep cold some hope for and a few try to make out will happen in the 7-10 day time range?

[Ali1977]

Pressure much higher over greenland on the GFS P and GFS by day 6, not sure if this is a good thing or bad but the NH chart looks impressive and defo no PV involved

Edited November 10, 2014 by Ali1977

[karlos1983]

Pressure much higher over greenland on the GFS P and GFS by day 6, not sure if this is a good thing or bad but the NH chart looks impressive and defo no PV involved

Higher the better/stronger Ali

[Winter Cold]

T144 on the GFS(P) 6Z does have a nice high over Greenland, but as far as I can see it doesnt really undercut the low, it mostly stays to our south, and then just as it starts to move then another one comes in 

 

[shaky]

T144 on the GFS(P) 6Z does have a nice high over Greenland, but as far as I can see it doesnt really undercut the low, it mostly stays to our south, and then just as it starts to move then another one comes in 

 

its a shame cos on another day those cold uppers north of Norway would be guaranteed to flood their way southwards across the UK but on this occasion I dont know why because to me everything looks set perfectly for it to happen!!

[492]

Picking up from the post by Nick F above and the anomaly charts have been pretty consistent in predicting the pattern shown in the links below. About 4-5 days ago when they began to show the idea of this extended trough into Europe with +ve heights and ridging north of this, see below

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

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

 

Monday/Tuesday for EC-GFS and the following day for NOAA, so good consistency here which gives a high probability of it actually developing. Just what detail will transpire from this basic upper air pattern is yet to be decided but perhaps not the deep cold some hope for and a few try to make out will happen in the 7-10 day time range?

ECMWF 6-10 day 500 MB chart is showing a closed circulation to the north of Scotland which is pretty rare and would help to cement the block. Whether it is still there in a day or two remains to be seen but this is significant. 

[shaky]

ECMWF 6-10 day 500 MB chart is showing a closed circulation to the north of Scotland which is pretty rare and would help to cement the block. Whether it is still there in a day or two remains to be seen but this is significant.

sorry what is a closed circulation or is it a shortwave or something?

[IDO]

its a shame cos on another day those cold uppers north of Norway would be guaranteed to flood their way southwards across the UK but on this occasion I dont know why because to me everything looks set perfectly for it to happen!!

 

 

Yes even when there are superb blocking highs you need the luck for the cold to hit the UK. The upcoming 10 odd days have a very rigid pattern at the 500hpa level as well as at the upper (850s), and the latter cold pools remain pretty much in situ spinning on an axis sending 2-3 reloads to their respective regions. When we get the stratospheric disruption in December down to the trop, then again if the pattern is like this coming one, you need the cards to fall right and you will get an extended cold spell. There are more mobile strat down warming's as well, spreading the cold a bit more. The next 8 days 850s show the static 850s flow for London:

 

 Very little spread.

 

The NH GFS P D10 chart remains of interest: 

 

Afterwards the Parallel becomes a lot less blocked on our side of the NH, so at D16: 

 

A continued trend but of course it could be the default FI GFS bias even in the new updated version. 

[stratty]

its a shame cos on another day those cold uppers north of Norway would be guaranteed to flood their way southwards across the UK but on this occasion I dont know why because to me everything looks set perfectly for it to happen!!

Like this  

[492]

sorry what is a closed circulation or is it a shortwave or something?

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html%C2'> At any given height level, 500mb in this case, it is where a cut off low or high forms in the normally smooth running contour lines around the hemisphere. It can sometimes indicate a weaker circulation in all or part of the hemisphere and may be more prone to blocking.

[Barry12]

For a day 6 charts that's brilliant, fully split pv

 

[bluearmy]

The ECM ens are a swing back to yesterday morning.

Anyone seeking cold solace in the control - don't. It's just a weak continental feed. No 'beasterly'

[tcc]

At this time, there are two things I'm looking out for, 1) Is to check how much rain is expected whilst we have the block to our east as there could well be some flooding especially in the West and 2) check to see if a PV develops properly and ends up over the Pole/Greenland!

 

Hopefully the first one isn't too much of an issue and for the second I'm hoping it keeps fragmented. That way we'll always have a chance of getting something wintry.

[Mucka]

To put a negative spin on a positive output. 

 

UKMO was probably the worse of the output this morning which is why it has had little mention. It has really been dragging its heals when it comes to building high pressure over Greenland or splitting the PV so it would be nice to see an improvement in its output.

 

 

It is a little out on its own with how it develops low pressure over the Arctic (N/NE of Greenland) and prevents and link up of polar heights so hopefully it will drop that.

 

It is still a decent chart by 144 with a renewed effort to build heights into Greenland but again low pressure would prevent any link up and the block would always want to sink back toward Scandi unless we get enough undercut to support a mid latitude cut off high. Looking pretty good upstream otherwise for further attempts at WAA toward Greenland courtesy of the jet digging South in the Atlantic so finely balanced overall for blocking to develop that could provide early cold/snow chances latter part of Nov.

