Model Output Discussion - 05/01/2016 18z onwards

[karlos1983]

18 minutes ago, Nicholas B said:

I was just looking at the ensembles Karlos, would seem there are a few more members keeping us cold from the 17th ( where most of the scatter/uncertainty starts), could be changes afoot showing here

Yeah, the model watching this week is going to be exhausting, but I think fruitful. I personally can't wait!

[feb1991blizzard]

2 minutes ago, Frosty. said:

Yes but I found the Gfs 6z to be very interesting as it keeps coldies in with a fighting chance of some wintry weather right to the end of the run and beyond. This week looks interesting too with some awkward situations for the professional forecasters as we see knife edge rain to sleet and wet snow situations developing through this week...at least it will feel like winter this week and hopefully next week too.

Oh yes - not disputing we will get the best week of the winter so far this week.

[mushymanrob]

id have thought the best chance of getting deep cold is for the ridge to our west, (which is unlikely to collapse as fast as the gfs insists) is for it to drift slowly towards scandinavia. this is not  unfeasible given the current projected pattern . but i admit ignores the gfs in favour of the noaa 500mb charts which suggests the ridge holds on much longer (to our west currently but theres plenty of time for an eastward progress).

[Troubleatmill]

10 minutes ago, Frosty. said:

Yes but I found the Gfs 6z to be very interesting as it keeps coldies in with a fighting chance of some wintry weather right to the end of the run and beyond. This week looks interesting too with some awkward situations for the professional forecasters as we see knife edge rain to sleet and wet snow situations developing through this week...at least it will feel like winter this week and hopefully next week too.

Yep, looking at the postage stamps for the 06z, there are a fair few that keep heights to our Northwest or over us rather than the Atlantic winning through easily, best ensembles for a couple of days I think,

Edited January 11, 2016 by Nicholas B

[mulzy]

FWIW the ECM parallel run is quite similar to the operational - though the high pressure at days 9-10 sits more on top of the UK rather than over central France.

Edited January 11, 2016 by mulzy

[Daniel*]

Interesting post from fergie if you have not seen it. 

 

 

[mountain shadow]

6 hours ago, Paul33 said:

Unfortunately the title "Model Discussion Thread" is a bit misleading to those of us who observe and try to learn. There are obviously various different models and various different ensembles out there such that those on here with a bias - for whatever reason - towards ramping mild or ramping cold will always find output from somewhere that appears to back his or her case.

Its frustrating but its entertaining and at times like this, it just underlines that no matter what your chosen model says, anything can happen !!!

I would say I have a decent level of model knowledge but I was trying to follow the run by the posts being made as I was on my phone.

So you can imagine the frustration when you have two contradictory posts right after one another. 

[chrisbell-nottheweatherman]

36 minutes ago, Earnest Easterly* said:

Interesting post from fergie if you have not seen it. 

 

 

This ought to be repeated until some of the more histrionic members here understand - at present, the Met Office has little confidence in the extended period due to model uncertainty.  Even the nearer-term is not entirely clear, let alone this time next week.  It's also interesting to note that he refers to models being overly progressive WRT the Atlantic sweeping-aside blocking Highs.  I'd be amazed if he wasn't referring to GFS there, among others.

[Frosty.]

The good news is the cold weather, once fully established looks like staying until well into next week which is better than some of the models were showing yesterday so it's going to gradually become colder this week with widespread frosts and icy patches and increasingly wintry showers and even some longer spells of rain, sleet and wet snow with the snow not exclusively across the hills or the north either, there could be some wintry surprises later this week as the main trough eventually edges further east and opens the door to a colder NW'ly airflow.

[johnholmes]

Nothing has changed in decades, ALMOST always if a cold spell lasts 3 or more days, the longer the more effect it has, then milder Atlantic air is predicted to move across the whole UK too quickly.

 

[Lukesluckybunch]

 So I'm not holding muh hope about this upcoming cold spell,I see temperatures in north averaging 1-3c and around 3-6c in the south. Not exactly a decent cold spell just below average more like.the coldes temps from Thursday through till tuesday, before it turns milder later next week.for a longer cold spell we really need the pressure rise this weekend to edge further north,as it appears to reach only north of Scotland then move east and topple! What we ideally need is a north and then west movement,to introduce those very cold bitter uppers! From the east.☺ I would appreciate some responses on this if you agree with what I'm saying.

