Model output discussion - cold spell approaching?

[IDO]

10 minutes ago, mushymanrob said:

Hi

Im not sure theres much of a difference between " The contour lines show the flow at 500 mb, which dictates the movement of surface weather systems, not the mean direction of surface flow." after all , doesnt the 500hpa strongly dictate the surface?

Agreed about the second para, but as these charts are the mean, surely for every northerly theres a westerly if the mean is northwesterly?

Well im not sure we are that far apart tbh, far be it for me, an amateur to argue against someone with qualifications, im not so sure theres much difference in what we are saying.

The weekend has no forecaster input so I would not take much notice of that Jan 10th 8-14 day chart. Tonight will be more helpful as it will be a blend of model runs with a pro-forecaster using their experience to give some substance to it.

[Man With Beard]

6 minutes ago, mountain shadow said:

Thanks Mushy.

I don't suppose you have an archived one of these with what a North Easterly would look like then?

Would help in future analysis maybe?

This came from the Feb 2018 Beast From The East (not a completely classic Scandi High but did have a flow backing NE)

Do we have a guide in the learning area on reading NOAA charts, and also northern blocking in general? I was thinking after last nights blow-up on the MOD thread how a link to pages explaining how to interpret these charts/features could have saved a lot of aggro! Happy to contribute a little though there would be far better people than me to do this! 

Edited January 11, 2021 by Man Without Beard

[sheikhy]

Ecm 06z further west at 72 hours!!!northern and eastern areas still in with a shout of significant snowfall!!

[I remember Atlantic 252]

1 minute ago, sheikhy said:

Ecm 06z further west at 72 hours!!!northern and eastern areas still in with a shout of significant snowfall!!

is there a 06Z? never knew

[Singularity]

29 minutes ago, mushymanrob said:

Hi

Im not sure theres much of a difference between " The contour lines show the flow at 500 mb, which dictates the movement of surface weather systems, not the mean direction of surface flow." after all , doesnt the 500hpa strongly dictate the surface?

Agreed about the second para, but as these charts are the mean, surely for every northerly theres a westerly if the mean is northwesterly?

Well im not sure we are that far apart tbh, far be it for me, an amateur to argue against someone with qualifications, im not so sure theres much difference in what we are saying.

Perhaps this makes clearer what I meant; even in this single timeframe chart (as opposed to 5-day mean), the 500 mb contours have a v shape across the North Atlantic with a mean northwesterly in the vicinity of the UK.

Yet the surface flow is bringing in cold air from the northeast and east at this time.

From what you've added since, it sounds like you didn't actually mean that there would be a predominantly north-westerly surface flow after all, rather that the high pressure ridge isn't suggested (by the NOAA chart) to stay in place to our west for very long, in which case I apologise for misinterpreting  your analysis!

Edit: Having said that, this chart from the GFS 00z run shows that the 500 mb contours can be from the northwest even with a massive surface ridge to our northwest or west. There's often some refraction of the flow down by the surface. 

Only in the most extreme setups, such as the 2018 BFTE, do we tend to see more than brief omega shapes to the 500 mb height contours with north easterly 500 mb flow on the eastern flank.

Edited January 11, 2021 by Singularity
I hope this qualifies as MOD! :s

[mushymanrob]

5 minutes ago, chionomaniac said:

Hi Mushy, If you average the flow out over 6 days and then place as 500hPA mean heights then there can be quite large differences between the 6 day 500hPA mean flow and the surface flows during that period. Th0se means were never meant to be read like that. The pressure anomalies are more important when working out likely stearing upper and surface flows as Kirkcaldy showed.

Yep, but we have to take both the pressure anomalies (red/blue dotted lines) with the green cotour lines,  the trick is to identify the mixture of both, (now its getting more complicated) .
But to date, and ive been using these for several years now, ive yet to see a prolonged surface flow thats been at a 90 degree angle to the green contour lines... however, that depends upon how close together they are... a slack flow as indicated by the green contour lines being further apart will allow the surface pressure anomaly to be nearer the mark...

To me, the current charts showing a mean northwesterly are too close together to allow much of a surface flow much away from the northwest.
 

4 minutes ago, IDO said:

The weekend has no forecaster input so I would not take much notice of that Jan 10th 8-14 day chart. Tonight will be more helpful as it will be a blend of model runs with a pro-forecaster using their experience to give some substance to it.

true, but doesnt preclude their value. Id be happier if tonights shift in favour of a more northerly flow.

 

4 minutes ago, Man Without Beard said:

This came from the Feb 2018 Beast From The East (not a completely classic Scandi High but did have a flow backing NE)

Do we have a guide in the learning area on reading NOAA charts, and also northern blocking in general? I was thinking after last nights blow-up on the MOD thread how a link to pages explaining how to interpret these charts/features could have saved a lot of aggro! Happy to contribute a little though there would be far better people than me to do this! 

HA HA.... ive just found that too... and that chart is what id hope to see for a prolonged northeasterly, which would vary between north and east.