 

 

Overall though it is pretty much as you were and wait for further runs. If we do eventually get a good wintry set up then there will be plenty of drama along the way as always but that is part of the fun. Keep an eye out for developments over the Arctic 72/96h.

Edited November 10, 2014 by Mucka

[MR EXTREMES]

The ECM ens are a swing back to yesterday morning.

Anyone seeking cold solace in the control - don't. It's just a weak continental feed. No 'beasterly'

Is this good or bad ?

[nick sussex]

More uncertainty today with the will it or won't the trough disruption be favourable.

 

As you can see the models are now less reluctant to separate the slow moving low near the UK from low heights to the nw, because of this any ridging to the ne is stopped from backing further west.

 

Added to this the movement of the PV chunk in Canada is uncertain, this is important to the amount of energy that goes into the Atlantic, because we're dealing with a block to the ne we do want to see sufficient upstream amplification to help sharpen any troughing near the UK which helps with any undercut, its essential to get sufficient lower heights into central/southern Europe to underpin the block.

 

The upstream amplification also helps to pull any lower heights away from Greenland, generally in these situations you'll find a developing shortwave engaging this the natural result of that phasing acts as a nw pull to those lower heights, if you follow the ECM from T144 to T192hrs you can see how colder air digs further south into the mid USA as the pattern amplifies and those low heights in north Greenland get pulled away at the same time.

 

Below is from the NCEP discussions:

 

THIS SOLUTION TEMPERED
THE SECOND COLD AIR INTRUSION INTO/THROUGH THE INTERMOUNTAIN WEST
BUT THE STRONG RIDGING UPSTREAM CAN STILL FAVOR A FARTHER
SOUTHWESTWARD PUSH OF ARCTIC AIR THAN THE MODELS MAY BE SHOWING
/SIMILAR TO HOW THE SHORT RANGE ARCTIC AIR INTRUSION WAS ONCE
FORECAST AT THE 5-7 DAY LEAD TIME/.

 

The suggestion here is that we might see more amplification rather than whats currently shown by the NWP. which would be helpful.

 

So the questions going forward are in relation to how troughing disrupts near the UK, in turn how far west does any blocking get, how resilient is the block to a possible PV onslaught if indeed we do see this set up in ne Canada, which of course results in how far south the jet will be.

 

A powerful PV does not finish off a cold UK solution but we do need to see the block put up a fight.

Edited November 10, 2014 by nick sussex

[bluearmy]

Is this good or bad ?

Depends if you want a proper cold spell. If so, it's less good.

[Tamara]

 

<. However, we should not expect the atlantic profile to improve sufficiently just yet, and the recent Fantasy Island -NAO modelling and Greenland High building of the ECM looks too premature imo.  

 

<the ECM once again looks culpable of over amplifying the atlantic pattern.

 

< The pattern looks to cycle, wash, spin, and repeat. Although I agree the GFS is prone to an eastwards bias of patterns, in contrast to the over amplifying errors of the ECM I do think that it is best to be prepared for some less than enjoyable model watching with suggestions of a fairly mild NW/SE split , temporarily, after the current period of model watching interest finishes.

 

< The next time around the SAI/ wave breaing -AO feedbacks will be stronger with greater repercussions hemispherically. It is common for a long period of AO phase dominancy (this season negative!) to be preceded by an opposite spike as zonal wind profiles with the polar field are re-shuffled. The AO/NAO lose their seasonal disconnect as we plough onwards into and through winter. Cold pooling to our NE will deepen and more extensive westwards and southwards. Over the coming month or so, resurgent tranches of wave activity are likely to draw deeper blood from the polar vortex that we increasingly pick up the scent

 

At the risk of posting a 'jam tomorrow' post - better then, than now, for sure

 

 

The model output this morning continues to consolidate the pattern for the short term with continued surface trough disruption and unsettled conditions for the UK against a macro NH pattern which is altogether much more appealing for the long term.

 

As expected, the models are converging on a solution in the 10 day period that excludes height rises over Greenland and any meaningful attempt to back Siberian cold westwards. The ECM has adjusted its bullish suggestions accordingly and consensus settles around a trough disruption graveyard just to our west or over the UK.  We might expect this cyclonic pattern to persist for the greater part of the 10 day period.

 

As the models thereafter start to fade the modest height anomaly to the north of the British Isles and the AO trends less negative, this heads towards the last week or so period of November where at face value the large scale pattern may look much less appealing than now (as referred to yesterday) but in fact it represents a time when interest of proper future cold prospects has greater justification than it does at present.

 

The latest words from the Italians, representing Cohen's very latest thinking on their stratospheric thread, give a very interesting insight into what is happening right now in the large scale NH pattern which increasingly looks to have significant repercussions on what lies ahead as we approach the pre-festive period. It should also increase anticipation very nicely of the imminent Cohen update on the conclusions from the finishing stats on the OPI.