Edited January 11, 2016 by Lukesluckybunch

[Timmytour]

9 minutes ago, johnholmes said:

Nothing has changed in decades, ALMOST always if a cold spell lasts 3 or more days, the longer the more effect it has, then milder Atlantic air is predicted to move across the whole UK too quickly.

 

Must admit.....I've seen many a cold spell anticipated over the years that you have not supported, so to speak, and it has ended up not amounting to anything.

So I take a lot of optimism from what you are saying here

[fromey]

1 minute ago, Lukesluckybunch said:

So I'm not holding muh hope about this upcoming cold spell,I see temperatures in north averaging 1-3c and around 3-6c in the south. Not exactly a decent cold spell just below average age more like.the coldes temps from Thursday through till tuesday, before it turns milder later next week.for a longer cold spell we really need the pressure rise this weekend to edge further north,as it appears to reach only north of Scotland then move east and topple! What we ideally need is a north and then west movement,to introduce those very cold bitter uppers! From the east.☺

hi, 

i think you need to go into the southwest discussion and read Ian Ferguson reply.

the met are struggling with any outcome at present so nothing is set in stone   

[johnholmes]

To 'try' and get some normality or perhaps objectivity into what may or may not happen.

The synoptic models have shown some degree of, shall we say, volatility over the last few days. From deep artic to mild SW'ly.

The truth lies between the two but erring more towards the cold specctrum rather than the mild one. My use of anomal charts gets derided by some but they remain the most likely upper air outcome in the 6-15 day time scale. 2 years of research winter and summer proved this with something like a 70% accuracy at the 10 day mark. If you look at the synoptic models, Gibby gives their statistics usually, and ECMWF almost always leads at any time scale and 10 days is no exception, sometimes a bit under 40% sometimes 40-45% accurate. So the figures show which version/model gives the most accurate end product at 500mb. Getting the surface pattern is even less accurate and, for various reasons of physics with moisture a major clulprit is much much more difficult.

The NOAA outputs have consistently since last Sunday/Monday kept the cold air over the UK, ECMWF anomaly has much of the time but not as consistently; GFS has given different ideas, especially latterly. To me the cold is on its way from those parts of Scotland that have been 'cold' for 2-3 days now. It will last into next week but gradually become mostly dry as both the upper ridge and its surface partner edge into the UK area. Currently, and I do not try to predict beyond 14-16 days ahead, it looks like remaining 'cold or rather cold' by meteorological definition for latish January over almost all the UK to 20-21st January, maybe a bit longer. Remember also that once cold is established trying to move it is usually a slow job. Forecasters have struggled with his dilemma for decades, long before the advent of computers. Since their arrival and the increasingly complex data they can assimilate and the accuracy very slowly increases with each new model this remains one of the problems that remains-moving mild air in too quickly.

Sorry if this post upsets some folk but I hope it gives as balanced a view without all the complex words and phrases that can be used but which, judging from some pm's I get, puzzles some folk.

links below for various sites that are worth watching

http://www.weathercharts.org/ukmomslp.htm

http://www.cpc.noaa.gov/products/predictions/610day/fxus06.html

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

http://www.meteociel.fr/modeles/naefs_cartes.php?code=0&ech=240&mode=0&map=1&runpara=

Edited January 11, 2016 by johnholmes

[bradymk]

Looks like the Met Office think the cold will at least last until the middle of next week. Could be some pretty cold temps as the high moves over us through the weekend. The uncertainty of the upcoming week aside though, Ed posted a few days ago about the positive anomalies starting to show up to our north west again by the end of the GEFS period. Still there today...

[karlos1983]

8 minutes ago, Timmytour said:

Must admit.....I've seen many a cold spell anticipated over the years that you have not supported, so to speak, and it has ended up not amounting to anything.