[sheikhy]

6 minutes ago, I remember Atlantic 252 said:

is there a 06Z? never knew

weather model ecmwf model - europe - surface pressure [base + 72] [base= 11-01-2021 06 utc]| weatheronline

WWW.WEATHERONLINE.CO.UK

---

Weather for UK, Ireland and the world. Sailing, Marine Weather, Weather maps, radar, satellite, climate, historic weather data, information about meteorology, reports, weather warning.

Yup!!!take a look!!

[Jason M]

50 minutes ago, Scott Ingham said:

So weather warnings out for 5-15cm above 150m and locally 30cm in northern england wednesday.

Who needs severe cold for snow haha!

You don't need it from this set up if you live in Rotherham . Bit northerly, bit of height = happy days.

Too far out to worry about detail but if I was living in northern parts of the UK I'd be starting to get excited looking at how things evolve. For those of us down in the South though its far from a done deal although hardly a disaster yet.

Looking through posts this morning the main two risks seem to be heights not declining enough over Iberia to allow the cold air south and / or west based -NAO. In reality these are the same thing in as you rarely get one without the other. Actually at face value there is a big risk here, but this might be a slightly lesser risk due to the SSW (maybe?).

For a long cold spell we are missing one key ingredient and that's stable high pressure to our north or northeast. The scenario screams for heights to build over Scandi behind the dropping trough but its been a feature of recent years that we can't seem to achieve stable heights at northern latitudes, so we normally have to feed of the scraps of a mid lat high. Without a stable high to our N or NE longevity will inevitably be limited.

So, in summary charts look somewhat better again today. For the northern half of the UK things look very good but its still in the balance and if I had to pick out an area where the risk of cold rain is highest it would be for us in the extreme SE (Essex, Kent, Suffolk) as we might end up too near the circulation of a low pressure system and end up with slightly warmer uppers again. Still likely to see snow in the SE from this set up but **possibly** not exclusively snow.  

To me we are therefore looking at a punchy 3-5 day cold spell but I'm still seeing no convincing evidence of a 'Beast'. Maybe a Rottweiler, but not a Beast. It still beats the 'Mouse from the Med' though!

[Jamie M]

Tweet from Mike Ventrice with ECMWF weeklies that peaks some interest.

[mountain shadow]

Thanks to Mushy, John and Man Without Beard. I think I understand now..

So, we need the anomalous heights more towards Iceland/Scandi than Greenland  then to get the Nor' Easters.

Edited January 11, 2021 by mountain shadow

[Premiere Neige]

2 hours ago, Severe Siberian icy blast said:

I don't understand why everyone's posting charts over t200 with BOOM, its got as much change of verifying as me loosing a stone in 1 wk. Just not gonna happen. 

Every t120 chart is different atm let alone anything after t144 at the very latest. 

At one point there's talk of snow this Wed Thurs I doupt thats gonna happen now but if we can't nail 4 days who's gonna nail 10?

Look for similarities, compare 12z with 12z and 0z with 0z 

We're struggling to get anything down past 8 days so I'd just look for trends, vortex position, Shape of the jet, pressure set up locations high and low. 

It's the same every year, stop getting emotionally tied up in the moment, I know you may like the chase but it's a painful choice 

8 days? I think most agreed last week that the period of interest was 20th onwards....

[mushymanrob]

3 minutes ago, Singularity said:

Perhaps this makes clearer what I meant; even in this single timeframe chart (as opposed to 5-day mean), the 500 mb contours have a v shape across the North Atlantic with a mean northwesterly in the vicinity of the UK.

Yet the surface flow is bringing in cold air from the northeast and east at this time.

From what you've added since, it sounds like you didn't actually mean that there would be a predominantly north-westerly surface flow after all, rather that the high pressure ridge isn't suggested (by the NOAA chart) to stay in place to our west for very long, in which case I apologise for misinterpreting  your analysis!

Yep, i dont have an argument against this... maybe i was not being very clear.

The NOAA charts for the duration show mean ridging over Greenland, troughing over Europe as pressure anomalies, with a mean northwesterly over the UK. The chart you posted above is dead in line with this, yes theres a northeasterly behind it, but theres a westerly in front, as it tracks southeastward across the country.

My point being that IMHO the NOAA charts do not support a sustained northeasterly as some of the more progressive charts showing a lengthy freeze suggest, but do allow for a shorter lived blast.

[Jason M]

1 minute ago, mushymanrob said:

Yep, i dont have an argument against this... maybe i was not being very clear.

The NOAA charts for the duration show mean ridging over Greenland, troughing over Europe as pressure anomalies, with a mean northwesterly over the UK. The chart you posted above is dead in line with this, yes theres a northeasterly behind it, but theres a westerly in front, as it tracks southeastward across the country.

My point being that IMHO the NOAA charts do not support a sustained northeasterly as some of the more progressive charts showing a lengthy freeze suggest, but do allow for a shorter lived blast.

And no reason why the NOAA charts should support this because there is very little support in the operational output for a lengthy freeze. A punchy winter cold spell yes, but not a full on freeze.

[mushymanrob]

5 minutes ago, mountain shadow said:

Thanks to Mushy, John and Man Without Beard. I think I understand now..

So, we need the anomalous heights more towards Iceland/Scandi than Greenland  then to get the Nor' Easters.

