Model output discussion - Jan 3rd onwards

[MATTWOLVES 3]

I had a feeling the mood may drop in here this morning after some dodgy output...Its all part of the bigger picture moving forward...the euros perhaps slower to latch on to the bigger picture..its a possibility...The GFS was first to signal blocking to the NW..and the others followed suite a few days later..This could be the case again..and must admit the outlook beyond 3 or so days at the moment is shrouded in low confidence...so for sure...do not throw in the towel,things are only just starting to shape up.

Latest from Marco P states a 30c warming so far at 10hpa,and a small amount of the warming already filtering down to to 30hpa level. It couples with the 100/150 hpa at the top of the trop..so there we have it...things are beginning to move and it looks to me that this could be a QTR event coming up.

[Vikos]

7 minutes ago, bluearmy said:

Reverse flow levels out before dropping again - as per all the forecasts over the past week .....

If we put trust in this chart, easterly currents in trop. are about to come yet,

 

BUT I don't know if this is yet a "positve thing", as there is a lag of really cold air masses to the (near) east to us.

 

[Youcan'tbecirrus]

49 minutes ago, Steve Murr said:

I know ( for a change ) its a slightly IMBY post but is 100% model related.

The high res models now working on T48 & below-

HIRLAM goes for 5-6cm over the hills in the SE - maybe low ground as well. Could be higher at the core of the streamer.

I am in a similar location Steve but for the short term seems to me the Beeb are definitely saying rain. I notice they say unsettled later this week so perhaps some hope there. I have been watching these models for probably 15- 20 years myself and, based on no scientific knowledge (which is why I prefer to just read what knowledgeable posters like yourself and a few others say) whatsoever, seemingly when it comes to winter prospects unless it is in the T72 range the chances of things going "wrong" are quite high. The almost total flip around in the models (ECM/UKMO) last night v this morning being just another example. Like I say though no scientific knowledge at all to back up that judgement.         

[Man With Beard]

27 minutes ago, wellington boot said:

Agree with this. I actually thought the UKMO nailed it a couple of times and got little credit, after being written off when it wasn't showing what people wanted.

The UKMO has done little wrong in this period, I believe? It does have the advantage of only going to D6 though, can't see the errors beyond  

Edit, just remembered, it got the micro low on 27th December wrong by 300 miles at T24. Bad day at the office that one

Edited January 3, 2021 by Man With Beard

[Tim Bland]

30 minutes ago, Speedbird said:

Isn't the red line average ?

Sorry yes, white line is average of runs (mean) and red line average for time of year 

[northwestsnow]

36 minutes ago, Uncertainy said:

Regardless of the short term conundrum the improvement in the day 10-15 EPS is significant as @mulzyhas highlighted. The long fetch SW feed runs are now in the minority and there is a bit more blocking showing up to our NW and to an extent N.

Here’s last night’s clusters at day 15 with 40% going for a long fetch SWer

The 0z for the same timestamp 

The signal for NW heights now stronger.

Cluster 2 looks most like cluster one from the 12z but it’s further south with the low anomaly and the GH heights look more influential. Cluster 3 looks excellent with w/ a Euro low / Gricelandic high similar to recently and the 1st cluster shows a general area of heights to the N but probably non-descript weather for us at the surface.

I continue to see a short milder spell day 8-9 to day 12-14 but evidence is building that it looks brief. No need to berate the models if this shows up as the signal has been there for about a week. If however we end up with a UK high in the holding pattern then it could well feel cold at the surface throughout...

GFS on its own in the mid term unfortunately but we’ll give it till tonight to make the call. If it was the one going flatter on its own we’d be discounting it. Hard to bet against the Euros here unfortunately

Would love to be wrong!

I certainly agree with you regarding the GFS/ EC UKMO standoff ...

Its excellent news that the eps are backing away from the long fetch SWly option  though.

Let's hope any unsettled or flatter phase is short lived...

All eyes on the ssw impacting the Trop...

[northwestsnow]

38 minutes ago, Tim Bland said:

A colder set of ensembles. This time yesterday the mean (white line) was just above the average (white line) so they are heading in the right direction to avoid a milder spell mid month... 

Excellent GEFS !!

They look really good for the week ahead...

[Frosty.]

Don’t give up guys, the GEFS 6z does redeem itself too a certain extent, even beyond mid month!..on the face of it, the mean May look crap, but look  at the 2m temps..hmm?..not mild is it?...on a more serious note, the mods..I mean the models may be having a wobble with all the ssw in the headlines..perhaps, before you know it, there will be bitterly cold easterly winds, dry powder snow and max temps of minus 7 Celsius ...19F if I’m not much mistaken..hmmmmm!!!!

 

[Stu_London]

just took a look at the 06z.

Toward the end exactly as you would expect strat destructed model output in FI - bits of PV strewn around like washing on a windy day.

It won't probably evolve exactly like the 06z but it will be fascinating over the next week or so. 