So I take a lot of optimism from what you are saying here

Yes, I think it just goes to show, without looking at the detail, which is impossible, the 500mb Anomaly charts are pretty consistent at picking out the overall trend. John has helped me to understand them, through using the PM button and I thank him for that, yet I'm still guilty now of forgetting to look at them, especially when cold is on the table, but that is usually because I dont want to see the end of a cold spell before it has even started. 

Edited January 11, 2016 by karlos1983

[Tamara]

The Global Wind Oscillation is now in Phase 7, in line with previous expectations, and accords with the Pacific Jetstream set to accelerate.

Wrt the second image previous GEFS forecast disclaimer exists as always with this product.  For these purposes focus on where the GWO is now  The way the Pacific is primed we can ignore any idea that this global atmosphere is going to lose too much momentum, despite the return of the MJO back to the Indian Ocean to start he next cycle

Meantime, momentum flux from the tropics remains signalled to be transported poleward into the medium term and points to continued amplification into the Atlantic towards Greenland. NWP modelling keeps adjusting the upstream amplification accordingly and hence, putting aside operational model (and some model watching) vicissitude, we keep seeing extensions day by day to the more meridional picture in the Atlantic.

The medium to longer term question continues to be how this amplification trickle calculates in terms of the upstream jet emerging out of the USA. We must not forget that lagged tropical feedback estimation time spoken about last week was circa at least a couple of weeks away from then (as is usually typical). The efforts and subsequent impressions of some modelling might give the impression this forcing has been and gone, but it hasn't. Worth repeating therefore the same mantra since last week, that we should put trust in letting the trend be the friend, and not obfuscate over face value intra day details and differences which detract from that and give false impressions.

The progressive options want to flatten the pattern, ahead of these changes fully incorporated, and re-introduce the 'same old' +AO/NAO regime. However, as we are seeing, the trend continues to be one that is seeing the amplification signal retained for longer and getting closer and closer to when that jet energy arrives out of the US.

So can we really be sure it is all set to head north and return us to a Euro ridge and sustained flat mobile pattern that easily? Especially with the troposphere/stratosphere boundary so highly disturbed and making modelling something of a lottery in itself - and also the increasing possibility of something potentially terminal arriving to knock out the upper vortex to follow these events late in the month.

The extended GEFS height anomalies continue to fully point to what is being described in this post with height anomalies resisting the progressive trend, and rooted towards Southern Greenland.  This regime is not coherent with any concentrated northerly jet and flat pattern.

 

Its clear that the extended EPS suite has an increasing raft of members that also support parity of this pattern. I would imagine that MOGREPS has similar members in its clusters as well

The overall evidence continues to be counter intuitive to return to any sustained strong vortex and euro ridge. That cracked windscreen is on borrowed time imo.

[mushymanrob]

14 minutes ago, karlos1983 said:

Yes, I think it just goes to show, without looking at the detail, which is impossible, the 500mb Anomaly charts are pretty consistent at picking out the overall trend. John has helped me to understand them, through using the PM button and I thank him for that, yet I'm still guilty now of forgetting to look at them, especially when cold is on the table, but that is usually because I dont want to see the end of a cold spell before it has even started. 

yep, me too, im a huge 'fan' of the noaa's as all year round they are very accurate for the timeframe given.

they are the first charts i view every morning, then i view the ops and doubt op runs that dont fit with what the noaa anomaly charts are saying (when consistent).

thats why i dont believe the current gfs runs that insist on getting rid of the ridge...

but i guess everyone has their fav data source, i would suggest though, following the noaa's... (and thats on the back of what john has been saying - i take no credit...)

[chionomaniac]

Day 15 EPS anomaly chart not too dissimilar as well @Tamara

[Methuselah]

Indeed peeps - the anomalies are the best rough guide to the next 10 days that there is...

[Mucka]

For me things are clearer this morning though in no way decided for 7 day+ prospects and how this cold spell can be reinvigorated or come to an end.

We now have good agreement on the solution of pushing some Atlantic energy through the ridge around T72  but then rebuilding out to 120/

This shortwave energy will slide down the ridge and could give snow for some though may also introduce some warmer sectors. Snow to low levels looks marginal, more especially on GFS which has a more complex trough and tends to keep the colder air to the North and West of the UK through the early stages. There will also be some showery spells from the trough itself.