 

I think that an endorsement will follow in this update that what we are seeing advertised in the models right now is a typical strong SAI pattern/progression. The role that Super-Typhoon Nuri plays in this, looks set to have accelerated the -AO feedback loops and might have mouth-watering prospects further down the line for seasonal shopping.

 

The position and depth of this low in tandem with the current heights between Russia and Scandinavia are ripely primed to activate serious wave propagation in the stratosphere. Obviously this type of hope and expectation is already documented in threads on these pages.

 

It does seem that what we might hear from the upcoming report is confidence expressed that a significant warming is set to occur in response to the current NWP situation. This warming looks primed to occur around the turn of the month, or soon after.

 

This means that fading of the present -AO spike, as I suggested in my post yesterday (and expect towards months end) could well be occurring right at the time when activity on the stratosphere thread is peaking ever higher towards anticipation of something much greater and more significant for these Isles than the cyclonic wash-out that the 'interesting' macro pattern promises right now.

 

Such a fading of the polar heights, as the -AO state (temporarily) relaxes, is a classic precursor to an even stronger rebound in December, again as stated by me yesterday.

 

A very wet and frankly dismal November is on the cards for many of us, but sludge and muck in November might lead to ice capable of bearing a duck towards Christmas  .

Edited November 10, 2014 by Tamara תָּמָר

[karlos1983]

I thought for my own benefit I would like to see what the verification was like for the GFS and the ECM @ days 7 and 8. so as I've done it, I'll share it.

 

You can cast your own votes as to which model gets closer to what actually hapened on this day, both models do pretty well at day 7 it has to be said, before they both lose it a bit at day 8, particularly GFS. which will please some members no doubt!!

 

GFS Day 7 

 

Actual 

 

ECM Day 7

 

Actual

 

GFS Day 8

 

Actual

 

ECM Day 8

 

Actual

 

Hopefully that comes out ok....  

 

Both appear to have been far too progressive imo.? 

Edited November 10, 2014 by karlos1983

[shaky]

What are the 12z runs looking like at the moment!!

[karlos1983]

What are the 12z runs looking like at the moment!!

 

Steady

 

+120 GFS

 

Edited November 10, 2014 by karlos1983

[johnholmes]

I am not sure I can agree with this comment Tamara?

As expected, the models are converging on a solution in the 10 day period that excludes height rises over Greenland and any meaningful attempt to back Siberian cold westwards

 

3 of the main anomaly charts show this process still continuing after showing it over the last 3-4 days pretty consistently? Or am I misreading you there.

I would also add that the AO and NAO at intervals beyond about 7 days show fairly poor accuracy but otherwise your eloquent comments on how things seem to be shaping up seems fine to me. By the way it is rare, at this time of the year, for the AO or NAO to stay -ve for more than 3-5 days according to something I read many months ago somewhere.

Just to add a comment about models and supposed bias. I say supposed as in my view this is something folk on here like to bandy around.

So I wrote to UK Met asking about this, see my e mail and their reply.

 In my understanding as the models started to become operational there was no model bias nor any human input to bias a model in any way.

On a weather site I belong the comment below is quite often seen

Can you please pass this e mail on to the Forecast Operational side for their comments please? I really would be most grateful if they can give me an answer, is their model bias input from human or nor not?

 

Very many thanks

 

John Holmes

 

Also in reference to your post, All models will have a starting platform & somewhere deep in the mix will be the long term mean & part of the build in terms of what the broad pattern characteristic will look like.

If the starting patter was the total INVERSE of what the characteristic should be - ALL models would mute out the signal over time to return to that normal base state- Time X

 

The GFS due to its eastward bias resets the pattern a lot quicker than the euros hence its hopeless in extended blocking scenarios..

 

Dear John

 

“The weather forecasting and climate models used by the Met Office and most other Met/Climate services are physical and not statistical models, which means that they work by trying to solve the equations describing real world atmospheric processes. Unlike statistical models, which work using analysed statistics of past events, physical models are more likely to produce a reasonable forecast in an unusual (or even not previously occurring) situation. This also means that there is no pre-programmed or hard-wired “mean stateâ€, but that the model should be able to reproduce the true mean state of the atmosphere when run over a long enough period (this is an important point for climate projections).

 

“That said, any model will still contain statistical biases, which in this case are due to imperfections in our modelling of physical processes rather than a mismatch between a pre-programmed mean and the “true†mean state. In the example provided, if a model has an “eastward†bias in the Atlantic, this is likely to be due to the model not quite capturing the correct physical processes to maintain N. Atlantic blocking. It is our role, as model developers, to improve the physical accuracy of the models to reduce these biases and improve the likelihood of the model producing a correct forecast in an unusual synoptic situation.â€

 

I hope this helps?

 

Kind regards

 

Dan

Edited November 10, 2014 by johnholmes

[Nick L]

Just a gentle reminder to avoid irrelevant one liners please, just clogs up the discussion.