[Met4Cast]

This cold spell really is naff lmao.

Look at that for a synoptic setup, and the best many of us can hope for in the coming days is some sleet? Very, very poor. Looking ahead, I think the GFSP might be quite close to the mark, no Greenland high but no collapse over the UK either, more of a high just sat out to the west of the UK. 

Seems to be a real struggle to get decently cold air anywhere near the UK this year.

Edited January 3, 2021 by Met4Cast

[Frigid]

At least it's not gonna be mild like Jan 2020, outlook on the 6Z GFS keeps the cold air for most of the run w/ a lot of snow potential. Hopefully something comes out of the SSW at months end. 

[Frosty.]

6 minutes ago, Frigid said:

At least it's not gonna be mild like Jan 2020, outlook on the 6Z GFS keeps the cold air for most of the run w/ a lot of snow potential. Hopefully something comes out of the SSW at months end. 

Aye pal, the Gfs 6z op does have its frigid moments..for sure..it’s nae bad actually considering some of the dross output in recent hours!..all too play for?  

[damianslaw]

16 hours ago, Bricriu said:

 

Continued variance between ECM and GFS as we move beyond 7/8 Jan which is the reliable timeframe cut off point. Differences are due to positioning and strength of low heights to our north. ECM wants to move these further east to North of Norway and combined with forcing of long wave trough out of USA seaboard the mid atlantic high is squeezed south as heights lower to our NW, end result is heights sinking to our SW and a milder westerly feed moving in, but not exactly a turbo charged atlantic.

GFS doesn't shift the low heights as far east, and instead deepens them, and this has the effect of inflating mid atlantic heights to Greenland more robustly, the low heights are able to drop through the UK beyond 8th, potential for significant snow if this comes off, as there will be sufficient cold air to tap into.

In the reliable, a wintry mix for many some sleet and snow showers possible more so Tuesday as we pull in slightly colder uppers from the easterly, troughs may form as instability grows. Wednesday sees heights ridge into mid atlantic, and light northerly flow moves in, but with slightly milder uppers, by Thursday colder uppers move in, and there could be a trough/frontal feature which would bring more widespread snow to northern parts in particular. Friday looks cold with snow showers.

[JoeShmoe]

2 hours ago, Penrith Snow said:

My own opinion is that this cold spell has been very half hearted and localised to the UK, you only gave to look at the lack of snow across Europe to see that. Without the SSW I think this cold spell would have been it for winter 2021 due to El Nina forcing, but the SSW which is a strong one will override everything else and has the potential to bring proper cold to Europe.

If had to bet my pension on it (glad I dont) I would bet on a  very cold February following the current SSW, milder weather in mid  January will be temporary IMO.

Andy

I would agree with this. I would take a weeks westerlies and a reset if it got rid of that Urals HP because until any real cold backs westwards we are feeding off scraps. Hopefully that’s what the SSW does if the cards fall right (big if obviously)

the whole uppers in an easterly debate is kind of being borne out now as most under 200m asl are seeing rain until Thursday 

Edited January 3, 2021 by JoeShmoe

[phil nw.]

Just looking at the latest ensemble graphs from both suites and it's clear that a large divergence in the 500 hPa pressure trends show up from day 6.This uncertainty the result of upstream modeling of the jet differently- already touched on in earlier posts.

Anyway the 2 pressure/thickness graphs below. 

Both operational runs are almost outliers for different reasons.As can be seen the ecm op going for much higher pressure the high toppling and flattening and the gfs op in favour of the trough dropping south.

The ecm mean chart by day 8 is likely to be nearer the mark with a sort of half way house.The high staying just out west keeping us cold.

I am sure there will be more surprises in the coming days as the models continue to move the furniture(500 hPa)pattern around.

So yes some uncertainty for the way the NH pattern will develop in week 2 but I just keep reminding myself that zonal winds reduction and then reversal are starting above us.When they get down to the lower atmosphere we will start to see increasing Arctic blocking and the reversal of the pattern (east to west) and we all know what's waiting to our north east!

 

 

 

Edited January 3, 2021 by phil nw.

[East_England_Stormchaser91]

3 hours ago, Ice Day said:

So at 240, the GFS is seeing a renewed push of heights into Greenland.

A very cold run this. 

However, can it really be right against the UKMO and ECM at relatively short range?  I doubt it, but will return at 3.30pm to find out.

I’ve seen chalk and cheese outputs at less than 48 hours out between the GFS and ECM before. BFTE I’m sure we had the same dramas happen! 

This could easily go right down to the wire. 

I will warn also, that in these setups, nothing is a certainty until you see the white stuff falling! Even with cross model agreement, all it takes is one sneeze (usually the UKMO) and that can cause a huge panic! 