That is the 5 day forecast which looks solid enough but thereafter there two possibilities as I see it. A forcing pattern will move the ridge/high East over the UK killing off any ppn but likely remaining cold at the surface however the degree of forcing is uncertain and this is where the real divergence could be at around day 6+.

Currently the ECM wants to drive the jet NE over the block and so slowly sink it into the continent

But if we wind back to 144/168 we can see that relatively small changes in the distribution of energy could give very different results as I posted this morning.

Hope casting?

Take a look at what GFS now wants to do.

It wants to try and force energy SE with low pressure disrupting against the ridge. This results on cut off heights over Greenland and pressure falling to our South and into NW Europe which will turn things less cold briefly (could also stay cold if pattern far enough West and enough disruption) but keep the pattern amplified behind.

If this new signal from GFS is correct there is scope for some big improvements depending on the strength of the ridge and the amount of energy we can get to disrupt SE and we may see more and more of this

If ECM is correct then it wills stay colder at the surface longer but with little prospect of snow or quickly renewed cold whereas if gFS is correct it will turn briefly milder with rain but then a quick return to cold longevity of which could be very brief or prolonged depending on solution of ridge/undercut/Greenland heights/ridge2.

There is a small chance of another solution which would be to get just enough energy under an ECM type block to sustain the high at a higher latitude for longer and then hope for a more favourable upstream pattern and further undercut with Scandinavian high being the ultimate solution however I currently see that as a longer road with more hurdles and less support.

Personally I hope GFS is on to something because it offers a quicker route to a reload of cold uppers and snow chances a;though it also gives a possibility of the atlantic getting in if the pattern is too flat upstream.

If big changes come they will be in the 120 to 168 period where the models have not yet resolved the distribution of energy.

Edited January 11, 2016 by Mucka

[legritter]

44 minutes ago, Frosty. said:

The good news is the cold weather, once fully established looks like staying until well into next week which is better than some of the models were showing yesterday so it's going to gradually become colder this week with widespread frosts and icy patches and increasingly wintry showers and even some longer spells of rain, sleet and wet snow with the snow not exclusively across the hills or the north either, there could be some wintry surprises later this week as the main trough eventually edges further east and opens the door to a colder NW'ly airflow.

I can only echo Frostys post at present .

Looking at all current data and charts i think this cold spell could hang on for some time ,Alot of ifs and buts after this week end and still the scope for surprises galore if our dice falls right .

A big question mark also come sat /sun with the possible inclusion of fronts approaching from the Atlantic and with this being 6/8 days away and models all over the place we could find ourselves in a real battleground situation ,no guarantee but i do feel the chance is there .

Great posts again on our top forum , and a snooze before the next set of runs ,Stellas all round gang ,i,ll have a half .

[Paul_1978]

To all intents and purposes it doesn't like like there will be an awful lot of snow to get excited about (looking at Liam Dutton's new blog from this afternoon), so I'm going to be keenly watching the models for something coming up with a bit more "bite"!

Will we get a Feb 1991 or Jan 1987? Who knows. It makes for good model watching though. 

Edited January 11, 2016 by Paul_1978

[SLEETY]

1 minute ago, Paul_1978 said:

To all intents and purposes it doesn't like like there will be an awful lot of snow to get excited about (looking at Liam Dutton's new blog from this afternoon), so I'm going to be keenly watching the models for something coming up with a bit more "bite"!

Will we get a Feb 1991 or Jan 1987? Who knows. It makes for good model watching though. 

milder westerly winds seems to be the outcome from mid next week,from the updated met office forecast ,so all this talk about ssw and greenland high building again doesnt seem to be favoured by met office at all

 

[Eskimo]

1 minute ago, SLEETY said:

milder westerly winds seems to be the outcome from mid next week,from the updated met office forecast ,so all this talk about ssw and greenland high building again doesnt seem to be favoured by met office at all

 

Yes, but they also never mentioned this upcoming cold spell until last week.