Yes...... id be far more confident of a longer lasting cold spell if those green contour lines became more North/South over the UK, they arent far off. OR if the green contour lines open out further, the closer they are, the stronger the flow.. if they are further apart then surface wind direction appears to be controlled more by the pressure anomaly (red dotted lines).

[Catacol]

Learning to squeeze a bit of weather time here at work now - and by golly this is a 192h chart to warm the cockles.....

Indeed - as Chio says it ain't over until the snow is on the ground...but if this is anything like accurate at 8 days then it would need a spectacularly unusual synoptic pathway from this point to prevent very cold air flooding in.....-12 850s to the NE with colder yet in behind....

[swebby]

26 minutes ago, Man Without Beard said:

This came from the Feb 2018 Beast From The East (not a completely classic Scandi High but did have a flow backing NE)

Do we have a guide in the learning area on reading NOAA charts, and also northern blocking in general? I was thinking after last nights blow-up on the MOD thread how a link to pages explaining how to interpret these charts/features could have saved a lot of aggro! Happy to contribute a little though there would be far better people than me to do this! 

Would that be a good example of the finger print of an Omega block sat between the UK/Iceland?

[mushymanrob]

2 minutes ago, swebby said:

Would that be a good example of the finger print of an Omega block sat between the UK/Iceland?

yes.

[carinthian]

Ok just have an update with specifics regarding UK snowfall Wed-Fri this week. Going by the graphics shown on the snow model, the front appears to push through slowly but has what looks like the makings of a returning cold front to lie across the east. So snow potential being flagged up for the Eastern Pennine region especially Thursday into Friday. Maybe some transient snowfall on Wednesday in Scotland and NE England. With-in the parameters a current 20% confidence rating with high complexity , so changes could be swift.

c

[Catacol]

6 minutes ago, Jason M said:

And no reason why the NOAA charts should support this because there is very little support in the operational output for a lengthy freeze. A punchy winter cold spell yes, but not a full on freeze.

I guess it depends on what you classify as operational output and what could be marked down as support. Until this displaced-vortex driven westerly interlude temps have been running at over 3 degrees below CET and we have a very distressed vortex that is displaced over Asia, set to run negative at 65N for at least another week and may yet end up being pummelled more. We have a new attempt coming up by the MJO to move into the more blocked forcings of 7/8/1 and an arctic high growing in strength as the vortex is away from home helping pump very cold air out the arctic. I'd say there is very good support for a pattern that could dig in for a week or more - which I guess then raises questions about what is defined as "lengthy". 

Feb 18 being discussed a bit today was truly remarkable. For me much more remarkable than what happened in 2010. Pulling out NOAA charts of Feb 18 seems to me a bit unfair - its like comparing every footballer out there with Messi or Ronaldo. This spell I dont think will go down quite as a historic one now because we didn't do away with the vortex properly....but a lengthy freeze of 1-2 weeks seems to me to be a definite possibility. Whether further attacks on the vortex can bring more of February into the game we will need to wait and see.

Or it may, after all, be 2-3 days and gone. The weather can be a cruel mistress.

[SLEETY]

13 minutes ago, Catacol said:

Learning to squeeze a bit of weather time here at work now - and by golly this is a 192h chart to warm the cockles.....

Indeed - as Chio says it ain't over until the snow is on the ground...but if this is anything like accurate at 8 days then it would need a spectacularly unusual synoptic pathway from this point to prevent very cold air flooding in.....-12 850s to the NE with colder yet in behind....

The ecm has been poor at this range,with not many charts verifying ,lets hope it verifies,as its beginning to feel like we are are chasing the cold in fl again 

[MATTWOLVES 3]

Check out those 6Z ens..quite a few Battleground scenarios appearing..The one I'm posting is a cracker.. also a chart from M Ventrice showing Europe and then the UK going really cold.. Im usually fed up on a Monday....but today I have a spring in me step..

[Frostbite1980]

5 minutes ago, MATTWOLVES said:

Check out those 6Z ens..quite a few Battleground scenarios appearing..The one I'm posting is a cracker.. also a chart from M Ventrice showing Europe and then the UK going really cold.. Im usually fed up on a Monday....but today I have a spring in me step..

Note the warm anomalies on the 2nd Feb returning to Eastern Europe.....not keen on that as easterlies could get watered down like the last cold spell although that is in la la land 

[daz_4]

2 minutes ago, MATTWOLVES said:

also a chart from M Ventrice showing Europe and then the UK going really cold.. Im usually fed up on a Monday....but today I have a spring in me step..

 

Does it though? Maybe I'm reading the chart wrong but I see most of the Europe average or slightly above and cold locked away in Scandinavia.

[Badgers01]

Not sure they show UK going really cold either, a temp anomaly of -1c still shows we are still marginal a little cooler but nothing too noteworthy yet .

[goosey007]

6 minutes ago, daz_4 said:

Does it though? Maybe I'm reading the chart wrong but I see most of the Europe average or slightly above and cold locked away in Scandinavia.

to me it must of some note worthy significance otherwise he would not have tweeted it.....signals/trends at that range. All promising stuff if your looking for cold and potentially snow