Edited January 3, 2021 by East_England_Stormchaser91

[Anthony Burden]

1 hour ago, MATTWOLVES said:

I had a feeling the mood may drop in here this morning after some dodgy output...Its all part of the bigger picture moving forward...the euros perhaps slower to latch on to the bigger picture..its a possibility...The GFS was first to signal blocking to the NW..and the others followed suite a few days later..This could be the case again..and must admit the outlook beyond 3 or so days at the moment is shrouded in low confidence...so for sure...do not throw in the towel,things are only just starting to shape up.

Latest from Marco P states a 30c warming so far at 10hpa,and a small amount of the warming already filtering down to to 30hpa level. It couples with the 100/150 hpa at the top of the trop..so there we have it...things are beginning to move and it looks to me that this could be a QTR event coming up.

Yes I totally agree troposphere reversal could take place within a short time frame .

[danm]

Lots of hand wringing in here today! No doubt that the UKMO and ECM have taken a turn for the worse in the mid term. However, does that mean it’s curtains for a significant U.K. cold spell off the back of this SSW? Not a chance. The vortex is being torn to shreds, the Atlantic is non existent and the impacts of this SSW and reversal will probably continue influencing our weather for the rest of the winter. 

Nothing is ever guaranteed, but I think we’d still be incredibly unlucky if most or all of the U.K. don’t see something significant by the end of the month. 
 

Edited January 3, 2021 by danm

[danm]

Just to add to my post above, Marco P at the Met has indicated that there could be a second warming event in the stratosphere come mid month. Tonnes to play for. 

Edited January 3, 2021 by danm

[feb1991blizzard]

5 minutes ago, danm said:

Just to add to my post above, Marco P at the Met has indicated that there could be a second warming event in the stratosphere come mid month. Tonnes to play for. 

Yes, that is what i have been banging the drum wrt, hopefully this time a proper split, this is what is likely to lead to proper cold end of month after a brief warm up, it is not hand wringing though, it is just pointing out that the warm up has been well signposted for a while now, based on ensemble forecasting experience.

[danm]

3 minutes ago, feb1991blizzard said:

Yes, that is what i have been banging the drum wrt, hopefully this time a proper split, this is what is likely to lead to proper cold end of month after a brief warm up, it is not hand wringing though, it is just pointing out that the warm up has been well signposted for a while now, based on ensemble forecasting experience.

Not suggesting you were Feb, but some posters have literally been throwing the towel in this morning. Even if the UKMO and ECM turn out to be correct at days 6-10, there seems little indication that we will remain in a flat profile for any significant length of time. 

[icedust]

I must apologise to many of you who regularly post on this forum. Until today, I have been thinking 'Why are all these people posting about 10 day forecasts as if the synoptics will bear any resemblance to these forecasts in 10 days time'.   In fact , until today I would look at T+240 charts to find out what was NOT going to happen. How wrong I have been!  

And now all that has changed. In my tier 4 lockdown this morning I have done some verification from the Meteociel site. I chose the past 2 significant changes of types that involved cold weather over the UK.

First the major development of the upper trough over W Europe on Dec26-Dec28. Best of the major models by far was the GFS OP. signalled at T+264 and nailed at T+240.

second the ECMWF which suggested the change at T+240 but a bit too far east with that diving depression. Then good from T+216. but it threw a wobbly at T+192

Third the GFS para which was OK but not until T+216. 

Next event was the easterly which started today and will likely last a few days.  best again by far was the GFS OP suggesting it at T+264, nailed at T+240, but it threw a wobbly at T+192, although it went off track at T+144

Second best was the GFS para, not too bad at T+216 and T+240, again it had a wobbly at T+192.  Third best the ECMWF which was poor at T+216 and T+240, then good from T+192.

I am having trouble uploading my working Word Doc table so the above summary will have to do.

So finally I attach the latest 2 GFS OP (the best model?) forecasts at T+240 to perhaps see what the future holds. Yes,I know some runs are better than others and these may not verify etc etc. and it has bad runs I could go on and on.  But I am now not as dismissive as I used to be.    

 

 

They both show a mid atlantic ridge with the northerly over the UK, OK one has a depression over us but the signal is clear, Cold. 

 

[legritter]

Very hard call for nxt thursday friday, 7/8th .Fax charts come tuesday could produce the goods , could be some happy people , past nxt weekend i think many models will struggle, lets hope tonights ECM will be a cold one .cheers .

[KTtom]

There have been some great explanations on 850 trmperatures and where we need to be for snowfall, Kris provided a nice piece in plain english for everyone to understand, can anyone do the same with dewpoints please, or point me in the right direction for a nice simple explanation of how these are calculated and their relevence to wintry conditions?  Thanks

[danm]

2 minutes ago, KTtom said:

There have been some great explanations on 850 trmperatures and where we need to be for snowfall, Kris provided a nice piece in plain english for everyone to understand, can anyone do the same with dewpoints please, or point me in the right direction for a nice simple explanation of how these are calculated and their relevence to wintry conditions?  Thanks

I think the simple explanation is you really want dew points to be at 0c or below. But I’ll defer to some more knowledgeable memebers!